Facile synthesis of 1,4-oxazines by ruthenium-catalyzed tandem N–H insertion/cyclization of α-arylamino ketones and diazo pyruvates

Herein, we report an efficient strategy for the rapid construction of 1,4-oxazines starting from simple alpha-amino ketones and diazo pyruvates under mild reaction conditions. This transformation is efficiently catalyzed by RuCl3 through a tandem N-H insertion/cyclization sequence via an enol formation. This reaction shows broad functional group tolerance, and the resulting 1,4-oxazine products show promising anticancer activities toward HCT116.