Acetic Anhydride → 6-Nitro-isochroman-1,3-dione

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Reaction Steps

A mixture of 2 carboxymethyl-4-nitro-benzoic acid (13 g, 57.7 mmol), acetic anhydride (5.45 mL, 57.7 mmol) and toluene (30 mL) were heated to reflux for 5 hrs. The solvent was removed under vacuum to yield 6-nitro-isochroman-1,3-dione (compound (3a) in Scheme 2) as a yellow solid (10.51 g, 88%). Borane tetrahydrofuran complex (35.6 mL, 1M in THF) was added dropwise over 40 min to a solution of 6nitro-isochroman-1,3-dione (2 g, 9.66 mmol) in THF (40 mL) at 0° C. The contents were stirred for 18 hrs at 25° C., cooled to 0° C., quenched with methanol (30 mL), and stirred for 1 hr. The solvents were removed under vacuum, ethyl acetate (30 mL) added and the organic phase washed with 10% aqueous hydrochloric acid. The aqueous acidic layer was reextracted with ethyl acetate (30 mL), the combined organic layers dried with magnesium sulfate, and evaporated under vacuum until 2 mL of ethyl acetate remained. This solution was filtered through silica gel washing with methylene chloride (30 mL) to remove impurities. The silica gel was flushed with ethyl acetate, solvent removed under vacuum to give a solid which was slurryed in methylene chloride and filtered to afford the diol as a white solid, 1.38 g, 73%.

Provenance & Evidence