74
S. Taniguchia et al.
LETTER
(4) Wang, Q. M.; Bruce, D. W. Synlett, 1995, 1267.
(5) Sessler, J. L.; Burrell, A. K. Topics in Current Chemistry,
1991, 161, 180.
refluxing for 1 h from the corresponding bis(hydroxyme-
thyl)arenes and pyrrole in a similar manner.
In order to demonstrate the usefulness of the newly-ac-
quired 2, the synthesis of porphyrins by the “3+1” method
was carried out; the condensation of 2 (1 mmol dm-3) with
an equimolar amount of 1 in chloroform in the presence of
BF3·MeOH according to the Lindsey method14 gave por-
phyrinogen in situ, which was then oxidized by chloranil
to afford porphine 5 in 31% yield (Scheme 2).15 As an ex-
ample of the b-substituted porphyrins, 2,3-diethylporphy-
rin (26%) was similarly prepared from 2 and 2,5-
bis(hydroxymethyl)-3,4-diethylpyrrole. Despite using a
high-dilution technique, our method is very easy to per-
form. Although porphine is the most basic compound in
the porphyrin chemistry and it has been more than sixty
years since its first synthesis,16 its preparation is still one
of the most difficult processes in organic synthesis.17 The
highest yield during porphine synthesis hitherto has been
8-10% which was accomplished by Longo and his co-
workers in the reaction of 2-(hydroxymethyl)pyrrole over
a period of 10 days in chromatographed ethylbenzene at
100°C.18 Our “3+1” type condensation using 2 would be a
superior method for the porphyrin synthesis.
(6) a) Furuta, H.; Asano T.; Ogawa, T. J. Am. Chem. Soc., 1994,
116, 767. b) Chmielewski, P. J.; Latos-Grazynski, L.; Rach-
lewcs, K.; Glowiak, T. Angew. Chem., Int. Ed. Engl., 1994,
33, 779. c) Liu, B. Y.; Brückner, C.; Dolphin, D. Chem. Com-
mun., 1996, 2141.
(7) Jasat, A.; Dolphin, D. Chem. Rev., 1997, 97, 2267.
(8) Happel, G.; Mathiasch, B.; Kämmerer, H. Makromol. Chem.,
1975, 176, 3317. Böhmer, V.; Chhim, P.; Kämmerer, H. Ma-
kromol. Chem., 1979, 180, 2503.
(9) Tschelinzew, W. W.; Maxorow, B. W. Chem. Zentr,1923,
1505.
(10) Compound 1: Can be stored for over 5 years at -20C° in a free-
zer. Colorless needle crystals, mp 115-116 °C (dec., acetone,
lit.9 117-118 °C). 1H NMR (90MHz, acetone-d6): δ=3.79 (br,
2H, OH), 4.48 (s, 4H, CH2), 5.84 (s, 2H, 3-H), 9.70 (br, 1H,
NH). Ms: m/z 127(M+, 54), 110(46), 96(14), 80(100), 53(14).
FTIR (KBr, cm-1) 3304, 3250, 2938, 2869, 1425, 1203, 1027,
775.
(11) Compound 2: Must be stored in a freezer. A colorless solid.
mp 97-98 °C (bp 186-194 °C/ 0.1 Torr). Tlc: Rf 0.90 (silica
gel, CH2Cl2). 1H NMR (90MHz, CDCl3): δ=3.74 (s, 4H, 5,10-
H), 5.86 (d, 2H, J=2.4, 7-,8-H), 5.93 (m, 2H, 3-,12-H), 6.07
(m, 2H, 2-,13-H), 6.50 (m, 2H, 1-,14-H), 7.36 (br, 1H, 16-
NH), 7.64 (br, 2H, 15-,17-NH). Ms: m/z 225(M+, 100),
158(52), 145(71), 80(74). FTIR (KBr, cm-1): 3415, 3338,
3085, 2898, 1097, 1026, 808, 800, 733, 725. Anal. for
C14H15N3: C, 74.64; H, 6.71; N, 18.65. Found: C, 74.69; H,
6.52; N, 18.82.
