Hydrochloric Acid → (RS)-[3-(tert-butyl-diphenyl-silanyloxy)-2,6-difluoro-phenyl]-hydroxy-acetic acid ethyl ester

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A solution under Ar of tert-butyl-(2,4-difluoro-phenoxy)-diphenyl-silane (102 g) and 1,1,4,7,7-pentamethyldiethylenetriamine (50.6 g) in DME (800 ml) was cooled to −70° C. before addition of 1.6 N n-BuLi in hexane (182 ml) over a period of 1 h. The yellow solution was stirred 1 h at −70° C. 50% glyoxalic acid ethylester in toluene (113 g) was added over a period of 1 h. The reaction mixture was stirred 2 h more at −70° C. before heating up over 1 h to 0° C. Sat. NH4 sol. (300 ml) was added and the pH was lowered to pH=6 with 2 N HCl. The product was extracted with AcOEt (2×400 ml). The organic layers were washed with brine (500 ml) and dried (Na2SO4) and the solvent was evaporated. CC (Hept to Hept/AcOEt 9:1) afforded 70.8 g (54%) of (RS)-[3-(tert-butyl-diphenyl-silanyloxy)-2,6-difluoro-phenyl]-hydroxy-acetic acid ethyl ester. Yellowish oil. MS 488.5 ([M+H]+).

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