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Transition Metal Reagents and Catalysts: Innovations in Organic Synthesis
Abstract
Contenido: Inicio de procesos industriales usando catalizadores homogéneos de metales de transición; Química básica de complejos de metales de transición y de sus patrones de reacción; Reacciones de halidas y de pseudohalidas orgánicas; Reacciones de los compuestos alílicos; Reacciones de dienos conjugados; Reacciones de los compuestos propargílicos; Reacciones de alquenos y alquinos; Reacciones sintéticas vía complejos de carbeno del metal de transición; Protección y activación por coordinación; Hidrogenación catalítica, hidrogenación de transferencia y hidrosilidación; Reacciones iniciadas y catalizadas por compuestos de paladio (II).
... The obvious reason for this is the cost of transition metal complexes for stoichiometric use. However, Professor Tsuji emphasized the advantages of using transition metal-catalyzed reactions that could not be attained by the classical reactions [1,2]. Furthermore, Professor Tsuji was interested in carbon-carbon bond-forming reactions and natural product synthesis. ...
... In an early investigation, allylic carbonates 1 and acetates were used as substrates to identify effective borates (R T : transferable group) and nickel catalysts (Scheme 1, Equation (1)). Trimethoxy borate 7 was studied first to find a nickel catalyst [10] and then advanced to borate 8, which possesses the 2,2-butanediol and methyl ligands [11]. ...
... Among the candidates Scheme 6. Allylic coupling reaction of 1a with phenylborates 31A-F. 1 2,3-Butanediol ligand consisted of dland meso-forms in a 4:1 ratio. ...
In the first part of this review, secondary carbon-carbon bond formation by using allylic coupling reactions with aryl and alkenyl borates is presented. Early investigations have revealed the suitability of a nickel catalyst and [RTB(OMe)3]Li (RT: transferable group). Due to their low reactivity, the borates were converted to more reactive congeners possessing an alkanediol ligand, such as 2,3-butanediol and 2,2-dimethyl-1,3-propanediol. Borates with such diol ligands were used to install aryl and alkenyl groups on the monoacetate of 4-cyclopentenyl-1,3-diol. Furthermore, alkenyl borates showed sufficient reactivity toward less reactive allylic alcohol derivatives with bromine atoms at the cis position, producing dieneyl alcohols. In the second part, copper-based and/or copper-catalyzed substitutions of secondary allylic picolinates, propargylic phosphonates, and alkyl (2-pyridine)sulfonates with RMgX are briefly summarized. The application of these reactions to the synthesis of biologically active compounds is also discussed.
... Among the transition metal catalysts, there are a number of reactions using a rhodium catalyst such as aldol-type reaction, 1,4-addition reaction, hydroacylation, and carbocyclization. [17][18][19][20] Furthermore, Rh-catalyzed coupling reactions have 3 undergone intense study, and it is even possible to insert a sp 3 carbon (Csp 3 ) into a molecule for the C-C bond formation. [21][22][23][24][25] We also reported an effective formation of a highly reactive rhodium-alkyl complex and its applications to reductive fluoroalkylation, [26,27] α-fluoroalkylation, [28][29][30][31][32] Reformatsky-Honda reaction, [33][34][35][36][37][38][39] reductive α-acylation, [40][41][42] reductive aldol reaction, [43][44][45] and reductive Mannich reaction (Scheme 1). ...
A novel Rh-catalyzed one-pot Ullmann homo-coupling reaction of Grignard reagents was achieved. The reaction with bromobenzenes having an electron-donating group or halogen group gave the corresponding homo-coupling products in good yields, although heterocyclic or aliphatic bromides did not give the products. A highly reactive Rh(III)-bis(aryl) complex would play an important role in giving the homo-coupling products in this reaction. The reaction was applied to the integrin inhibitor that was being developed in parallel. As the result, we synthesized a novel inhibitor for integrins which is critical for several diseases.
... Due to the importance of olefins in the synthesis of lead molecules, a variety of preparative methodologies have been developed. Particularly, the Heck reaction is one of the most popular methods in the synthesis of aryl-substituted olefins [7][8][9]. Aryl halides are the most commonly employed aryl palladium precursors in the Heck reaction. ...
... Palladium catalysis has engaged in many asymmetric/symmetric synthetic transformations, such as carbon-carbon and carbon-nitrogen bond formation, which is the most common technique for bond formation in process chemistry and medicinal chemistry. Many reactions are well known to feature palladium metal as a catalyst, such as Suzuki, Heck, Buchwald-Hartwig, and Stille cross-coupling reactions; Tsuji-Trost allylation and Wacker transformation; and many processes, such as carbonylation, hydrogenation, pericyclic reactions, and cycloisomerization [19][20][21][22][23][24][25]. ...
