Nitric Acid → 6-Nitro-2,3-dihydro-1H-indene-1-carboxylic acid

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Reaction Steps

A solution of 1-indancarboxylic acid (30 g), prepared according to the method of Hansen et al. Helv. Chim. Acta 1982, 33, 325-343, in dichloromethane (50 ml) was mixed with concentrated sulphuric acid (300 ml) at −10° C. A mixture of 100% HNO3 (11.4 g) in concentrated H2SO4 (96 ml) was added dropwise under vigorous stirring below −10° C. After stirring for one hour at 10° C., the mixture was poured onto ice. Extraction with ethyl acetate (2×300 ml), drying (anh. MgSO4) and finally evaporation of the organic solvent afforded 42 g of the title compound. Mp: 126-130° C. 5-Nitro-3-benzothiophencarboxylic acid was prepared from 3-bromo-5-nitrobenzothiophene via the corresponding 3-cyanobenzothiophene derivative according to EP Pat. No. 88-301073 (CA110(9):75203y (1988), J. Amer. Chem. Soc. 1948, 70, 1955, and J. Chem. Soc.(c) 1967, 1899.

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