Cannabidiol → Tetrahydrocannabinol

Participants

Reaction Conditions

Reaction Steps

To a nitrogen inerted, stirred solution of cannabidiol (21.2 g, 67.1 mmol) in dichloromethane (370 mL) was added, by syringe pump, commercial tri-isobutylaluminum solution (1 M in hexanes, 6.7 mL, 10 mol %) over 4.5 hours. The temperature of the reaction mixture was maintained at 20-25° C. and the mixture was stirred overnight. Additional charges of triisobutylaluminum solution (1 M in hexanes, 2.67 mL added, 4 mol %) were made over the next day to drive the reaction to >99% conversion by HPLC analysis. The reaction was quenched by addition of water (250 mL), stirred 30 minutes, combined with a slurry of celite in dichloromethane (10.0 g in 70 mL dichloromethane) and then clarified. The reactor and filter cake were rinsed with dichloromethane (50 mL) and the combined filtrates distilled under reduced pressure (25° C. pot temperature, 22 inches of vacuum) to about 50 mL volume. Toluene (106 mL) was added and the solvents again removed under reduced pressure. More toluene (106 mL) was added and removed under reduced pressure and then the dichloromethane-free residue was reconstituted in toluene (100 mL). HPLC analysis showed 95.6% delta-9-tetrahydrocannabinol, 1.1% cis-tetrahydrocannabinol, and no cannabinol. (Sunfire C18 5u, 4.6 mm×150 mm, 1 ml/min, gradient 80% 0.1% TFA/water and 20% 0.05% TFA/acetonitrile to 100% 0.05% TFA/acetonitrile over 15 minutes, delta-9 tetrahydrocannabinol: rt=15.1 min). The yield was estimated at 95%. The solution was stored under nitrogen until needed for preparation of the camphorsulfonate derivative.

Provenance & Evidence