Herein, we described the synthesis and X-ray crystal structure of the new [Pd(3)2Cl2] complex with 1,2,3-triazole-based ligand (3). In the unit cell, there are two [Pd(3)2Cl2] molecules, and the asymmetric unit comprised half of this formula due to the presence of an inversion symmetry element at the Pd(II) center. The monoclinic unit cell volume is 1327.85(6) Å3, with crystal parameters of a = 10.7712(2) Å, b = 6.8500(2) Å, and c = 18.2136(6) Å, while β = 98.851(2)°. The structure comprised two trans triazole ligand units coordinated to the Pd(II) ion via one of the N-atoms of the triazole moiety. In addition, the Pd(II) is further coordinated with two trans chloride groups, where each of the trans bonds is equidistant. The crystal structure of the [Pd(3)2Cl2] complex was compared with that for free triazole ligand 3. It was found that the coordinated ligand showed less twist around the C–N bond compared to free triazole ligand 3. The molecular packing of the latter is found controlled by short O…H, N…H, C…N, and C…C interactions in addition to the short Cl…F interhalogen and π–π interactions. H…H (23.5%), Cl…H (14.4%), N…H (14.3%), and O…H (11.2%) are the most dominant contacts. In the [Pd(3)2Cl2] complex, no significant interhalogen or π–π interactions were detected. In this case, Cl…H (31.1%), H…H (16.7%), O…H (11.6%), and F…H (9.7%) are the most dominant contacts.
... NADPH bioorganic molecule (1) On the other hand, catalysis represents one of the most powerful tools to transform molecules (Rawat et al., 2022), and usually, transition metals are used to build this kind of molecules because of their redox, optical and/or magnetic properties (Tsuji, 2002). In terms of green chemistry, the use of first row bioavailable transition metals as base of catalysts is preferred mainly because of their abundance and reincorporation into the biological processes (McCleverty, 1999). ...
This article provides insight into the music of the late Renaissance and early Baroque in Italy. Com-poser Claudio Monteverdi was one of the most important figures in the music of the early Italian Baroque. We consider the events that led to the creation of the new early Baroque style – Seconda pratica - (second practice) and describe the significant changes in vocal music that took place with the aim to depart from strict counterpoint at the turn of the 16th century. Keywords: Claudio Monteverdi; Seconda pratica; Venetian school; Madrigalisms; Ornamentation
... NADPH bioorganic molecule (1) On the other hand, catalysis represents one of the most powerful tools to transform molecules (Rawat et al., 2022), and usually, transition metals are used to build this kind of molecules because of their redox, optical and/or magnetic properties (Tsuji, 2002). In terms of green chemistry, the use of first row bioavailable transition metals as base of catalysts is preferred mainly because of their abundance and reincorporation into the biological processes (McCleverty, 1999). ...
Hantzsch dihydropyridines represent an important source of hydrogen to be transfered to other un-saturated organic molecules, leading the formation of pyridine aromatic ring as driving force. The hydrogen transfer process was evaluated using 1,4-dyhydropyridines and heterogeneous cobalt cat-alyst supported over N-doped activated carbon. The 4-position of the dihydropyridine ring was sub-stituted with H (4a), Me (4b) and Ph (4c) groups, showing that only 1 reacted to yield the correspond-ing pyridine compound indicating that the presence of steric hindrance took place on the reaction. Additionally; three solvents –tetrahydrofuran (THF), acetone, and acetonitrile– were tested, showing reactivity only with unsaturated ones, but not with THF. This observation indicates that dihydro-pyridine works as hydrogen donor and solvent as hydrogen aacceptor in the hydrogen transfer pro-cess.
... Moreover, in most of the C-S cross-coupling reactions, stable disulfides can be formed through easy oxidative homocoupling S-S reaction of thiols [35][36][37][38][39][40]. Consequently, the catalytic activity of transition metals in C-S cross-coupling reaction is less explored than the other cross-coupling reactions [1,[41][42][43][44][45][46], due to the disadvantages associated with these methods. To gain sustainable synthetic methods, instead of free thiols various sulfur reagents have been applied in the synthesis of various aryl sulfides and their derivatives such as: thiourea [47][48][49][50][51][52][53][54][55][56][57][58], potassium thiocyanate [59][60][61][62], carbon disulfide [63][64][65], S 8 [56,58,[66][67][68][69][70] and sodium thiosulfate [71]. ...
Herein a prominent, efficient, facile and environmentally benign catalytic activity of γ-Fe2O3/talc/CuII NPs (as a superparamagnetic composite with average diameter of about 20-30 nm) has been shown in C–S cross-coupling reactions. A wide variety of aryl iodides, aryl bromides and aryl chlorides with electron-donating or electron-withdrawing substituents reacted with S8 or thiourea forming the corresponding substituted diphenyl sulfides under eco-friendly and mild process conditions. The results demonstrated remarkable catalytic activity of the nanostructured catalyst such as chemoselectivity and functional group tolerance. γ-Fe2O3/talc/CuII NPs as a magnetic catalyst was stable under reaction conditions and can be recycled at least five times with minimal loss of catalytic activity. Moreover, the use of commercially available and chemically stable sulfur transfer agent, eco-friendly and low-cost solvent and base as well as operational simplicity and easier work-up procedure make this method a promising candidate for potential applications in some organic reactions.
