Pazhamalai Anbarasan

Tryptamine- and phenethylamine-derived imides were selectively monotrifluoromethylated using CF3TMS. Subsequent methanesulfonic acid mediated cyclization of the intermediate hemiaminals afforded the α-trifluoromethylated amine derivatives via the formation of trifluoromethylated acyliminium ions, in one pot. The strategy was applicable to the both inter- and intramolecular versions. Furthermore, the utility of the present method was demonstrated through the synthesis of trifluoromethylated analogues of harmicine and crispine A. © 2014 American Chemical Society.

A rhodium-catalyzed cyanation of chelation assisted C-H bonds is described employing N-cyano-N-phenyl-p-methylbenzenesulfonamide as an efficient cyanating reagent. The present method allowed the synthesis of various benzonitirle derivatives in good to excellent yield. A number of chelating groups are also effective in the present cyanation of C-H bonds. In addition, the developed methodology was applied in the formal synthesis of the isoquinoline alkaloid, menisporphine. © 2013 American Chemical Society.

An efficient tandem rhodium(II)/squaramide relay catalysis of readily accessible indole derivatives and N-sulfonyl-1,2,3-triazoles has been developed for the enantioselective synthesis of dihydro-β-carbolines in good yield and enantioselectivity. The developed reaction involves selective insertion of in situ generated azavinyl rhodium carbene onto the C3-H bond of indole derivatives and subsequent squaramide-catalyzed enantioselective intramolecular aza-Michael reaction. Furthermore, the potential of the strategy was demonstrated through the ready conversion to potent tetrahydro-β-carbolines and the tetracyclic alkaloid core structure.

Efficient synthesis of 3-aminoquinolines has been demonstrated from readily accessible N-sulfonyl-1,2,3-triazoles and o-acylaniline derivatives. This transformation involves the generation of C-C and C-N bonds through insertion of rhodium azavinyl carbenoid into a N-H bond followed by cyclization and aromatization. The important features include good functional group tolerance, synthesis of indoloquinoline, and isolation of N-H-inserted product, a potential intermediate.

An efficient rhodium-catalyzed synthesis of dihydro-3,1-benzoxazine derivatives has been accomplished from aniline-derived 1,3-amino alcohols and N-sulfonyl-1,2,3-triazole. The developed reaction demonstrates the new reactivity of azavinyl carbenes and allows access to diverse substituted dihydro-3,1-benzoxazines in good yields. Importantly, the reaction was readily extended to diols and could be used for selective protection of amino alcohols with N-sulfonyl-1,2,3-triazole as the protecting reagent.

A general and efficient synthesis of diarylacetate, a diarylmethine derivative, was accomplished through rhodium catalyzed direct arylation of diazo compounds with arylboronic acids. The reaction tolerates various boronic acid derivatives and functional groups. Notably, chemoselective arylation of diazo compounds over other electrophiles were demonstrated. The efficacy of the developed methodology is shown by the expeditious synthesis of the core structure of diclofensine.

Rhodium catalyzed synthesis of substituted tetrahydropyridines was accomplished from readily accessible thio-tethered N-sulfonyl-1,2,3-triazoles. The reaction involves tandem rhodium catalyzed 1,2-sulfur migration in β-thio-α-diazoimines, generated from thio-tethered N-sulfonyl-1,2,3-triazoles, to thio-substituted 1-azadiene and subsequent self aza-Diels-Alder reaction. Interestingly, the methodology was effectively extended to the synthesis of fused tetrahydropyridines, dihydropyridines and cyclohexenes through the in situ trapping of the intermediate, 1-azadiene, with various dienophiles such as enol ether, enamine, ketene S,S-acetal, alkyne, alkene and diene. Furthermore, the direct conversion of propargyl sulfides to (fused)-tetrahydropyridines was also achieved through the successful integration of copper and rhodium catalysts in one-pot.

An efficient palladium catalyzed diastereoselective synthesis of 2,2,3-trisubstituted dihydrobenzofurans has been accomplished in good yield as a single diastereomer. The transformation involves in-situ generation of oxonium ylide from 2-hydroxyphenyl substituted enone and diazo compound followed by intramolecular trapping via Michael addition. Successful integration of the developed method with intramolecular aldol condensation afforded potent dibenzofuran derivatives in good yield.

Abstract: Efficient rhodium-catalyzed Sommelet-Hauser type rearrangement of 3-diazoindolin-2-ones with α-thioesters has been accomplished for the synthesis of C4-thioalkylated oxindoles. The developed reaction offers the selective functionalization of C4-position of oxindole via generation of S-ylide and [2, 3]-sigmatropic rearrangement and allows access to diverse C4-thioalkylated oxindoles in good to excellent yield. Furthermore, the method was successfully extended to the synthesis C4-selenoalkylated oxindoles employing the corresponding α-selenoester. Graphic abstract: Efficient rhodium-catalyzed Sommelet-Hauser type rearrangement of 3-diazoindolin-2-ones with α-thio/α-seleno-esters have been disclosed for the synthesis of C4-thio/selenoalkylated oxindoles.[Figure not available: see fulltext.].

A diastereoselective palladium catalyzed carbenylative amination of ortho-vinylaniline with 3-diazoindolines-2-one have been accomplished for the synthesis of various tetrasubstituted indoline fused spirooxindole with good yields and diastereoselectivity. Notable features of the method include construction of two contiguous tetrasubstituted carbon stereocenters via C−N and C−C bond formation in single operation, wide functional group tolerance and high atom and step economy. Importantly, the present reaction was also extended to one-pot conversion of tosylhydrazones and ortho-vinylanilines to spirooxindole derivatives. (Figure presented.).