Patent US7399872

providing a reaction mixture comprising CBD in dry methylene chloride;

adding BF3Et2O to the reaction mixture;

stirring the ice cold reaction mixture under a nitrogen atmosphere;

adding NaHCO3 to the reaction mixture;

allowing the mixture to separate into an aqueous phase and an organic phase;

removing the organic phase;

washing the organic layer with water; and

eluting Δ9-THC from the organic phase, purity of the eluted Δ9-THC being greater than 97%.