Enantioselective N-Allylic Alkylation of N-Propargylsulfonamides with Morita-Baylis-Hillman Carbonates and Sequential Electrophilic Cyclization

The enantioselective N-allylic alkylation of N-propargylsulfonamides with racemic Morita-Baylis-Hillman (MBH) carbonates catalyzed by modified cinchona alkaloids has been investigated. The alkylation products from MBH carbonates with a 4-methoxyphenyl group underwent ipso-iodocyclization to give optically active azaspirocyclohexadienones via electrophilic activation of alkyne group with iodine monochloride. In contrast, ortho-selective intramolecular Friedel-Crafts reaction occurred for intermediates from MBH carbonates with other electron-rich or neutral aryl or heteroaryl substitutions via the same activation strategy, delivering multifunctional 2-benzazepine frameworks in a highly enantioenriched form.