Cooperative Dual Organocatalytic Asymmetric Decarboxylative[4+3]Annulations With Benzoxazinanones

Vinyl and ethynyl benzoxazinanones have unique reactivity and are common reaction precursors of heteroatom-dipole intermediates,which can be used to build up chiral heterocyclic molecules in structural diversity.However,most of those reactions only work well for either allyl or propargyl benzoxazinanone substrates.In particular,the activation of allyl and propargyl functionalities relies on different metal catalysts.Currently,palladium and iridium catalysts could activate the decarboxylation of vinyl benzoxazinanone to afford allyl dipole intermediates,while copper catalysts could activate the decarboxylation process of ethynyl benzoxazinanones to afford Cu-allenylidene species.The two dipole intermediates can participate in the[4+n]cycloaddition reaction as four-atom building blocks.We have developed a general activation mode for decarboxylation of aryl,alkene,and alkyne substituted benzoxazinanone.The cooperative catalysis of a Lewis base and a chiral N-heterocyclic carbene enables the highly enantioselective[4+3]annulation of benzoxazinanones with isatin-derived enals,which efficiently synthesized chiral spirobenzazepinone with up to 98%ee.DMAP acts to be a strong nucleophilic Lewis base to promote the decarboxylation of different types of 4-substituted benzoxazinanones to smoothly give the key aza-ortho-xylylene intermediates,thereby enabling the reaction to tolerate a much broader scope of electrophilic substrates than transition-metal-catalyzed variants.