Regioselective nucleophilic addition of 3-aryl-5-difluoromethyl-isoxazoles to aldehydes

A series of 5-difluoromethyl-isoxazoles 2 were prepared, and their regioselective nucleophilic addition to aldehydes was investigated. It was found that the nucleophilic difluoromethylation of aldehydes with 5-difluoromethyl-isoxazoles could be efficiently and uniquely achieved in the presence of LDA as a base that provides a large steric hindrance. In contrast, 3,4,5-trisubstituted 5-difluoromethyl isoxazoles were alternatively afforded as the sole product in moderate yields when n-BuLi was used as the base.

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► 5-Difluoromethyl-isoxazoles were applied as efficient nucleophilic reagents.
► The proper use of base play an important role.
► Aldehydes could be difluoromethylated by treatment of LDA as a base.
► Isoxazoles merit superior atom-economical feature in fluoroalkylation reactions.