Jiao and Lash
a period of 90 min. During this time, small portions of the
sodium benzyloxide solution were periodically added. When
the vapor temperature reached 200 °C, a final portion of
sodium benzyloxide was added, and stirring was continued for
5 min. The hot solution was then poured into an ice cold
mixture of methanol (80 mL), water (50 mL), and acetic acid
(1 mL). The resulting precipitate was suction filtered and
recrystallized from ethanol to give the benzyl ester (11.33 g;
88%) as white needles, mp 109.5-110 °C; IR (Nujol mull) ν
3310 (st, sh, NH), 1660 cm-1 (st, CdO); 1H NMR (CDCl3) δ
1.42 (9H, s), 2.40 (3H, s), 2.58 (3H, s), 5.34 (2H, s), 7.30-7.41
(5H, m), 8.62 (1H, br s); 13C NMR (CDCl3) δ 14.0, 16.8, 32.0,
33.3, 65.6, 116.6, 128.1, 128.2, 128.4, 128.6, 128.8, 136.6, 161.1.
Anal. Calcd for C18H23NO2: C, 75.75; H, 8.12; N, 4.91. Found:
C, 75.80; H, 8.40; N, 5.10.
Benzyl 5-Acetoxymethyl-4-tert-butyl-3-methyl-1H-pyr-
role-2-carboxylate (10). Lead tetraacetate (95%; 18.1 g) was
added to a solution of pyrrole 9b (11.0 g) in acetic acid (90
mL) and acetic anhydride (9 mL), and the resulting mixture
was stirred at room temperature for 3 h. The mixture was
poured into ice-water, and the resulting precipitate was
filtered and washed well with water. Recrystallization from
chloroform-petroleum ether (60-90°) gave the acetoxy-
methylpyrrole (12.6 g; 88%) as white crystals, mp 104-105
°C. An analytical sample was obtained as fluffy white micro-
needles by recrystallization from hexanes, mp 108-109 °C.
IR (Nujol mull) ν 3302 (st, sh, NH), 1740 (st, acetoxy-CdO),
1668 cm-1 (st, pyrrole-CdO); 1H NMR (CDCl3) δ 1.38 (9H, s),
2.08 (3H, s), 2.51 (3H, s), 5.19 (2H, s), 5.30 (2H, s), 7.30-7.43
(5H, m), 8.94 (1H, br s); 13C NMR (CDCl3) δ 13.6, 21.2, 31.8,
33.4, 59.9, 65.9, 119.2, 125.9, 127.6, 128.3, 128.4, 128.8, 131.8,
136.6, 161.2, 171.3. Anal. Calcd for C20H25NO4: C, 69.95; H,
7.34; N, 4.08. Found: C, 70.14; H, 7.50; N, 3.90.
2,5-Bis(5-benzyloxycarbonyl-3-tert-butyl-4-methyl-2-
pyrrolylmethyl)-3,4-diethyl-1H-pyrrole (6). 3,4-Diethyl-
pyrrole27 (0.50 g) and benzyl 5-acetoxymethyl-4-tert-butyl-3-
methylpyrrole-2-carboxylate (2.46 g) were dissolved in 2-pro-
panol (15 mL) and acetic acid (2 mL). The resulting solution
was stirred and refluxed under an atmosphere of nitrogen for
16 h. The mixture was allowed to cool to room temperature
and further cooled in an ice bath. The resulting precipitate
was filtered, washed with cold ethanol, and dried in vacuo
overnight to give the tripyrrane (2.02 g; 72%) as a white
powder, mp 212-213 °C dec. 1H NMR (CDCl3) δ 1.16 (6H, t, J
) 7.5 Hz), 1.33 (18H, s), 2.43 (4H, q, J ) 7.5 Hz), 2.53 (6H, s),
4.00 (4H, s), 5.24 (4H, s), 7.14 (1H, br s), 7.3-7.4 (10 H, m),
8.40 (2H, br s); 13C NMR (CDCl3) δ 13.9, 16.4, 17.9, 26.8, 31.9,
33.3, 65.6, 117.4, 121.6, 121.8, 128.1 (2), 128.3, 128.5, 128.9,
129.0, 136.8, 160.6; ei ms (70 eV) m/z (rel intensity) 689.5 (M+),
406 (100), 271 (19), 268 (40), 256 (30), 136 (54), 135 (60), 122
(28), 91 (94). Anal. Calcd for C44H55N3O4: C, 76.60; H, 8.04;
N, 6.09. Found: C, 76.05; H, 8.14; N, 5.95.
