Hydrochloric Acid → 1,3-Dimethyl-1,2,3,4-tetrahydroquinoxaline

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Reaction Steps

To a stirred solution of 0.2 mole (34.8 g) of 1,3-dimethyl-2-oxoquinoxaline in 300 ml of dry tetrahydrofuran is added dropwise 0.24 mole (240 ml of 1 M) diborane in tetrahydrofuran. The solution is stirred one additional hour, then heated at its reflux temperature for one day. After cooling, about 40 ml of water is added, followed by 2 equivalents of 4N hydrochloric acid. The solution is heated at reflux for one hour, then evaporated to provide a solid residue. The residue is dissolved in water. The solution is basified and then extracted with diethyl ether. The ether is dried, then evaporated to provide an oil. Distillation provides 1,3-dimethyl-1,2,3,4-tetrahydroquinoxaline, b.p. 85° C/0.1 mm of Hg. Analysis: Calculated for C10H14N2 : %C, 74.0; %H, 8.7; %N, 17.4; Found: %C, 74.2; %H, 8.9; %N, 17.3.

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