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To a solution of 2C-B freebase (7.24 g, 27.8 mmol) and phthalic anhydride (4.5 g, 30 mmol) in 100 mL of DMF (distilled) was added 4A molecular sieves. The reaction mixture was heated under reflux overnight and, after cooling, was suction filtered to remove the molecular sieves. Treatment with CH2Cl2 resulted in the formation of yellow needles. Recrystallization from EtOH provided 7.57 g (69%) of 2,5-dimethoxy-4-bromophenyl-2- (phthalimidoamino)-ethane, mp 141.5-142°C.
The above phtalimide (7.57 g, 19.4 mmol) and cuprous cyanide (2.0 g , 22.3 mmol) in 150 mL of DMF were heated under reflux for 5 h. The mixture was poured into a solution containing hydrated ferric chloride (6 g), 1.48 mL of concentrated HCl, and 9 mL of water. The solution was maintained at a temperature of 60-70°C for 20 min. to decompose the complex and then extracted with CH2Cl2. The orgranic phase was washed with diluted aqeuous HCl (100mL), dried (MgSO4) and evaporated to give a white solid. Recrystallization from EtOH provided 5.96 g (91%) of 2,5-dimethoxy-4-cyanophenyl-2-(phthalimidoamino)-ethane as white needles, mp 194-195°C.
The above phtalimide (9.2 g, 27.38 mmol) and hydrazine (2.2 mL, 68.55 mmol, 98%) in 50 mL of anhydrous EtOH were heated under reflux for 15 min. After the mixture was cooled, the phthalazinedione was filtered off, and the filtrate was evaporated to give a solid residue. The solid was dissolved in H2O and extracted with CHCl3. The organic extract was washed with aqeous Na2CO3 (10%, 3x100mL), dried (Na2SO4) and evaporated to give 3.6 g (64%) 2C-CN. The HCl salt (precipitated from ether) was recrystallized from EtOH, mp 220-222°C.