Hydrochloric Acid → 2-Diallylamino-8-chloro-1,2,3,4-tetrahydronaphthalene

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Reaction Steps

To a solution of 8-chloro-2-tetralone (5.0 gm, 27.8 mMol) in toluene (50 mL) were added freshly distilled (b.p.=112° C.) diallylamine (7 mL, 56.7 mMol) and p-toluenesulfonic acid (500 mg), and the reaction mixture was stirred at reflux for 3 hours with constant water removal (Dean-Stark trap). The reaction mixture was then cooled to room temperature and volatiles removed in vacuo to give a brown-orange, viscous residue. To a solution of this residue in tetrahydrofuran (100 mL) was added sodium cyanoborohydride (3 gm, 47.7 mMol), and the resulting suspension was saturated with hydrogen chloride. The resulting mixture was stirred at room temperature for 18 hours. The reaction mixture was then poured into water (300 mL) and made basic with aqueous sodium hydroxide. After stirring for two hours at room temperature the reaction mixture was poured into ice and made strongly acidic with concentrated hydrochloric acid. The aqueous solution was extracted with diethyl ether and the organic phase discarded. The remaining aqueous was made strongly basic with aqueous sodium hydroxide and was extracted with dichloromethane. The combined organic extracts were dried over sodium sulfate and concentrated in vacuo to give a violet liquid. Purification on a basic alumina column (Activity I, dichloromethane) gave a colorless oil (1.7 gm, 24%). The hydrochloride salt was formed and recrystallized (ethanol/diethyl ether) to give a colorless solid (m.p.=117°-118° C.).

Provenance & Evidence