2,5-Bis(5-carboxy-3-tert-butyl-4-methyl-2-pyrrolyl-
methyl)-3,4-diethyl-1H-pyrrole (11a). The foregoing tri-
pyrrane dibenzyl ester (1.00 g) was dissolved in freshly distilled
anhydrous THF (150 mL) and placed in a hydrogenation
vessel. The solution was diluted with methanol (50 mL) and
triethylamine (20 drops) was added. After air was flushed from
the vessel with nitrogen, 200 mg of 10% palladium on activated
carbon was added and the resulting mixture shaken under an
atmosphere of hydrogen at 40 psi for 16 h. The catalyst was
removed by suction filtration and the solvent evaporated under
reduced pressure while maintaining the temperature below
30 °C. The residue was taken up in 3% aqueous ammonia
solution (ca. 50 mL) and the mixture cooled to 5 °C with the
aid of an ice-salt bath. The solution was neutralized to a litmus
endpoint with glacial acetic acid, maintaining the temperature
below 5 °C throughout. The mixture was allowed to stand for
1 h at 0 °C. Following suction filtration, the solid was washed
exhaustively with deionized water to remove all traces of acid.
The solid was dried overnight in vacuo to give the tripyrrane
dicarboxylic acid (700 mg; 98%) was a pink powder, mp 109-
1
110 °C dec. H NMR (CDCl3) δ 1.13 (6H, t, J ) 7.4 Hz), 1.33
(18H, s), 2.45 (4H, q, J ) 7.4 Hz), 2.52 (6H, s), 4.06 (4H, s),
7.20 (1H, br s), 8.55 (2H, br s); 1H NMR (d6-DMSO) δ 0.92
(6H, t, J ) 7.6 Hz), 1.13 (18H, s), 2.17 (4H, q, J ) 7.6 Hz),
2.34 (6H, s), 3.88 (4H, s), 8.31 (1H, br s), 10.22 (2H, s), 11.84
(2H, br s); 13C NMR (d6-DMSO): δ 13.3, 16.2, 17.1, 25.7, 31.4,
32.5, 117.6, 119.0, 122.2, 125.9, 127.6, 128.9, 162.4. Anal. Calcd
for C30H43N3O4: C, 70.70; H, 8.50; N, 8.24. Found: C, 71.35;
H, 8.73; N, 7.83.
9,18-Di-tert-butyl-13,14-diethyl-8,19-dimethyloxypyri-
porphyrin (14a). Tripyrrane dicarboxylic acid 11a (100 mg)
was stirred with TFA (5 mL) under an atmosphere of nitrogen
for 10 min. The solution was diluted with dichloromethane (95
mL), followed immediately by the addition of hydroxypyri-
dinedialdehyde 12b19 (29.7 mg), and the mixture was stirred
under nitrogen, in the dark, for a further 16 h. After neutral-
ization by the dropwise addition of triethylamine, DDQ (47
mg) was added and the resulting solution was stirred in the
dark for an additional 1 h. The mixture was washed with water
and chromatographed on Grade 3 alumina, eluting first with
dichloromethane and then with chloroform. A deep green
fraction was collected with chloroform and recrystallized from
chloroform-methanol to give the title porphyrin analogue (26.2
mg; 25%) as dark bluish purple crystals, mp 288-290 °C. UV-
vis (CHCl3) λmax (log ꢀ) 320 (4.36), 350 (4.07), 427 (5.34), 442
(5.05), 590 (4.36), 609 (4.40), 658 nm (3.04); UV-vis (TFA-
