Bismuth(III) triflate: Novel and efficient catalyst for Claisen and Fries rearrangements of allyl ethers and phenyl esters

Article abstract of DOI:10.1081/SCC-120030693

Bismuth(III) triflate catalyzed Claisen and Fries rearrangements of allyl phenyl ethers and phenyl acetates have been presented. The reaction proceeds smoothly and yields corresponding rearranged products in good yields. The bismuth triflate displays higher activity over the corresponding La, Yb, and Sc triflates.

Full text of DOI:10.1081/SCC-120030693

This article was downloaded by: [USC University of Southern California]
On: 03 October 2014, At: 21:51
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer
House, 37-41 Mortimer Street, London W1T 3JH, UK
Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic
Chemistry
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/lsyc20
Bismuth(III) Triflate: Novel and Efficient Catalyst for
Claisen and Fries Rearrangements of Allyl Ethers and
Phenyl Esters
B. Sreedhar a , V. Swapna a & Ch. Sridhar a
a Inorganic Chemistry Division , Indian Institute of Chemical Technology , Hyderabad, 500
007, India
Published online: 21 Aug 2006.
To cite this article: B. Sreedhar , V. Swapna & Ch. Sridhar (2004) Bismuth(III) Triflate: Novel and Efficient Catalyst for
Claisen and Fries Rearrangements of Allyl Ethers and Phenyl Esters, Synthetic Communications: An International Journal
for Rapid Communication of Synthetic Organic Chemistry, 34:8, 1433-1440, DOI: 10.1081/SCC-120030693
To link to this article: http://dx.doi.org/10.1081/SCC-120030693
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of
the Content. Any opinions and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied
upon and should be independently verified with primary sources of information. Taylor and Francis shall
not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other
liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 8, pp. 1433–1440, 2004
Bismuth(III) Triflate: Novel and Efficient
Catalyst for Claisen and Fries
Rearrangements of Allyl Ethers
and Phenyl Esters
*
B. Sreedhar, V. Swapna, and Ch. Sridhar
Inorganic Chemistry Division, Indian Institute of Chemical Technology,
Hyderabad, India
ABSTRACT
Bismuth(III) triflate catalyzed Claisen and Fries rearrangements of allyl
phenyl ethers and phenyl acetates have been presented. The reaction
proceeds smoothly and yields corresponding rearranged products in
good yields. The bismuth triflate displays higher activity over the corres-
ponding La, Yb, and Sc triflates.
Key Words: Claisen rearrangement; Allyl ethers; Fries rearrangement;
Phenyl esters; Bismuth(III) triflate.
*
Correspondence: B. Sreedhar, Inorganic Chemistry Division, Indian Institute of
Chemical Technology, Hyderabad 500 007, India; Fax: 91-40-27160921; E-mail:
sreedharb@iict.res.in.
1433
DOI: 10.1081/SCC-120030693
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

