Bromoform → Methyl 1,1-dibromo-5-(2,2-dimethylpropionylamino)-1,1a,2,7b-tetrahydrocyclopropa[c]chromene-4-carboxylate

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Reaction Conditions

Reaction Steps

Methyl 7-(2,2-dimethylpropionylamino)-2H-chromene-8-carboxylate (Intermediate 45, 2.372 g) and benzyl triethyl ammonium chloride (0.373 g) were suspended in bromoform (6.45 mL) and aqueous sodium hydroxide solution (50%, 3.64 mL) was added dropwise. The resultant black suspension was heated to 60° C. for 2 hours. After cooling, the mixture was partitioned between water and ethyl acetate. The emulsion formed was filtered through a pad of Celite and the organic layer was decanted off. The aqueous was re-extracted with ethyl acetate and the combined organic layers were dried (MgSO4) and filtered. The filtrate was concentrated in vacuo and the residue was purified by chromatography on silica, eluting with a mixture of ethyl acetate and cyclohexane, with a gradient of 2.5-15% to give methyl 1,1-dibromo-5-(2,2-dimethylpropionylamino)-1,1a,2,7b-tetrahydrocyclopropa[c]chromene-4-carboxylate (1.557 g) as an off-white solid.

Provenance & Evidence