Asymmetric Organocatalytic Assembly of Oxindoles Fused with Spiro‐3,4‐dihydropyrans with Three Contiguous Stereocenters Consisting of Vicinal Quaternary Centers

Abstract

Diverseb ispiro-3,4-dihydropyrans consisting of oxindole moietiesw itht hree contiguous chiralc enters and vicinal quaternary stereocenters were synthesized with very good yields of up to 92 %a nd excellent enantioselectivity of up to 99 % ee by using ap roline-derived thiourea organocatalyst.

Further developments of β,γ-unsaturated α-ketoesters as versatile synthons in asymmetric catalysis

“…In addition, without the assistance of amines, [4 + 2] annulations between β,γ -unsaturated α -ketoesters and aldehydes were viable. In 2016, a proline-derived thiourea catalyzed asymmetry [4 + 2] cycloaddition of β,γ -unsaturated α -ketoesters and cyclic β -oxoaldehydes was reported by the Kesavan group ( scheme 16 B) ( Vishwanath et al., 2016 ). The transformation was supposed to start with a 1,4-Michael addition of β,γ -unsaturated α -ketoesters, followed by a hemiacetalization cyclization.…”

Organocatalyzed Oxa-Diels–Alder Reactions: Recent Progress

“…The method enabled the formation of a 3,4-dihydro­pyran ring as part of a complex molecular topology. 30b…”

Non-Covalent Organocatalyzed Domino Reactions Involving Oxindoles: Recent Advances

“…The synthesis of spiro-3,4-dihydropyrans 62 bearing three stereocenters with vicinal quaternary ones has been reported by Kesavan and co-workers through the use of catalyst XI (5 mol %) in toluene at room temperature ( Scheme 18 a) [ 48 ]. Supported by the obtained syn configuration of the secondary alcohol and the cyclopentanone moiety, the authors defend an inverse-electron-demand hetero-Diels-Alder reaction pathway of oxindole α-ketoester 29 with cyclic β-oxoaldehyde 61 rather than a cascade transformation via Micheal addition/hemiketalization.…”