Efficient one-pot synthesis of 1,3-diaryl-3H-benzo[f]chromenes using ferric hydrogensulfate

Article abstract of DOI:10.1016/j.cclet.2010.07.007

An efficient and easy method for one-pot three-component synthesis of 1,3-disubstituted-3H-benzo[f]chromenes by the condensation of naphtol, aromatic aldehyde derivatives and phenylacetylene in the presence of ferric hydrogensulfate [Fe(HSO₄)

Full text of DOI:10.1016/j.cclet.2010.07.007

Available online at www.sciencedirect.com
Chinese Chemical Letters 21 (2010) 1423–1426
www.elsevier.com/locate/cclet
Efficient one-pot synthesis of 1,3-diaryl-3H-benzo[f]chromenes
using ferric hydrogensulfate
a
a
Hossein Eshghi a, , Gholam Hossein Zohuri , Saman Damavandi ,
*
Mohammad Vakili b
a Department of Chemistry, School of Sciences, Ferdowsi University of Mashhad, Mashhad 91775-1436, Iran
b School of Chemistry, Damghan University of Basic Sciences, P.O. Box 36715-364, Damghan, Iran
Received 12 April 2010
Abstract
An efficient and easy method for one-pot three-component synthesis of 1,3-disubstituted-3H-benzo[f]chromenes by the
condensation of naphtol, aromatic aldehyde derivatives and phenylacetylene in the presence of ferric hydrogensulfate [Fe(HSO4)3],
has been described. The catalyst displayed high activity which afforded the corresponding 1,3-disubstituted-3H-benzo[f]chromenes
in satisfying yields. Alkyl-substituted phenols were examined and the corresponding benzopyran derivatives were synthesized in
moderate yields. Heterogeneous nature of the using catalyst made it reusable for further chemical reactions.
# 2010 Hossein Eshghi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: 1,3-Disubstituted-3H-benzo[f]chromenes; Ferric hydrogensulfate; One-pot synthesis; Naphtopyran; Benzopyran
Naphtopyrans are an important class of photochromic compounds and the classical molecules which have the
ability to generate a yellow colour on being irradiated with UV light [1]. Their photochromic behavior is based on a
reversible pyran ring opening induced upon near UV irradiation that converts a colourless form to a set of quasi-planar
forms constituting a system with a distinct absorption spectrum [1,2]. 2-Amino-4H-chromenes and their derivatives
are of considerable interest as they possess a wide range of biological properties [3,4] such as spasmolytic, diuretic,
anticoagulant, anticancer [5], antitumor, antiproliferative, antiviral and antianaphylactic activities [6,7]. Thus, the
development of a new methodology for the direct synthesis of 1,3-disubstituted-3H-benzo[f]chromenes which does
not need to use a stoichiometric amount of highly reactive catalyst and can be carried out under mild conditions would
be highly desirable. However, recently some studies have been devoted to the preparation of benzo[f]chromenes [8–
12].
In the present study, ferric hydrogenesulfate [Fe(HSO4)3], was introduced as an efficient catalyst for synthesis of
the 1,3-disubstituted-3H-benzo[f]chromenes (naphthopyrans) by one-pot three-component coupling of naphthol,
phenylacetylene and aromatic aldehyde derivatives (Scheme 1).
* Corresponding author.
E-mail address: heshghi@ferdowsi.um.ac.ir (H. Eshghi).
1001-8417/$ – see front matter # 2010 Hossein Eshghi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2010.07.007

[(Scheme_1)TD$FIG]
1424
H. Eshghi et al. / Chinese Chemical Letters 21 (2010) 1423–1426
Scheme 1.
1. Experimental
Chemicals were either prepared in our laboratories or purchased from Merck, Fluka and Aldrich Chemical
Companies. All yields refer to isolated products. The products were characterized by comparison of their physical data
with those of known samples or by their spectral data. IR spectra were recorded on a Shimadzu-IR 470
spectrophotometer. 1H NMR spectra were recorded on a Bruker 100-MHz spectrometer in chloroform as the solvent
and TMS as internal standard. Ferric hydrogensulfate was prepared according to previously reported procedure
[13,14].
1.1. General procedure to synthesis of 1,3-disubstituted-3H-benzo[f]chromenes
A mixture of naphthol (1 mmol), phenylacetylene (1.1 mmol), aldehyde (1 mmol) and ferric hydrogensulfate
(0.1 mmol) was refluxed in acetonitril for the appropriate time (Table 1). The reaction was followed by TLC and after
completion of the reaction the catalyst was recovered through filtration simply. The residue was concentrated in vacuo.
The resulting crude product was purified by column chromatography on silica gel to afford the pure product.
1
Representative H NMR spectral data for the selected products:
1,3-Diphenyl-3H-benzo[f]chromene (entry 1): 1H NMR (100 MHz, CDCl3): d 6.90–7.10 (m, 7H), 7.25–7.40 (m,
5H), 7.40–7.55 (m, 4H), 5.9 (d, 1H, J = 1.5 Hz), 4.90 (d, 1H, J = 1.5 Hz).
3-(2-Bromophenyl)-1-phenyl-3H-benzo[f]chromene (entry 2): 1H NMR (100 MHz, CDCl3): d 7.20–7.50 (m, 8H),
7.55–7.70 (m, 7H), 6.10 (d, 1H, J = 5 Hz), 4.85 (d, 1H, J = 5 Hz).
1
3-(4-Methoxyphenyl)-1-phenyl-3H-benzo[f]chromene (entry 3): H NMR (100 MHz, CDCl3): d 7.46–7.55 (m,
10H), 6.96–6.99 (m, 5H), 5.80 (d, 1H, J = 3.5 Hz), 4.80 (d, 1H, J = 3.5 Hz), 3.75 (s, 3H).
2. Result and discussion
Using b-naphtol, phenylacetylene as the alkyne and benzaldehyde as the aldehyde component in a stoichiometric
ratio of 1:1.1:1 and 0.1 equiv. ferric hydrogensulfate (based on the aldehyde component), we designed a reaction as a
model in order to find the optimum reaction solvent and the results are shown in Table 1.
As it can be seen in Table 1, among the various solvents investigated, CH3CN was found to be the best choice.
However, benzene and toluene afforded satisfying yields. Moderate and poor yields were obtained when the reactions
were carried out in C2H4Cl2 and THF respectively. As it can be seen in Table 1, the catalyst could be reused without
significant loss of its catalytic activity until at least 5 times.
Table 1
Influence of solvent on Fe(HSO4)3-catalyzed reaction of b-naphtol, phenyl acetylene and benzaldehyde and reusability study.
Solvent
Acetonitril
Toluene
Benzene
Dichloroethane
THF
Yielda,b
82
78d
73
76e
68
ꢀ75f
42
70g
ꢀ20
Reusabilityc
70h
a
All the reactions were carried out under reflux conditions for 5 h.
Isolated yields.
b
c
Reusability of the recovered catalyst was investigated in CH3CN as the optimum solvent.d–h Reusability of the recovered catalyst in new runs
from run 2(d) to run 6(h).

