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The first o-iodoxybenzoic acid (IBX) mediated oxidation of unactivated amines to imines is described. A range of meso-pyrrolidines were shown to be suitable substrates. The chemical space was further explored with one-pot oxidative Ugi-type and aza-Friedel-Crafts reactions, which proved to be highly diastereoselective.
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In the title compound, [Ni(C11H15N2S)(C7H7OS)] or [Ni(NNImS)(4-OCH3PhS)] (NNImS = 2-{[2-(dimethylamino)ethyl]iminomethyl}benzenethiolato), the NiII cation is coordinated by a tridentate NNImS ligand and a monodentate thiolate ligand giving an N2S2 coordination set defining an almost square-planar environment. The Ni—Namine bond in the coor...
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... Recent accomplishments achieved in this area using iodine (V) reagents are reported in this section. In 2015, Orru and co-workers for the first time reported the oxidation of unactivated amines 21 to the corresponding imines 22 using IBX 1 as an oxidant (Scheme 5) [75]. Delightedly, a number of aliphatic meso-pyrrolidines 21 were oxidized selectively by IBX 1 to furnish bi-and tricyclic 1-pyrrolines 22 in 70-97% yield. ...
The chemistry of hypervalent iodine reagents has now become quite valuable due to the reactivity of these compounds under mild reaction conditions and their resemblance in chemical properties to transition metals. The environmentally friendly nature of these reagents makes them suitable for Green Chemistry. Reagents with a dual nature, such as iodine(III) reagents, are capable electrophiles, while iodine(V) reagents are known for their strong oxidant behavior. Various iodine(V) reagents including IBX and DMP have been used as oxidants in organic synthesis either in stoichiometric or in catalytic amounts. In this review article, we describe various oxidation reactions induced by iodine(V) reagents reported in the past decade.
... o-Iodoxybenzoic acid (IBX) 1 has a widespread applicability as an oxidant in a number of organic transformations. It is used as a selective reagent for numerous transformations, like oxidation of allylic and benzylic alcohols 11,[28][29][30] , amines [31][32][33][34] , and dehydrogenation of carbonyls 35 , etc. IBX (1) was firstly used for selective oxidation of alcohols by Frigerio and Santagostino in 1994. 36 However, the usefulness of IBX (1) was limited due to its insolubility in almost all solvents except DMSO. ...
... C. de Graaff et al. unveiled that IBX promoted mild and selective oxidation of unactivated cyclic amines (2b) to imines (25), employing a range of aliphatic meso-pyrrolidines (2b) as substrates (Supplementary Figure S10) (de Graaff et al., 2015) The protocol was further applied for diastereoselective oxidative Ugitype and aza-Friedel-Crafts reactions (26, 27) (Supplementary Figures S11,S12). Authors assessed the efficacy of different commercially available hypervalent iodine reagents, such as (diacetoxy) iodobenzene (PIDA), Dess-Martin periodinane (DMP), [bis(trifluroacetoxy)]iodo benzene (PIFA), and o-iodoxybenzoic acid (IBX). ...
O-Iodoxybenzoic acid (IBX) is a very mild and efficient hypervalent iodine synthetic reagent useful to carry out several selective oxidations. The present review highlights research reports on IBX-assisted transformations in heterocyclic derivatives, particularly from 2010 onward.
... This oxazole synthesis was replicated in 2005, when J. Zhu reported the synthesis of 5-aminooxazoles via a UZ-3CR, surveying several amines, aldehydes, and amino acid-derived isocyanides. Thus, 5-aminooxazole 95 was obtained in 90% isolated yield via the reaction between heptanal (92), morpholine (93) and isocyanide 94 (Scheme 14b). This reaction proceeded readily in MeOH, but the authors found out that nonpolar aprotic solvents (such as toluene) were also suitable in the presence of additives. ...
... On the other hand, the imine giving 478i is exo-configured and has a more planar structure, making the attack easier from either face of the molecule. 93 The work reported by G. Feng in 2015, is an example in which the amine oxidation was achieved by means of the use of a ruthenium photocatalyst and visible light. Once the optimal conditions were established, the authors investigated the reaction scope by surveying different N-aryl THIQs (479a-f, selected due to their important biological activity), alkyl and aryl isocyanides 481a-g and carboxylic acids 482a-k, obtaining good to excellent yields in each case, which showed the general character of this transformation. ...
