Carbonium ion rearrangements in reactions of cyclopropylcarbinyl and cyclobutyl derivatives

Abstract

1-Methylcyclopropylcarbinylamine and 1-methylcyclobutylamine on treatment with aqueous nitrous acid gave only 1-methylcyclobutanol, while [beta]-methylallylcarbinylamine gave predominantly [beta]-methylallylcarbinol and 1-methylcyclobutanol, with smaller amounts of of [alpha]-methyl-[beta]-methylallyl alcohol and [beta]-methyl-[gamma]-methylallyl alcohol and possibly 2-3% of 1-methylcyclopropylcarbinol. The 1-methylcyclobutanol from 1-methylcyclopropylcarbinyl-C[superscript 14]-amine contained only 2.6 of the total C[superscript 14]-activity in C-3. The corresponding reaction in acetic acid gave 1-methylcyclobutyl acetate with 3.1% of the C[superscript 14] in C-3. 1-Methylcyclopropylcarbinyl chloride solvolyzes in 50% aqueous ethanol ca. 10 times faster than 1-methylcyclobutyl chloride and about as fast as t-butyl chloride. It was concluded that the above carbonium-ion type reactions of 1-methylcyclobutyl and 1-methylcyclopropylcarbinyl derivatives are best accounted for by formation, as the important reaction intermediate, of an unsymmetrical, nonclassical carbonium ion, structurally similar to the classical 1-methylcyclobutyl cation.