Sayan Shee

Indian Institute of Science | IISC · Department of Organic Chemistry

Axially chiral diaryl ethers, a distinguished class of atropisomers possessing unique dual C-O axis, hold immense potential for diverse research domains. In contrast to the catalytic enantioselective synthesis of conventional single axis bearing atropisomers, the atroposelective synthesis of axially chiral ethers containing flexible C-O axis remain...

Although the atroposelective synthesis of biaryls and related compounds bearing axially chiral C-C bonds are well-known, the synthesis of axially chiral C-N bond-containing compounds are relatively less explored, and the construction of axially chiral N-N bonds has received only scant attention. Demonstrated herein is the N-heterocyclic carbene (NH...

The enantioselective synthesis of functionalized pyrazoloquinolin-3-ones via N-heterocyclic carbene-catalyzed cascade reaction of α-bromoenals with 2-aminoaryl N-tosyl hydrazones is reported. The in situ-generated α,β-unsaturated acylazoliums underwent an aza-Michael-Mannich-lactamization sequence to afford the tricyclic products bearing three cont...

The N-heterocyclic carbene (NHC)-organocatalyzed [3 + 3] annulation of 2-bromoenals with β-oxodithioesters resulting in the enantioselective synthesis of dihydrothiopyranones is presented. The chiral α,β-unsaturated acylazoliums generated from 2-bromoenals and carbenes underwent smooth interception with the sulfur nucleophiles to furnish the sulfur...

The organocatalytic strategies for the reversal of normal mode of reactivity (umpolung) leading to the unconventional access to the synthesis of various organic molecules have received considerable attention in the last three decades. Among the various catalysts employed for reactivity umpolung, the N‐heterocyclic carbene (NHC)‐based catalysts are...

The ubiquity of ε-lactones in various biologically active compounds inspired the development of efficient and enantioselective routes to these target compounds. Described herein is the enantioselective synthesis of indole-fused ε-lactones by the N-heterocyclic carbene (NHC)-Lewis acid cooperative catalyzed dynamic kinetic resolution (DKR) of in sit...

N-Heterocyclic carbene (NHC)-catalyzed umpolung of cyclopent-4-ene-1,3-diones that proceeds via the generation of nucleophilic deoxy-Breslow intermediates is presented. The carbene generated from a commercially available thiazolium salt catalyzed the cross-coupling between cyclopent-4-ene-1,3-diones and isatins to furnish the functionalized oxindol...

NHC-catalyzed cascade reaction of enals with suitably substituted β-(hetero)aryl enones allowing the enantioselective synthesis of tetra-substituted tetralines and tetrahydro indolizines is presented. The catalytically generated chiral α,β-unsaturated acylazoliums from enals...

The N-heterocyclic carbene (NHC)-catalyzed intramolecular cyclization of N-substituted pyrrole 2-carboxaldehydes under oxidative conditions allowing the facile synthesis of pyrrolo-oxazinone derivatives is reported. The keys to the success of this strategy are the generation of acylazoliums using NHC and the base-mediated formation of the enolate....

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 ax...

NHC-catalyzed atroposelective synthesis of N-aryl succinimides having an axially chiral C−N bond via the desymmetrization of N-aryl maleimides is presented. The reaction proceeds via the Stetter-aldol cascade of dialdehydes with prochiral N-aryl maleimides followed by oxidation. Preliminary studies on the rotation barrier for the C−N bond and detai...

The NHC-catalyzed desymmetrization of cyclic-1,3-diketones allowing the enantioselective construction of tricyclic β-lactones with five contiguous stereocenters, including two quaternary stereocenters, has been developed. The mild and operationally simple addition of α-bromoenals to cyclopentane-1,3-diketone derivatives proceeds via the initial for...

N-Heterocyclic carbene catalyzed enantioselective functionalization of 3-aminobenzofurans at the C2-position was realized using 2-bromoenals as the coupling partner. The reaction proceeds via generation of chiral α,β-unsaturated acylazoliums and follows an aza-Claisen rearrangement. The initially formed dihydropyridinone undergoes ring-opening cata...

Functionalization of the indole N-H bond for enantioselective synthesis of biologically important pyrroloquinoline derivatives has been reported under oxidative N-heterocyclic carbene catalysis conditions. The interception of catalytically generated chiral α,β-unsaturated acylazoliums with the indole derivatives proceeds in an aza-Michael/Michael/l...