Nuclear magnetic resonance spectra of carbanions. IX. Carbanions produced by reactions of methyl-substituted pyridines with n-butyllithium

Abstract

Methyl-substituted pyridines were allowed to contact with n-butyllithium in n-hexane. The reaction products were dissolved with tetrahydrofuran (THF) or 1,2-dimethoxyethane (DME) and checked with PMR measurements. The metal-proton exchange reaction occurred at the α-methyl group. 2,4-Lutidine and 2,4,6-collidine in DME were metallated at the γ-methyl group. The metallated positions have been confirmed by chemical shift considerations. The extra charge in the prepared carbanions is largely delocalized into the aromatic ring. The methylene carbon atom in the carbanions is near sp2-hybridized. The two methylene protons in the α-picolyl carbanions show magnetic nonequivalence in the lower-temperature measurements. © 1973.