Boron trifluoride etherate → 1-Tert-butyl 4-ethyl 3-oxoazepane-1,4-dicarboxylate

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Reaction Steps

To a 0° C. solution of 3-oxo-piperidine-1-carboxylic acid tert-butyl ester (11.3 g, 56.7 mmol) in Et2O (170 mL) was added BF3.Et2O (7.2 mL, 56.7 mmol) and ethyl diazoacetate (7.2 mL, 68.0 mmol) dropwise over 30 min. After an additional 1 h, satd. aq. NaHCO3 was added and the solution was stirred for 1 h, then was extracted with Et2O (2×). The combined organic layers were washed with brine, dried and concentrated. The resulting residue was purified via SiO2 chromatography (10-30% EtOAc/hexanes) to give 5.48 g (34%) of 3-oxo-azepane-1,4-dicarboxylic acid 1-tert-butyl ester 4-ethyl ester. In addition, 5.25 g (32%) of the more polar 4-oxo-azepane-1,3-dicarboxylic acid 1-tert-butyl ester 3-ethyl ester was isolated.

Provenance & Evidence