Chemistry of the phenoxathiins and isosterically related heterocycles. XXV . Synthesis of 1,6‐diazathianthrene from 3‐mercaptopyridin‐2(1H)‐thione via a novel dehydrothiolation reaction in the presence of triethylamine

Abstract

The generation of the dianion of 3‐mercaptopyridin‐2(1H)‐thione with triethylamine in N,N‐dimethylform‐amide followed by reaction in the presence of 2‐chloronitrobenzene fails to give 1‐azathianthrene which is formed in good yield when sodium hydride was employed as the base. The principle product isolated from the reaction was instead 1,6‐diazathianthrene. Mechanistic considerations are discussed.

[2-(Trimethylsilyl)ethoxy]methyl (SEM) as a novel and effective imidazole and fused aromatic imidazole protecting group

“…Many of the imidazole nitrogen protecting groups that have been commonly used often are not removable under reaction conditions compatible with other functional groups in the molecule.1 There have been several recent advances in imidazole protection, notably the diethoxymethyl1 and trityl groups.2 However, the diethoxymethyl group is extremely moisture-sensitive, while trityl-protected imidazoles are often obtained in poor yields.3 4We required a novel imidazole protecting group which was easily introduced, stable, selectively removed, and which assisted purification. 4,5 (1) Curtis, N. J.; Brown, R. S. J. Org. Chem.…”

“…1977, 20, 721. (4) Matthews, D. P.; Whitten, J. P.; McCarthy, J. R. Synthesis, in press. (5) McCarthy, J. R.; Matthews, D. P.; Whitten, J. P. Tetrahedron Lett. 1985, 26, 6273.…”

“…liquids in 64-85% yield (see Table I). Using similar procedures, the SEM group was also introduced as a N protecting group on the fused aromatic imidazole derivatives benzimidazole, 4-azabenzimidazole, and even on the highly insoluble 2,2/-bi-lif-imidazole4,10 to give distillable, stable liquids (5)(6)(7) in good yields. Removal of the SEM group from alcohols and pyrroles has been reported to proceed with concentrated anhydrous tetrabutylammonium fluoride solutions.7,8 We have found that reaction of SEM-imidazoles with 1 M tetrabutylammonium fluoride solutions at reflux resulted in good yields of the deprotected imidazoles.…”

“…"Yield after distillation. 6Compounds 1, 2, [4][5][6][7] gave satisfactory analytical data (±0.4%; C, , N). Compound 3 Anal.…”