Rh2(R-TPCP)4-Catalyzed Enantioselective 3+2-Cycloaddition between Nitrones and Vinyldiazoacetates

摘要

Rhodium-catalyzed reaction of vinyldiazoacetates with nitrones results in a formal [3+2]-cycloaddition to generate 2,5-dihydroisoxazoles with high levels of asymmetric induction. The cascade reaction begins with a vinylogous addition event, followed by an iminium addition ring-closure/hydride migration/alkene isomerization cascade. Dirhodium tetrakis(triarylcyclopropane carboxylates) are the optimum catalysts for this process.