Reaction of arylamidoximes with dimethyl acetylenedicarboxylate and diethyl chlorofumarate. Stereochemistry of the adducts and the derived 1,2,4-oxadiazines

It was shown that the addition of benzamidoxime to dimethyl acetylenedicarboxylate was predominantly cis-oid in methanol or acetonitrile solution and mainly trans-oid when benzene was the solvent. The stereochemistry of the cis-oid ( 4a ) and trans-oid ( 5 ) adducts was deduced by transformation into the oxadia-zinones ( 7a and 8a ) which, upon hydrolysis and subsequent reaction with acetic anhydride, gave the furo-2,3-c]-1,2,4-oxadiazine ( 9 ) and the symmetrical anhydride ( 10 ), respectively. The reaction of diethyl chlorofumarate with the sodium salt of benzamidoxime produced the oxadiazinone ( 8c ).