1,2-Bis(phenylsulfinyl)ethane

Abstract

[6099-21-4/21461-90-5] C14H14O2S2 (MW 278.38) InChI = 1S/C14H14O2S2/c15-17(13-7-3-1-4-8-13)11-12-18(16)14-9-5-2-6-10-14/h1-10H,11-12H2 InChIKey = CSZMCUCIIIAHQD-UHFFFAOYSA-N InChI = 1S/C14H14O2S2/c15-17(13-7-3-1-4-8-13)11-12-18(16)14-9-5-2-6-10-14/h1-10H,11-12H2 InChIKey = CSZMCUCIIIAHQD-UHFFFAOYSA-N (allylic CH oxidation; allylic CH amination; CH to CO bond formation; CH to CN bond formation; macrolactonization; heterobimetallic catalysis; 3-component coupling; oxidative Heck-arylation; streamlining synthesis; serial ligand catalysis) Physical Data: meso: mp = 155 °C; racemic: mp = 116 °C. Solubility: soluble in a wide range of common organic solvents including dioxane, THF, methylene chloride, acetone, ethanol, nitromethane, toluene, DMSO, DMF, ethyl acetate, TBME, and diethyl ether. Form Supplied in: white powder/white crystals. Typical impurities are the mono-sulfide and the mono-sulfone that result from under or over oxidation of the disulfide (respectively). Anylysis of Reagent Purity: Meso-1,2-bis(phenylsulfinyl)ethane: 1H NMR (500 MHz, CDCl3) δ 7.56–7.52 (m, 10H), 3.05 (s, 4H). 13C NMR (500 MHz, CDCl3) δ 142.29, 131.55, 129.63, 124.10, 47.06. IR (neat) 3048.84, 2970.01, 2922.41, 1442.10, 1036.34, 745.45, 695.70 cm−1; racemic-1,2-bis(phenylsulfinyl)ethane: 1H NMR (500 MHz, CDCl3) δ 7.51–7.48 (m, 10H), 3.40 (m, 2H), 2.74 (m, 2H). 13C NMR (125 MHz, CDCl3) δ 142.55, 131.53, 129.64, 124.08, 47.94. IR (neat, cm−1) 3053.16, 2911.39, 1443.77, 1084.88, 1042.50, 748.52. HRMS (ESI) m/z calculated for C14H14O2S2Na [M + Na]+: 301.0333, found 301.0320. Preparative Methods: a 50-mL round bottomed flask (RBF) was charged with a stir bar, 2 g (8.12 mmol, 1 equiv) of 1,2-bis(phenylthio)ethane, and 12.2 mL of acetic acid. A solution of H2O2 (50 wt%, 16.24 mmol, 1.0 mL, 2 equiv) in acetic acid (6.7 mL) was added dropwise at room temperature with rapid stirring. After approximately 15 min the heterogeneous solution became homogeneous and turned a pale yellow. An additional 8 mL of acetic acid was then added and the solution was allowed to stir for 24 h at room temperature. The acetic acid was removed with mild heating (45 °C) under high vacuum to yield the meso-and racemic-1,2-bis(phenylsulfinyl)ethane as a pale yellow solid in 92% yield (2.088 g). Scalable to >20 g Purification: (1) The pale yellow solid may be emulsified in cold ethanol and cold filtered to remove acetic acid and yield a white powder mixture of meso and racemic isomers. (2) Recrystallization may be performed by dissolving the solid in minimal refluxing acetone. The solution is cooled to room temperature, followed by placement in a −20 °C freezer. The meso isomer crystallizes first as small white clumps; followed by the racemic isomer as long white needles. Multiple crops are often taken by concentrating the mother liquor and repeating the above procedure. This method efficiently separates the meso and racemic isomers. (3) Silica gel flash column chromatography may be performed as described by Still et al.1 using EM reagent silica gel 60 (230–240 mesh) and 3% MeOH:CH2Cl2 (∼0.4 Rf by TLC). Column chromatography is effective in separating under/overoxidized side products; however, meso/racemic isomers are inseparable via column chromatography. Handling, Storage, and Precautions: stored under ambient conditions with no decomposition observed for >3 years.