Synthesis of chiral tetronic acid derivatives via organocatalytic conjugate addition of ethyl 4-chloro-3-oxobutanoate to nitroalkenes

Asymmetric conjugate addition of ethyl 4-chloro-3-oxobutanoate to nitroalkenes and subsequent intramolecular cyclization had been developed. This one-pot reaction provided tetronic acid derivatives in good yields and with excellent enantioselectivities. 6′-Demethyl quinine was found to be the best catalyst for the conjugate addition and AcOLi was identified as the best base for the intramolecular cyclization. Various β-aryl, heteroaryl, and alkyl nitroalkenes are generally applicable in the reaction.