@article {42434, title = {N-Heterocyclic carbene-catalyzed diastereoselective synthesis of β-lactone-fused cyclopentanes using homoenolate annulation reaction}, journal = {Chemical Communications}, volume = {51}, year = {2015}, month = {MAY}, pages = {9559-9562}, abstract = {

NHC-catalyzed annulation of enals with 2-enoylpyridines or 2-enoylpyridine\ N-oxides leading to the diastereoselective synthesis of β-lactone-fused cyclopentanes is reported. The reaction proceeds\ via\ the generation of homoenolate equivalent intermediates and tolerates a broad range of functional groups.

}, doi = {10.1039/C5CC02960K}, author = {Mukherjee, Subrata and Mondal, Santigopal and Patra, Atanu and Gonnade, Rajesh G. and Biju, Akkattu T.} } @article {43352, title = {N - heterocyclic - carbene - catalyzed umpolung of imines}, journal = {Angewandte Chemie International Edition}, volume = {56}, year = {2017}, month = {MAR}, pages = {2730 - 2734}, type = {Article}, abstract = {

N-Heterocyclic carbene (NHC) catalysis has been widely used for the umpolung of aldehydes, and recently for the umpolung of Michael acceptors. Described herein is the umpolung of aldimines catalyzed by NHCs, and the reaction likely proceeds via aza-Breslow intermediates. The NHC-catalyzed intramolecular cyclization of aldimines bearing a Michael acceptor resulted in the formation of biologically important 2-(hetero)aryl indole 3-acetic-acid derivatives in moderate to good yields. The carbene generated from the bicyclic triazolium salt was found to be efficient for this transformation.

}, doi = {10.1002/anie.201611268}, author = {Patra, Atanu and Mukherjee, Subrata and Das, Tamal Kanti and Jain, Shailja and Gonnade, Rajesh Ghanshyam and Biju, Akkattu T.} } @article {45769, title = {N-Heterocyclic carbene-catalyzed aldol-lactonization of ketoacids via dynamic kinetic resolution}, journal = {ACS Catalysis}, volume = {7}, year = {2017}, month = {JUN}, pages = {3995-3999}, type = {Article}, abstract = {

N-Heteroryclic carbene (NHC)-catalyzed enantioselective aldol lactonization of acyclic ketoacids, proceeding via dynamic kinetic resolution, is presented. The carbene generated from the chiral anninoinclanol-derived triazolium salt in the presence of LiCl was the key for the success of this transformation. The reaction allowed the diastereoselective and enantioselective synthesis of cyclopentane-fused beta-lactones having three contiguous stereocenters. The reaction products are shown to undergo substrate-controlled beta-lactone opening in the presence of amines to afford succinimide derivatives with four contiguous stereocenters.

}, keywords = {aldol lactonization, beta-lactones, DKR strategies, ketoacids, N-heterocyclic carbenes, organocatalysis}, issn = {2155-5435}, doi = {10.1021/acscatal.7b00681}, author = {Mondal, Santigopal and Mukherjee, Subrata and Das, Tamal Kanti and Gonnade, Rajesh and Biju, Akkattu T.} } @article {44644, title = {N-Heterocyclic carbene-catalyzed enantioselective synthesis of spiro-glutarimides via alpha,beta-unsaturated acylazoliums}, journal = {Organic Letters}, volume = {20}, year = {2018}, month = {AUG}, pages = {4499-4503}, abstract = {

NHC-catalyzed enantioselective [3 + 3] spiro-annulation of alpha,beta-unsaturated aldehydes with cyclic beta-ketoamides allowing the preparation of synthetically and biologically important spiro-glutarimide derivatives has been reported. The interception of the ketoamides with catalytically generated chiral alpha,beta-unsaturated acylazoliums proceeds in a Michael addition-intramolecular amidation pathway to deliver the spirocyclic products with good yield, diastereoselectivity, and enantioselectivity.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.8b01799}, author = {Mondal, Santigopal and Ghosh, Arghya and Mukherjee, Subrata and Biju, Akkattu T.} } @article {44535, title = {N-Heterocyclic carbene-catalyzed michael-michael-lactonization cascade for the enantioselective synthesis of tricyclic delta-lactones}, journal = {Organic Letters}, volume = {20}, year = {2018}, month = {MAY}, pages = {2952-2955}, abstract = {

Enantioselective synthesis of tricyclic delta-lactones with three contiguous stereocenters has been demonstrated by the N-heterocyclic carbene (NHC)-catalyzed functionalization of benzylic C(sp(3))-H bonds. The NHC-catalyzed reaction of enals with dinitrotoluene derivatives under oxidative conditions proceeds via the chiral alpha,beta-unsaturated acylazoliums and produces the delta-lactones in good yields and excellent diastereoselectivity and enantioselectivity. This mild and atom-economic cascade reaction takes place in a Michael/Michael/lactonization sequence and tolerates a broad range of functional groups.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.8b00998}, author = {Mukherjee, Subrata and Ghosh, Arghya and Marelli, Udaya Kiran and Biju, Akkattu T.} } @article {47386, title = {NHC-catalyzed desymmetrization of N-aryl maleimides leading to the atroposelective synthesis of N-Aryl succinimides}, journal = {Angewandte Chemie-International Edition}, volume = {60}, year = {2021}, month = {MAY }, pages = {12264-12268}, type = {Article}, abstract = {

Although the construction of axially chiral C-C bonds leading to the atroposelective synthesis of biaryls and allied compounds are well-known, the related synthesis of compounds bearing axially chiral C-N bonds are relatively rare. Described herein is the N-heterocyclic carbene-catalyzed atroposelective synthesis of N-aryl succinimides having an axially chiral C-N bond via the desymmetrization of N-aryl maleimides. The NHC involved intermolecular Stetter-aldol cascade of dialdehydes with prochiral N-aryl maleimides followed by oxidation afforded N-aryl succinimides in good yields and ee values. Preliminary studies on rotation barrier for the C-N bond, the temperature dependence, and detailed DFT studies on mechanism are also provided.

}, keywords = {asymmetric catalysis, axial chirality, desymmetrization, N-heterocyclic carbenes, organocatalysis}, issn = {1433-7851}, doi = {10.1002/anie.202016938, Early Access Date = APR 2021}, author = {Barik, Soumen and Shee, Sayan and Das, Soumik and Gonnade, Rajesh G. and Jindal, Garima and Mukherjee, Subrata and Biju, Akkattu T.} }