The stereoselective synthesis of tetrahydrothiopyrano[2,3-b]indole skeletons via tandem reaction of indoline-2-thiones to BaylisaHillman adduct acetates

Indoline-2-thiones (5) were applied as 1,3-dinucleophiles in a tandem reaction with BaylisaHillman adduct acetates (4) to give novel tetrahydrothiopyrano[2,3-b]indole skeletons (6). The effect of different solvents, bases, and catalysts on the yields and stereochemical outcome was studied in detail. The results indicated that acetonitrile as solvent and K2CO3 as base, under reflux conditions, were the optimum conditions. Products 6aa6l were obtained in high diastereoselectivity and yield (up to 94%).