Thiophenols, chromatography

The gas-liquid chromatography with mass spectrometric detection (GLC-MS) analysis of the electrolyzed solution has shown that thiophenol is the only reduction product and the S—S bond cleavage is quantitative. Such a mechanism of bond breaking was confirmed by electrochemical studies. In cyclic voltammograms, anodic and cathodic peak potentials were the same for thiophenol and diphenyl disulfides thus the same species were participating in these processes. Electrode reactions of diphenyl disulfide are given by the following equations [166] ... 

Oxidation with p-phenoxyphenyltellurinic anhydride diphenyl disulphide (typical procedure) Thiophenol (0.215 g, 2 mmol) is added to a stirred solution of the anhydride (0.210 g, 0.33 mmol) in HOAc (2 ml,) under argon. The mixture is stirred for 1 h at room temperature. After evaporation under vacuum, the residue is extracted with CHjClj. The organic phase is washed with H2O, 5% aqueous Na2C03 and HjO. SiOj column chromatography yields diphenyl disulphide (0.154 g (86%)) as colourless crystals (from CH2Cl2/EtOH) (m.p. 58-60°C) and the ditelluride (0.167 g (83%)) as purple crystals (from CH2Cl2/EtOH) (m.p. 93-95°C). 

A solution of 0.55 g (5.0 mmol) of thiophenol in 3 mL of hexane is added at 25 CC to 5 ml. (5.0 mmol) of 1.0 M triethylaluminum in hexane, and the mixture is stirred at this temperature for 20 min. After addition of 5mL of 1,2-dichloroethane. a solution of 2.0 mmol of allyl vinyl ethyl ether substrate in 3 mL of 1,2-dichlorocthane is added to the aluminum reagent at 25 C. and the mixture stirred for the appropriate lime. The mixture is diluted with 20 mL of Et2() and poured into 1 M HCI. The organic layer is separated, combined with three additional extracts of the aqueous layer, and washed with two 20-mL portions of brine. The ethereal layer is dried over anhyd Na,SO, and concentrated. The crude product is purified by column chromatography or preparative TLC (hexane/EtOAc). 

General procedure for preparation of 2-amino-4-(phenylthio)-4//-chromene-3-carbonitrile 6 In an oven-dried screw cap test tube, a mixture of sahcyhc aldehyde 1 (1 mmol), malononitrile 2 (1 mmol), thiophenol 5 (1 mmol) and sodium formate (10 mol%) was stirred with 4 mL of ethanol at room temperature for 2-3 h. On completion of the reaction as monitored by TLC, the product was precipitated out and filtered the filtrate was preserved for reuse. The crude residue was subjected to column chromatography using silica gel (60-120 mesh) and petrol ether-ethyl acetate mixture to obtain pure product 6, characterized by analytical and conventional spectroscopic methods. 

Typical thiophenol workup Iodine monochloride (l.OM in DCM, 1.3 equiv) is added dropwise to a solution of the MOM or BOM protected homoaUyhc alcohol (1 equiv) in toluene (0.01 M) at 78 °C. After 10 minutes, Et3N (3 equiv) is added in one shot followed by thiophenol (1.4 equiv). The reaction is warmed to room temperature, stirred for 2 hours, and quenched with a halfhalf mixture of saturated NaHC03 and Na2S203. After extraction, the concentrated crude material is purified by column chromatography on silica gel to provide 68. 

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