(12) Compound 3: A pale yellow solid, mp 82-83 °C (bp 158-160
°C/ 0.1 Torr). Tlc: Rf 0.95 (silica gel, CH2Cl2). 1H NMR
(90MHz, CDCl3): δ=3.95 (s, 4H, CH2), 5.95 (s, 2H, 3-,4-H),
6.00 (m, 2H, 3’-H), 6.13 (m, 2H, 4’-H), 6.65 (m, 2H, 5’-H),
8.00 (br, 2H, NH). Ms: m/z 226(M+, 100), 159(49), 146(78),
80(47). FTIR (KBr, cm-1): 3376, 3351,3336, 3129, 3105,
2886, 2830, 1563, 1182, 1113, 1013, 802, 719, 708. Anal. for
C14H14N2O: C, 74.31; H, 6.24; N, 12.38. Found: C, 74.03; H,
6.31; N, 12.40.
(13) Compound 4: Must be separated by silica gel column
(CH2Cl2) before the distillation. A colorless viscous oil, bp
198-203 °C/ 0.1 Torr. Tlc: Rf 0.83 (silica gel, CH2Cl2). 1H
NMR (90MHz, CDCl3): δ=1.27 (s, 9H, CH3), 3.87 (s, 4H,
CH2), 5.38 (br, 1H, OH), 6.02 (m, 2H, 3’-H), 6.08 (m, 2H,
4’-H), 6.53 (m, 2H, 5’-H), 7.04 (s, 2H, 3-,5-H), 8.09 (br, 2H,
NH). Ms: m/z 308(M+, 40), 242(45), 226(100), 80(21). FTIR
(neat): 3391, 3098, 2961, 2905, 2868, 1485, 1203, 1025, 719
cm-1. Anal. for C20H24N2O: C, 77.89; H, 7.84; N, 9.08. Found:
C, 77.52; H, 7.93; N, 8.79.
In conclusion, tripyrrane (2) was first isolated in good
yield by a simple operation from the readily available 2,5-
bis(hydroxymethyl)pyrrole and excess pyrrole and suc-
cessfully applied to the synthesis of porphine in an im-
proved yield. This new synthesis of tripyrrane would also
serve the chemistry of porphyrin and homoporphyrin.
Acknowledgement
(14) Lee, C. -H.; Lindsey, J. S. Tetrahedron, 1994, 50, 11427 and
references cited therein.
We thank the Hitachi Chemical Co., Ltd., for the microanalyses.
(15) The yield was determined by UV analysis of the Soret band
(λmax: 396.5 nm, εmax: 264,000 dm3·mol-1·cm-1): Krol, S. J.
Org. Chem., 1959, 24, 2065.
(16) Fischer, H.; Gleim, W. Justus Liebigs Ann. Chem., 1935, 521,
157.
(17) Neya, S.; Yodo, H.; Funasaki, N. J. Heterocyclic Chem., 1993,
30, 549.
(18) Longo, F. R.; Thorne, E. J.; Adler, A. D.; Dym, S. J. Hetero-
cyclic Chem., 1975, 12, 1305.
References and Notes
(1) Arsenault, G. P.; Bullock, E.; MacDonald, S. F. J. Am. Chem.
Soc., 1960, 82, 4384. Tarlton, E. J.; MacDonald, S. F.; Bataz-
zi, E. J. Am. Chem. Soc., 1960, 82, 4389.
(2) Lash, T. D. Chem. Eur. J., 1996, 2, 1197.
(3) Bonnett, R. The Porphyrins; Dolphin, D., Ed.; Academic:
New York, 1978, Vol.1, p 17.
Synlett 1999, No. 1, 73–74 ISSN 0936-5214 © Thieme Stuttgart · New York