Reaction of .GAMMA.-bromoacetoacetyl compounds with benzamide oxime derivatives: Synthesis of 4H-1,2,4-oxadiazine derivatives.

Abstract

Reaction of benzamide oxime derivatives (1) with ethyl γ-bromoacetoacetate in the presence of an acidic catalyst gave a mixture of geometrical isomers of 3-aryl-5-ethoxycarbonylmethylene-5, 6-dihydro-4H-1, 2, 4-oxadiazine derivatives (5) in 60-75% yields. On separation of the mixtures by HPLC, the (Z)-ester (5-I) was obtained as the main product (60-70% yields) together with the (E)-ester (5-II) (3-5% yields). The structures of these isomers were determined by analysis of the IR and NMR spectra. Methyl γ-bromoacetoacetate, p-methyl-γ-bromoacetoacetanilide and p-toluamide O-(γ-bromoacetoacetyl) oxime were also reacted with 1 to afford the corresponding 3-aryl-5-(substituted) methylene-5, 6-dihydro-4H-1, 2, 4-oxadiazine derivatives (8-I, 8-II, 9, and 10) in moderate yields.