An efficient and convenient synthesis of furocoumarins via Pechmann reaction on ZnCl2/Al2O3 under microwave irradiation

Article abstract of DOI:10.1080/10426500307819

Furocoumarins were rapidly synthesized via Pechmann condensation of 6-hydroxybenzofurans with ethylacetoacetate catalyzed by ZnCl₂/Al₂O₃ under solvent-free condition.

Full text of DOI:10.1080/10426500307819

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Phosphorus, Sulfur, and Silicon and the Related
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An Efficient and Convenient Synthesis of
Furocoumarins via Pechmann Reaction on ZnCl 2 /Al 2
O 3 Under Microwave Irradiation
a
b
a
Abbas Shockravi , Majid M. Heravi & Hassan Valizadeh
a
Teacher Training University, Tehran, Iran
b
Azzahra University, Vanak, Tehran, Iran
Published online: 27 Oct 2010.
To cite this article: Abbas Shockravi , Majid M. Heravi & Hassan Valizadeh (2003) An Efficient and Convenient Synthesis of
Furocoumarins via Pechmann Reaction on ZnCl 2 /Al 2 O 3 Under Microwave Irradiation, Phosphorus, Sulfur, and Silicon and
the Related Elements, 178:1, 143-147, DOI: 10.1080/10426500307819
To link to this article: http://dx.doi.org/10.1080/10426500307819
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Phosphorus, Sulfur and Silicon, 2003, Vol. 178:143–147
Copyright �C 2003 Taylor & Francis
1
042-6507/03 $12.00 + .00
DOI: 10.1080/10426500390170273
AN EFFICIENT AND CONVENIENT SYNTHESIS OF
FUROCOUMARINS VIA PECHMANN REACTION ON
ZnCl /Al O UNDER MICROWAVE IRRADIATION
2
2
3
a
b
a
Abbas Shockravi, Majid M. Heravi, and Hassan Valizadeh
a
Teacher Training University, Tehran, Iran and Azzahra
University, Vanak, Tehran, Iranb
(Received July 16, 2002; accepted August 4, 2002)
Furocoumarins were rapidly synthesized via Pechmann condensa-
tion of 6-hydroxybenzofurans with ethylacetoacetate catalyzed by
ZnCl /Al O under solvent-free condition.
2
2
3
Keywords: Al
2 3
O ; furocoumarins; microwave irradiation; Pechmann
condensation; ZnCl
2
The beneficial effects of furocoumarins have been investigated over a
vast number of years. The ancient Egyptians recognized the ability
1
of furocoumarins to treat skin disorders. Furocoumarins have been
utilized to treat psoriasis and vitiligo as well as bacterial and viral
2
infections. Since furocoumarins have achieved medical significance,
convenient synthetic routes are needed to generate the parent three-
ring backbone.
Furocoumarins have been synthesized by many different routes, but
the majority of these routes employ many steps and often result in very
3
low yields. Total synthesis of linear furocoumarins recently have been
4
achieved via an intramolecular Diels-Alder reaction and by benzannu-
lation reaction of carbene complexes with acetylenes respectively.
We have shown that the Pechmann reaction could be achieved
quickly using microwave irradiation of the reagents in household mi-
crowave oven.6 In continuation of our interest in conducting of or-
7
ganic synthesis on inorganic supports and solventless system, we de-
vised a one-step formation of the pyrone ring of furocoumarins 2 on
˚
P2O5/molecular sieve 3 A by microwave activated Pechmann reaction of
Address correspondence to Abbas Shockravi, Faculty of Chemistry, Teacher Training
University, 49 Dr. Moffateh Avenue, Tehran, Iran. E-mail: abbas shockravi@yahoo.co.uk
1
43

1
44
A. Shockravi et al.
6
-hydroxybenzofurans and ethylacetoacetate. Through this route furo-
coumarins were not synthesized in good yields and undesired products
were produced. Other types of solid supports were also compared and
ZnCl2/Al2O3 was found to give the best yields.
The reaction is conducted by exposure of a mixture of 6-hydroxyben-
zofurans, ethylacetoacetate, ZnCl2 and Al2O3 to microwave irradiation
(
Scheme 1). Most of benzofuranic compounds disappeared within a few
minutes as determined by TLC.
SCHEME 1
In summary the method describes a noticeble improvement in the re-
action condition for the preparation of the pyrone ring of furocoumarins
by the Pechmann reaction and takes advantages of both solventless con-
dition reaction and microwave activation.
EXPERIMENTAL SECTION
Al2O3 powder (60 G neutral, Type E) was purchased from Merck Chem-
ical Co. MP(s) were recorded on Electrothermal 9100 apparatus and are
1
uncorrected. H-NMR spectra were recorded on a 250 MHz Spectroscop
1
3
or 60 MHz Bruker and C-NMR spectra were recorded on a 250 MHz
Spect-using TMS as an internal standard. IR spectra were measured
on a Perkin-Elmer model 854.
GENERAL PROCEDURE
An appropriate hydroxy benzofuran (10 mmol), ethyl acetoacetate
(
10 mmol), ZnCl2 (10 mmol) and Al2O3 (3 g) were mixed thoroughly
using a spatula in a beaker. The beaker was placed in a household mi-
crowave oven. The progress of the reaction was monitored by TLC. The
residue was taken up in hot chloroform and filtered. The filtrate was
evaporated to dryness and the crude produce was dissolved in chloro-
form and was purified by dry-column flash chromatography on silica
gel (Merck kieselgel 60, 0.015–0.040 mm) using n-hexane/ethyl acetate
for elution, from which an analytical sample by recrystallization from
suitable solvent was prepared. Melting points, yields, reaction times,
and crystallizing solvents are given in Table I.

