Solvolysis of vinyl iodonium salts. New insights into vinyl cation intermediates

Solvolysis of some vinyl iodonium salts carrying an excellent leaving group is examined, focusing on whether or not a classical primary, vinyl cation can be generated. Formation of the primary cation is voided, when possible, by participation of the beta substituent in the heterolysis to form a vinylenebenzenium ion or a secondary vinyl cation. Definitive evidence against a primary vinyl cation is provided by a chirality, probe approach in the solvolysis of 4-methylcyclohexylidenemethyl iodonium salt.