Trifluoroacetic acid → 21H,22H-Porphine

Participants

Reaction Steps

Samples of 5-mesityldipyrromethane (264 mg, 1.0 mmol), aldehyde 30 (195 mg, 0.50 mmol) and aldehyde 32 (105 mg, 0.50 mmol) were dissolved in CH2Cl2 (100 mL, undistilled) and then TFA (0.137 ml, 1.78 mmol) was added slowly over 30 s. The reaction mixture was stirred at rt for 30 min, and then DIEA (0.3 mL, 1.8 mmol) and a solution of p-chloranil (370 mg, 1.5 mmol) in THF (20 mL) was added and the mixture was stirred at rt for a further 6 h. Next the reaction mixture was evaporated to one-third of its initial volume and filtered through a silica pad (CH2Cl2/hexanes, 1:1). Fractions containing the second purple band were collected and chromatographed (silica, CH2Cl2/hexanes, 1:1; then CH2Cl2) to afford a slightly impure product. A second column (silica, CH2Cl2) was performed to obtain 56 mg of pure porphyrin (10.3%). 1H NMR δ −2.55 (s, 2H); 1.31 (t, J=7.2 Hz, 3H), 1.90 (s, 12H), 2.68 (s, 6H), 3.51 (m, 2H), 4.12 (5, H), 4.40 (s, 2H), 4.73 (s, 2H), 5.61 (brt, 1H), 7.34 (s, 6H), 7.56, 7.64 (AA′BB′, 4H), 7.9-8.4 (m, 8H), 8.7-9.0 (m, 8H); LD-MS obsd 1089.0, 1018.0 [M+ —CH3CH2NHCO]; FAB-MS obsd 1085.3766, calcd exact mass 1085.3790 (C71H59N5OSFe); λabs (CH2Cl2) 422, 516, 551, 590, 647 nm.

Provenance & Evidence