Dimethyl-l,2-ethanediyl bis methanesulfonate

The white crystalline solid product is pure enough for the next step, but an analytical sample is recrystallized as follows. A sample (0.45 g) is dissolved in dry dichloromethane (5 mL) and the solution is filtered through a 2-mL glass filter with 25- to 50-p porosity. The solution is then diluted with methanol (3 mL) and the dichloromethane is carefully distilled off on a steam bath. Crystallization begins almost immediately on cooling. After 2 h at room temperature, the mixture is placed in the freezer ( — 25°C) for 15 h. The mixture is filtered through a 2-mL glass filter with 25- to 50-p porosity and the white crystalline solid is washed with three 5-mL portions of methanol 

The simplest and the least technically demanding method of isolating S,S-CHIRAPHOS from the reaction mixture is by the formation of its very insoluble bis(thiocyanato-N)nickel(II) complex. The nickel selectively separates the S.S-CHIRAPHOS from other phosphine species in the reaction mixture. 

A one-necked, 1000-mL, round-bottomed flask (not under argon) is equipped with a Teflon-coated magnetic stirring bar and is charged with nickel acetate tetrahydrate (11.12 g, 44.7 mmol) and sodium thiocyanate (14.48 g, 178.6 mmol). To the solids is added warm (50°C) 95% ethanol (250 mL). The mixture is stirred until all of the solids have dissolved to give a green solution. 

The organic layer obtained from the phosphide reaction still under argon is rapidly transferred by cannula into the stirred-nickel(II) solution. A yellow-brown precipitate forms immediately. The aqueous layer from the phosphide reaction, still in the reaction flask under argon, is extracted with three successive 50-mL portions of diethyl ether added via syringe, and the diethyl ether extracts are transferred by cannula into the nickel(II) mixture. The stirring of the mixture is continued for about 5 min and then it is filtered through a 170-mL glass filter with 25- to 50-// porosity and washed sequentially with two 60-mL portions of 95% ethanol and three 60-mL portions of pentane. The air-stable yellow-brown precipitate is then sucked dry on the frit. 

---