A method for the oxygenation of tertiary C-H bonds of N-alkylamidines and N-(2-alkylaryl)-amidines is described that utilizes the CuBr center dot SMe2/2,2'-bipyridine catalytic system under an O-2 atmosphere and provides dihydrooxazoles, and 4H-1,3-benzoxazines. The oxygen atom is incorporated from atmospheric molecular oxygen during the present process.