The photochemical reactions of indane-1-thiones 4 were examined. Irrad
iation of indane-1-thiones 4c-d bearing delta-hydrogen atoms in the si
de chain gave cyclic thiol derivatives 5c-d via delta-hydrogen atom ab
straction by the excited thiocarbonyl sulfur. Irradiation of 2-allylin
dane-1-thiones 4e-h afforded the multifused thietanes 7e-h by intramol
ecular [2 + 2] cycloaddition between C=S and C=C bonds.