(S)-(-)-2,2'-Bis(di-p-tolylphosphino)-1, 1'-binaphthyl → 5-nitro-3-phenylsulfanyl-1-(2-trimethylsilanylethoxymethyl)-1H-indazole

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5-Nitro-3-phenylsulfanyl-1-(2-trimethylsilanylethoxymethyl)-1H-indazole can be obtained in the following way: 2 g of 3-iodo-5-nitro-1-(2-trimethylsilanylethoxymethyl)-1H-indazole and then 0.88 g of sodium thiophenate are added to a solution, under argon, of 0.11 g of palladium acetate, of 0.36 g of (R)-(+)-2,2′-bis(di-p-tolylphosphino)-1,1′-binaphthyl and of 0.64 g of sodium tert-butoxide in 40 ml of toluene. The reaction mixture is heated at a temperature in the region of 80° C. for 21 hours, and is then cooled to a temperature in the region of 20° C. After dilution with 100 ml of ethyl acetate and 80 ml of water and then settling out, the aqueous phase is extracted with 100 ml of ethyl acetate. The organic extracts are pooled, washed with 60 ml of a saturated aqueous sodium chloride solution, dried over magnesium sulfate, filtered and then concentrated to dryness under reduced pressure (2 kPa) at a temperature in the region of 25° C. The residue thus obtained is filtered through silica (particle size 15-35 μm), eluting with pure dichloromethane. The filtrate is concentrated to dryness under reduced pressure (2 kPa) at a temperature in the region of 20° C. The residue is purified by chromatography under argon pressure (50 kPa), on a column of 80 g of silica (particle size 40-63 μm), eluting successively with pure cyclohexane then with cyclohexane/ethyl acetate (95/5; 90/10 by volume) mixtures. The fractions containing the expected product are pooled and concentrated to dryness under reduced pressure (2 kPa) at a temperature in the region of 25° C. 1.08 g of 5-nitro-3-phenylsulfanyl-1-(2-trimethylsilanylethoxymethyl)-1H-indazole are thus obtained in the form of an orange oil (Rf=0.35, silica gel thin layer chromatography, eluent: cyclohexane/ethyl acetate (80/20 by volume)).

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