Ethanol → Dioxino[2,3-g]quinoline-8-carboxylic acid methyl ester hydrobromic acid salt

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Reaction Steps

To a mixture of 9-chloromethyl-7-oxo-2,3,6,7-tetrahydro[1,4]dioxino[2,3-g]quinoline-8-carboxylic acid methyl ester (Intermediate 5, 25 g), in 1,2-dichloroethane (DCE, 90 mL) is added a solution of phosphorus oxybromide (44 g, 2 eq) in DCE (90 mL). The resultant mixture is heated at reflux for 4.0 h, and then cooled to <15° C. Ethanol (91 mL, 20.0 eq) is added while keeping the temp <20° C. The mixture is then allowed to warm to room temperature and stirred overnight. The mixture is filtered and the solid is washed with DCE (30 mL). The solid is dried under high vacuum (about 1 mm Hg) at room temperature overnight to yield 7-bromo-9-bromomethyl-2,3-dihydro[1,4)]dioxino[2,3-g]quinoline-8-carboxylic acid methyl ester hydrobromic acid salt as a yellow solid. HRMS (EI+): calc for C15H13Br2NO4: 428.9211, Found: 428.9238.

Provenance & Evidence