Ketosulfonyl indoles in the regiodefined synthesis of tryptophols and related indole derivatives.

Reduction of ketosulfonyl indoles with sodium borohydride provides a ready entry to tryptophols in a regiocomplementary fashion with respect to the traditional oxirane ring-opening by indoles under Friedel-Crafts conditions. Compared to traditional β-ketosulfones, ketosulfonyl indoles show a peculiar behavior since they undergo a Lewis acid promoted elimination of the arylsulfonyl group allowing the preparation of indolyl-substituted 1,4-dicarbonyl derivatives.