More than 60 years have passed since I. Ugi synthesized the first α-amidoamides in one experimental step involving a combination of aldehydes, amines, carboxylic acids and isocyanides, a multicomponent reaction (MCR) known later as the Ugi four-component reaction (U-4CR), in honor of the pioneer of the modern MCR-based organic synthesis. Then, a broad variety of valued molecules (α-aminoamides) in various fields of science and technology have been synthesized via a three-component version of the Ugi reaction (U-3CR or truncated Ugi reaction), which makes use of a carbonylic component (aldehydes or ketones), amines and isocyanides. Moreover, some variants of the U-3CR have been developed, including its combinations with further processes such as functionalizations, condensations, cross couplings, cyclizations, ring openings, rearrangements, and so on. Also, some robust computational calculations for understanding the energy profiles of Ugi-type 3CR have been performed. All these topics are in the scope of the present review, which covers selected works mainly from the last decade, focusing on relevant contributions to heterocyclic chemistry, and especially on novel and complex reaction mechanisms. The manuscript has been categorized by the name/type reaction approach, aiming to give readers novel insights for further investigations.
... High-resolution mass spectra (HRMS) were recorded on a Thermo Scientific Exactive "ORBITRAP" spectrometer using H2O/MeOH mixed with 0.1% formic acid as mobile phase. 2-Iodoxybenzoic acid (IBX), 1 tryptoline 1a, 2 6-bromotryptoline 1b, 3 6-methoxy-1,2,3,4-tetrahydroisoquinoline 6b, 4 3,4-dihydro-βcarboline 5, 5 3,4-dihydrohydroisoquinoline (DHIQ) 17, 6 N(2)-benzyl-tryptoline 21, 7 C(1)phenyl-tryptoline 23, 8 benzylisocyanide 2d, 9 2-bromobenzylisocyanide 2e, 10 phenethylisocyanide 2f, 11 1-(2-isocyanoethyl)-4-methoxybenzene 2g, 12 4-(2isocyanoethyl)-1,2-dimethoxybenzene 2h, 13 1-bromo-2-isocyanobenzene 2k, 14 3-(2isocyanoethyl)-1H-indole 2m, 15 (3aR,4R,7S,7aS)-2,3,3a,4,7,7a-hexahydro-1H-4,7epoxyisoindole 10, 16 were prepared and characterized as previously reported. ...
Present study describes a robust and general method for the synthesis of C(1)-carboxamides through IBX-mediated oxidative addition of isocyanides to the tryptolines and 1,2,3,4-tetrahydroisoquinolines. In this transformation, IBX plays a dual role of oxidant as well as Lewis acid to activate the imine facilitating the isocyanide addition. Detailed mechanistic investigations were performed by isotopic labeling and real-time NMR experiments. The method was utilized for the gram scale syntheses of two alkaloids alangiobussine and alangiobussinine in 63 % and 45 % overall yield respectively.
... The oxidation of amines with hypervalent iodine reagents has been described in the literature. [168][169][170] However, the release of water by iodosylbenzene during the Hofmann rearrangement requires the concurrent presence of the iodine reagent and the amine to avoid addition of water to the isocyanate. When 3,4,5-trimethoxybenzylamine was used (entry 4), a large peak of imine 367 ( Figure 17) was detected, and formation of the desired ureid was not observed. ...
... There has been a successful application of IBX-promoted one pot methodology via oxidative cyclisation leading to benzimidazole [24]. IBX-mediated oxidation of inactivated cyclic amines has been reported [25]. However, the use of IBX is limited to an oxidant and not as an electrophilic agent. ...
Aim and Objective: We explore the role of IBX as an electrophilic agent towards the synthesis of flavones. The main objective was to work within the framework of green chemistry by using eco-friendly, less toxic, iodine-hypervalent reagent to carry out a facile conversion to flavones. Material and Methods: The use of 1equivalent of IBX under refluxing condition in DMSO was the best employed method for the synthesis of flavones. All the synthesised compounds were characterised by spectroscopic methods such as IR,¹H NMR and¹³C NMR spectroscopy. Results: In total, we successfully synthesized fifteen flavones derivatives in very good yields by using iodine-hypervalent reagent. This method was proved to be the best method as it involved simple workup procedure i.e. by adding water to the reaction mixture followed by filtration of the solid product. The formation of the product was confirmed by IR, NMR and their characteristic melting points. Conclusion: A new and first approach towards the synthesis of flavones using non-toxic and eco-friendly hypervalent iodine (V) reagent, IBX has been demonstrated. Such a methodology has been well-extended towards the synthesis of hydroxy, and bromo flavones. The work signifies the electrophilic character of IBX, which is an oxidant.
