Vicinal di-functionalization of #alpha#,#beta#-unsaturated ketones via manganese carbene intermediates: synthesis of #gamma#-acyl-#sigma#-lactones by cascade Michael addition/aldol/transesterification reactions

摘要

The carbene-enolate complexes generated upon reaction of the carbene anion [Cp'(CO)_2Mn=C(OEt)CH_2]~- with benzylidene acetone and chalcone react with benzaldehyde to form the 6-membered oxacyclocarbene complexes Cp'(CO)_2Mn=CCH_2CH(Ph)CH(C{O}R)CH(Ph)O (R=Me, Ph). The latter, which can be regarded as the result of cascade Michael addition/aldol/transesterification reactions, are readily oxidized by air to release the corresponding #gamma#-acyl-#sigma#-lactones.