Mild and efficient allylation of indoles and amides using Amberlyst-15 as a recyclable heterogeneous catalyst

Article abstract of DOI:10.1080/00397911.2010.545162

A mild and efficient allylation of indoles and amides in the presence of a catalytic amount of Amberlyst-15 has been described in this context. The recyclable heterogeneous catalytic system is practical and facile for the synthesis of C- and N-allylated d

Full text of DOI:10.1080/00397911.2010.545162

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Mild and Efficient Allylation of Indoles
and Amides Using Amberlyst-15 as a
Recyclable Heterogeneous Catalyst
Zhe Liu a , Dong Wang a , Yanchao Wu a & Yongjun Chen a
a Institute of Chemistry, Chinese Academy of Sciences (ICCAS),
Center for Molecular Sciences , Beijing , China
Accepted author version posted online: 17 Nov 2011.Published
online: 27 Feb 2012.
To cite this article: Zhe Liu , Dong Wang , Yanchao Wu & Yongjun Chen (2012) Mild and Efficient
Allylation of Indoles and Amides Using Amberlyst-15 as a Recyclable Heterogeneous Catalyst,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 42:12, 1813-1823, DOI: 10.1080/00397911.2010.545162
To link to this article: http://dx.doi.org/10.1080/00397911.2010.545162
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Synthetic Communications1, 42: 1813–1823, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.545162
MILD AND EFFICIENT ALLYLATION OF INDOLES AND
AMIDES USING AMBERLYST-15 AS A RECYCLABLE
HETEROGENEOUS CATALYST
Zhe Liu, Dong Wang, Yanchao Wu, and Yongjun Chen
Institute of Chemistry, Chinese Academy of Sciences (ICCAS),
Center for Molecular Sciences, Beijing, China
GRAPHICAL ABSTRACT
Abstract A mild and efficient allylation of indoles and amides in the presence of a catalytic
amount of Amberlyst-15 has been described in this context. The recyclable heterogeneous
catalytic system is practical and facile for the synthesis of C- and N-allylated derivatives
and would be of importance for the development of the accordingly functional complex
molecules.
Keywords Allylation; Amberlyst-15; heterogeneous catalysis; recyclable
INTRODUCTION
Allylation of C- and heteroatom-nucleophiles have attracted much attention in
modern organic chemistry. Indole and its derivatives are important and reactive
nucleophiles, existing in a number of pharmaceutical molecules and naturally occur-
ring products that show significant bioactivities and broad applications in pharma-
ceutical, material, industrial, and agrochemical fields.[1] Recently, allylation[2–8] of
Received July 22, 2010.
Address correspondence to Zhe Liu, Institute of Chemistry, Chinese Academy of Sciences
(ICCAS), Center for Molecular Sciences, Beijing, China. E-mail: liuzhe@iccas.ac.cn
1813

