The 9-decalyl and related cations. IV. Generation of cis- and trans-2-t-Butyl-9-decalyl cations through σ-routes by acetolysis

Abstract

The synthesis and solvolytic behaviour (in buffered acetic acid) of cis- and trans-9-t-butylspiro[4,5]-dec-6-yl p-toluenesulfonate (5) and (6) are described. The two compounds solvolyse with anchimeric assistance and undergo ring expansion with complete stereospecificity; the cis- and trans-esters yield trans- and cis-2-t-butyl-9-decalyl cation (8) and (7), respectively. To account for the stereospecificity, it is proposed that (6) must solvolyse through a boat conformation of the six-membered ring. Ring contraction (c. 8%), with the formation of the 1-(3'-t-butylcyclopentyl)cyclopentyl cation (presumably trans (36)), also takes place in the acetolysis of (6).    

The possible role of ion-pairs in the reactions of (5) and (6) is examined. It is concluded that the anion in an ion-pair might be involved in olefin formation only when it (the anion) is ideally located for proton abstraction in the initially formed ion-pair (or that formed by conformational interconversion of the cationic moiety).