4-Methylmorpholine → (S)-tert-butyl 1-cyclohexyl-4-diazo-3-oxobutan-2-ylcarbamate

Participants

Reaction Conditions

Reaction Steps

To a solution of (S)-2-(tert-butoxycarbonylamino)-3-cyclohexylpropanoic acid (37 g, 0.136 mmol) in anhydrous THF (300 mL) cooled to −20° C. was added dropwise N-methylmorpholine (16.6 mL, 0.15 mmol), followed by isobutyl chloroformate (20 mL, 0.15 mmol) and the reaction mixture was stirred at −20° C. for 30 min. The mixture was warmed to 0° C., and an etheral solution of CH2N2 (0.8 mol) was added. Stirring was continued overnight at rt. Excess diazomethane was decomposed by addition of acetic acid. The mixture was diluted with ether, washed with brine, satd aq NaHCO3 and brine to give a solution of crude (S)-tert-butyl 1-cyclohexyl-4-diazo-3-oxobutan-2-ylcarbamate (48 g, 100%), which was used without isolation.

Provenance & Evidence