When the 1, 3, 4-oxadiazine 2, one of three known isomers formed by cycloaddition of 2, 5- dimethyl-3, 4-diphenyl-cyclopentadienone and dimethyl azodicarboxylate, is isomerized by MeO--MeOH to the hydrazone 4, the MeO of the ester group of 2 is lost and MeO is incorporated into 4 from the solvent. In acid, eg trifluoroacetic acid, demethylation of 2 gives 14 in which the ester Me is lost. The hydrazone 4 also gives 14 with acid, but by a different ...
