Hydrochloric Acid → methyl 5-oxo-6,7,8,9-tetrahydro-5H-benzo[7]annulene-6-carboxylate

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Reaction Conditions

Reaction Steps

A mixture of benzosuberone (8 g, 50 mmol) and neat dimethyl carbonate (45 mL) at ambient temperature under N2 was treated with NaH (60% in mineral oil, 4 g, 100 mmol) in 0.1 mL of dry MeOH, heated at 80° C. for 3 hours, cooled to ambient temperature, treated with 2 N HCl (55 mL) and extracted with ethyl acetate. The organic layer was washed with brine, dried (MgSO4) and concentrated to provide the title compound as an oil, as a 3:1 mixture of enol and keto forms of product by NMR spectroscopy. The NMR of the main enol form was: 1H NMR (CDCl3) δ 2.03-2.16 (m, 4H), 2.64 (m, 2H), 3.82 (s, 3H), 7.23 (m, 1H), 7.33 (m, 2H), 7.62 (m, 1H), 12.6 (bs, 1H). MS (M+H)+ m/z 219.

Provenance & Evidence