SYNTHESIS AND STRUCTURE OF FUNCTIONALIZED DERIVATIVES OF THE CLEFT-SHAPED MOLECULE DITHIOSALICYLIDE

Conformationally rigid molecules whose structures define cavities and clefts have potential uses as receptors,1-3 catalysts,4,5 and as molecular building blocks in the construction of new materials.6 Dithiosalicylides are a class of conformationally well-defined, cleft-shaped molecules.7,8 NMR7 and X-ray crystallographic8 studies have shown that dithiosalicylide (1) adopts a boat conformation where the aromatic rings form a shallow “vshaped” pocket in which the dihedral angle between the aromatic rings is approximately 65 °.8 Although dithiosalicylides are not conformationally locked, as is the case for the structurally related Kagan’s ether1,2 and Troeger’s base3 compounds, the inversion barrier between the enantiomeric boat conformations is quite high (∼25 kcal/ mol).7 As part of investigations9-11 into the chemistry of 3H1,2-benzodithiol-3-one 1-oxide and related compounds, we recently developed a simple preparation of dithiosalicylide from 3H-1,2-benzodithiol-3-one (2).12,13 Treatment of 2 with triphenylphosphine provides good yields of 1, presumably via dimerization of a benzothietan-2-one (3) or ketene (4) intermediate (Scheme 1).14 We describe here the application of this protocol to the preparation of dithiosalicylide analogs that present larger cavities than the parent compound and to several analogs that may be amenable to further functionalization. In addition, we present the crystal structures of two dithiosalicylides that show that the compounds form discrete, selfincluded dimers and that interactions between the dimers give rise to interesting supramolecular structures.