Isopropenyl chloroformate → Prop-1-en-2-yl (1-methylcyclopropanecarbonyl)carbamate

A −78° C. solution of 1-methylcyclopropanecarboxamide (1.35 g, 13.62 mmol) in THF (30 mL) was treated drop-wise with lithium bis(trimethylsilyl)amide (1 M THF, 17.7 mL, 17.7 mmol), stirred for 0.5 h, treated drop-wise with a solution of isopropenyl chloroformate (1.94 mL, 17.7 mmol) in THF (5 mL), stirred at −78° C. for 1 h, then allowed to warm to RT and stirred for 1 h. The mixture was quenched with satd. NaHCO3, extracted with EtOAc (3×) and the combined organics were dried over Na2SO4 and concentrated to dryness to afford crude prop-1-en-2-yl (1-methylcyclopropanecarbonyl)carbamate (2.9 g, 116%) which was used without further purification.