1-(4-Chlorobenzoyl)piperazine → 3-[4-(4-Chloro-benzoyl)-piperazin-1-yl]4-hydroxy-pyrrolidine-1-carboxylic acid tert-butyl ester

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Reaction Steps

This is an example of Procedure B in Scheme 1 above. 6-Oxa-3-aza-bicyclo[3.1.0]hexane-3-carboxylic acid tert-butyl ester (0.5 g 1 eq) and (4-Chloro-phenyl)-piperazin-1-yl-methanone (0.6 g 1 eq) were dissolved in CH3CN (5 mL). Ca(OTf)2 (0.456 g, 0.5 eq) was added into the mixture. Reaction mixture was stirred at RT for overnight, then 80-85° C. for 8 h. After concentrating and adding EtOAc 20 mL to the residue, the organic phase was washed with H2O, dried over Na2SO4. The resulting oil was purified by column chromatography (EtOAc:MeOH:Et3N 10:1:0.01) to give 1.01 g of desired product as a sticky oil (92% yield). * It is important to note that during workup, the organic phase should be washed with H2O and saturated NaCl solution, not saturated NaHCO3 solution.

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