Microwave-assisted regioselective N-alkylation of cyclic amidines

A simple and efficient methodology for regioselective alkylation of exocyclic nitrogen of cyclic amidines was developed by microwave-assisted heating in the presence of amines. Novel N-alkylated 3,4-dihydropyrazino[2,1-b]quinazolin-6-ones were prepared in good yields. The reaction occurred via a transamination (addition–elimination) process involving a first attack of the amine on the electrophilic carbon of the amidine function.