Organocatalytic Michael Addition of Indoles to Activated Alkenes in Water

Significance

Reported is a Michael addition of indole derivatives to activated olefins in water, catalyzed by carbohydrate-based tolylsulfonyl hydrazines. The reaction does not proceed in the absence of catalyst and is, as expected, regioselective at the indole 3-position. The authors propose that the tolylsulfonyl hydrazine is the effective catalytic functional group and that the carbohydrate portion acts as a surfactant. Evidence for this claim is given in that the reaction does not proceed when the carbohydrate portion is replaced by a phenyl group, and the reaction is poorly catalyzed by sodium dodecyl sulfonate. Interestingly, this reaction proceeds poorly in organic solvents such as THF or CH₂Cl₂.