1-Pentyne, 5-chloro- → (+/-)-2-(2-Amino-5-chloro-3-(t-butyldimethylsilyloxy)phenyl)-4-cyclopropyl-1,1,1-trifluoro-3-butyn-2-ol

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Reaction Steps

To a stirred, cooled (0° C.) solution of 31.8 mL (300 mmol) of 5-chloro-1-pentyne in 250 mL of THF was added 252 mL (630 mmol) of 2.5M n-BuLi in hexanes over 20 min. Over the course of the addition the internal temperature had warmed to ambient temperature, and the mixture was stirred at this temperature for 40 min. The reaction was cooled to -20° C. and treated with a solution of 32.7 g (97.4 mmol) of 2'-amino-5'-chloro-3'-(t-butyldimethylsilyloxy)-2,2,2-trifluoroacetophenone in 50 mL of THF over 10 min. The dark solution was stirred an additional 30 min. and the cold bath was removed. The reaction was stirred 5 min and poured into 800 mL of 0° C. 1N citric acid with rapid stirring. The mixture was extracted twice with ether, and the combined organic extracts were washed with water then brine, dried (MgSO4), and concentrated under reduced pressure. Chromatography on silica gel (elution with hexanes then 3:1 hexanes-ether) afforded 28.8 g (70%) of (±)-2-(2-amino-5-chloro-3-(t-butyldimethylsilyloxy)phenyl)-4-cyclopropyl-1,1,1-trifluoro-3-butyn-2-ol as an off-white solid, mp 125°-126° C. 1H NMR (300 MHz, CDCl3) δ7.22(d, 1H, J=2.2 Hz); 6.76(d, 1H, J=2.2 Hz); 4.86(br. s, 1H); 4.39(br. s, 2H); 1.32-1.43(m, 1H); 1.02(s, 9H); 0.79-0.92(m, 4H); 0.27(s, 3H); 0.26(s, 3H). High resolution mass spec: calculated for C19H26NO2ClF3Si(M+H)+ : 420.1373, found: 420.1363.

Provenance & Evidence