... Homogeneous transition-metal (TM) catalysis has made great contributions to modern synthetic chemistry 1 . Engineering of TM-based molecular catalysts played a crucial role, which enabled new catalytic modes that led to useful synthetic reactions with enhanced selectivity and efficiency. ...
Catalyst design is a key research area in modern synthetic chemistry. Engineering of molecular catalysts in homogeneous catalysis brings about new catalytic modes that enable efficient synthetic transformations. In this regard, design of novel ligands for transition-metal catalysis have played a major role. Olefins have been emerging as a significant class of steering ligands in transition-metal catalysis, which are known to serve as innocent ligands that provide electronic and steric tuning of the metal center. However, it is unknown whether a distinct type of olefin ligand that contrasts the common innocent feature is possible. Here we show that a novel type of heteroatom-cycloolefin hybrid ligand functions as a non-innocent ligand in palladium catalysis, which exhibits covalent catalytic function that enables efficient ipso,ortho-difunctionalization of iodoarenes. Detailed mechanistic study revealed that this ligand undergoes reversible covalent bonding between the substrate and the cycloolefin unit, which forms key organopalladium intermediates to enable new reactivity. Our results demonstrate a novel design concept that utilizes unstrained cycloolefin as a covalent catalytic module, opening an avenue to a more general transition metal/olefin cooperative catalysis.
... So far, the modular creation of differently deuterated methyl and methylene groups in covalent molecules remains a fundamental challenge [20][21][22][23][24][25][26][27][28] (Fig. 1a). Organic transition metal species are involved in catalytic reactions [29][30][31] and are prevalent in medicinal chemistry 14,32 and materials science 33,34 . In a β-H elimination reaction, the metal picks up a hydrogen atom in an alkyl metallic species. ...
Deuterium-incorporated compounds are of high interest owing to their importance in the pharmaceutical industry, organic synthesis and materials science. So far, the integration of deuterium into the inert, saturated magic methyl or methylene groups of covalent molecules remains challenging. Here, we present a 1,4-H delivery of allylic metallic species to provide a highly stereoselective and straightforward approach to 3-methyl-2(E)-enals or -enones from readily available 2,3-allenols and organoboronic acids. The reaction accommodates many synthetically versatile functional groups as well as multi-pharmacophores, and is not limited to the formation of 3-methyl derivatives. By applying 1,4-H or D delivery, deuterium atom(s) from differently deuterated allenols can be edited into the methyl or methylene groups of versatile organic skeletons, resulting in the efficient formation of 4-monodeuterated, 1,4- and 4,4-doubly deuterated, and 4,4,4-triply deuterated 2(E)-enals or -enones. These powerful platform molecules can provide straightforward paths to other deuterated compounds for different purposes. Deuterated compounds are of high interest to the pharmaceutical industry; however, modular creation of differently deuterated methyl and methylene groups in organic skeletons is challenging. Now, this has been achieved by introducing the concept of transition-metal-mediated 1,4-H or D delivery.
... The mechanistic details of these processes have been reviewed. [7][8][9][10][11] The palladium-catalyzed cyclization of vinylic/aryl halides or triflates containing alkenes, dienes, alkynes, and arenes via oxidative addition/reductive elimination reactions provides a powerful method to a various pyran and furans heterocycles [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] Among them pyran is core structure of various natural products. Numerous synthetic efforts for the preparation of pyran rings have been reported by different groups. ...
Pyrans constitute an important class of 6-member heterocycles with one oxygen atom. Together with its benzo derivatives, pyrans can formulate a prevalent verity of natural and synthetic products with industrial applications. This is an important core molecule having versatile use with its derivatives in pharmaceuticals, dye industry, catalysis, agrochemicals and many more. Several methods for the preparation of pyran derivatives have been reported earlier. This article reports the development of an efficient method for the construction of a fused pyran ring by intramolecular Heck reaction followed by β-H elimination from O-allylated ether. A tetracyclic pyran ring has also been synthesized by intramolecular Heck reaction followed by C–H bond activation from O-methallylated ether.
... 4 Chemical catalysis today has attained a high level of sophistication, as exemplified by the large number of reactions that have been discovered and our growing insight into mechanism and catalytic species. [5][6][7] An emerging frontier in chemical catalysis is the integration of synthetic metal catalysts with living systems. [8][9][10][11][12][13] Fundamentally, these efforts are driven by intellectual curiosity. ...
Although abiotic catalysts are capable of promoting numerous new-to-nature reactions, only a small subset has so far been successfully integrated into living systems. Research in intracellular catalysis requires an interdisciplinary approach that takes advantage of both chemical and biological tools as well as state of the art instruments. In this Perspective, we will focus on the techniques that have made studying metal-catalyzed reactions in cells possible using representative examples from the literature. Although the lack of quantitative data in vitro and in vivo has somewhat limited progress in the catalyst development process, recent advances in characterization methods should help overcome some of these deficiencies. Given its tremendous potential, we believe that intracellular catalysis will play a more prominent role in the development of future biotechnologies and therapeutics.
