Acetic Acid → rac-ethyl (1R,2R)-1-amino-2-ethylcyclopropane-1-carboxylate

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Reaction Steps

(1R,2S)-1-tert-Butoxycarbonylamino-2-vinyl-cyclopropanecarboxylic acid ethyl ester (400 mg, 1.57 mmol) was dissolved in methanol (5 ml) and added to a suspension of azodicarboxylic acid dipotassium salt (1.46 g, 7.5 mmol; cf. D. J. Pasto et al., Organic Reactions 40 (1991), 91-155) in methanol (10 ml). Acetic acid (1.12 g, 18.8 mmol) was added in the course of 10 min and the mixture was stirred for 1 h at room temperature. Azodicarboxylic acid dipotassium salt (1.46 g) and acetic acid (1.12 g) were added once again and the mixture stirred for 1 h. LC/MS analysis then indicated complete conversion. The volatiles were evaporated, the residue was partitioned between EA and a saturated sodium hydrogencarbonate solution, and the combined organic extracts were dried over sodium chloride, decanted over a small plug of silica gel and evaporated to dryness. The obtained intermediate was dissolved in a mixture of DCM (5 ml) and TFA (1 ml) and stirred for 1 h at room temperature. The volatiles were evaporated, and the residue was partitioned between diethyl ether and saturated sodium hydrogencarbonate solution. The combined organic extracts were dried over sodium chloride, decanted and evaporated to dryness to yield the title compound.

Provenance & Evidence