Solvomercuration-demercuration. 7. Regio- and stereochemistry of the oxymercuration-demercuration of alkyl-substituted cyclohexenes and cyclopentenes

Controlling factors determining the regiochemistry of intramolecular alkoxymercuration

“…1 In a cyclic system, 3-methylcyclohexene exclusively gave 3-methylcyclohexanol, the regiochemistry of which was explained in terms of the relative stabilities of the two possible regiochemical transition states during the attack of the nucleophiles on their mercurinium ion intermediates. 2 In contrast to the cyclohexene series, the results for the flexible cyclopentenes are not attributable to any reasonable explanation.…”

“…In order to examine the factors determining the regiochemistry of symmetrically substituted carbon-carbon double bonds in the formation of oxacyclic compounds by intramolecular alkoxymercuration, the reaction of (E)-5-phenylpent-4-en-1-ol (1), the p-methyl analogue, (E)-5-(p-methylphenyl)pent-4-en-1-ol (2) and the p-methoxy analogue, (E)-5-(p-methoxyphenyl)pent-4-en-1-ol (3), were carried out with mercuric acetate and their regioselectivity was compared with that obtained from the methoxymercuration of (E)-β-methylstyrene (4) and (E)-anethole (5). The products were characterized by demercuration with NaBH 4 .…”

Regio- and stereoselectivity in the solvomercuriation and intramolecular alkoxymercuriation of cyclic unsaturated alcohols

“…The oxymercuriation of 8 has already been reported, by Brown et al in 1979. 3 The reaction pathways for 8 are illustrated in Scheme 1. The heats of formation for the two conformers of 8 and four diastereomeric mercurinium ion intermediates were calculated using the MO method (Table 2).…”

“…2 Since 3-methylcyclohexene gave mainly trans-3-methylcyclohexanol, Brown pointed out that the regio-and stereochemistry are determined by the difference in the relative stabilities of the two possible transition states caused by the gauche interactions between the forming bond of the nucleophile with the mercurinium ion moiety and the bonds in the molecule. 3 In this article, we present the results of a study designed to evaluate the role of the polar substituent on the regio-and stereochemistry in the solvomercuriation of cyclic olefinic alcohols. The intramolecular alkoxymercuriation of cyclohexenylalkanols was also examined.…”