Highly regio-, diastereo- and enantioselective deracemization of axially chiral 3-alkylideneoxindoles.

The first catalytic asymmetric dynamic resolution of unprotected racemic 3-(4-alkylcyclohexylidene)indolin-2-ones via a one-step direct vinylogous Michael reaction with chalcones was realized using a chiral N,N'-dioxide/Sc(iii) complex catalytic system. A variety of (Z)-4-alkyl-2-((3-oxo-1,3-diarylpropyl)cyclohexylidene)-indolin-2-ones with three stereogenic centers at ξ-, γ- and δ'-positions were obtained in up to 95% yield, 98% ee and 99/1 dr. A possible transition state was proposed to explain the origin of the stereoselectivity.