A New Synthesis of Imines via Grignard- and Cuprate Additions toN-Trimethylsilylformamides

Abstract

The addition reaction of organolithium and organomagnesium reagents to N,N-disubstituted amides is a facile method for the synthesis of aldehydes and ketones. –6 Especially N-methyl-Nformylaminopyridine and N-formylpiperidine were shown to formylate efficiently a wide variety of Grignard reagents. We recently described that the reaction of aryllithium compounds with N-trimethylsilyl-N-alkylor N-arylamides yields imines. We now wish to report the formation of imines from the reaction of N-trimethylsilyl-N-alkylor N-arylformamides 1, with Grignard reagents (Scheme A), and Homoand Heterocuprates (Scheme B). Thus the reaction of N-trimethylsilylN-phenylformamide with 1.3 equivalents of isopropylmagnesium bromide at – 80°C in tetrahydrofuran gave imine 2 (R = isopropyl, R = phenyl) in 94 % yield. The result of the