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1‐(Methylthiomethyl)benzotriazole

O. Denisko
Published 2003 · Chemistry

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[183164-38-7] C8H9N3S (MW 179.25) InChI = 1S/C8H9N3S/c1-12-6-11-8-5-3-2-4-7(8)9-10-11/h2-5H,6H2,1H3 InChIKey = XIBSFNFXWRFAMG-UHFFFAOYSA-N (bifunctional reagent for the coupling of alkyl halides, or carbonyl compounds, by a CO bridge; methylthiomethylene group donor in the synthesis of methylthiomethyl ketones from aromatic aldehydes; precursor in the synthesis of thioacylsilanes) Physical Data: white plates, mp 60 °C. Solubility: soluble in ether, THF, ethyl acetate, CH2Cl2, CHCl3, and DMSO. Analysis of Reagent Purity: 1H NMR (CDCl3) δ 2.15 (s, 3H), 5.72 (s, 2H), 7.43 (t, J = 8.2 Hz, 1H), 7.55 (t, J = 8.2 Hz, 1H), 7.71 (d, J = 8.2 Hz, 1H), 8.10 (d, J = 8.2 Hz, 1H); 13C NMR (CDCl3) δ 14.7, 50.7, 110.1, 120.0, 124.1, 127.4, 131.8, 146.4. Preparative Methods: can be prepared by Pummerer reaction of benzotriazole, DMSO, and acetic anhydride.1, 2 The product is usually obtained as a mixture of benzotriazol-1-yl (strongly predominates, crystalline) and benzotriazol-2-yl (oil) isomers which, although separable by column chromatography, can be used together in all the reactions discussed below. The major impurity is 1-acetylbenzotriazole; the formation of which could be suppressed dramatically by a slight modification in the procedure,3 which includes slow addition of a concentrated solution of benzotriazole in 2 equiv of DMSO to a warm (80–90 °C) mixture of acetic anhydride with 2 equiv DMSO. (Caution: overheating above 100 °C triggers a vigorous exothermic reaction.) Purification: recommended isolation and purification steps include3 (1) distilling excess Ac2O and DMSO off the reaction mixture under reduced pressure; (2) dissolving the residue in ether or CH2Cl2 and washing off unreacted benzotriazole with an aq Na2CO3 solution; (3) removing the solvent and distillation of the residue under reduced pressure. This last distillation allows for removal of the residual 1-acetylbenzotriazole (bp 96–97 °C/1.5 mm Hg) from a mixture of (methyl thiomethyl)benzotriazole isomers (125–150 °C/1 mm Hg). Handling, Storage, and Precautions: hygroscopic, shelf-stable, foul odor.
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