NMR Studies of Picolyl-type Carbanions. VIII. Anions Produced by Reactions of Alkyl-substituted Pyridines with Butyllithium

Article abstract of DOI:10.1246/bcsj.58.2294

The 1H and 13C NMR spectra have been observed for the anions, produced from methyl-, ethyl-, and isopropylpyridines, in tetrahydrofuran (THF).Two kinds of anions are formed concomitantly by lithium-proton exchange and addition of butyllithium from 2-ethyl, 2-isopropyl, 4-methyl, and 4-ethylpyridines.The former reaction tends to occur at the substituent bonded to the position adjacent to nitrogen, and the latter one occurs at the position adjacent to nitrogen without substituent.In the anions formed by the exchange from 2- and 4-ethylpyridines, a specific ring protonis coupled to the α-carbon, and, further, the ortho- or meta-protons (or -carbons) in the latter anion are nonequivalent respectively at room temperature.The α-carbons in these anions are virtually sp2-hybridized.