Tert-Butyl nitrite → 9-Isopropylidene-5-nitro-1,4-dihydro-1,4-methano-naphthalene

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A solution containing 6-nitroanthranilic acid (3) (19.65 g, 0.108 mol) and commercially available 6,6-dimethylfulvene (4) (17.2 g, 0.162 mol) in dimethoxyethane (DME, 125 mL) was added dropwise over 50 min to a stirred, 70° C. solution of tert-butylnitrite (90%, 17.3 g, 0.151 mol) in DME (350 mL). The mixture was stirred for 1 h and was cooled to room temperature. The reaction mixture was evaporated to yield a crude thick black oil which was directly subjected to silica gel chromatography eluting with ethyl acetate in petroleum ether (0-5% gradient) to afford 10 g of the crude product as a yellow oil, which partially crystallized on standing. Recrystallization from heptane gave the title compound (6.5 g, 26.5%) as a pale yellow solid: 1H NMR (300 MHz, DMSO) δ 7.70 (d, 1H), 7.42 (d, 1H), 7.09-7.01 (m, 1H), 7.00-6.92 (m, 2H), 5.33 (bs, 1H), 4.45 (bs, 1H), 1.55 (s, 6H); EIMS m/z 227.

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