Enantioselective Synthesis of Chiral Pyrazolo[3,4‐d]azepin‐7(2H,4H,8H)‐one Derivatives through a Sequential Michael Addition and Reductive Ring‐Closing Strategy

An asymmetric Michael addition of ethyl ester 1-phenyl-pyrazolone-3-acetic acid and nitroalkene catalyzed by a squaramide organocatalyst was studied for providing access to chiral pyrazoles, which facilitated the subsequential one-pot reductive ring closing process to give a series of biologically important chiral pyrazolones with seven-membered lactam frameworks in good yields with excellent enantioselectivities (up to 99% ee).