反应详情

To a mixture of 70.5 mL (262 mmol) tributyltin hydride and 1.08 g (6.55 mmol) 2,2'-azobis(2-methylpropionitrile) (AIBN) in 50 mL of hexane at 80° C. was added a solution of 117 g (131 mmol) crude phenyl-carbamothioic acid O-[(3β)-25-[[(1,1-dimethylethyl)dimethylsilyl]oxy]-3-[[dimethyl(1,1,2-trimethylpropyl)silyl]oxy]cholesta-5,7,16-trien-23-yn-22-yl] ester in 1.5 L of hexane over 45 min. After refluxing for 1 hr, additional tributyltin hydride (35 mL, 131 mmol) and AIBN (1.07 g, 6.52 mmol) were added. After 30 min. of refluxing, the mixture was cooled to room temperature and stirred for 1 hr. The precipitate was filtered, and the filtrate was concentrated. The residue was dissolved in 200 mL of hexane and purified by filtration through 425 g of silica gel. The column was eluted with hexane and then with 20% toluene in hexane. The fractions containing the product were combined and concentrated to give 114 g (overweight) of crude [[(3β)-25-[[(1,1-dimethylethyl)dimethylsilyl]oxy]cholesta-5,7,16-trien-23-yn-3-yl]oxy]dimethyl(1,1,2-trimethylpropyl)silane as a light yellow oil. This crude material was used in the next step. An analytical sample was obtained by chromatographic purification followed by crystallization from ethyl acetate/methanol (1:1): mp 62°-66° C.; Anal Calcd. for C41H70O2Si2 : C, 75.62, H, 10.84; Si, 8.63. Found C, 75.12; H, 10.77; Si, 8.55.

1. temperatureAfter refluxing for 1 hr
2. temperatureAfter 30 min. of refluxing
3. filtrationThe precipitate was filtered
4. concentrationthe filtrate was concentrated
5. dissolutionThe residue was dissolved in 200 mL of hexane
6. filtrationpurified by filtration through 425 g of silica gel
7. washThe column was eluted with hexane
8. additionThe fractions containing the product
9. concentrationconcentrated