Ozonolysis of Highly Methylated 1,2-Bis(methylene)cycloalkanes. Influence of the Methyl Substituents on the Course of the Reaction

In the ozonolyses of highly methylated 3,3,4,4,5,5-hexamethyl-1,2-bis(methylene)cyclopentane (1a) and 3,3,6,6-tetramethyl-1,2-bis(methylene)cyclohexane (1b), the epoxidation competed with the cleavage of the C−C double bond, whereas only the latter process was observed in the case of the nonmethylated 1,2-bis(methylene)cycloalkanes 1c,d. Competition experiments revealed that the reactivity of the highly methylated 1,2-bis(methylene)cycloalkanes 1a,b is significantly smaller than that of the nonmethylated ones (1c,d), suggesting that the formation of the primary ozonides 2c,d occurs by a concerted 1,3-dipolar cycloaddition process.