CESIUM DITHIOLATE BASED SYNTHESES OF KETO-FUNCTIONALIZED THIO-CROWN ETHERS EMPLOYING THE NOVEL BUILDING-BLOCK 1,3-DIMERCAPTOACETONE - MOLECULAR-STRUCTURES OF 2,5,9,12-TETRATHIA-7-OXO-(13)-M-BENZENOPHANE AND 1,4,7,10,13-PENTATHIACYCLOHEXADECAN-15-ONE

Cyclization of the bis cesium thiolate (generated in situ) of 1,3-dimercaptoacetone (1) with alpha,omega-dihalides in DMF affords the corresponding cyclic thioethers in good yields, providing an efficient alternative route to keto-functionalized thio-crown ethers. A previously suggested dimeric structure for 1 is supported by NMR spectra, which also allow distinction between cis and trans isomers of 1. Equilibration between the isomers can also be followed by NMR. The molecular structures of two specific thio-crown ethers have been determined by X-ray crystallography. Crystal data for 2,5,9,12-tetrathia-7-oxo-(13)-m-benzenophane (8) at 130 K: triclinic, space group P-1; a = 7.230(1) angstrom, b = 8.690(1) angstrom, c = 13.253(1) angstrom, alpha = 83.153(7)-degrees, beta = 84.257(6)-degrees, gamma = 85.575(6)-gamma, Z = 2, mu(Mo Kalpha) = 5.5 cm-1, R = 0.029 (R(w) = 0.041) for 3082 reflections (I greater-than-or-equal-to 2.5sigma(I)). Crystal data for 1,4,7,10,13-pentathiacyclohexadecan-15-one (9) at 140 K: monoclinic, space group P2(1)/a; a = 16.558(1) angstrom, b = 5.399(1) angstrom, c = 16.734(1) angstrom, beta = 90.28(5)-degrees, Z = 4, mu(Mo Kalpha) = 7.3 cm-1, R = 0.048 (R(w) = 0.66) for 3021 reflections (I greater-than-or-equal-to 3sigma(I)).