A carbon-13 nuclear magnetic resonance study of protonation in Imidazo[4,5-c]pyridines

Abstract

A carbon-13 n.m.r. study of protonation in various imidazo[4,5- c]pyridines has revealed that imidazo[4,5-c]pyridine and its 1- and 3- methyl derivatives are protonated at N5; 6-chloroimidazo-[4,5- c]pyridine and its 1-methyl derivative are protonated at N 3 but the 3- methyl analogue protonates at N 1; and 2-methylthioimidazo[4,5- c]pyridine (and also its 5-methyl derivative) protonate at both N 1 and N 3, but 1- and 3-methyl-2-methylthioimidazo[4,5-c]pyridine protonate at N 5.