Three-component one-pot construction of 2-aryl-3-benzylbenzo[4,5]imidazo[1,2- <i>a</i> ]pyrimidines using solid calcium carbide as an alkyne source

A concise method for the construction of 2-aryl-3-benzylbenzo[4,5]imidazo[1,2-<i>a</i>]pyrimidines using solid calcium carbide as an alkyne source, 2-aminobenzimidazoles, and (hetero)aromatic aldehydes as substrates through one-pot three-component procedure is described. The target products were effectively obtained through A³ coupling, 6-<i>endo-dig</i> cyclization, isomerization, and dehydration cascade processes. The salient features of this protocol are the use of an inexpensive, abundant and easy-to-handle solid alkyne source instead of flammable and explosive gaseous acetylene, low-cost catalyst, wide functional tolerance, satisfactory yield, and simple workup procedure. The reactions can also be carried out on a gram scale.