Carbene Reactions with Cis Azo Functions. Formation of Ester Azines from Δ3-1,3,4-Oxadiazolines

Article abstract of DOI:10.1021/jo00176a024

Thermolysis of a 2-alkoxy-2,5,5-trialkyl-Δ³-1,3,4-oxadiazoline (1), either neat or in a solvent such as benzene, leads to a carbonyl ylide intermediate which fragments to carbonyl compounds and carbenes.The latter attack the parent oxadiazoline at the azo function, presumably to form azomethine imine ylides.The latter ylides then fragment to form carbonyl compounds and azines such as R¹(R²O)C=NN=C(OR²)R¹, R¹(R²O)C=NN=C(R³)2 and (R³)2C=NN=C(R³)2.The mechanism proposed is supported by results of studies of the dependence of the azine and propeneyields on the initial oxadiazoline concentration.More propene and less (R³)2C=NN=C(R³)2 are obtained at low oxadiazoline concentrations, as would be expected if both arise from dimethyl carbene.