Regioselective Synthesis of 3‑Aminoimidazo[1,2‑<i>a</i>]‑pyrimidines under Continuous Flow Conditions

Multicomponent synthesis of 3-aminoimidazo­[1,2-a]­pyrimidines usually affords a product mixture containing varying amounts of the corresponding 2-amino regioisomer. Modified methods, particularly microwave heating, have been employed to suppress formation of this side-product, but none of the revised protocols are readily amenable to scale. A continuous flow adaptation was found to offer improved regioselectivity toward the targeted 3-amino regioisomer with significantly shorter reaction times and also widened the scope of the reaction to permit the use of aliphatic aldehyde building blocks.