... The chemistry of organopalladium derivatives have very rich chemistry, and can easily be prepared and handled of the plethora of known transition metal complexes. The facile redox interchange between the two stable Pd(II)/Pd(0) oxidation states is mainly responsible for the rich chemistry enjoyed by palladium compounds [1,2]. Cyclopalladated complexes have long been the subject of intense study mainly due to their potential applications in many areas, including organic synthesis, material science, organometallic catalysis, biological and medicinal chemistry [3][4][5][6][7]. ...
A series of heteroleptic mononuclear cyclopalladated benzo[h]quinolinate complexes of general formula [Pd(bzq)(Ph2PCH2PPh2C(H)C(O)C6H4-p-R)]ClO4 (bzq = 7,8-benzoquinoline; R = Cl (C¹), Br (C²), NO2 (C³), OCH3(C⁴)), were synthesized by the reaction of [Pd(bzq)(μ-Cl)]2 with 0.5 equiv of phosphorus ylides [Ph2PCH2PPh2C(H)C(O)C6H4-p-R] in CH2Cl2 solvent at room temperature. Bridge splitting with stabilized phosphorus ylides afforded new mononuclear palladacycle derivatives with two five-membered rings. The formation of the complexes was ascertained by elemental analysis, IR, UV–visible and NMR spectroscopic methods. All of the complexes exhibited absorption bands at high energy due to the intraligand transitions [¹IL π → π*] and absorptions at lower energy, which are attributed to MLCT transition [(Pd,4d) π → π* (bzq)]. The influence of the R substituent and different solvents on the UV–visible absorption of all complexes was also investigated. Furthermore, palladacycle C³ was employed as an efficient catalyst in the Suzuki‐Miyaura coupling reactions of various aryl halides and phenylboronic acids in the mixed EtOH/H2O media.
This study aimed to describe the preparation of novel PEPPSI type Pd(II)-NHC complexes bearing N-benzyladamantyl substituted imidazolidin-2-ylidene group. All synthesized compounds were characterized by using 1H-NMR and 13C-NMR spectroscopies, FTIR, and elemental analysis techniques. One of the objectives of this study was the synthesis of Pd-NHC complexes with AChE/BChE inhibition activities. Among all the tested compounds, complexes 4b and 4c were found to have the most high potential AChE and BChE inhibitory activities with IC50 values of 21.57 ± 0.23 Mm and 15.78 ± 0.39 Mm, respectively. Conducting molecular docking studies helped us in gathering crucial information about the main binding interactions of inhibitors and enzymes, and the results were in agreement with the biological evaluation. The synthesized Pd-NHC complexes were employed for catalyzing the direct C2- and C5-arylation reaction between aryl (hetero) halide and a variety of heterocyclic systems. In both cases (C2 and C5-arylation), Pd-NHC complexes catalysts provided access to the arylated heterocycles in good to high yields in the presence of 1 mol% catalyst loading at 150°C. The DFT theoretical investigation showed that the Pd-NHC complexes were of ML2X2 type, where the the Pd(II) cation had a square planar geometry. The interaction energies obtained by energy decomposition analysis (EDA) demonstrated that the 4d and 4e complexes were more stable in the presence of more methyl substituents. The chemical indicators demonstrated that the less stable 4c complex was more reactive in regard to the chemical hardness, chemical potential, and electrophilicity values.
Controlling the transformation of versatile and reactive allenes is a considerable challenge. Herein, we report an efficient silylboronate-mediated cross-coupling reaction of organic fluorides with allenes to construct a series of sterically demanding α-ethynyl-containing all-carbon quaternary centers (ACQCs), using catalyst-free silyl-radical-relay reactions to selectively functionalize highly inert C–F bonds in organic fluorides. The key to the success of this transformation lies in the radical rearrangement of an in situ-generated allenyl radical to form a bulky tertiary propargyl radical; however, the transformation does not show efficiency when using the propargyl isomer directly. This unique reaction enables the cross-coupling of a tertiary carbon radical center with a C(sp²)–F bond or a benzylic C(sp³)–F bond. α-Ethynyl-containing ACQCs with (hetero)aromatic substituents and benzyl were efficiently synthesized in a single step using electronically and sterically diverse organic fluorides and allenes. The practical utility of this protocol is showcased by the late-stage functionalization of bioactive molecules and the modification of a liquid crystalline material.
