Methyl chloroformate → methyl (1aRS,7bSR)-5-[N-(2-bromo-4-fluorobenzenesulfonyl)-N-(methoxycarbonyl)amino]-1,1a,2,7b-tetrahydrocyclopropa-[c]chromene-4-carboxylate

Participants

Reaction Steps

A solution of methyl (1aRS,7bSR)-5-(2-bromo-4-fluorobenzenesulfonylamino)-1,1a,2,7b-tetrahydrocyclopropa[c]chromene-4-carboxylate (Intermediate 41, 1.7 g) in THF (20 mL) was added to a suspension of sodium hydride (70% oil dispersion, 0.2 g) in THF (10 mL). The resultant solution was stirred for 30 minutes then methyl chloroformate (0.53 g) was added. The resultant mixture was stirred at room temperature overnight. Saturated aqueous sodium bicarbonate was added and the mixture was extracted with ethyl acetate, dried (Na2SO4) and filtered. The filtrate was evaporated to dryness and the residue was purified by chromatography on silica, eluting with a mixture of ethyl acetate and petroleum ether (30%) to give methyl (1aRS,7bSR)-5-[N-(2-bromo-4-fluorobenzenesulfonyl)-N-(methoxycarbonyl)amino]-1,1a,2,7b-tetrahydrocyclopropa-[c]chromene-4-carboxylate (1.6 g) as a white solid.

Provenance & Evidence