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Z. LIU ET AL.
indole derivatives, in both intermolecular and intramolecular manners, has attracted
much attention and has been applied to elegant synthesis of indolic alkaloids.
The Friedel–Crafts allylation of indoles and amides with allylic alcohols or
esters usually employed precious transition metals such as Pd,[9–13] Mo,[14] or
Co[15] as catalysts. However, poor regioselectivity[10,13,14] or harsh reaction con-
ditions (high temperature) limited their practical applications. Although allylation
of aromatic compounds with allylic or benzyl alcohols can be promoted by some
Lewis acids,[16–22] such as Sc(OTf)3,[17,18] Hf(OTf)4, Cl2Si(OTf)2,[19] or Ce(SO4)3,[20]
stoichiometric amounts of Lewis acids were often required. Recently, Qin et al.
reported an efficient protocol of N-allylation catalyzed by Bi(OTf)3,[22] but additives
and bases were indispensable for this transformation. All this encourages us to
develop more efficient, highly regioselective, operationally simple, and general
allylation protocols.
In recent years, economical, environmentally benign, and green chemistry[23,24]
has prevailed in modern organic chemistry, and this gives rise to developments of
various heterogeneous catalytic transformations. These novel methodologies make
the synthetic process safe, clean, efficient, and inexpensive. The purification process
can be simplified, and the employment of toxic organic solvents is always decreased.
Amberlyst-15 has been emerged as an efficient heterogeneous catalyst because many
organic reactions[25–30] can been catalyzed or promoted by this powerful ion-
exchange resin. It is a cheap and nonhazardous solid acid catalyst and can be easily
handled and removed from the reaction mixtures by simple filtration. The recovered
catalyst can be recycled consecutively several times without an obvious decrease of
catalytic efficiency. In this contribution, we describe an efficient allylation of indoles
and amides using Amberlyst-15 as heterogeneous catalyst in a recyclable manner.
RESULTS AND DISCUSSION
As an extension of our previous work, various reaction conditions were
initially screened in both organic and aqueous media, and the results are summarized
in Table 1. The experimental data indicated that in organic solvents this
Amberlyst-15-catalyzed allylation could be achieved to exclusively give the desired
product of 3-allylated indole without any by-products (entries 1–4). However, trace
yield was afforded in pure water at room temperature (entry 5). To our delight, acet-
onitrile was found to be the best solvent in which indole could be mildly transformed
into an allylated product with an isolated chemical yield of 86% at room temperature
Table 1. Amberlyst-15-catalyzed allylation of indole in different solvents
Entry
Solvent
Temperature
Yielda (%)
1
2
3
4
5
CH2Cl2
CH2Cl2
CH3CN
THF
Rt
72
69
Reflux
Rt
Rt
86
61
Water
Rt
Trace
aIsolated yield.

HETEROGENEOUS AMBERLYST-15-CATALYZED ALLYLATION
1815
by utilizing catalytic Amberlyst-15 (30 mg=1 mmol). See Fig. 1. As for the regioselec-
tivity, no N-allylated or bisallylated[10,13,14] by-products were observed (entry 3).
Encouraged by these results, we then reacted various indoles with allylic acet-
ates to explore the generality of this protocol under the optimized conditions. As
shown in Table 2 and Fig. 2, various indoles could be transformed to produce good
yields and good purity of the desired products after flash chromatograph or simple
filtration without further purifications (entries 1–7 and 9). However, 5-methoxy
indole and 7-azaindole were not reactive in the model reaction (entries 8 and 11).
2-Methyl furan could also be converted into the corresponding product in good yield
(81%, entry 10). All products are characterized by NMR, infrared (IR), and mass
spectrometry.
To further extend the substrate scope for this catalytic approach, other
nucleophiles besides indoles, such as sulfonamides, carbamates, and carboxamides,
were also employed to explore the generality (Table 3 and Fig. 3). Under the opti-
mized conditions, these N-nucleophiles could be easily transformed into desired
C-N linked allylated products in excellent yields (entries 1–5), except that because
low nucleophilicity resulted from a strong electron-withdrawing functional group,
4-nitrobenzenesulfonamide showed decreased reactivity to giving product in a
reasonable yield (entry 6). To the best of our knowledge, this is the first report
that C- and N-nucleophiles could be readily converted into corresponding allylated
products just with catalytic Amberlyst-15 under solid-acid and heterogeneous
catalysis, in which involvement of metals, additives, and complex conditions were
avoided.[22]
With these satisfactory results, we next investigated recyclable allylation by
simply recycling and reusing the catalyst Amberlyst-15. Four indoles were employed
in a four-cycle allylation reaction, and excellent yields were observed without any
obvious decrease of catalytic efficiency (Table 4 and Figs. 4 and 5), which further
proved high efficacy of this catalytic strategy. The allylation could be achieved with
acceptable yields to afford the corresponding products after Amberlyst-15 were
reused up to seven cycles within 12 hours, which indicated the availability to perform
this transformation in such an efficient and recyclable manner.
Considering the simplicity, this heterogeneous catalytic strategy might be easily
applied to parallel (multichannel) synthetic chemistry with high through-put of
allylated products in a readily operational way. The product can be isolated with
common filtration, and recovered Amberlyst-15 can be used for a couple of cycles.
Because efficient, high-yielding, environmentally benign, and catalyst-recyclable
syntheses are of great importance for both academic and industrial organic synthesis,
our protocol would give possible access to the rapid and efficient allylation of indoles
Figure 1. Screening of reaction conditions of Amberlyst-15–catalyzed allylation of indole.