ORDER
REPRINTS
1434
Sreedhar, Swapna, and Sridhar
The rearrangement reactions like Claisen and Fries have become one of
the most powerful tools for carbon–carbon bond formation in organic syn-
thesis.[1] They have widespread synthetic applications due to the simplicity
of the protocol and the high degree of stereoselectivity and functional group
reorganization. The (3,3)-sigmatropic shift (Claisen rearrangement) of allyl
aryl ethers provides a convenient access to o-allyl phenols, precursors to a
variety of natural products including chromones and coumarenes.[2] The
Fries rearrangement of phenyl acetates provides a synthetically useful route
for the preparation of hydroxy aryl ketones.[3] Products such as 4-hydroxyace-
tophenone, 4-hydroxybenzophenone, 4-hydroxypropeionones, and others are
commercially important drug intermediates[4] that are derived from the
Fries rearrangement.
Since the first report on Lewis acid mediated Claisen and Fries rearrange-
ments, several new reagents with unique acidic character were studied for
their effectiveness in Claisen, Fries, and related rearrangements.[5] Several
Lewis acids such as AlCl3 in quantities more than stoichiometric amounts
are known to catalyze these reactions The scope of bismuth compounds has
been considerably widened during the last decade and has been found to be
a very useful catalyst in many organic transformations.[6–10] Recently we
have evaluated the higher activity of bismuth(III) triflate over lanthanum tri-
flates in the allylation of aldehydes and imines with allyl tributyl stannane.[11]
Kobayashi et al. have reported effective Fries rearrangement using group 3
and 4 metal triflates and have observed that they are stable Lewis acids in
water and can be successfully applied as catalysts to several carbon–carbon
bond forming reactions.[12] Based on these studies we are evaluating the
Claisen and Fries rearrangements with bismuth(III) triflate. We are particu-
larly interested in bismuth(III) triflate because it is highly catalytic in nature,
relatively stable, insensitive to air and moisture, and can be easily prepared
from commercially available inexpensive materials such as bismuth(III)
oxide, and triflic acid.[13] The results from our study are presented herein.
Initially, reaction of p-cresyl allyl, crotyl, and prenyl ether (Sch. 1) with
5 mol% of bismuth(III) triflate in methanol or benzene was very sluggish and a
conversion of 5–10% was observed even after 24 h. However, efficient
migration takes place in the case of allyl ether in acetonitrile at reflux tempera-
ture to give ortho Claisen shift product in 80% yield. In the case of crotyl
ether, [3,3] and [1,3] shifts were observed and yields were 60% and 40% of
the corresponding rearranged phenols. p-Cresyl prenyl ether efficiently
rearranges to o-substituted product at room temperature with bismuth(III)
triflate but at higher temperature rapid reaction takes place and forms
2,2-dimethylchroman in high yields (90%). The study was extended to
several allyl ethers, and the results are summarized in Table 1. In the case
of 2,6-dimethoxy allyl phenyl ether (Table 1, entry 2), allyl group selectively

ORDER
REPRINTS
Bismuth(III) Triflate
1435
Scheme 1.
rearranges to 95% para allylated product due to the presence of two electron
releasing groups, that accelerate the rearrangement and so the conversion is
very high (95%), while in the case of o-methoxy phenyl allyl ether (Table 1,
entry 3) a mixture of both ortho and para rearranged phenols is obtained and
the rate of conversion to ortho is more when compared to para substituted phe-
nol. On the other hand, the rearrangement of p-nitro phenyl allyl ether was not
possible even after 24 h, but deprotection of allyl group takes place and forms
p-nitro phenol, which can be attributed to the electron withdrawing nature of
the nitro group. [3,3] and [1,3] shifts were observed when the p-cresyl crotyl
ether (Table 1, entry 5) undergoes Claisen rearrangement, and yields both the
products, 50% and 40% respectively. p-Cresyl prenyl ether (Table 1, entry 6)
efficiently rearranges to o-substituted product at room temperature with bis-
muth(III) triflate, but at higher temperature rapid reaction takes place and
forms 2,2-dimethylchroman in high yields (90%).
Initially, we studied the Fries rearrangement of phenyl acetate using
5 mol% of bismuth(III) triflate and acetonitrile as solvent at room temperature
(Sch. 2). The reaction is very sluggish and a conversion of 20% was observed
after 12 h. However, when similar reaction was carried out in toluene at room
temperature it yielded 40% of the rearranged product after 6 h. On increasing
the reaction temperature from room to 1008C, phenyl acetate selectively
rearranges to 4-hydroxy acetophenone and the yield is more than 60%
along with 5–10% of 2-hydroxy phenyl acetate. Encouraged by this result,
we have carried out the Fries rearrangement of a variety of esters in order
to understand the scope and reactivity and the results are summarized in
Table 2.

ORDER
REPRINTS
1436
Sreedhar, Swapna, and Sridhar
Table 1. Bi(OTf)3 catalyzed Claisen rearrangement of allyl phenyl ethers.
Entry
1
Starting materials
Productsa
Time (min)
20
2
10
3
4
15
120
5
6
15
10
aBased on isolated yields.

ORDER
REPRINTS
Bismuth(III) Triflate
Table 2. Bi(OTf)3 catalyzed Fries rearrangement of phenyl acetates.
1437
Entry
1
Starting material
Time (h)
1.5
Productsa
Yielda (%)
60
2
3
4
1
3
1
80
60
80
5
2
55
aBased on isolated yields.
It is clear from Table 2 that the reaction was completed in 1–3 h. In
every case, the reactions proceeded smoothly using a catalytic amount of
bismuth(III) triflate to afford the corresponding hydroxy acetophenones in
good yields. p-cresyl acetate (Table 2, entry 2) rearranges to ortho substituted
2-hydroxy 5-methyl acetophenone, while, p-nitro phenylacetate (Table 2,
entry 3) rearranges to ortho substituted 2-hydroxy 5-nitro acetophenone, but
Scheme 2.

