Effect of methoxyl group position on the regioselectivity of ammonia substitution reactions involving 3,3'-dichloro-2,2'-binaphthoquinones

A series of methoxyl-substituted 3,3'-dichloro-2,2'-binaphthoquinones 2 were prepared and evaluated for regioselectivity in ammonia substitution reactions. Biquinone 2b underwent regiospecific amination at the unsubstituted chloronaphthoquinone unit whereas the isomeric biquinone, 2c, produced moderate regioselectivity (85:15). Biquinone 2d, however, showed no level of regioselectivity demonstrating that the position of the methoxyl group influences the regiochemistry. The intramolecular hydrogen bond in biquinone 5 altered the regioselectivity. Semiempirical calculations revealed comparatively larger LUMO coefficients at the chlorinated carbons that underwent preferential substitution.