1816
Z. LIU ET AL.
Table 2. Allylation of indoles catalyzed by Amberlyst-15
Entry
1
Indole
Time (h)
Product
Yielda (%)
12
3a
86
2
3
4
10
8
3b
3c
3d
98
97
89
8
5
6
10
3e
3f
98
97
8
7
8
9
10
12
8
3g
3h
3i
91
Trace
98
10
11
8
3j
81
—
15
Nrb
aIsolated yield.
bNr ¼ no reaction.

HETEROGENEOUS AMBERLYST-15-CATALYZED ALLYLATION
1817
Figure 2. Broad scope of Amberlyst-15–catalyzed allylation of indoles.
and amides, as well as other suitable electrophiles in heterogeneous catalytic
synthetic chemistry.
CONCLUSION
In summary, a mild, efficient and regioselective allylation of indoles and
amides has been described in this contribution, which were accomplished in the pres-
ence of commercially available solid-acid catalyst Amberlyst-15 in a heterogeneous
catalytic system and the catalyst could be reused for seven times without obvious
diminished efficiency. Applications of this practical protocol to the synthesis of func-
tional complex molecules are being investigated in our laboratory.
EXPERIMENTAL
1H NMR spectra were recorded on a Brucker 300 (300-MHz) spectrometer.
Chemical shifts are reported in parts per million (ppm) from tetramethylsilane
(TMS) with solvent resonance as the internal standard (deuterochloroform:
d ¼ 7.27 ppm). Data are reported as follows: chemical shift, multiplicity (s ¼ singlet,
singlet, d ¼ doublet, t ¼ triplet, q ¼ quartet, br ¼ broad, m ¼ multiplet), and coupling
constants (Hz). 13C NMR spectra were recorded on a Brucker 300 (75-MHz) spec-
trometer with complete proton decoupling. Chemical shifts are reported in ppm from
TMS with the solvent as the internal standard (deuterochloroform: d ¼ 77.0 ppm).
Electron impact (EI) and high-resolution mass spectrometry (HRMS) were per-
formed on GCT-MS Micromass UK. Infrared (IR) analyses were obtained with a
Brucker Fourier transform (FT)–IR spectrophotometer. IR spectra are expressed
by wavenumber (cmꢀ1). Elemental analyses were carried out using a Flash EA
1112 analyzer. Melting points were uncorrected. Chromatographic purification
was done with 200- to 300-mesh silica gel, eluting with ethyl acetate and petroleum
ether. Thin-layer chromatography (TLC) was performed on glass-backed silica
plates precoated with silica. The dispatched reaction components were then visua-
lized under ultraviolet light to be separated.
Representative Procedure for the Preparation of 3-Allylated Indoles
Indole 1a (117 mg, 1 mmol) and 1,3-diphenylprop-2-enyl acetate 2 (252 mg,
1 mmol) were added into a flask at room temperature. Acetonitrile (8 ml) was then
poured, and the resulting mixture was vigorously stirred. Amberlyst-15 (30 mg)
was added, and the mixture was stirred for 12 h, monitored by TLC. After the

1818
Z. LIU ET AL.
Table 3. Allylation of N-nucleophiles catalyzed by Amberlyst-15
Entry
N-Nuclephile
Time (h)
Product
Yielda (%)
1
2
3
PhSO2NH2(4a)
24
91
CbzNH2(4b)
18
97
Methacrylamide(4c)
20
81
4
5
6
p-Toluenesulfonamide(4d)
20
16
16
90
93
34
PhCONH2(4e)
4-Nitrobenzenesulfonamide(4f)
aIsolated yield.
completion of reactions, the solvent was evaporated and the clean product was
afforded after simple flash chromatography (266 mg, 86%). The spectral (NMR
and MS) and analytical data of the unknown compounds are given. The spectral

