Stereoselective synthesis of 3-spiropiperidino indoleninesviaSN2-type ring opening of activated aziridines with 1H-indoles/Pd-catalyzed spirocyclization with propargyl carbonates

Abstract

3-Spiropiperidino indolenines have been synthesized via novel Lewis acid-catalyzed SN2-type ring opening of activated aziridines with 1H-indoles followed by Pd-catalyzed dearomative spirocyclization with propargyl carbonates in up to 88% yields. The step and pot-economic transformation comprises sequential C–C, C–N, and C–C bond forming steps generating two stereogenic centers including an all-carbon quaternary stereocenter to furnish the products in diastereomerically pure (dr >99 : 1) forms with excellent enantiomeric excess (ee up to >99%). The synthetic versatility of the strategy has been illustrated by converting the synthesized products into spirocyclic indolenine 2-piperidinones, dihydropiperidines, and 5-alkynylated piperidines.