Chromocarb → 3,4-dihydro-2H-1-benzopyran-2-carboxylic acid

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Reaction Steps

A mixture of the compound from Example 8 (20.0 g, 105 mmol), and 10% palladium on activated carbon (2.0 g) in acetic acid (200 mL) was placed under hydrogen pressure (60 psig) in a Parr hydrogenation apparatus. After 22.5 hours the mixture was removed from the hydrogen atmosphere and filtered through a pad of Celite. The Celite pad was washed with ethyl acetate (800 mL), and the combined filtrate concentrated to give a brown oil. The oil was dissolved in ethyl acetate (500 mL) and extracted with saturated NaHCO3 (4×125 mL). The aqueous phase was acidified to pH=2 with concentrated HCl and extracted with ethyl acetate (4×100 mL). The combined organic phase was washed with saturated aqueous sodium chloride solution (100 mL), dried (MgSO4), and concentrated to give a colorless solid (18.0 g, 96%). Mp 97.5-99° C.; 1H NMR (300 MHz, DMSO-d6) δ12.96 (br s, 1H), 7.03 (m, 2H), 6.78 (m, 2H), 4.74 (dd, J=6.4 Hz, J=3.9 Hz, 1H), 2.73 (m, 1H), 2.63 (m, 1H), 2.03 (m, 2H).

Provenance & Evidence