Reaction Steps
Sodium formate (0.075 g, 1.1 mmol) was added to a suspension of 2-amino-4-chloro-6-methyl-10,10-dioxo-10,11-dihydro-5-oxa-10lambda*6*-thia-dibenzo[a,d]cycloheptene-8-carboxylic acid ethyl ester (0.420 g, 1.1 mmol) [prepared by hydrolysis of compound of Example 1 and followed by esterification with ethanol/H2SO4] in formic acid (25 mL) and refluxed for 1.5 h. The reaction mixture was cooled and poured into ice water (100 mL). The solid precipitated was filtered, washed with water and dried. The crude product was purified by column chromatography (silica gel, 1% methanol in chloroform) to obtain the title compound. Yield: 0.21 g (47%); mp 202-204° C.; 1H NMR (DMSO-d6, 300 MHz): δ 1.31 (t, 3H, OCH2CH3), 2.64 (s, 3H, CH3), 4.31 (q, 2H, OCH2CH3), 5.25 (s, 2H, CH2, trans minor isomer), 5.33 (s, 2H, CH2, cis major isomer), 7.34 (d, 1H, Ar, trans minor isomer), 7.50 (d, 1H, Ar, trans minor isomer), 7.69 (d, 1H, Ar, cis major isomer), 7.86 (d, 1H, Ar, cis major isomer), 8.10 (s, 1H, Ar), 8.15 (s, 1H, Ar), 8.31 (s, 1H, CHO, cis major isomer), 8.80 (d, 1H, CHO, trans minor isomer), 10.43 (d, 1H, NH, trans minor isomer), 10.57 (s, 1H, NH, cis major isomer); MS: m/e (ES−) 408 (M−1); analysis: C18H16ClNO6S requires C, 52.75; H, 3.93; N, 3.42; Cl, 8.65; S, 7.82. found: C, 52.47; H, 3.86; N, 3.36; Cl, 8.81; S, 7.67%.