CHCl3) λmax (log ꢀ) 436 (5.37), 594 (4.08), 633 (4.13), 649 nm
1
(4.16); H NMR (CDCl3) δ -3.01 (1H, s), -2.89 (1H, s), 1.84
(6H, t, J ) 7.6 Hz), 2.36 (9H, s), 2.37 (9H, s), 3.83 (3H, s), 3.89
(3H, s), 3.88 (4H, q, J ) 7.6 Hz), 7.95 (1H, d, J ) 9.6 Hz), 9.35
(1H, d, J ) 9.6 Hz), 9.67 (1H, s), 10.34 (1H, s), 10.36 (1H, s),
11.09 (1H, s); 1H NMR (TFA-CDCl3) δ -1.2 (2H, br), 1.70 (6H,
t, J ) 7.6 Hz), 2.17 (9H, s), 2.18 (9H, s), 3.62 (3H, s), 3.66 (3H,
s), 3.86-3.93 (4H, 2 overlapping quartets), 8.73 (1H, d, J )
9.6 Hz), 9.82 (1H, d, J ) 9.6 Hz), 10.10 (1H, s), 10.73 (1H, s),
10.74 (1H, s), 10.97 (1H, s); 13C NMR (CDCl3) δ 14.8, 15.2, 18.4
(2), 20.0, 34.9, 36.4, 99.5, 99.9, 103.2, 107.7, 131.2, 133.6, 134.6,
135.6, 136.7, 137.8, 138.6, 139.3, 143.1, 143.5, 144.3, 145.1,
145.2, 154.1, 154.7, 185.5; 13C NMR (TFA-CDCl3) δ 15.0, 15.2,
16.9, 17.0, 20.2, 33.5, 36.8 (2), 101.8, 102.0, 103.8, 107.4, 132.5,
133.0, 134.1, 141.8, 141.9, 142.7, 143.3, 144.0, 146.1, 146.2,
148.6, 148.7, 149.2, 149.5, 176.0; ei ms (70 eV) m/z (% rel
intensity) 534 (M+, 100), 519 (12), 506 (3.7), 491 (4.0), 267 (M2+
,
4.9); hr ms calcd for C35H42N4O m/z 534.3358, found 534.3359.
11,16-Diphenyloxypyriporphyrin (19). 19 was prepared
by using the foregoing conditions from diphenyltripyrrane 18
in 2% yield. Dark purple crystals (chloroform-methanol), mp
>260 °C. UV-vis (CHCl3) λmax (rel intensity) 310 (0.10), 430
(1.00), 441 (infl., 0.65), 535 (0.055), 577 (0.059), 615 (0.033),
677 nm (0.0097); UV-vis (2% TFA-CHCl3) λmax (rel intensity)
448 (1.00), 461 (infl., 0.73), 601 (0.059), 650 nm (0.037); 1H
NMR (CDCl3) δ -3.11 (1H, s), -2.99 (1H, s), 7.74-7.82 (6H,
m), 7.93 (1H, d, J ) 9.5 Hz), 8.14-8.18 (4H, m), 8.66-8.69
(2H, AB quartet, J ) 4.5 Hz), 8.98 (2H, d, J ) 5 Hz), 9.31 (1H,
d, J ) 9.5 Hz), 9.32 (1H, d, J ) 4 Hz), 9.42 (1H, d, J ) 4 Hz),
1
9.77 (1H, s), 10.93 (1H, s); H NMR (TFA-CDCl3) δ 0.4 (2H,
br), 8.02-8.08 (6H, m), 8.45-8.48 (4H, m), 8.58 (1H, d, J )
10 Hz), 8.60-8.63 (2H, AB quartet, J ) 4.8 Hz), 8.81 (2H, d,
J ) 4.8 Hz), 9.14 (1H, d, J ) 5.2 Hz), 9.25 (1H, d, J ) 4.8 Hz),
9.69 (1H, d, J ) 10 Hz), 10.04 (1H, s), 10.93 (1H, s); ei ms (70
eV) m/z (% rel intensity) 492 (21), 491 (39), 490 (M+, 100), 462
([M - CO]+, 19), 518 (12), 505 (3.3), 490 (6.6), 278 (M2+, 10);
hr ms calcd for C33H22N4O m/z 490.1794, found 490.1786.
9,18-Di-tert-butyl-13,14-diethyl-8,19-dimethyl-21-carba-
benzo[b]porphyrin (16a). The title porphyrinoid was pre-
pared from tripyrrane 11a (100 mg), indene dialdehyde 1528
(34 mg), TFA (2 mL), and dichloromethane (98 mL) with the
(27) Sessler, J. L.; Mozaffari, A.; Johnson, M. R. Org. Synth. 1991,
70, 68.
(28) Arnold, Z. Collect. Czech. Chem. Commun. 1965, 30, 2783.
3900 J. Org. Chem., Vol. 68, No. 10, 2003