(+/-)-6-Benzyl-3,3-dimethylmorpholine-2,5-dione and its 5-monothio and 2,5-dithio derivatives

The morpholine ring of the title dione, C(13)H(15)NO(3), shows a boat conformation that is distorted towards a twist-boat, with the boat ends being the two Csp(3) atoms of the ring. The benzyl substituent is in the favoured 'exo' position. In the monothione derivative, (+/-)-6-benzyl-3,3-dimethyl-5-thioxomorpholin-2-one, C(13)H(15)NO(2)S, this ring has a much flatter conformation that is midway between a boat and an envelope, with the dimethyl end being almost planar. The orientation of the benzyl group is 'endo'. The dithione derivative, (+/-)-6-benzyl-3,3-dimethylmorpholine-2,5-dithione, C(13)H(15)NOS(2), has two symmetry-independent molecules, which show different puckering of the morpholine ring. One molecule has a flattened envelope conformation distorted towards a screw-boat, while the conformation in the other molecule is similar to that in the monothione derivative. Intermolecular hydrogen bonds link the molecules in the three compounds, respectively, into centrosymmetric dimers, infinite chains, and dimers made up of one of each of the symmetry-independent molecules.