HETEROGENEOUS AMBERLYST-15-CATALYZED ALLYLATION
1819
Figure 3. Amberlyst-15–catalyzed allylation of various N-nucleophiles.
properties of the remaining known compounds matched well with and can be
referred to those reported earlier.
Ethyl 3-[(E)-1,3-Diphenyl-allyl]-1H-indole-2-carboxylate (3d)
White solid. Mp 60–62 ꢁC. 1H NMR (300 MHz, CDCl3): d ¼ 1.42 (t, J ¼ 7.1 Hz,
3H), 4.42 (q, J ¼ 5.3 Hz, 2H), 6.14 (d, J ¼ 7.4 Hz, 1H), 6.49 (d, J ¼ 15.9 Hz, 1H), 6.89
(m, J ¼ 15.9 Hz, 1H), 6.95–7.53 (m, 14H), 8.83 (s, 1H). 13C NMR (75 MHz, CDCl3):
d ¼ 14.5, 44.6, 60.9, 111.9, 120.2, 122.9, 123.4, 125.0, 125.4, 126.2, 126.3, 126.9,
127.2, 128.2, 128.2, 128.5, 131.5, 131.6, 136.2, 137.4, 143.2, 162.2. IR (film): 3422,
3058, 3027, 1692, 1246, 968, 746, 697 cmꢀ1. HRMS (EI): m=z calcd. for
C26H23NO2: 381.1729; found: 381.1730. Elemental analylsis: calcd for C26H23NO2:
C, 81.86; H, 6.08; N, 3.67. Found: C, 81.19; H, 6.21; N, 3.67.
3-[(E)-1,3-Diphenyl-allyl]-6-fluoro-1H-indole (3g)
1
Green oil. H NMR (300 MHz, CDCl3): d ¼ 5.04 (d, J ¼ 7.2 Hz, 1H), 6.4 (d,
J ¼ 15.8 Hz, 1H), 6.67 (m, J ¼ 15.8 Hz, 1H), 6.76–7.34 (m, 14H), 7.74 (s, 1H). 13C
NMR (75 MHz, CDCl3): d ¼ 46.3, 97.3, 97.7, 108.1, 108.5, 118.9, 120.6, 120.7,
Table 4. Recyclable allylation of indoles catalyzed by Amberlyst-15
Entry
1
Indole
Product
3b
Yielda (%) (Cycles 1, 2, 3, 4, 7)
98, 97, 93, 91, 83
2
3
3c
3e
97, 97, 96, 94, 79
98, 97, 97, 95, 82
4
3i
98, 96, 92, 91, 80
aIsolated yield.

1820
Z. LIU ET AL.
Figure 4. Amberlyst-15–catalyzed allylation of indoles in a recyclable manner.
122.9, 123.0, 123.5, 126.4, 126.6, 127.4, 128.5, 128.6, 128.6, 130.8, 132.4, 136.6, 136.7,
137.5, 143.2, 158.5, 161.6. IR (CDCl3): 3430, 3059, 3025, 1625, 1138, 967, 745,
699 cmꢀ1. HRMS (EI): m=z calcd. for C23H18FN: 327.1423; found: 327.1413.
Methyl 3-[(E)-1,3-Diphenyl-allyl]-1H-indole-5-carboxylate (3i)
Yellow powder. Mp 125–127 ꢁC. 1H NMR (300 MHz, CDCl3): d ¼ 3.85 (s, 3H),
5.14 (d, J ¼ 7.1 Hz, 1H), 6.39 (d, J ¼ 15.8 Hz, 1H), 6.69 (m, J ¼ 15.8 Hz, 1H), 6.91 (d,
J ¼ 1.5 Hz, 1H), 7.15–8.21 (m, 13H), 8.37 (s, 1H). 13C NMR (75 MHz, CDCl3):
d ¼ 45.8, 51.9, 110.9, 120.1, 121.5, 122.7, 123.6, 124.1, 126.4, 126.5, 126.6, 127.3,
128.5, 128.5, 130.9, 132.3, 137.4, 139.3, 143.1. IR (film): 3419, 3026, 1694, 1110,
970, 750, 699 cmꢀ1. HRMS (EI): m=z calcd. for C25H21NO2: 367.1572; found:
367.1577. Elemental analylsis: calcd. for C25H21NO2: C, 81.72; H, 5.76; N, 3.81.
Found: C, 81.11; H, 6.00; N, 3.72.
2-[(E)-1,3-Diphenyl-allyl]-2-methyl-furan (3j)
1
Yellow oil. H NMR (300 MHz, CDCl3): d ¼ 2.34 (s, 3H), 4.93 (d, J ¼ 7.3 Hz,
1H), 5.98 (d, J ¼ 2.1 Hz, 1H), 6.05 (d, J ¼ 2.1 Hz, 1H), 6.48 (d, J ¼ 15.9 Hz, 1H), 6.65
Figure 5. Efficient allylation in the presence of Amberlyst-15 in a recyclable manner. (Figure is provided in
color online.)