This study incorporates the assembly of development methodologies of microwave-acti-vated protocol involving transition metal catalysts for the synthesis of numerous biologically im-portant heterocycles during the past few years. Herein, it highlights the potential of transition metal salts as catalysts in multicomponent reactions performed under microwave conditions for the for-mation of oxygen, nitrogen, and sulphur-containing bioactive heterocycle moieties. Microwave-activated organic synthesis has been well-utilized as an alternative to conventional methodology in pharmaceutical companies due to its potential to significantly improve the rate and consequently diminish the time span of the synthetic process. The traditional methods involving transition metal catalysts for synthesizing bioactive heterocyclic molecules are prolonged and, thus, difficult to meet the requirements for the timely supply of these important compounds. In our review, our main focus is on integrating such synthetic strategies involving transition metal catalysis with a microwave-activated multicomponent approach for developing bioactive heterocycles.
The efficiency of the formation of C–C bonds under palladium catalysis often depends on the nature of the carboxylate ligand and carboxylic acids or alkali metal carboxylates additives. This review which is Part C of a trilogy devoted to the topic, highlights the influence of the carboxylate units on domino diarylation and annelation reactions. The plausible reaction mechanisms are presented with, as far as possible, personal comments.
The efficiency of the formation of C–C bonds under palladium catalysis often depends on the nature of the carboxylate ligand and carboxylic acids or alkali metal carboxylates additives. This review which is Part B of a trilogy devoted to the topic, highlights the influence of the carboxylate unit on the hydro(hetero)arylation, hydroalkenylation and hydroalkylation reactions. The plausible reaction mechanisms are presented with, as far as possible, personal comments.
This short review presents an overview of the effectiveness of β-bromoaldehyde as synthetic tool in organic chemistry. Few groups have reported significant contributions on β-bromoaldehyde. The aim of our short review was to give an overview of the latest advances in the chemistry of βbromoaldehyde from their preparation to their transformations and applications in organic synthesis of some heterocyclic and carbocyclic molecules by using palladium-catalyzed reaction.
Single metal/multiligand catalysis (SMMLC) has recently been raised for highly efficient and selective synthesis of valuable compounds. As a newly emerged member of SMMLC, ligand relay catalysis (LRC) injects new...
The preparation of diimidazolium salt HBDIM 1, a precursor for a di‐NHCs ligand, from cheap and easily available agent hexabenzylhexaazaisowurtzitane (HBIW) is reported. Under basic conditions, HBDIM undergoes facile deprotonation to in situ generate CageCarbene, which could efficiently coordinate to transition‐metals, such as, Au, Cu or Pd, to give the corresponding bimetallic complexes 2–4. These complexes were isolated and fully characterized, including X‐ray diffraction of their single crystals. It was found that the steric hinderance of CageCarbene is similar to that of SIMes but smaller than that of IPr, and electronically, CageCarbene is a strong σ‐donator similar to SIMes and a stronger σ‐donator than IPr. Further studies showed that complexes 2–4 were highly reactive to catalyze up to 17 reactions. Control experiments utilizing a N‐benzyl‐substituted monoimidazolium salt showed much lower catalytic reactivity when it was bound to Au or Cu, but exhibited similar reactivity for the Pd complex. Kinetic studies showed that the low reactivity of the monodentate carbene‐ligated Au or Cu complex was due to the low stability of the complex under the reaction conditions.
Vinylarenes represent an important class of core skeleton embedded in natural products, organic materials, and pharmaceutical molecules. Therefore, numerous efforts have been devoted to developing efficient methods for their preparation. Among them, transition-metal-catalyzed oxidative coupling of arenes and alkenes has proved to be a powerful method due to its high atom and step economy. Although a wide range of oxidative alkenylations of arenes have been developed, the alkenes employed in most cases are still limited to electron-deficient alkenes. Reported herein is a Rh(III)-catalyzed C-H cross-coupling of benzoxazinones and simple unactivated styrenes to furnish a variety of vinylarene scaffolds. This established protocol is characterized by wide functional group compatibility, high yields, and excellent regio- and chemo-selectivity. Mechanistic studies and gram-scale experiments on this high-value conversion are disclosed. Moreover, the potential utility of this method was highlighted by a series of further transformations.
Quinolinones, of which the quinolin-4(1H)-one ring system can be highlighted, represent an exciting class of nitrogen heterocycles. The quinolinone motif can be found in many natural compounds and approved drugs for several diseases. This chapter is a comprehensive survey of the methods for the synthesis of quinolin-2(1H)-ones, quinolin-4(1H)-ones, and their thio- and amino derivatives, and is an update to the previous Science of Synthesis chapter (Section 15.4), covering the period between 2003 and 2020.
Iodohydrins and corresponding ethers were synthesized by an electrochemical process using inexpensive and non‐toxic ammonium iodide. This transformation was applied to a panel of alkenes, giving products without the need of external hazardous oxidants, reductants or metal catalyst. This protocol showed a general efficiency to synthesize valuable iodinated molecules with yields from 19% to 90%.