ORDER
REPRINTS
1438
Sreedhar, Swapna, and Sridhar
due to the electron withdrawing nature of the latter, the reaction takes longer
time. In case of 2,6-dimethoxyphenyl acetate (Table 2, entry 4), it rearranges
to p-acylated product selectively within 1 h.
In summary, a highly efficient method for the Claisen rearrangement of
allyl, crotyl, and prenyl ethers, and Fries rearrangement of phenyl acetates cata-
lyzed by bismuth(III) triflate in acetonitrile and toluene in good to excellent
yields under milder reaction conditions is described. The use of bismuth(III)
triflate catalyst is these rearrangements is economical as the catalyst can be
prepared from inexpensive materials [bismuth(III) oxide and triflic acid].
The catalyst not only improved the yields but also shortened the reaction
times. Thus, bismuth(III) triflate mediated Claisen and Fries rearrangement
reactions are simple and high yielding for the rearrangement of allyl ethers
and phenyl esters.
EXPERIMENTAL
Typical Experimental Procedure for Claisen Rearrangement
To a stirred solution of p-cresyl allyl ether (1 mmol) in acetonitrile (5 mL)
at reflux temperature was added bismuth triflate (5 mol%). The mixture was
stirred until reaction was completed as indicated by TLC. The reaction mix-
ture was concentrated under reduced pressure and purified by silica gel col-
umn chromatography to get the pure product.
Typical Experimental Procedure for Fries Rearrangement
To a stirred solution of phenyl acetate (1 mmol) in toluene (5 mL) at reflux
temperature was added bismuth triflate (5 mol%). The mixture was stirred
until reaction was completed as indicated by TLC. The reaction mixture
was concentrated under reduced pressure and purified by silica gel column
chromatography to get the pure product.
ACKNOWLEDGMENTS
Ch. Sridhar thanks the Council of Scientific and Industrial Research,
New Delhi, India for awarding Senior Research Fellowship.

ORDER
REPRINTS
Bismuth(III) Triflate
1439
REFERENCES
1. (a) Rhoads, S.J.; Raulins, N.R. Organic Reactions; Wiley: New York,
1974; Vol. 22; (b) Wipf, P. Comprehensive Organic Synthesis;
Trost, B.M., Ed.; Pergamon Press: Oxford, 1991; Vol. 5, 827;
(c) Martin, R. Org. Prep. Proced. Int. 1992, 24, 369; (d) Stoughton, R.W.
The Fries reaction with a-naphthol esters. J. Am. Chem. Soc. 1935, 57,
202.
2. Cagniant, D. Recent advances in the chemistry of benzo[b]furan and its
derivatives. Part I: Occurence and synthesis. Adv. Heterocycl. Chem.
1975, 18, 358.
3. Crouse, D.J.; Hurlbut, S.L.; Wheeler, M.S. Photo Fries rearrangements of
1-napthyl esters in the synthesis of 2-acylnapthoquinones. J. Org. Chem.
1981, 46, 374.
4. Bhushan, M.K.; Virendra, R.M. Fries rearrangement at atmospheric
pressure using microwave irradiation. Synth. Commun. 1999, 29, 1195.
5. Lutz, R.P. Catalyssis of the Cope and Claisen rearrangements. Chem.
Rev. 1984, 84, 205.
6. (a) Suzuki, H.; Ikegami, T.; Matano, Y. Bismuth in organic transform-
ations. Synthesis 1997, 249; (b) Marshall, J.A. Chemtracts 1997, 10,
1064; (c) Vidal, S. Bismuth(III) derivatives: new catalysts. Synlett.
2001, 1194.
7. (a) Desmurs, J.R.; Labrouillere, M.; Le Roux, C.; Gaspard, H.;
Laporterie, A.; Dubac, J. Surprising catalytic activity of bismuth (III)
triflate in the Friedel-Crafts acylation reaction. Tetrahedron Lett. 1997,
38, 8871; (b) Repichet, S.; Leroux, C.; Dubac, J. Bismuth(III) trifluoro-
methanesulfonate: a chameleon catalyst for the Friedel-Crafts acylation.
Eur. J. Org. Chem. 1998, 1998, 2743.
8. (a) Repichet, S.; Leroux, C.; Hernandez, P.; Dubac, J.; Desmurs, J.R. Bis-
muth(III) trifluoromethane sulfonate: an efficient catalyst for the sulfonyl-
ation of arenes. J. Org. Chem. 1999, 64, 6479; (b) Repichet, S.; Le
Roux, C.; Dubac, J. Bismuth(III) halides: remarkable doping agents for
triflic acid in the catalytic sulfonylation of arenes. Tetrahedron Lett.
1999, 40, 9233.
9. (a) Laurent-Robert, H.; Le Roux, C.; Dubac, J. Allylation of aldehydes
with allyltin compounds in acidic aqueous media-A catalytic version.
Synlett. 1998, 1138; (b) Garrigues, B.; Gonzaga, F.; Robert, H.;
Dubac, J. Bismuth(III) chloride or triflate-catalyzed dienophilic activity
of a-ethylenic aldehydes and ketones. J. Org. Chem. 1997, 62, 4880;
(c) Robert, H.; Garrigues, B.; Dubac, J. The carbonyl-Diels–Alder reac-
tion catalyzed by bismuth (III) chloride. Tetrahedron Lett. 1998, 39, 1161.

