@article {47626, title = {Enantioselective synthesis of 5,6-dihydroindolizines by N-heterocyclic carbene (NHC)-catalyzed core-structure-inspired strategy of azolium-enolate cascade}, journal = {Organic Letters}, volume = {23}, year = {2021}, month = {JUL }, pages = {5223-5228}, type = {Article}, abstract = {The core-structure motivated design has allowed the enantioselective synthesis of 5,6-dihydroindolizines via N-heterocyclic carbene (NHC) catalysis. The NHC-catalyzed reaction of alpha,beta-unsaturated aldehydes with the suitably substituted pyrrole derivatives proceed via the initial generation of alpha,beta-unsaturated acylazoliums from enals, and enolates from pyrroles and the reaction culminated in an efficient cascade process involving the Michael-aldol-lactonization-decarboxylation sequence to afford the products in reasonable yields and high selectivities. The method is further extended to the construction of spirocyclic 5,6-dihydroindolizines.}, issn = {1523-7060}, doi = {10.1021/acs.orglett.1c01761}, author = {Ghosh, Arghya and Shee, Sayan and Barik, Shilpa and Gonnade, Rajesh G. and Biju, Akkattu T.} } @article {48358, title = {Enantioselective synthesis of dihydrothiopyranones via NHC- catalyzed [3+3] annulation of 2-bromoenals with beta-oxodithioesters}, journal = {Organic Letters}, volume = {24}, year = {2022}, month = {DEC}, pages = {8848-8853}, type = {Article}, abstract = {

The N-heterocyclic carbene (NHC)-organocata-lyzed [3 + 3] annulation of 2-bromoenals with fi-oxodithioesters resulting in the enantioselective synthesis of dihydrothiopyranones is presented. The chiral a,fi-unsaturated acylazoliums generated from 2-bromoenals and carbenes underwent smooth interception with the sulfur nucleophiles to furnish the sulfur heterocycles in satisfactory yields/selectivity. The regioselective formation of dihydrothiopyranones over the competing dihydropyranones is noteworthy.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.2c03642}, author = {Barik, Shilpa and Shee, Sayan and Gonnade, Rajesh G. and Biju, Akkattu T.} } @article {48760, title = {NHC-catalyzed enantioselective synthesis of tetracyclic δ-lactones by (4+2) annulation of ortho-quinodimethanes with activated ketones}, journal = {Organic Letters}, volume = {25}, year = {2023}, month = {OCT }, pages = {7852-7857}, type = {Article}, abstract = {

The N-heterocyclic carbene (NHC)-catalyzed generation of ortho-quinodimethanes (o-QDMs) from 9H-fluorene-1-carbaldehydes followed by the interception with activated ketones resulting in the enantioselective synthesis of tetracyclic delta-lactones is presented. High diastereoselectivity of products, remote C-(sp(3))-H functionalization, broad substrate scope, and mild reaction conditions are the notable features of the present (4 + 2) annulation.

}, issn = {1523-7060}, doi = {10.1021/acs.orglett.3c03076}, author = {Sarkar, Deeptanu and Barik, Shilpa and Shee, Sayan and Gonnade, Rajesh G. and Biju, Akkattu T.} } @article {48752, title = {N-heterocyclic carbene-catalyzed atroposelective synthesis of N-N axially chiral 3-amino quinazolinones}, journal = {ACS Catalysis}, volume = {13}, year = {2023}, month = {JUN }, pages = {8752-8759}, type = {Article}, abstract = {

Although the atroposelective synthesisof biaryls and related compoundsbearing axially chiral C-C bonds is well-known, the synthesisof axially chiral C-N bond-containing compounds is relativelyless explored, and the construction of axially chiral N-N bondshas received only scant attention. Demonstrated herein is the N-heterocycliccarbene (NHC)-catalyzed selective amidation reaction, leading to theatroposelective synthesis of N-N axially chiral 3-amino quinazolinones.The NHC-catalyzed reaction of quinazolinones containing a free N-Hmoiety with \& alpha;,\& beta;-unsaturated aldehydes under oxidativeconditions furnished the atropisomeric quinazolinone derivatives undermild conditions and broad scope. Preliminary studies on experimentaland density functional theory-based N-N rotational barrierdetermination are also presented.

}, keywords = {amino quinazolinones, asymmetriccatalysis, axial chirality, N-heterocycliccarbenes, organocatalysis}, issn = {2155-5435}, doi = {10.1021/acscatal.3c01709}, author = {Balanna, Kuruva and Barik, Soumen and Barik, Shilpa and Shee, Sayan and Manoj, Niket and Gonnade, Rajesh G. and Biju, Akkattu T.} }