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A silicon group plays distinctive role in controlling many organic reactions. In this context a β‐silylmethylene malonate (β‐SMM) can be considered as a versatile reagent in organic synthesis to introduce a silicon group in strategic positions of organic frameworks for further manipulations. In addition to the chemistry exhibited by alkylidene and arylidene malonates, a β‐SMM shows unique reactions attributed to the silicon group. The derived products exhibit enormous potential for the rapid generation of useful intermediates/products which are otherwise difficult to accomplish. This account chronicles our systematic approach beginning from the synthesis of β‐SMMs from readily available starting materials, and their use in complexity generation through novel and/ or known reactions. Reactions using β‐SMMs such as synthesis of 1‐substituted vinylsilanes and their Pd‐catalyzed cross‐coupling, organocatalytic asymmetric addition of methyl ketones, aldehydes, nitroalkanes and pyrazol5‐ones, and asymmetric 1,3‐dipolar cycloaddition with azomethine ylides are highly influenced by the silicon group.
Indeed, all the heterocycles comprises of either “C–C, C–N, C–S or C–O” bonds in their skeleton and construction of these bonds has laid the foundation stone of organic chemistry. The present researchers are continually attempting to develop new strategies for synthesizing miscellaneous structurally divergent molecular entities and these bond forming reactions are the fundamental tools. As a consequence, a colossal upheaval is witnessed in development of benign and sustainable synthetic routes for green bond-forming reactions envisaging carbon–carbon/heteroatom. This chapter is aimed towards highlighting the recent developments perceived in “C–C, C–N, C–S or C–O” bondconstruction especially emphasising greener perspectives i.e. carbocatalysis.
Herein we report our study on the development of a catalytic one-pot process, showing the challenges and advantages encountered all over the way. At the end, we developed a regioselective, environmentally friendly, and operationally simple method to explore the reactivity of functionalized propargylic alkynes through three copper-catalysed reactions in a single reaction vessel. The sequence consisted of a hydroboration, azidation, and 1,3-dipolar cycloaddition and led to the regioselective formation of vinyl 1,2,3-triazoles in good yields.
Since its inception in 1960s, the Tsuji–Trost reaction, an allylic substitution reaction with diverse nucleophiles such as phenols, amines, thiols, and active methylene compounds, has remained as one of the most useful and widely used organic reactions for the construction of C–C and C–heteroatom bonds. Allylic compounds such as allylic acetates, alcohols, halides, and carbonates undergo this transformation which plays an important role in the total synthesis of various natural products. The competence to incorporate synthetically demanding allylic functionalities makes it a beneficial tool for the synthesis of complex molecules. Over the last two decades, major advancements for this unique and facile Tsuji–Trost allylation reaction have been made with special emphasis to develop greener and sustainable protocols. This chapter presents an update on the significant progress focusing on the newly designed catalytic systems with high efficiency, the use of eco-friendly solvents or solvent-free conditions, low or room temperature conditions and waste management, along with future outlook.
The construction of a carbon-carbon bond is the most fundamental aspect of synthetic chemistry. In this study, we developed a catalyst-free SN2′ reaction of β-OTf-substituted enamides with aromatics to obtain aryl-substituted aza-1,4-dicarbonyl compounds that can be in situ transformed into aryl-imidazole, aryl-thiazole, and aryl-oxazole in one-pot operation, thus achieving C-H heteroarylation of aromatics. This simple, efficient, clean and scalable strategy, which provides difficult-to-realize biaryl products, is compatible with various aromatics having varying complexities. This method can be used for the late-stage modification of various commercial pharmaceuticals or functional materials and offers an orthogonal approach for constructing biaryl compounds.
Catalyst design is a key research area in modern synthetic chemistry. Engineering of molecular catalysts in homogeneous catalysis brings about new catalytic modes that enable efficient synthetic transformations. In this regard, design of novel ligands for transition-metal catalysis have played a major role. Olefins have been emerging as a significant class of steering ligands in transition-metal catalysis, which are known to serve as innocent ligands that provide electronic and steric tuning of the metal center. However, it is unknown whether a distinct type of olefin ligand that contrasts the common innocent feature is possible. Here we show that a novel type of heteroatom-cycloolefin hybrid ligand functions as a non-innocent ligand in palladium catalysis, which exhibits covalent catalytic function that enables efficient ipso,ortho-difunctionalization of iodoarenes. Detailed mechanistic study revealed that this ligand undergoes reversible covalent bonding between the substrate and the cycloolefin unit, which forms key organopalladium intermediates to enable new reactivity. Our results demonstrate a novel design concept that utilizes unstrained cycloolefin as a covalent catalytic module, opening an avenue to a more general transition metal/olefin cooperative catalysis.
