Maddi Sridhar Reddy

• Ph. D
• Principal Investigator at CSIR-Indian Institute of Chemical Technology

We report herein a palladium‐catalyzed, site‐selective cyclative annulation of o‐alkynyl arylamides with maleimide for the stereoselective construction of succinimide‐fused benzoxazine derivatives. This operationally simple and modular protocol provides access to polycyclic frameworks. The other associated features are high functional group compati...

Although challenging, the distant C−H functionalization with precision is quite rewarding and has long been intriguing. Tailoring an appropriate template accomplishes the job but the prerequisite sets the limitation. We herein unveil our discovery of annulation of alkynes on to two distant (from directing group) C−H bonds through rollover cyclometa...

Rh-catalyzed C−H activation of arenes for oxidative annulations with alkynes stands out as a protocol for polycyclic scaffolds. This perspective drives us to disclose herein a rhodium catalyzed regioselective triple annulation of enaminones with hydroxyl-alkynoates via double C−H functionalization for polycyclic naphtho-pyran scaffolds. Secondary c...

Rh‐catalyzed C−H activation of arenes for oxidative annulations with alkynes stands out as a protocol for polycyclic scaffolds. This perspective drives us to disclose herein a rhodium catalyzed regioselective triple annulation of enaminones with hydroxyl‐alkynoates via double C−H functionalization for polycyclic naphtho‐pyran scaffolds. Secondary c...

The C−H functionalization strategy provides access to valuable molecules that previously required convoluted synthetic attempts. Dual C−H unsymmetrical functionalization, with a single bifunctional reagent, is an effective tactic. Propargyl alcohols (PAs), despite containing a reactive C≡C bond, have not been explored as building blocks via oxidati...

Quantum leap in the field of C‐H functionalization has expediently provided comprehensive solutions to access valuable molecules that previously required convoluted synthetic attempts. Dual C‐H functionalization, unsymmetrically, with a single bifunctional reagent is an incisive tactic. Propargyl alcohols (PAs), despite containing reactive C≡C bond...

The C−H functionalization strategy provides access to valuable molecules that previously required convoluted synthetic attempts. Dual C−H unsymmetrical functionalization, with a single bifunctional reagent, is an effective tactic. Propargyl alcohols (PAs), despite containing a reactive C≡C bond, have not been explored as building blocks via oxidati...

We disclose herein a Rh(III)-catalyzed migratory three-point double annulation of o-alkenyl phenols with propargyl alcohols for de novo construction of naphtho furan derivatives in a regio- and chemoselective manner. The protocol orchestrates two new rings with four new bonds in one operation without the need for any additive. Necessary labeled and...

Metal-catalyzed cyclizative cross-coupling reactions have attracted enormous attention due to their unique cascade nature. We demonstrated , herein, a dual-cyclizative coupling of ynone oxime ethers with acrylamides for the synthesis of methylene-linked isoxazolyl 2-oxindoles. The cascade was triggered by a palladium(II)-catalyzed ynone oxime ether...

An unprecedented [2+2+1] hydrative annulation of 1,6‐enynes with terminal alkynes is achieved using catalytic cationic Rh(I). Thus, a modular assembly of cyclopenta[b]benzofuranols with two consecutive quarternary stereocenters is achieved from readily available alkynes. The reaction is proposed to go through a sequence of 5‐membered rhoda‐cycle fo...

The efficiency and selectivity of annulation reactions are often difficult to control in the presence of multiple potential reactive centers, like in the case of allylic sulfur ylides (ASY). Here, we describe a novel base mediated [3+3] benzannulation of ASY and readily available alkynones, which accomplishes the regioselective formation of multisu...

[4 + 2] oxidative Diels-Alder reaction of readily available alkynols with maleimide is achieved for the rapid access of pthalimide-fused multicyclic compounds. The reaction is proposed to go through a sequence of Sc(OTf)3-catalyzed electrophilic cyclization, ligand exchange with Cp*-free cobalt, and C-H activation followed by maleimide insertion.

