Reductive Amination-Annulation Route to N-Substituted Dihydro-1,4-Benzoxazin-2-ones

Significance

A synthesis of previously unknown 4-benzyl- and 4-alkyl-3,4-dihydro-1,4-benz­oxazin-2-one derivatives 3 from the reaction of 2-(hydroxyphenylamino)acetates 1 with aldehydes 2 is described. The reaction proceeds by initial reductive amination of 1 with benzaldehyde derivative 2, followed by spontaneous lactonization to 3, which were isolated in moderate to good yields. The parent 3,4-dihydro-1,4-benzoxazin-2-one 4 was obtained by simple catalytic hydrogenation of 3 (R^¹ = H, R^² = Ph). Compound 1 was obtained from corresponding aminophenol derivative and ethyl-2-bromoacetate.