DELOCALIZED NITROGEN CARBANIONS IN S(RN)1 REACTIONS

S(RN)1 reactions can be performed with nitrogen carbanions as nucleophiles, and generally the reaction leads to a mixture of isomers. In the case of the pyrrolyl anion, position 2 is about four times more reactive than position 3. When the ortho positions of pyrrole are substituted by alkyl groups, the reactivity of position 2 increases while that of position 3 decreases. With tert-butyl groups as the substituents, no reaction at position 2 is observed. With the indolyl anion as the nucleophiIe, no substitution at position 2 or at the phenyl ring is observed, and only one product corresponding to monosubstitution at position 3 is obtained. Imidazolyl anions react preferentially at position 4 (5), and substitution of position 2 by a methyl group makes the coupling regioselective.