Solvolytic studies with 2-methyl[1-13C]-1-propyl tosylate

Abstract

Solvolysis of 2-methyl[1-13C]-1-propyl tosylate was carried out in HOAc or CF3COOH without or with the presence of 2.0 equivalents of NaOAc or CF3COONa, respectively. Isobutyl, sec-butyl and tert-butyl products were obtained. With the use of 13C as label, isotopic scramblings were analyzed by 13C nmr, avoiding the necessity of chemical degradations associated with the use of 14C. There was no isotopic scrambling in the isobutyl product and scrambling of the 13C-label was observed only between C-2 and C-3 in the sec-butyl product, indicating 1,2-hydride shifts in the sec-butyl cation. In contrast to the involvement of equilibrating protonated methylcyclopropane intermediates observed in the trifluoroacetolysis of [1-14C]-1-butyl tosylate, the present results indicated that protonated methylcyclopropane intermediates did not play a significant role in the acetolysis or trifluoroacetolysis of isobutyl tosylate.