A Remarkable Stereoselectivity in the Oxymercuration-Demercuration of Norbornene, 7,7-Dimethylnorbornene, and Related Derivatives

Orbital mixing rule

“…If such a bond is thought to be described by two atomic hybrids pointing each one toward the other, there will be a larger electron density in the region between the two atoms for two reasons: (a) each atomic hybrid is projected into the internuclear region and consequently the unit positive charge placed on the nucleus becomes relatively more deshielded on the outer region around the bond axis; (b) the formation of the bond produces a further piling up of electrons in the overlap region and consequently the outer regions of the bond become even more depleted of electrons with respect to the simple summation of the two atomic hybrid distributions. (10) For the definition of the atomic hybrid moments and for the corresponding decomposition of the molecular dipole moment into partial contributions, see, for example, C. A. Coulson "Valence", Oxford University Press, London, 1961.…”

Oxymercuration-demercuration and hydroboration-oxidation of endo-tricyclo[5.2.2.02,6]undeca-3,8-diene. Stereospecific oxymercuration leading to the 4-exo-hydroxy derivative

“…22,26,27 The result is in complete agreement with what is expected from the oxymercuration reaction of norbornene. 25,28 Norbornene has been shown to undergo oxymercuration quite rapidly, yet with exo cis addition mechanism. This exceptional reactivity was ascribed to a high strain of the molecule with steric congestion on the endo side.…”

Cyclization to Stereoisomeric Hexahydro-3,6-pentaleno[1,6-cd]pyran- 1(3H)-ones. A Model Study Explains the Preference for Trans Products

“…Installation of the tertiary hydroxyl group at C-1 via oxymercuration required that the dimethyl acetal first be replaced by a dioxolane ring as in 9 . In sharp contrast to the highly exo-stereoselective response to electrophilic attack exhibited in general by diquinanes, treatment of 9 with mercuric acetate under basic conditions provided 10 and 11 in a ratio of 1:2. Furthermore, the rate of consumption of 9 was rather slow, more than 12 h being required to achieve complete conversion.…”