Methanol → 9-Chloromethyl-7-oxo-2,3,6,7-tetrahydro[1,4]dioxino[2,3-g]quinoline-8-carboxylic acid methyl ester

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Reaction Conditions

Reaction Steps

A 4-necked 12-L round-bottom flask is equipped with a mechanical stirrer and 500-mL addition funnel. Under nitrogen, the flask is charged with 1-(7-amino-2,3-dihydro-benzo[1,4]dioxin-6-yl)-2-chloro-ethanone (Intermediate 4, 595 g, 2.61 mol), triethylamine (474 mL, 3.40 mol), and anhydrous acetonitrile (3.5 L). The solution is cooled to 0° C., then methyl malonyl chloride (364 mL, 3.40 mol) is added over 35 min. The cooling bath is removed and the mixture is stirred for 5 h. To the resultant slurry is added 25% sodium methoxide in methanol (596 mL, 2.61 mol) over 10 min. After being stirred at ambient temperature for 2 h, the now very thick yellow slurry is diluted with water (3 L). The precipitate is collected on a Buchner funnel and washed with water (3 L). The yellow solid is dried in vacuo. at 60° C. yielding 9-chloromethyl-7-oxo-2,3,6,7-tetrahydro[1,4]dioxino[2,3-g]quinoline-8-carboxylic acid methyl ester as a yellow solid. This crude product is used for the next step without further purification. Recrystallization from MeOH-DMSO (1:1) gave an analytical sample: mp>300° C. (dec.). 1H NMR (DMSO-d6, 400 MHz) d 3.85 (s, 3H), 4.32 (s, 2H), 4.36. (s, 2H), 4.83 (s, 2H), 6.83 (s, 1H), 7.40 (s, 2H), 12.0 (s, 1H). Elemental analysis: Calculated for C10H10ClNO3: C, 54.29; H, 3.91; N, 4.52. Found: C, 53.68; H, 3.84; N, 4.48. HRMS (EI+): Calculated for C10H10ClNO3: 309.0404. Found: 309.0405.

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