H. Eshghi et al. / Chinese Chemical Letters 21 (2010) 1423–1426
1425
Table 2
Results of one-pot three-component synthesis of naphtopyran and benzopyran derivativesa.
Entry
Naphtol
Aldehyde
Productb
Time (h)
3.5
Yield (%)c
82
[TD$INLINE]
[DT$INLE]
1
[DT$INLE]
[TD$INLINE]
[DT$INLE]
2
4
76
[DT$INLE]
[TD$INLINE]
3
4
E
4.5
2
71
84
[DT$INLE]
[TD$INLINE]
[DT$INLE]
[TD$INLINE]
[DT$INLE]
5
4
75
[DT$INLE]
[TD$INLINE]
[DT$INLE]
6
7
I
4
6
77
72
[TD$INLINE]
[DT$INLE]
[DT$INLE]
[TD$INLINE]
[DT$INLE]
8
9
2.5
80
[DT$INLE]
[DT$INLE]
5.5
7
67
55
[TD$INLINE]
[DT$INLE]
[DT$INLE]
10
[TD$INLINE]
[DT$INLE]
a
Reaction conditions: 1.0 equiv. of naphthol, 1.0 equiv. of aldehyde, 1.1 equiv. of phenylacetylene, 10 mol% ferric hydrogenesulfate and reflux
condition.
b
The products were identified by 1HNMR and IR spectra.
c
Isolated yields.
To generalize the study, a- and b-naphtol, various aldehydes derivatives and phenylacetylene were employed in the
multi-component one-pot reaction. The results are illustrated in Table 2. Electron withdrawing substitution on
aldehyde compounds accelerated the multi-component reaction to some extent, however aromatic aldehydes bearing
electron releasing group could react successfully and afford the corresponding products in good yields. In order to
extend our study, alkyl-substituted phenols were examined under the optimized reaction conditions. Although the
reactions were done properly, but the corresponding benzopyrans were obtained in longer times. The reaction was
carried out using phenol and phenol with electron withdrawing substitutions (e.g. 4-chlorophenol and 4-nitrophenol)
instead of alkyl-substituted phenols. The reactions were failed and no corresponding products were isolated.

[(Scheme_2)TD$FIG]
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H. Eshghi et al. / Chinese Chemical Letters 21 (2010) 1423–1426
Scheme 2.
The proposed mechanism for three-component synthesis of naphtopyran derivatives has been shown in Scheme 2.
The reaction probably precedes via in situ generation of ortho-quinone methides (A) (OQMs) [15]. On the basis of
several literatures [16,17], it is believed that the coupling reaction proceeds by terminal C–H bond activation by ferric
hydrogensulfate catalyst. The Fe-alkyl acetylide (B) intermediate would attack on OQMs (A) by a Michael-type
addition or by a Diels–Alder reaction (Scheme 2). Protometallation regenerates the catalyst for further reactions.
Replacement of the phenylacetylene with 1-phenyl-1-propyne could not afford the corresponding product and the
reaction of naphtols, 1-phenyl-1-propyne and benzaldehyde was failed. According to, although the Diels–Alder
reaction might be conceivable, but due to failure of the reaction using 1-phenyl-1-propyne, the mentioned mechanism
in Scheme 2 is more probable.
3. Conclusion
In conclusion, 1,3-disubstituted-3H-benzo[f]chromenes (naphthopyran and benzopyran derivatives) were
synthesized successfully in the presence of catalytic amount of ferric hydrogensulfate as an efficient, inexpensive
and heterogeneous catalyst. This new approach provided moderate to high yield of the corresponding products with the
simple experimental and work up procedure.
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