Corner Attack on endo- and exo-Tricyclo2,4>oct-6-ene by Deuterium and Mercuric Ions: The Effect of Electrophile on Reaction Course

Article abstract of DOI:10.1021/jo00276a036

Reaction of endo-tricyclo<3.2.1.0^2,4>oct-6-ene (1) with mercuric acetate in methanol gave 2b as the major product of reaction after stereospecific reduction with sodium-mercury amalgam in sodium deuteroxide, along with 3b and 4b.In contrast 4-endo-deuterio-2-endo-methoxybicyclo<3.2.1>oct-6-ene (2b) is formed as a minor product from acid-catalyzed reaction of endo-tricyclo<3.2.1.0^2,4>oct-6-ene (1) with methanol-d₁.Methoxymercuration of exo-tricyclo<3.2.1.0^2,4>oct-6-ene (8) occurs at the double bond to give 7-exo-(acetoxymercurio)-6-exo-methoxy-exo-tricyclo<3.2.1.0^2,4>octane (9c; 89percent).Acid-catalyzed addition of methanol to exo-tricyclo<3.2.1.0^2,4>oct-6-ene (8) gave 6-exo-methoxy-exo-tricyclo<3.2.1.0^2,4>octane (9a; 15percent) and 6-exo-methoxytricyclo<3.2.1.0^2,7>octane (11) in a process involving corner attack of the electrophile.This tricyclic compound rearranges to 5-exo-methoxybicyclo<2.2.2>oct-2-ene (10a; 55percent).The preference for corner attack by mercuric ion and deuteron with C2-C4 bond cleavage in the reactions of 1 and 8 is rationalized and the competition between reaction at cyclopropane and addition to the double bond discussed.