1-Bromo-3,4-dichlorobenzene (1.35 g, 5.98 mmol) in THF (10 mL) was added drop-wise to a solution of n-BuLi (1.6 M in hexanes, 4 mL) at −78° C. The mixture was stirred for 40 min at −78° C. A solution of 9-oxo-3-aza-spiro[5.5]undecane-3-carboxylic acid tert-butyl ester (1 g, 3.74 mmol) in THF (10 mL) was added drop-wise and the mixture was stirred for 1 h at −78° C. The reaction was quenched with aqueous ammonium chloride and the aqueous layer was extracted twice with diethyl ether. The combined organic phase was washed with brine dried (sodium sulfate), filtered and evaporated to give 2.2 g of crude material. Precipitation in heptane and diethyl ether gave 547 mg of 9-(3,4-dichloro-phenyl)-9-hydroxy-3-aza-spiro[5.5]undecane-3-carboxylic acid tert-butyl ester. LC-ESI-HRMS of [M+H]+ shows 296.0983 Da. Calc. 296.09728 Da, dev. 3.4 ppm.
