Smooth photocatalytic preparation of 2-substituted 1,3-benzodioxoles.

A mild and general method for the synthesis of potentially bioactive 2-substituted-1,3-benzodioxoles is presented. This is based on the photocatalyzed activation of methylene hydrogen atoms in the presence of tetrabutylammonium decatungstate (TBADT). The method gave yields ranging from 46-77 % with no interference by benzene ring substituents, such as OR, COOMe, Me, or CHO. The OH group interfered, but protection regenerated the reactivity. 5-Chloro-1,3-benzodioxole was converted into a safrole derivative through a one-pot process involving two consecutive irradiations, at 366 nm for the photocatalyzed alkylation at position 2 and at 310 nm for the alkylation at position 5.