@article { ISI:000295259700041, title = {N-Heterocyclic carbene catalyzed umpolung of michael acceptors for intermolecular reactions}, journal = {Angewandte Chemie-International Edition}, volume = {50}, number = {36}, year = {2011}, month = {AUG}, pages = {8412-8415}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

eahciM! The N-heterocyclic carbene catalyzed umpolung of Michael acceptors proceeds through the formation of a deoxy-Breslow intermediate (see scheme; EWG=electron-withdrawing group). This nucleophilic species can react with other Michael acceptors in an intermolecular fashion, thereby resulting in the formation of homo- or heterodimeric olefins. This {\textquotedblleft}Michael umpolung{\textquotedblright} should become a valuable method for the formation of densely functionalized olefins.

}, keywords = {carbenes, Michael acceptors, nitrogen heterocycles, organocatalysis, umpolung}, issn = {1433-7851}, doi = {10.1002/anie.201103555}, author = {Biju, Akkattu T. and Padmanaban, Mohan and Wurz, Nathalie E. and Glorius, Frank} } @article { ISI:000371566100001, title = {Recent advances in N-heterocyclic carbene (NHC)-catalysed benzoin reactions}, journal = {Beilstein Journal of Organic Chemistry}, volume = {12}, year = {2016}, month = {MAR}, pages = {444-461}, publisher = {BEILSTEIN-INSTITUT}, address = {TRAKEHNER STRASSE 7-9, FRANKFURT AM MAIN, 60487, GERMANY}, abstract = {

N-Heterocyclic carbenes (NHCs) have emerged as a powerful class of organocatalysts that mediate a variety of organic transformations. The Benzoin reaction constitutes one of the earliest known carbon-carbon bond-forming reactions catalysed by NHCs. The rapid growth of NHC catalysis in general has resulted in the development of a variety of benzoin and benzoin-type reactions. An overview of such NHC-catalysed benzoin reactions is presented.

}, keywords = {acyloin reaction, benzoin reaction, N-heterocyclic carbenes, organocatalysis, umpolung}, issn = {1860-5397}, doi = {10.3762/bjoc.12.47}, author = {Menon, Rajeev S. and Biju, Akkattu T. and Nair, Vijay} } @article {46021, title = {N-Heterocyclic carbene-catalyzed umpolung of imines for the enantioselective synthesis of dihydroquinoxalines}, journal = {ACS Catalysis}, volume = {9}, year = {2019}, month = {MAY}, pages = {4065-4071}, type = {Article}, abstract = {

N-heterocyclic carbene (NHC) organocatalysis is widely employed for the umpolung of aldehydes and recently to the umpolung of Michael acceptors and aldimines. Described herein is the NHC-organocatalyzed umpolung of aldimines for the enantioselective synthesis of nitrogen heterocycles. The bisimines generated from the condensation of 1,2-phenylenediamines and salicylaldehydes undergo intramolecular cyclization in the presence of a chiral NHC catalyst, resulting in the formation of dihydroquinoxalines in moderate to good yields and er values. Detailed DFT studies shed light on the role of -OH groups in stabilizing the initially generated aza-Breslow intermediates via intramolecular hydrogen bonds. Preliminary photophysical studies on the synthesized dihydroquinoxalines revealed that these molecules can be used for the sensing of various acids and bases.

}, keywords = {dihydroquinoxalines, imines, N-heterocyclic carbenes, organocatalysis, umpolung}, issn = {2155-5435}, doi = {10.1021/acscatal.9b00737}, author = {Das, Tamal Kanti and Ghosh, Avik and Balanna, Kuruva and Behera, Pradipta and Gonnade, Rajesh G. and Marelli, Udaya Kiran and Das, Abhijit Kumar and Biju, Akkattu T.} }