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

Article abstract of DOI:10.1021/jo00073a019

Cyclization of the bis cesium thiolate (generated in situ) of 1,3-dimercaptoacetone (1) with α,ω-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-benzophane (8) at 130 K: triclinic, space group P-1; a = 7.230(1) Angstroem, b = 8.690(1) Angstroem, c = 13.253(1) Angstroem, α = 83.153(7) deg, β = 84.257(6) deg, γ = 85.575(6) deg, Z = 2, μ(Mo Kα) = 5.5 cm^-1, R = 0.029 (R_w = 0.041) for 3082 reflections (I >/= 2.5?(I)).Crystal data for 1,4,7,10,13-pentathiacyclohexadecan-15-one (9) at 140 K: monoclinic space group P2₁/a; a = 16.558(1) Angstroem, b = 5.399(1) Angstroem, c = 16.734(1) Angstroem, β = 90.28(5) deg, Z = 4, μ(Mo Kα) = 7.3 cm^-1, R = 0.048 (R_w = 0.66) for 3021 reflections (I >/= 3?(I)).