One-pot synthesis of 2-(trifluoromethyl)pyridines from N-silyl-1-aza-allyl anions with trifluoroacetylketene diethyl ketal or (E)-1,1,1-trifluoro-4-phenylbut-3-en-2-one

Abstract

The reaction of N-silyl-1-aza-allyl anions with trifluoroacetylketene diethyl ketal and (E)-1,1,1-trifluoro-4-phenylbut-3-en-2-one are described. The anions, which were prepared from an α-silyl carbanion of 3-methyl-5-(trimethylsilylmethyl)isoxazole [or 3-methyl-2-(trimethylsilylmethyl)pyridine] and para-substituted benzonitriles (R = H, p-Me, p-OMe, p-Cl, p-CF₃), reacted with a slight excess of trifluoroacetylketene diethyl ketal or (E)-1,1,1-trifluoro-4-phenylbut-3-en-2-one in dry tetrahydrofuran to afford the corresponding 2-(trifluoromethyl)pyridine derivatives in 75, 71, 78, 48, 46, 60, 83% yield, respectively.