The engineering of molecular catalysts in homogeneous catalysis enables new catalytic modes, which leads to efficient synthetic transformations. In this regard, the design of ligands for transition metal catalysis has played a major role. In transition metal catalysed reactions, olefins can serve as steering ligands by tuning the electronic and steric nature of the metal centre. Here we report unstrained olefin ligands that bear a P or S coordination site for use in the Pd-catalysed Catellani reaction. This olefin ligand shows a covalent catalytic function and enables an efficient ipso,ortho-difunctionalization of iodoarenes. Mechanistic analysis reveals a reversible covalent bonding between the substrate and the cycloolefin unit of the ligand, which forms key organopalladium intermediates to enable a new reactivity. Our results demonstrate a design concept that employs hybrid cycloolefin ligands as a covalent catalytic module, which opens up possibilities for further cooperative catalysis with other transition metal–olefin hybrids. Taking inspiration from palladium–norbornene cooperative catalysis, Catellani-type reactions are now performed using a hybrid olefin ligand with a P or S coordination site. This olefin ligand enables efficient ipso,ortho-difunctionalization of iodoarenes. Mechanistic studies show the formation of organopalladium intermediates that comprise both the substrate and the hybrid olefin ligand.
Novel N‐containing porous carbon supported Pd heterogeneous catalysts have been derived by carbonization of gelatin (GEL)/chitosan/PdCl2 (GEL/CS/PdCl2) and GEL/polyvinyl pyrrolidone/PdCl2 (GEL/PVP/PdCl2) blends under N2 atmosphere at 800°C. The microstructure of the resultant N‐containing carbon supported Pd heterogeneous catalysts can be tailored by the nature of the blended polymers. Much larger specific surface area, better dispersion of Pd0/PdO nanoparticles, higher Pd and N contents are found in the case of N‐containing porous carbon supported Pd heterogeneous catalysts derived from GEL/CS/PdCl2 blend system. When the mass ratio of GEL to CS is kept at 1/1, the surface area of 644.8 m2/g, rich porous structure, N % of 7.2%, and Pd0/PdO nanoparticles sized below 3 nm are obtained in the derived Pd@N‐C‐GEL/CS(1/1) catalyst. It shows excellent catalytic efficiency (higher than 90%) in Heck coupling reaction of aromatic halides and alkenes, and high recycling stabilities both in aqueous (9 runs) and organic (15 runs) phase. The high activity and stability of the novel Pd@N‐C‐GEL/CS(1/1) catalyst have been attributed to a combination of high porous structure, strong chelation of Pd species, high thermal stability, and good solvent‐resistant performances.
The Pd catalyzed cross-coupling reactions have played a crucial role in accomplishing different valuable organic transformations. These transformations involve the use of homogeneous as well as heterogeneous Pd catalysts. A large variety of ligands have been applied in Pd catalyzed coupling reactions. Traditionally, these transformations are carried out by various phosphine-based ligands. The phosphine ligands are suffering from poor air, moisture, and thermal stability. Hence, in recent years phosphine-free ligands such as N-heterocyclic carbenes and amines have been attracted great attention in the field of catalysis. Though the N-containing ligands have comparatively low reactivity as compared to phosphine and carbene-based ligands, most importantly, these complexes have broad scope in catalysis, as they represent a low cost, less toxicity, good moisture, thermal and air stability as well as environmentally friendly. In this review, we present the developments made in the field of Pd complexes of N and O donor ligands in various cross-coupling reactions.
Catalyst design is a key research area in modern synthetic chemistry. Engineering of molecular catalysts in homogeneous catalysis brings about new catalytic modes that enable efficient synthetic transformations. In this regard, design of novel ligands for transition-metal catalysis have played a major role. Olefins have been emerging as a significant class of steering ligands in transition-metal catalysis, which are known to serve as innocent ligands that provide electronic and steric tuning of the metal center. However, it is unknown whether a distinct type of olefin ligand that contrasts the common innocent feature is possible. Here we show that a novel type of heteroatom-cycloolefin hybrid ligand functions as a non-innocent ligand in palladium catalysis, which exhibits covalent catalytic function that enables efficient ipso,ortho-difunctionalization of iodoarenes. Detailed mechanistic study revealed that this ligand undergoes reversible covalent bonding between the substrate and the cycloolefin unit, which forms key organopalladium intermediates to enable new reactivity. Our results demonstrate a novel design concept that utilizes unstrained cycloolefin as a covalent catalytic module, opening an avenue to a more general transition metal/olefin cooperative catalysis.
Highly regio- and stereoselective palladium-catalyzed C1-vinylation of β-naphthols (2) has been reported using easily accessible CF3-allyl carbonates (1). The regioselective nucleophilic -attack of CF3-π-allyl-Pd-intermediate is the key to furnish (Z)-CF3-vinylnaphthols...
Complexes of transition metals with chiral ligands are considered as catalysts. Among metal-containing organic complexes with semiconducting properties, compounds of the porphin series occupy a special place in electrocatalytic studies. The properties of the porphyrin macrocycle, their role in catalysis, and the influence of the nature of the metal on the catalytic properties of the complex are considered.
