Pyrrole → 5,10,15,20-Tetrakis(1-methylimidazol-5-yl)porphyrin

Participants

Reaction Steps

To a refluxing solution of propionic acid (400 mL) and 1-methylimidazole-5-carboxaldehyde (53, 2.0 g, 18.16 mmol), prepared according to literature procedure (Dener, J. M.; Zhang, L-H.; Rapoport, H. J. Org. Chem. 1993, 58, 1159-1166), was added pyrrole (1.26 mL, 18.16 mmol). The reaction was covered with foil then heated under reflux for 5 h. Upon cooling, the reaction mixture was exposed to air for 60 h. The propionic acid was then removed by vacuum distillation. The residue was dissolved in 10% MeOH/CH2Cl2, then adsorbed onto silica gel (6 g). Purification by column chromatography (gradient elution, 5-10% MeOH/CH2Cl2) provided porphyrin 54 as a purple solid (600 mg, 21%): 1H NMR (300 MHz, CDCl3) δ −2.80, −2.75 (2 s, 2 H, atropisomer NH), 3.42-3.58 (multiple s, 12 H, atropisomer N—CH3), 7.87-7.98 (multiple s, 4 H, atropisomer), 8.06 (s, 4 H), 8.95-8.99 (multiple s, 8 H, atropisomer).

Provenance & Evidence