Sulfuric Acid → (3aR,4E,7aS)-4-(bromomethylene)-3a,4,5,6,7,7a-hexahydro-7a-methyl-3H-indene-1-carbaldehyde

Participants

Reaction Conditions

Reaction Steps

The crude product of N-[(1Z)-{(E,3aS,7aR)-7-(bromomethylene)-octahydro-3a-methyl-2-oxoindene-3-ylidene}methyl]-N-phenethylacetamide (Compound 28) (178 mg, 0.428 mmol) was dissolved in methanol (2 ml), and sodium borohydride (20 mg, 0.529 mmol) was added thereto at 0° C. After stirring the resulting mixture for 10 minutes, the solvent was removed by evaporator. The residue was dissolved in ethyl acetate, and the resulting mixture was passed through a small amount of silica gel to obtain a crude product (154 mg). The obtained crude product (146 mg, 0.349 mmol) was dissolved in tetrahydrofuran (2 ml), and 2 N sulfuric acid (0.5 ml) was added thereto. The resulting mixture was heated to 70° C. and stirred for 4.5 hours. After cooling, the reaction solution was diluted with diethyl ether, and water was added thereto. The resulting mixture was extracted with diethyl ether. The combined organic layer was washed with saturated aqueous sodium hydrogen carbonate and with saturated brine, dried over magnesium sulfate, and evaporated under reduced pressure to obtain a crude product (140 mg). The crude product was purified by flash column chromatography to obtain (3aR,4E,7aS)-4-(bromomethylene)-3a,4,5,6,7,7a-hexahydro-7a-methyl-3H-indene-1-carbaldehyde (84 mg, 94%).

Provenance & Evidence