... After considering the NMR data confirmed by the X-ray analysis of HMF-derived norcantharimide analogues obtained in the previous study [27], the spatial structure of the Diels-Alder adducts was confirmed (see the Supplementary Materials). Chemical shifts of the diastereomeric protons at the articulated position were characterized by a singlet at 3.5-3.7 ppm in the 1 H-NMR spectra, while the signals of the appropriate protons in the exo products (compounds norcantharimide [28] and 10-exo) were observed in the stronger magnetic fields at 2.9-3.1 ppm. Additional confirmation of the stereo configuration of compounds 10-exo and 10-endo was accomplished by nuclear Overhauser effect spectroscopy (NOESY) and analysis of the obtained spectral data (see the Supplementary Materials). ...
... After considering the NMR data confirmed by the X-ray analysis of HMF-derived norcantharimide analogues obtained in the previous study [27], the spatial structure of the Diels-Alder adducts was confirmed (see the Supplementary Materials). Chemical shifts of the diastereomeric protons at the articulated position were characterized by a singlet at ~3.5-3.7 ppm in the 1 H-NMR spectra, while the signals of the appropriate protons in the exo products (compounds norcantharimide [28] and 10-exo) were observed in the stronger magnetic fields at ~2.9-3.1 ppm. Additional confirmation of the stereo configuration of compounds 10-exo and 10-endo was accomplished by nuclear Overhauser effect spectroscopy (NOESY) and analysis of the obtained spectral data (see the Supplementary Materials). ...
Reductive amination of 2,5-diformylfuran (DFF) was used to implement the transition from bio-derived 5-hydroxymethylfurfural (HMF) to pharmaceuticals. The synthesized bis(aminomethyl)furans were utilized as building blocks for the construction of new derivatives with structural cores of naturally occurring biologically active compounds. Using the one-pot procedure, which included the Diels–Alder reaction followed by hydrogenation of the double bond, bio-derived analogues of the anticancer drug norcantharidin were obtained. The cyclization process was diastereoselective, and resulted in the formation of tricyclic products with the endo configuration. Analysis of cytotoxycity for the resulting tricyclic amine-containing compounds showed an increase of anticancer activity as compared with the unsubstituted norcantharimide.
... At the reflux, IBX also demonstrates the ability to oxidize alcohols as a suspension in ethyl acetate, 1,2-dichloroethane, THF, or toluene in satisfactory yield (More and Finney 2002;Moorthy et al. 2004). IBX oxidation of amines provides the corresponding imine products and is considered to undergo an ionic mechanism (Nicolaou et al. 2003(Nicolaou et al. , 2004 and affords a new way to synthesize N-substituted pyrroles (Murthy and Nageswar 2011;de Graaff et al. 2015) and bis-amides (Singh et al. 2017). We herein report the first successful IBX oxidization of amines to produce aldehydes (Scheme 1). ...
IBX oxidation of secondary aryl amines has been applied towards their functional group transformation to aldehydes using a facile post-process with satisfactory yields. The oxidation of N-benzylmethylamine was used as a model substrate and suggested that the ratio of IBX oxidant to amine should be 2:1. Subsequently, several aryl amines were subjected to these standard conditions, which revealed that the oxidative activity depends on the electronic and steric structures of the substituent groups in the substrates. The oxidative selectivity to secondary amines was also discovered.
Imines are certainly important constituents of many biomolecules, pharmaceuticals, agrochemicals, and fine chemicals. This review article highlights the standard protocols reported so far for the selective synthesis of imines via catalyzed and non-catalyzed (i) oxidative coupling of primary amines and (ii) oxidation of secondary amines in the presence of some competent/resourceful oxidants other than molecular O2 such as tert-butyl hydroperoxide (TBHP), H2O2, hypervalent iodines, persulfate, hypochlorite, electroactive species and graphene oxide. Indeed, the use of such oxidants offers a cost-effective experimental set-up, operational simplicity and also minimization of by-products. The cooperativity between catalyst, amine substrate, and oxidant is discussed in this review to understand the proposed mechanisms. Three consolidated data tables (Table 1, 2 & 3) are prepared to provide the summary of optimized reaction conditions (type of catalyst, type of oxidant, choice of solvent, amine-to-oxidant ratio, reaction time/temperature, conversion of amine, yield/selectivity of imine) of each article published to have a comparison.
