(11aS)-1,5,11,11a-Tetra-hydro-1-benzo-thieno[3,2-f]indolizin-3(2H)-one.

The absolute configuration of the title compound, C14H13NOS, was assigned from the synthesis and confirmed by the structure determination. There are two independent mol-ecules in the asymmetric unit. The central six-membered ring of the indolizine moiety adopts an envelope conformation, with the greatest deviations from the mean planes being 0.569 (3) and 0.561 (3) Å for the indolizine bridgehead C atoms of the two mol-ecules. The benzothieno ring attached to the indolizine ring system is planar to within 0.015 (3) Å in both mol-ecules. In the crystal, weak C-H⋯O and C-H⋯π inter-actions lead to the formation of a three-dimensional framework structure.