An expedient route to highly functionalized 2H-chromene-2-thiones via ring annulation of β-oxodithioesters catalyzed by InCl3 under solvent-free conditions

A convenient and one-pot synthesis of 3-aroyl/heteroaroyl-2H-chromene-2-thiones and benzo[f]2H-chromene-2-thiones has been developed by the condensation of β-oxodithioesters and salicylaldehydes/α-hydroxynaphthaldehydes in the presence of indium trichloride under solvent-free conditions. The reaction is operationally facile, readily scalable, and offers rapid entry into differentially substituted chromene-2-thione scaffolds.