A regio- and stereoselective synthesis of unsymmetrically substituted pentafulvenes is reported via the condensation of readily available ynones and amino crotonates under very mild conditions. The mechanism of this 3+2 annulation involved a vinylogous Michael addition followed by an intramolecular enamine aldol condensation. Substrates with o-brom...

Here,wehavedemonstratedastrategicrapidapproachforthesynthesisofbenzonitrilesandcyanofluorenesviathe[3+3]benzannulationofreadilyavailablealkynonesandα-cyanocrotonates,a protocolparexcellenceforarylnitriles.Thisdecarboxylativeannulationhasbeenassistedsolelybyabasewithouttheneedforany catalyst.Theonlyby-productisEtOH(andCO2)andtheproductis cleanlyfilt...

2-Aminoindole-3-carboxylates undergo a Lewis-acid-catalyzed decarboxylative annulation with ynals to afford dihydrochromeno-fused δ-carbolines through a 2,3-aza migration, via a spirocyclic intermediate generated from an initial [3 + 2] spirocycloaddition. Brønsted acid interference changes the path from a [3 + 2] to a [4 + 2] addition. 2-Aminoindo...

A general method for highly functionalized 2-pyrones via a base-mediated sequential vinylogous addition and cyclization of γ-phosphonyl/sulfonyl crotonates and ynones are described. An exclusive E-geometry with respect to the newly generated olefin substituent at C3 of pyrone was observed. Imino glyoxalates and glycine imines similarly reacted with...

A rhodium catalyzed copper mediated double oxidative annulation of propargylamino phenyl benzamides is developed. A quick assembly of tri, tetra and penta cyclic pyrido/isoquinolo‐quinoxilines are thus achieved from readily available linear substrates. The reaction is shown to be very general by accommodating a large variety of substrates in the tr...

A facile route to 3-sulfonylated and 3-(1-benzotriazolyl)-benzofurans is achieved from readily available o-hydroxyphenyl propargyl alcohols (o-HPPAs) and bench-top sodium sulfonylates and benzotriazoles with no assistance of any reagent or catalyst. Bifunctional o-quinone methides (o-QMs) were the putative reaction intermediates ensued from dehydra...

A syn arylative nickelation followed by nucleophilic syn selective cyclization of o-propargyloxy benzaldehydes is achieved towards the synthesis of chromanol skeletons with alkenyl substitution at C3. The capture of the intermediate vinyl nickel in its cis geometry is done also with Michael acceptor to synthesize 4-alkylated derivatives. This proto...

Phosphorylation and dephosphorylation are the key mechanisms for mycobacterial physiology and play critical roles in mycobacterial survival and in its pathogenesis. Mycobacteria evade host immune mechanism by inhibiting phagosome – lysosome fusion in which mycobacterial protein tyrosine phosphatase A (TP) plays an indispensable role. Tyrosine kinas...

The stereoselective E ‐iodosulfonylation of internal alkynes for synthesizing highly defined tetrasubstituted olefins using sodium phenyl sulfinate and iodine has been achieved. Most of the alkynes explored are non‐symmetrical and the regioselection is under full control. Arylalkynes with various electron‐withdrawing groups like keto, aldehyde, est...

A formal intramolecular vicinal 1,2-diamination of alkynes is achieved for the synthesis of indole-cyclic urea fused derivatives through double cyclization process from readily available aminophenyl propargyl alcohols. This sequential triple C-N bond construction event was possible using isocyanate as urea precursor and Ag(I) catalyst as alkyne act...

Addition of arylboronic acids to directing group tethered acetylenes in a regio and stereoselective manner using an inexpensive catalytic system is achieved for the first time to access highly sought after allyl/homoallyl alcohol/amine units. The apparent vinylnickel intermediate was successfully trapped by the Michael electrophiles to get defined...

A stereoselective Meyer—Schuster rearrangement of 1-aryl-3-phenoxypropargyl alcohols gives Z-α,β-unsaturated β-aryl carboxylates under ambient conditions.

Access to furanyl- and pyrrolyl-3-carboxamides from readily available 3-alkyne-1,2-diols and 1-amino-3-alkyn-2-ols using isocyanate as amido surrogate is demonstrated. The approach constitutes a successful unprecedented combination of heteropalladation and isocyanate insertion, a new avenue for novel amide bond constructions. The mechanism likely i...