We are entering an era that emphasizes greenness and sustainability. Based on such a philosophy, it is critical to uncover novel and original sustainable reaction modes for future green chemical syntheses. The cross-dehydrogenative coupling (CDC) reaction has thus been widely developed as one of the most sustainable and efficient synthesis strategies for constructing C-C bonds. This review summarizes the development of this field over the past 20 years, with a discussion on future trends and directions: from the original reaction model at the beginning and its development in the first decade, to extensive research in the second decade. The latest development sees the emergence of alternative forms of energy inputs (photoredox, mechano, microwave, electrochemical, continuous-flow and solar quantum dots) to facilitate CDC reactions, gradually replacing the classical form of thermal energy, which will inspire broader applications and innovations in the future.
Transition-metal catalysed C-H activations are efficient, simple, mild, cost-effective, stereo selective and many of them are environmentally sustainable transformations. These were the dominant reasons which consistently inspired scientists to explore...
The 1,2‐diketone structural motif is present in various natural products and compounds of biological significance. In addition, these compounds are frequently used as precursors or intermediates in several synthetically important organic transformations. The transition‐metal catalysis plays an essential role for the generation of several carbon–carbon and carbon–heteroatom bonds to access diverse heterocyclic compounds. This metal‐catalyzed approach has been frequently used for the synthesis of these valuable 1,2‐diketones. This review summarizes the various approaches involving the transition metal‐catalyzed synthesis of 1,2‐diketones from easily accessible staring materials.
The detailed reaction mechanisms of gold-catalyzed reactions of 2,1-benzisoxazoles with propiolates and ynamides have been investigated with the aid of density functional theory calculations. Our investigation focused on the different...
A Ni‐deposited carbon nitride material was developed as a fully heterogeneous dual photocatalyst. Visible light‐driven C–O cross‐coupling is demonstrated free of organic ligands and additives. This dual catalytic system operates with very low nickel loadings and the heterogeneous photocatalyst can be easily recycled.
Abstract
Ni‐deposited mesoporous graphitic carbon nitride (Ni‐mpg‐CNx) is introduced as an inexpensive, robust, easily synthesizable and recyclable material that functions as an integrated dual photocatalytic system. This material overcomes the need of expensive photosensitizers, organic ligands and additives as well as limitations of catalyst deactivation in the existing photo/Ni dual catalytic cross‐coupling reactions. The dual catalytic Ni‐mpg‐CNx is demonstrated for C–O coupling between aryl halides and aliphatic alcohols under mild condition. The reaction affords the ether product in good‐to‐excellent yields (60–92 %) with broad substrate scope, including heteroaryl and aryl halides bearing electron‐withdrawing, ‐donating and neutral groups. The heterogeneous Ni‐mpg‐CNx can be easily recovered from the reaction mixture and reused over multiple cycles without loss of activity. The findings highlight exciting opportunities for dual catalysis promoted by a fully heterogeneous system.
Ni‐deposited mesoporous graphitic carbon nitride (Ni‐mpg‐CNx) is introduced as an inexpensive, robust, easily synthesizable and recyclable material that functions as an integrated dual photocatalytic system. This material overcomes the need of expensive photosensitizers, organic ligands and additives as well as limitations of catalyst deactivation in the existing photo/Ni dual catalytic cross‐coupling reactions. The dual catalytic Ni‐mpg‐CNx is demonstrated for C–O coupling between aryl halides and aliphatic alcohols under mild condition. The reaction affords the ether product in good‐to‐excellent yields (60–92 %) with broad substrate scope, including heteroaryl and aryl halides bearing electron‐withdrawing, ‐donating and neutral groups. The heterogeneous Ni‐mpg‐CNx can be easily recovered from the reaction mixture and reused over multiple cycles without loss of activity. The findings highlight exciting opportunities for dual catalysis promoted by a fully heterogeneous system.
A palladium-catalyzed synthetic strategy has been developed for one-pot synthesis of functionalized spiro(indoline-3,2′-quinazolin)-2-one derivatives from 2-aminobenzonitriles, arylboronic acids and isatins. This cascade strategy proceeds via successive C–C and two C–N bond formations in a single reaction vessel.
Studies of environmentally benign catalytic methods are of great value in modern chemical synthesis, especially the chemo‐selective construction of chemical bonds under green conditions. This work elucidates such preferential synthesis of C−N bond over C−O bond via selective N‐arylation of 3‐aminophenols using 1,3‐bis‐[2‐hydroxyphenyl] imidazolium chloride (IHPHCl) and copper iodide as catalyst (1 mol %) in aqueous medium. Presence of chelating group (−OH) on IHPHCl enhances N‐selectivity. Overall this is a simple and green method for selective N‐arylation of 3‐aminophenols with good substrate scope and yields (60–88 %). GC‐MS, HRMS and other spectroscopic techniques were utilised in detailing the kinetics and mechanistic aspects.
Pd‐catalyzed allylic alkylation of C‐based nucleophiles using both chiral and achiral allenamides is described. High yields were obtained to provide synthetically valuable (E)‐enamide products in high E : Z‐selectivity while generating a quaternary carbon atom. Some potential stereocontrolled applications of the resultant (E)‐enamide functionality are described.
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