Chirality probe approach to reactive intermediates

Molecular chirality of 4-methylcyclohexylidenemethyl iodonium salt is used to probe the chirality of intermediate state of the reaction. A possible achiral intermediate, primary vinyl cation is excluded for the reactions of the iodonium salt under any reaction conditions employed, while achiral 5-methyl-cycloheptyne, formed via rearranged cation, is involved in the reaction with sulfonate. The reaction is extended to generation of some small ring cycloalkynes. Vinylic SN2 mechanisms are also proposed.