To a suspension of 1h (210 mg, 0.59 mmol) in 10 mL ethanol was added an aqueous solution (2 mL) of hydroxylamine hydrochloride (127 mg, 1.83 mmol). Then 2 mL 1 N NaOH was added dropwise to the reaction mixture and the mixture was stirred at 55° C. for 3 h. After completion of the reaction, the residue was absorbed on silica gel and purified by column chromatography to give compounds 2e-cis (85 mg) and 2e-trans (50 mg). 1H NMR (300 MHz, DMSO-d6) δ 11.95 (s, 1H), 8.35 (s, 1H), 7.91-7.89 (m, 2H), 7.50-7.44 (br, 3H), 6.85 (s, 2H), 3.73 (s, 6H), 3.70 (s, 3H). MS (ESI) m/z 393.1 (M+Na)+; 368.9 (M−H)−.