ORDER
REPRINTS
1440
Sreedhar, Swapna, and Sridhar
10. (a) Yanagisawa, A.; Morodome, M.; Nakashima, H.; Yamamoto, H.
Allyation of aldehydes with allyltin compounds in acidic aqueous
media-A catalytic version. Synlett. 1997, 1309; (b) Loh, T.-P.; Xu, J.
¨
Trifluoromethane sulphonic acid: a Bronsted acid catalyst for the addition
of allyltributylstannanes to carbonyl compounds in water. Tetrahedron
Lett. 1999, 40, 2431.
11. Choudary, B.M.; Sridhar, Ch.; Raja Sekhar, Ch.V. Highly efficient allyl-
ation of aldehydes and three component synthesis of homoallylamines
using bismuth triflate catalyst. Synlett. 2002, 10, 1694.
12. Kobayashi, S.; Moriwaki, M.; Hachiya, I. The catalytic Fries rearrange-
ment and o-acylation reactions using group 3 and 4 metal triflates as
catalysts. Bull. Chem. Soc. Jpn. 1997, 70, 267.
13. Orita, A.; Tanahashi, C.; Kakuda, A.; Otera, J. Highly efficient and versa-
tile acylation of alcohols with Bi(OTf)3 as catalyst. Angew. Chem., Int.
Ed. 2000, 39, 2877.
Received in India November 10, 2003

Request Permission or Order Reprints Instantly!
Interested in copying and sharing this article? In most cases, U.S. Copyright
Law requires that you get permission from the article’s rightsholder before
using copyrighted content.
All information and materials found in this article, including but not limited
to text, trademarks, patents, logos, graphics and images (the "Materials"), are
the copyrighted works and other forms of intellectual property of Marcel
Dekker, Inc., or its licensors. All rights not expressly granted are reserved.
Get permission to lawfully reproduce and distribute the Materials or order
reprints quickly and painlessly. Simply click on the "Request Permission/
Order Reprints" link below and follow the instructions. Visit the
U.S. Copyright Office for information on Fair Use limitations of U.S.
copyright law. Please refer to The Association of American Publishers’
Fair Use in the Classroom.
(AAP) website for guidelines on
The Materials are for your personal use only and cannot be reformatted,
reposted, resold or distributed by electronic means or otherwise without
permission from Marcel Dekker, Inc. Marcel Dekker, Inc. grants you the
limited right to display the Materials only on your personal computer or
personal wireless device, and to copy and download single copies of such
Materials provided that any copyright, trademark or other notice appearing
on such Materials is also retained by, displayed, copied or downloaded as
part of the Materials and is not removed or obscured, and provided you do
not edit, modify, alter or enhance the Materials. Please refer to our
Website
User Agreement for more details.
Request Permission/Order Reprints
Reprints of this article can also be ordered at
http://www.dekker.com/servlet/product/DOI/101081SCC120030693