Hydrochloric Acid → ethyl (1S,2R)-1-amino-2-vinyl-cyclopropanecarboxylate;hydrochloride

Participants

Reaction Conditions

Reaction Steps

To a solution of potassium tert-butoxide (11.55 g, 102.9 mmol) in THF (450 mL) at −78° C. was added the commercially available N,N-dibenzyl imine of glycine ethyl ester (25.0 g, 93.53 mmol) in THF (112 mL). The reaction mixture was warmed to 0° C., stirred for 40 min, and was then cooled back to −78° C. To this solution was added trans-1,4-dibromo-2-butene (20.0 g, 93.50 mmol), the mixture stirred for 1 h at 0° C. and was cooled back to −78° C. Potassium tert-butoxide (11.55 g, 102.9 mmol) was added, the mixture immediately warmed to 0° C., and was stirred one more hour before concentrating in vacuo. The crude product was taken up in Et2O (530 mL), 1N aq. HCl solution (106 mL, 106 mmol) added and the resulting biphasic mixture stirred for 3.5 h at rt. The layers were separated and the aqueous layer was washed with Et2O (2×) and basified with a saturated aq. NaHCO3 solution. The desired amine was extracted with Et2O (3×) and the combined organic extract was washed with brine, dried (MgSO4), and concentrated in vacuo to obtain the free amine. This material was treated with a 4N HCl solution in dioxane (100 mL, 400 mmol) and concentrated to afford (1R,2S)/(1S,2R)-1-amino-2-vinylcyclopropane carboxylic acid ethyl ester hydrochloride as a brown semisolid (5.3 g, 34% yield) identical to the material obtained from procedure A, except for the presence of a small unidentified aromatic impurity (8%).

Provenance & Evidence