Hydrochloric Acid → 3,4-Dihydro-6,7-dimethoxy-2(1H)-isoquinolinepropanamine

To a stirred solution of 2-(2-cyanoethyl)-1,2,3,4-tetrahydro-6,7-dimethoxyisoquinoline (5.70 g, 23.1 mmol, 1.0 equiv) in anhydrous THF (20 mL) under argon was added a solution of BH3 in THF (1.0 M, 81 mL, 81 mmol, 3.5 equiv) at room temperature. The mixture was stirred at reflux for 4.5 hours and then cooled to room temperature. Aqueous HCl (6 N, 130 mL) was added cautiously at room temperature and stirring was continued for 2.5 hours at 55-60° C. The mixture was cooled to 0° C., basified to pH 10-11 by addition of 6 N aq. NaOH, and extracted with CH2Cl2 (3×100 mL). The combined organic solutions were dried over MgSO4 and concentrated. To a solution of the residue in CH2Cl2 (20 mL) was added HCl in ether (1.0 M, 40 mL, 1.7 equiv). The resulting solution was added dropwise into ether (250 mL) with swirling. The precipitate was filtered and washed with ether (3×100 mL). This solid was taken up in water (50 mL), which was basified to pH 10 by addition of 1 M aqueous NaOH, and extracted with CH2Cl2 (3×100 mL). The combined organic solutions were dried over MgSO4 and concentrated to give 5.10 g (88%) of white solid, which was characterized spectroscopically.

1. temperatureat reflux for 4.5 hours
2. stirringstirring
3. temperatureThe mixture was cooled to 0° C.
4. extractionextracted with CH2Cl2 (3×100 mL)
5. dry with materialThe combined organic solutions were dried over MgSO4
6. concentrationconcentrated
7. filtrationThe precipitate was filtered
8. washwashed with ether (3×100 mL)
9. additionwhich was basified to pH 10 by addition of 1 M aqueous NaOH
10. extractionextracted with CH2Cl2 (3×100 mL)
11. dry with materialThe combined organic solutions were dried over MgSO4
12. concentrationconcentrated

ORD record

ord-67f28cd06e7f4bf69cd3695a8573a7d7

Source dataset

uspto-grants-2001_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06310076B1