HETEROGENEOUS AMBERLYST-15-CATALYZED ALLYLATION
1821
(m, J ¼ 15.9 Hz, 1H), 7.28–7.46 (m, 10H). 13C NMR (75 MHz, CDCl3): d ¼ 13.7,
48.5, 106.1, 107.6, 126.5, 126.8, 127.5, 128.4, 128.6, 128.6, 130.2, 131.4, 137.2,
141.5, 151.5, 154.3. IR (CDCl3): 3059, 3027, 1599, 1218, 965, 745, 697 cmꢀ1. HRMS
(EI): m=z calcd. for C20H18O: 274.1400; found: 274.1355.
N-[(E)-1,3-Diphenyl-allyl]-methacrylamide (5c)
1
Pale yellow solid. Mp 119–121 ꢁC. H NMR (300 MHz, CDCl3): d ¼ 1.96 (s,
3H), 5.33 (s, 1H), 5.73 (s, 1H), 5.84 (t, J ¼ 7.1 Hz, 1H), 6.35 (m, J ¼ 15.9 Hz, 1H),
6.42 (d, J ¼ 7.9 Hz, 1H), 6.52 (d, J ¼ 15.9 Hz, 1H), 7.18–7.35 (m, 10H). 13C NMR
(75 MHz, CDCl3): d ¼ 18.8, 54.9, 119.8, 126.6, 127.2, 127.7, 127.8, 128.6, 128.8,
128.9, 131.7, 136.5, 140.1, 140.9, 167.5. IR (CDCl3): 3304, 3060, 3028, 1654, 1616,
1522, 1210, 967, 746, 696 cmꢀ1. HRMS (EI): m=z calcd. for C19H19NO: 277.1467;
found: 277.1469.
N-[(E)-1,3-Diphenyl-allyl]-4-nitro-phenylsulfonamide (5f)
1
White solid. Mp 169–171 ꢁC. H NMR (300 MHz, CDCl3): d ¼ 5.19–5.29 (m,
2H), 6.08 (m, J ¼ 15.9 Hz, 1H), 6.41 (d, J ¼ 15.9 Hz, 1H), 7.16–7.27 (m, 10H), 7.85
(d, J ¼ 8.7 Hz, 2H), 8.10 (d, J ¼ 8.7 Hz, 2H). 13C NMR (75 MHz, CDCl3):
d ¼ 60.3, 123.9, 126.5, 127.1, 127.3, 128.3, 128.4, 128.7, 128.9, 133.1, 135.5, 138.7,
146.7. IR (CDCl3): 3278, 1528, 1344, 1157, 736, 695 cmꢀ1. HRMS (ESI): m=z calcd.
for C21H18N2O4S: 394.1000; found: 393.0915 (Mþ ꢀ H).
ACKNOWLEDGMENTS
We thank the National Natural Science Foundation of China and Chinese
Academy of Sciences for financial support.
REFERENCES
1. Sundberg, R. J. Indoles; Academic Press: San Diego, 1996.
2. Trost, B. M.; Quancard, J. Palladium-catalyzed enantioselective C-3 allylation of
3-substituted-1H-indoles using trialkylboranes. J. Am. Chem. Soc. 2006, 128, 6314.
3. Bandini, M.; Melloni, A.; Piccinelli, F.; Sinisi, R.; Tommasi, S.; Umani-Ronchi, A. Highly
enantioselective synthesis of tetrahydro-ß-carbolines and tetrahydro-c-carbolines via
Pd-catalyzed intramolecular allylic alkylation. J. Am. Chem. Soc. 2006, 128, 1424.
4. Yadav, J. S.; Reddy, B. V. S.; Basak, A. K.; Narsaiah, A. V.; Prabhakar, A.; Jagadeesh, B.
First example of the C-alkylation of indoles with Baylis–Hillman acetates. Tetrahedron
Lett. 2005, 46, 639.
5. Westermaier, M.; Mayr, H. Electrophilic allylations and benzylations of indoles in neutral
aqueous or alcoholic solutions. Org. Lett. 2006, 8, 4791.
6. Prajapati, D.; Gohain, M.; Gogoi, B. J. Novel gallium-mediated C3-allylation of indoles
and pyrroles in aqueous media promoted by Bu4NBr. Tetrahedron Lett. 2006, 47, 3535.
7. Yadav, J. S.; Reddy, B. V. S.; Muralikrishna, P.; Srinivas, C. Zinc-mediated Barbier reac-
tions of pyrroles and indoles: A new method for the alkylation of pyrroles and indoles.
Tetrahedron Lett. 2002, 43, 5185.