An efficient route for the synthesis of the title 2-azidomethyl heterocycles (IV) and (II), resp., based on Ag(I)-catalyzed intramolecular cyclization and γ-allylic azidation of readily available propargyl alcohols is developed.

Depending on the tether between the substrates′ bromoalkyne and the hydroxy or tosylamino group, respectively, the selective formation of saturated or unsaturated lactams, unsaturated lactones, oxazinones or α-bromoketones is observed.

The title reaction proceeds under mild conditions and tolerates a wide range of functional groups in both partners.

Palladium catalyzed conversion of 1‐(2‐aminophenyl)‐propargyl alcohols to 3‐alkynyl quinolines is realized via a cascade that involves aminopalladation, oxidative coupling with alkynes and dehydration. The method is shown to have a broad substrate scope with respect to propargyl alcohols as well as alkynes. Vinyl ketones as coupling partners in the...

An unusual Pd-catalyzed isocyanide assisted 5-exo-dig reductive cyclization of 1-(2-hydroxyphenyl)-propargyl alcohols is achieved for 2-alkyl/benzyl benzofurans. The reaction features a high substrate scope, insensitivity to air, and excellent product yielding. Further, a direct metal-free C-H functionalization (azidation, alkoxylation, and hydroxy...

A highly general palladium catalysed regioselective hydroalkynylation of ynamides for versatile enamide building blocks with an alkyne tether is achieved with an N-substitution dependent stereoselectivity switch under very mild reaction conditions.

We describe herein a silver-catalyzed conversion of 1-(2-aminophenyl)-propargyl alcohols to 4-substituted 3-tosylaminoquinolines using TsN3 as an amino surrogate. Controlled reactions reveal the pathway consisting of Ag(I)-catalyzed 5-exo-dig cyclization, catalyst-free (2 + 3) cycloaddition, and ring-expansive rearrangement via nitrogen expulsion....

Conjugated enynes, enol ethers, and enynones are versatile building blocks that can be elaborated by a wide variety of synthetic transformations. The selective synthesis of such units is a prerequisite for their effective utilization. The synthesis of conjugated 2-phenoxyenynes through a palladium-catalyzed cross-addition of terminal alkynes to phe...

A method to prepare 3‐substituted‐2‐formylindole derivatives from N ‐Boc‐ ortho ‐aminoaryl ketones and ethoxyacetylene through a cascade of reactions in a single operation that included a nucleophile‐triggered 5‐ exo‐dig cyclization and an acid‐mediated 1,3‐allyl alcohol isomerization (1,3‐AAI) is described. A variety of aryl, vinyl and alkynyl gro...

We herein present the iodo Meyer-Schuster rearrangement of 3-alkoxypropargyl alcohols for α-iodo-α,β-unsaturated esters using iodine or NIS in dichloromethane at ambient temperature. Substrates prepared from both aldehydes and ketones are found to be equally good feedstock for the reaction to produce β-mono- and -disubstituted products. Irrespectiv...

A novel palladium-catalyzed approach to 2-benzofuranyl/indolylacetamides from 1-(o-hydroxy/aminophenyl)propargylic alcohols and isocyanides is described. The reaction proceeds through a cascade that includes oxy/aminopalladation, isocyanide insertion, and 1,4-hydroxyl migration. No oxidant or ligand is needed to promote the cascade, and the reactio...

The reaction between readily accessible propargyl acetates and sulfonyl azides in presence of CuI catalyst yielded trans α, β-unsaturated N-tosylamides via N-sulfonyl ketimine formation followed by a probable 1,3-OAc migration ([3,3]-sigmatropic rearrangement). The reaction was very general allowing all kinds of substitution, i.e. alkyl, aryl (elec...

A convenient and general synthesis of various 4-substituted-3-iodocoumarins and 4,5-disubstituted-3-iodobutenolides is described via an exclusive 6-endo-dig-iodocyclization of 3-ethoxy-1-(2-alkoxyphenyl)-2-yn-1-ols and 5-endo-dig-iodocyclization of 1-alkoxy-4-ethoxy-3-yn-1,2-diols respectively. The reaction is carried out in very mild conditions us...

