Pyrazolines: Iv. Rearrangement of Alkyl Groups During the Pyrolysis of 4,4-Dialkyl-3-Cyano-3-Carbomethoxy-Δ1-Pyrazolines

A number of 4,4-dialkyl-3-cyano-3-carbomethoxy-Δ1-pyrazolines have been synthesized. Pyrolysis of these pyrazolines yielded cyclopropane and olefin products. The formation of olefin products by rearrangement of an alkyl group from C4 to C5 of the pyrazoline system suggests that positive charge is developed on C5 in the transition state. Ionic character in the transition state was also indicated by the fact that the rate of pyrolysis is faster in polar than in nonpolar solvents.