Synthesis of 8-substituted 5H,9H-6-oxa-7-aza-benzocyclononene-10,11-dione-11-O-methyloximes, a new [1,2]-oxazonine ring system

Reaction of (2-bromomethyl-phenyl)-methoxyimino-acetic acid methyl ester 4 with oximes 1 in the presence of NaH/DMF yields 8-substituted 5H,9H-6-oxa-7-aza-benzocyclononene-10,11-dione-11-O-methyloximes 3 together with the expected open chain compounds 2. Some spectroscopic data as well as synthetic and mechanistic aspects of the formation of the novel compounds 3 are discussed.