Cu-catalyzed A(3) coupling of ethoxyacetylene, pyrrolidine and salicylaldehydes led to a concomitant cycloisomerization followed by hydrolysis of the resultant vinyl ether to afford coumarins in a cascade process. The reaction proceeded through exclusive 6-endo-dig cyclization and is compatible with halo and keto groups giving coumarins in good to...

A new cycloisomerization strategy for the synthesis of coumarins and quinolinones is described. The addition of ethoxyacetylide to 2-hydroxyacetophenones directly resulted in 4-substituted coumarins by 6-endo-dig cycloisomerisation of the intermediate 3-ethoxy-1-(2-hydroxyphenyl)-2-propyn-1-ols. Under similar conditions, 2-aminoacetophenone produce...

A practical method for the synthesis of substituted quinolines from 2-aminoarylketones (via 1-(2-aminoaryl)-2-yn-1-ols) using mild and simple reaction conditions is described. A study of several electrophiles in various reaction conditions is presented. Out of three electrophilic iodine sources (I2, NIS and ICl) studied, I2 was found to work effici...

An efficient conversion of 4-bromo-3-yn-1-ols to γ-butyrolactones via AuCl(3)-catalyzed electrophilic cyclization (hydroxyl-assisted regioselective hydration) in wet toluene is described. Various secondary and tertiary alcohols including benzylic systems were found to be equally reactive with moderate to excellent yields obtained in all cases.

Hg(II) salts are identified as highly efficient catalysts for the versatile construction of spiroketals from alkyne diols in aqueous conditions. Monounsaturated spiroketals and furans were accessed with equal ease when propargylic triols (or propargylic diols) were subjected to similar conditions. Even the semiprotected alkyne diols gave the corres...

A full account of the synthesis of hippuristanol and its analogues is described. Hecogenin acetate was identified as a suitable and economical starting material for this work, and substrate-controlled stereoselection was obtained throughout the construction of the key spiroketal unit. Suárez cyclization was first used, but Hg(II)-catalyzed spiroket...

The steroidal natural product hippuristanol targets eukaryotic translation initiation factor (eIF)4A which plays a pivotal role in translation in eukaryotic cells. Now an efficient synthesis of hippuristanol from 11-ketotigogenin is reported. The synthesis features a rapid construction of a spiroketal unit via Hg(OTf)(2)-catalyzed oxidation/spiroke...

A stereoselective and convergent formal approach to Salicylihalamide A and B is achieved through our recently developed strategy for the construction of polyketide precursors via Prins cyclisation. The approach mainly relies upon reductive opening of 1-iodomethyl cyclic ethers, Mitsunobu inversion and ring closing metathesis along with Prins cyclis...

All done! A full account of the total synthesis of ouabagenin and ouabain has been described. The synthesis was achieved through a polyanionic cyclization strategy. Degradation studies provide an ultimate proof for a key intermediate observed in the synthesis. magnified image A full account of the total synthesis of ouabagenin and ouabain is descri...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A full account of the total synthesis of (+)-cassaine ( 1) using the transannular Diels-Alder (TADA) reaction as the pivotal construction is described. The strategy began from Evans' oxazolidine 8, the only chiral source used for the total stereochemical outcome of the target molecule. The key intermediate 3 was obtained from 8 in 10 steps in 40% o...

A stereoselective and convergent approach to basiliskamides A and B is achieved through our recently developed strategy for the construction of polyketide precursors via Prins cyclisation. The approach mainly relies upon reductive opening of 1-iodomethyl cyclic ethers, Mitsunobu inversion, Takai olefination and Stille coupling along with Prins cycl...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

(Chemical Equation Presented) The highly oxygenated steroid ouabagenin (1b) and its glycoside ouabain (1a) were prepared by a strategy based on a polyanionic cyclization. Starting building blocks A and B were combined to give the key intermediate C and transformed into 1b in 27 steps. Finally, ouabagenin (1b) was converted into ouabain (1a) in six...

