Isolation and characterization of nitrogen heterocycle-organolithium reaction intermediates

Abstract

Several intermediates from the reactions of nitrogen heterocycles with organolithium compounds were successfully isolated and were characterized by their proton magnetic resonance (pmr) spectra. Using TMED (N,N,N',N ' -tetramethylethylenediamine) and THF ( tetra - hydrofuran) as solvents, the pmr parameters were obtained for the intermediates from the reaction of phenyllithium with the following nitrogen heterocycles: pyridine ; 4-t-butylpyridine; 3-picoline ; 3,5-lutidine; 4-phenylpyridine; quinoline; 6-methylquinoline; 7- methylquinoline; and 8-methylquinoline. The pmr spectrum of the 2-phenylpyridine-phenyllithium intermediate was also taken in THF. Also, the pmr parameters were reported for the intermediates from the reactions of t-butyllithium with pyridine, 3 -picoline , 4 --t-butylpyridine , and quinoline, respectively. In the case of the reaction with 3 -picoline , the pmr spectrum of the reaction mixture gave evidence of the existence of two isomeric intermediates resulting from 1 ,2 - and 1 ,6 -addition of the t-butyllithium to the 3 --picoline..