Organocatalytic asymmetric desymmetrization of cyclopentene-1,3-diones via a formal diaza–ene reaction with donor–acceptor hydrazones†

Herein we disclose a catalytic asymmetric desymmetrization of cyclopentene-1,3-diones via a formal diaza–ene reaction/tautomerization with donor–acceptor hydrazones. The H8-TRIP catalyst was found to be effective for this reaction. Chiral cyclopentane 1,3-diones with a hydrazone motif were obtained in good to high yields with excellent diastereo- and good to high enantioselectivities. The scope of the reaction was broad and a few applications including a pyrazole formation reaction have been demonstrated.