At RT, 2.61 g of rac-tert-butyl [2-(4-chlorophenyl)-2-hydroxyethyl]carbamate (Example 45A, 9.62 mmol), 1.42 g of phthalimide (9.62 mmol) and 3.78 g of triphenylphosphine (14.43 mmol) were initially charged in abs. THF. 4.03 g (14.43 mmol) of diisopropyl azodicarboxylate were then added dropwise, and the mixture was stirred at RT for 30 min. The reaction mixture was concentrated and purified by silica gel chromatography (mobile phase: cyclohexane:ethyl acetate 10:1). This gave 2.92 g of the title compound (55% of theory, purity about 73%).
