506
P.P. Liu et al. / Chinese Chemical Letters 23 (2012) 505–508
Fig. 1. The structures of unsubstituted porphine and 5-formylporphyrin.
3
cooled off, washed with water and extracted with 25 mL CH Cl . The organic solvent was evaporated to dryness and
0 min. TLC analysis (1/1 v/v; CH Cl /hexane) showed exhaustion of the starting material. The reaction mixture was
2 2
2
2
the residue was recrystallized (CH Cl /CH OH). Compound 4 was obtained as a copper-colored powder. Yield 51 mg,
2
2
3
9
3%. UV/vis (CH Cl ) lmax, nm (e): 391.5 (449200), 488.5 (16700), 520.5 (10000), 548.0 (8400).
2
2
5-Formylporphyrin (2): compound 4 (140 mg, 0.377 mmol), dissolved in 60 mL 1, 2-dichloroethane, was added
into the freshly obtained Vilsmeier reagent prepared by N, N-dimethylformamide (DMF, 1.2 mL, 15.5 mmol) and
POCl (9.6 mmol) under Ar protection. Reaction proceeded at 85 8C for 1 h. After cooling off, sulfuric acid (3 mL,
3
9
until no green color being observed. CH Cl was added to extract the product and the organic phase was washed with
8%) was added and stir continued for 10 min. The reaction mixture was poured into aqueous NaOH and was stirred
2
2
water to neutrality. The organic solvent was evaporated to dryness and the residue was purified by silica-gel column
chromatography using CH Cl as the eluent. The major purple band was collected and recrystallized (CH Cl /
2
2
2
2
CH OH). Compound 2 was obtained as a blue/violet powder. Yield 89 mg, 70%. UV/vis (CH Cl ) l , nm (e): 407.0
3
2
2
max
+
357300), 509.5 (17900), 548.0 (25000), 581.5 (15600), 635.0 (22600). ESI-HRMS calcd. for [M+H] C H N O:
(
21 15 4
1
3
Hmeso), 10.17 (d, 2H, J = 4.4 Hz, H ), 9.49 (d, 2H, J = 4.4 Hz, H ), 9.39 (d, 2H, J = 4.4 Hz, H ), 9.36 (d, 2H,
39.1246, found: 339.1225. H-NMR (400 MHz, CDCl ): d 12.52 (s, 1H, CHO), 10.27 (s, 2H, Hmeso), 10.25 (s, 1H,
3
b
b
b
J = 4.0 Hz, H ), À3.05 (s, 2H, NH).
b
5-Formylnickel(II)porphyrin (10): compound 7 (37 mg, 0.101 mmol), dissolved in 60 mL 1, 2-dichloroethane, was
added into the freshly obtained Vilsmeier reagent prepared by DMF (1.2 mL, 15.5 mmol) and POCl (9.6 mmol) under
3
Ar protection. Reaction proceeded at 85 8C for 1 h. The reaction mixture was cooled off to obtain dark green reaction
mixture which majorly contained the iminium salt of 7. Treatment of the dark green mixture with sulfuric acid (3 mL,
98%, stir at room temperature for 15 min) or with trifluoroacetic acid (4 mL, reflux at 80 8C for 2 h) did not obtain
compound 6, since no compound 2 was detected in the hydrolyzed product. The reaction mixture was poured into
aqueous NaOH and was stirred until no green color being observed. CH Cl was added to extract the product and the
2
2
Scheme 1. Synthetic route of 5-formylporphyrin. (a) (1) BF
PrOH (1/1, v/v), 90 8C, 1 h; (c) Cu(OAc) O, CHCl -MeOH, reflux 30 min; (d) (1) Vilsmeier reagent, CH
ÁH
3) NaOH (aq).
3
ÁEt
2
O, CH
2
Cl
2
as solvent, argon protection, 4 h, (2) DDQ, reflux, 1 h; (b) H SO
2
4
/i-
2
2
3
2
ClCH Cl, reflux, 1 h (2) H SO , 5 min
2
2
4
(