Corner Attack on exo- and endo-Tricyclo2,4>octane by Deuteron and Mercuric Ions

Article abstract of DOI:10.1021/jo00267a029

Reaction of endo-tricyclo<3.2.1.0^2,4>octane (1) with deuteron in methanol-d1 gave a mixture (62:38) of methoxy ethers 3b and 4b from cleavage of the most substituted cyclopropane bond.The reaction proceeds by attack of deuterium at the corner of the cyclopropane.Trapping of the intermediate cation 5b is competitive with rearrangement to the nonclassical cation 6b.Reaction of exo-tricyclo<3.2.1.0^2,4>octane (2) under similar conditions gave methoxy ether 11b, which results from rupture of an external cyclopropyl bond, and methoxy ether 12b formed from rapture of the internal cyclopropyl bond with inversion at the site of both electrophilic and nucleophilic attack.Reaction of hydrocarbon 1 with mercuric acetate in methanol gave 4-endo-(acetoxymercurio)-2-endo-methoxybicyclo<3.2.1>octane (3c) from attack of the mercuric ion at the corner of the cyclopropane and nucleophilic attack by methanol with inversion without molecular rearrangement.Similar reaction of the exo hydrocarbon 2 gave product 12c from internal bond rupture without molecular rearrangement and with inversion of configuration at the site of electrophilic and nucleophilic attack.In addition an almost equal quantity of 11c, a product of rupture of the external cyclopropyl bond, was formed.The stereochemistry of mercuric ion and deuteron attack at C2 at the corner of the cyclopropane ring of 1 and 2 is rationalized by consideration of the symmetry and energy of the molecular orbitals involved.