Influence of Steric Effect on the Pseudo-Multicomponent Synthesis of N -Aroylmethyl-4-Arylimidazoles.

A pseudo-three-component synthesis of N -aroylmethylimidazoles 3 with three new C-N bonds formed regioselectively under microwave conditions was developed. Products were obtained by reacting two equivalents of aroylmethyl bromide (ArCOCH 2 Br, 1 ) with the appropriate amidine salt (RCN 2 H 3 .HX, 2 ) and with K 2 CO 3 as a base in acetonitrile. The bicomponent reaction also occurred, giving the expected 4(5)-aryl-1 H -imidazoles 4 . Notably, the ratio of products 3 and 4 is governed by steric factors of the amidine 2 (i.e., R = H, CH 3 , Ph). Therefore, a computational study was carried out to understand the reaction course regarding product ratio ( 3 / 4 ), regioselectivity, and the steric effects of the amidine substituent group.