Regio- and stereoselectivity in halomethoxylation of 7-phenyl-1-phenylsulfonyltricyclo[4.1.0.02,7]heptane

The reaction of 7-phenyl-1-phenylsulfonyltricyclo[4.1.0.0(2,7)]heptane with N-halo(chloro, bromo, iodo)succinimide in methanol led to the formation of a single product of conjugate syn-addition to the central C(1)-C(7) bond of the norpinane structure with a halogen atom in the geminal position to the sulfonyl substituent. The stereochemical result of the addition originates from the features of the reaction intermediate structure, a norpinanyl cation of a benzyl type where the reaction site is shielded from the nucleophile attack from the anti-direction by the sulfonyl group whose oxygen atom is approached to the reaction site to a distance of similar to 1.45 according to the nonempirical calculations by the 6-31G method; this distance is nearly by half less than the sum of van der Waals radii of Ca <-O.