PYRAZOLINES: VI. THE STEREOCHEMISTRY IN THE PYROLYSIS OF PYRAZOLINES FOR THE C3 AND C5 POSITIONS OF THE PYRAZOLINE MOLECULE

Abstract

Cis- and trans-3.5-Dimethyl-3-carbomethoxy-Δ¹-pyrazoline (IV and V) have been separated, and product analysis for the pyrolysis and photolysis of these compounds has been completed. The cyclopropane products are formed with some change in the relative configuration of the cis–trans groups in both reactions. The α,β-unsaturated olefin product is formed stereospecifically with IV, yielding methyl 2-methyl-cis-2-pentenoate (XI), and with V, yielding methyl 2-methyl-trans-2-pentenoate (X). The results of the pyrolysis and photolysis of cis,trans-3,4,5-trimethyl-3-carbomethoxy-Δ¹-pyrazoline are also described. The product studies and some kinetic studies are the basis of a new mechanism proposed for the pyrolysis of pyrazolines.