Vinylogous functionalization of 4-alkylidene-5-aminopyrazoles with methyl trifluoropyruvates

A valuable vinylogous addition reaction between 4-alkylidene-5-aminopyrazoles and alkyl trifluoropyruvates leading to highly functionalized tertiary alcohols bearing a trifluoromethyl group and a pyrazole ring is presented. The corresponding trifluoromethyl alcohols are obtained in moderate to good yields (up to 80%) and high diastereoselectivity (up to 7:1).