Das stark oxygenierte Steroid Ouabagenin (1 b) und dessen Glycosid Ouabain (1 a) wurden durch eine Folge anionischer Cyclisierungen synthetisiert. Die Ausgangsverbindungen A und B wurden zum Schlüsselintermediat C gekuppelt und in 27 Stufen in 1 b umgewandelt (siehe Schema). Von 1 b führten sechs weitere Stufen zu 1 a.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

The stereoselective total synthesis of tarchonanthuslactone, a polyketide natural product, has been achieved. The synthesis exploits the high stereochemical control in the Prins cyclisation along with ring closing metathesis (RCM) as a key step.Graphical abstract

A highly stereoselective synthesis of (+)-cryptocarya diacetate is achieved through our recently developed strategy for the construction of 1,3-diols via Prins cyclisation. The route relies mainly on the reductive cleavage of allylic ethers, ozonolysis and Wittig olefination along with Prins cyclisation.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Stereoselective syntheses of (−)-tetrahydrolipstatin have been achieved via two divergent approaches through Prins cyclisations as the key steps. PCC mediated oxidative cleavage, Frater alkylation, Keck allylation, Sharpless asymmetric epoxidation and allylic cleavage were the other key steps employed.

A new approach for the stereoselective synthesis of polyketide precursors containing anti-1,3-diol units flanked by a variety of alkyl branches and functional groups through a Prins cyclisation and reductive cleavage sequence is described.

The scope of the Prins cyclisation, the higher stereoselective synthesis of multisubstituted tetrahydropyrans from aldehydes and homoallylic alcohols, is expanded. A new approach for the stereoselective synthesis of polyketide precursors containing anti-1,3-diols, flanked by a variety of alkyl branches and functional groups is described. The approa...

An efficient and flexible approach for the total synthesis of (−)-tetrahydrolipstatin is described. The main features of the synthetic strategy are a stereocontrolled radical cyclization and the successful utilization of commercially available S-malic acid.

Reactions of homoallylic alcohols with aldehydes in the presence of acid catalysts gave multisubstituted tetrahydropyrans with the creation of one to three new stereogenic centres in a single-pot process. The utility of this approach is extended to the enantioselective syntheses of (+)-prelactones B, C and V.

For Abstract see ChemInform Abstract in Full Text.

A variety of aldehydes and homoallylic alcohols undergo smoothly Prins-cyclization on the surface of solid acids such as H-ZSM-5 zeolite or Amberlyst-15® ion-exchange resin in 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid to afford the corresponding tetrahydropyranols in high yields with cis-diastereoselectivity. The recovered ionic...

For Abstract see ChemInform Abstract in Full Text.

Alkynylsilanes and allyltrimethylsilane undergo smooth coupling with acid chlorides in the presence of 5 mol% of indium tribromide under mild conditions to afford the corresponding alpha,beta-acetylenic ketones and beta,gamma-unsaturated ketones in excellent yields in a short reaction time with high selectivity.

Alkynylsilanes undergo coupling smoothly with acid chlorides in the presence of molecular iodine under mild reaction conditions to afford the corresponding alpha,beta-acetylenic ketones in excellent yields in a short reaction time with high selectivity.

1-n-Butyl-3-methylimidazolium chloroaluminate [bmim]Cl·AlCl3 (N = 0.56−0.67) ionic liquid has been employed as an alternative reaction medium to conventional acid catalysts for Prins cyclizations, to produce 4-chlorotetrahydropyran derivatives in excellent yields and in short reaction times. The ionic liquid plays a dual role as both catalyst and s...

D-Glycals react smoothly with alkynylsilanes in the presence of a catalytic amount of molecular iodine under mild and convenient reaction conditions to afford the corresponding alkynyl sugars in excellent yields with high alpha-selectivity.

For Abstract see ChemInform Abstract in Full Text.

Molecular iodine is found to catalyze efficiently the addition of trimethylsilyl cyanide to a range of simple and functionalized ketones under very mild and convenient conditions to afford the corresponding cyanohydrin trimethylsilyl ethers in excellent yields in a short reaction period with high selectivity. α,β-Unsaturated ketones selectively aff...