145

1
46
A. Shockravi et al.
Selected Spectroscopic Data for 2a
1
HNMR � (CDCl3, 250 MHz): 2.52 (s, 3H, 4-Me), 6.32 (s, 1H, olefinic CH),
.43–8 (m, 8H, aromatic protons), 1 CNMR (CDCl3, 60 MHz): 19.6, 100,
3
7
1
�
14, 116, 117, 122, 124, 127, 128, 129, 131, 143, 152, 153, 157, 161, IR,
�
1
(KBr disc): 1695 cm
.
Selected Spectroscopic Data for 2b
1HNMR � (CDCl3, 60 MHz): 2.27 (s, 3H, Me), 2.53 (s, 3H, 4-Me), 6.28
(
1
s, 1H, olefinic CH), 7.2–7.8 (m, 7H, aromatic protons), IR, � (KBr disc):
710 cm .
�
1
Selected Spectroscopic Data for 2c
1HNMR � (CDCl3, 250 MHz): 2.29 (s, 3H, Me), 2.51 (s, 3H, 4-Me), 6.23
(
s, 1H, olefinic CH), 7.3 (s, 1H, aromatic proton), 7.46 (s, 1H, aromatic
1
3
proton), 7.58 (s, 1H, aromatic proton), CNMR (CDCl3, 60 MHz): 6.72,
1
1
8.1, 19.1, 100.8, 111.7, 113, 114.4, 115.26, 126.25, 141.3, 114.5, 152,
�
1
61, IR, � (KBr disc): 1710 cm
.
Selected Spectroscopic Data for 2d
1HNMR � (CDCl3, 250 MHz): 2.13 (s, 3H, Me), 2.39 (s, 3H, Me), 2.50 (s,
3
H, 4-Me), 6.4 (s, 1H, olefinic CH), 7.28 (s, 1H, aromatic proton), 7.50
1
3
(
s, 1H, aromatic proton), CNMR (CDCl3, 60 MHz): 6.7, 14.8, 19.9, 97,
1
00.1, 109.4, 111, 114, 114.5, 127, 151, 152, 155.3, 161.4, IR, � (KBr
�
1
disc): 1700 cm
.
Selected Spectroscopic Data for 2e
1HNMR � (CDCl3, 60 MHz): 2.13 (s, 3H, Me), 2.27 (s, 3H, Me), 2.39 (s,
3
H, Me), 2.51 (s, 3H, 4-Me), 6.24 (s, 1H, olefinic CH), 7.5 (s, 1H, aromatic
�
1
proton), IR, � (KBr disc): 1705cm
.
Selected Spectroscopic Data for 2f
1HNMR � (CDCl3, 60 MHz): 2.15 (s, 3H, Me), 2.3 (s, 3H, Me), 2.52 (s,
3
1
H, 4-Me), 6.31 (s, 1H, olefinic CH), 7.3 (s, 1H, aromatic proton), 7.4 (s,
�
1
H, aromatic proton), IR, � (KBr disc): 1695 cm
.
REFERENCES
[
1] M. A. Pathak, D. M. Kramer, and T. B. Fitzpatrick, Sunlight and Man (University of
Tokyo Press, Tokyo, 1973).

Furocoumarins
147
[
[
2] a) E. P. Gasparro, Psoralen DNA Photobiology (CRC Press, Inc., Boca Raton, FL,
989); b) J. D. Parrish, The Science of Photomedicine (Plenum Press, New York, 1982).
3] a) J. D. Regan and E. J. Bisagni, Photochem. Photobiol., 14, 23 (1992); b) K. D.
Kaufman, D. J. Erb, J. M. Blok, R. W. Carlson, D. J. Knoechel, L. Mcbride, and
T. J. Zeitolw, Heterocyclic Chem., 19, 1051 (1982); c) J. K. Maclead and B. R. Worth,
Tetrahedron Lett., 13, 237 (1972); d) P. None and E. Honkanen, J. Heterocyclic Chem.,
1
1
7, 985 (1980).
4] K. Hayakawa, M. Yodo, S. Ohsuki, and K. Kanematsu, J. Am. Chem. Soc., 106, 6735
1984).
[
(
[
[
5] W. D. Wulff, J. S. Mccallum, and F. A. Kunng, J. Am. Chem. Soc., 110, 7419 (1988).
6] A. Shockravi, H. Valizadeh, and M. M. Heravi, Phosphorous, Sulfur, and Silicon
(in press).
[
7] A. Shockravi, H. Sharghi, H. Valizadeh, and M. M. Heravi, Phosphorus, Sulfur, and
Silicon, 177, 2555–2559 (2002); b) M. M. Heravi, D. Ajami, M. M. Mojtahedi, and M.
Ghasemzadeh, Tetrahedron Lett., 40, 561 (1999); c) M. M. Heravi, D. Ajami, and M.
M. Mojtahedi, J. Chem. Res., 261 (2000); d) M. M. Heravi, D. Ajami, K. Aghapoor,
and M. Ghasemzadeh, Chem. Commun., 833 (1999); e) A. Shockravi, H. Sharghi, H.
Valizadeh, and M. M. Heravi, Indian J. Heterocyclic Chem., (accepted).