Regioselective two step synthesis of 3-substituted 2-aminoimidazo[1,2-a]pyrimidines

A two step procedure for the regioselective synthesis of 3-substituted-2-aminoimidazo[1,2-a]pyrimidines is described. The key step is a Dimroth rearrangement of a mixture of 2 and 3-substituted aminoimidazo[1,2-a]pyrimidines that yields quantitatively one regioisomer. Reaction screening for the rearrangement step is reported. A multicomponent isocyanide based reaction is chosen as the preferred way for the synthesis of the precursors. Elucidation of regiochemistry has been done by X-ray determination of some representative compounds.