Regioselective alkylation of the trifluoromethyl analog of Hagemann's ester

The reactivity of the enolate of the 4-carbethoxy-3-trifluoromethyl-cyclohe x-2-enone (1) toward electrophiles has been studied and compared with that of the parent Hagemann's ester. presence of the CF3 group could allow the s elective introduction of substituents at three different sites. With alkyl halides the C-2 alkylation is completely favored. High selectivity is direc ted to the C-4 site with ethyl chloroformate, and only O-silylation occurre d with a silylated chloride. (C) 2001 Elsevier Science B.V. All rights rese rved.