Carbon tetrabromide → methyl 7-[bis-(tert-butoxycarbonyl)amino]-4H-furo[2,3-c]-chromene-6-carboxylate

Participants

Reaction Steps

Carbon tetrabromide (2.66 g) was added to a solution of methyl 6-[bis-(tert-butoxycarbonyl)amino]-2-hydroxy-3-(2-hydroxymethylfuran-3-yl)-benzoate (Intermediate 4, 2.65 g) and triphenyl phosphine (2.1 g) in DCM (40 mL) and the resultant solution was stirred at room temperature for 1 hour. The mixture was evaporated to dryness and DMF (60 mL) and cesium carbonate (5.59 g) were added to the residue. The resultant mixture was stirred for 1 hour, then partitioned between ethyl acetate and water. The organic layer was separated, 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 cyclohexane with a gradient of 5-25% to give methyl 7-[bis-(tert-butoxycarbonyl)amino]-4H-furo[2,3-c]-chromene-6-carboxylate (0.735 g) as a gum which crystallised on standing.

Provenance & Evidence