Ag(i)-catalyzed asymmetric (2+4) annulation reaction of 5-alkenyl thiazolones: synthesis of enantioenriched spiro[cyclohexenamines-thiazolones]

Abstract

The first metal-catalyzed (2+4) annulation of 5-alkenyl thiazolones and α,α-dicyanoalkylidenes has been developed via vinylogous Michael/cyclization/isomerization reaction. This (2+4) annulation reaction is catalyzed by a chiral Ag-(R)-DTBM-SEGPHOS catalyst, delivering enantioenriched spiro[cyclohexenamines-thiazolone] having contiguous quaternary and tertiary stereocenters in good to excellent yield (up to 80%) and excellent stereoselectivities (up to 97% ee and >20 : 1 dr). This methodology has high functional group tolerance and produces a broad range of enantioenriched products under mild reaction conditions.