Intramolecular Steric Factors in the Thermolysis of 4-Alkylidine-1-pyrazolines

Article abstract of DOI:10.1021/ja00265a029

Secondary deuterium kinetic isotope effects and product proportions are measured for several methyl-substituted 4-methylene-1-pyrazolines and deuterated isotopomers.The kinetic data support a single-bond-cleavage mechanism, and the products indicate that three modes of ring closure are required.Evidence is presented for a series of monomethyl compounds to suggest that the mechanism is more complex than a two-step scheme would predict and that the interconversion of a series of intermediates 46 is required.