Stereoselective Azine Formation in the Decomposition of Phenyldiazomethanes

Article abstract of DOI:10.1021/ja00187a037

The bimolecular dimerization of phenyldiazomethane (1) and 1-diazo-1-phenylethane (2) to form the corresponding azines (3 and 4) is stereoselective for the E,Z isomer (>95:5 E,Z:E,E).The E,Z isomer can be isolated from the reaction of 2, and it can be observed but not isolated from the reaction of 1.Both (E,Z)-3 and -4 revert thermally to the more stable E,E isomer.The kinetic parameters of this process were determined for (E,Z)-4: E_a = 22.3 kcal/mol, log A = 11.2.The stereoselectivity is accounted for within the context of the accepted mechanism for azine formation via diazo compound dimerization.