1822
Z. LIU ET AL.
8. Ma, S.-M.; Yu, S.-C. Palladium-catalyzed functionalization of indoles with 2-acetoxy-
methyl substituted electron-deficient alkenes. Tetrahedron Lett. 2004, 45, 8419.
9. Kimura, M.; Futamata, M.; Mukai, R.; Tamaru, Y. Pd-catalyzed C3-selective allylation
of indoles with allyl alcohols promoted by triethylborane. J. Am. Chem. Soc. 2005, 127,
4592.
10. Bandini, M.; Melloni, A.; Umani-Ronchi, A. New versatile Pd-catalyzed alkylation of
indoles via nucleophilic alyllic substitution: Controlling the regioselectivity. Org. Lett.
2004, 6, 3199.
11. Trost, B. M.; Krische, M. J.; Berl, V.; Grenzer, E. M. Chemo-, regio-, and enantioselective
Pd-catalyzed allylic alkylation of indolocarbazole pro-aglycons. Org. Lett. 2002, 4,
2005.
12. Wenkert, E.; Angell, E. C.; Ferreira, V. F.; Michelotti, E. L.; Piettre, S. R.; Sheu, J.-H.;
Swindell, C. S. Synthesis of prenylated indoles. J. Org. Chem. 1986, 51, 2343.
13. Billups, W. E.; Erkes, R. S.; Reed, L. E. Palladium-catalyzed allylation of indoles. Synth.
Commun. 1980, 10, 147.
14. Malkov, A. V.; Davis, S. L.; Baxendale, I. R.; Mitchell, W. L.; Kocovsky, P.
Molybdenum(II)-catalyzed allylation of electron-rich aromatics and heteroaromatics.
J. Org. Chem. 1999, 64, 2751.
15. Mukhopadhyay, M.; Iqbal, J. Co(III)DMG-catalyzed synthesis of allylamides from allyl
alcohols and acetonitrile. J. Org. Chem. 1997, 62, 1843.
16. Yasuda, M.; Somyo, T.; Baba, A. Direct carbon–carbon bond formation from alcohols
and active methylenes, alkoxyketones, or indoles catalyzed by indium trichloride. Angew.
Chem. Int. Ed. 2006, 45, 793.
17. Tsuchimoto, T.; Tobita, K.; Hiyama, T.; Fukuzawa, S.-I. Scandium(III) triflate–catalyzed
Friedel–Crafts alkylation reactions. J. Org. Chem. 1997, 62, 6997.
18. Tsuchimoto, T.; Tobita, K.; Hiyama, T.; Fukuzawa, S.-I. Scandium(III) triflate–catalyzed
Friedel–Crafts alkylations with benzyl and allyl alcohols. Synlett. 1996, 557.
19. Shiina, I.; Suzuki, M. The catalytic Friedel–Crafts alkylation reaction of aromatic com-
pounds with benzyl or allyl silyl ethers using Cl2Si(OTf)2 or Hf(OTf)4. Tetrahedron Lett.
2002, 43, 6391.
20. Li, J.-H.; Liu, W.-J.; Yin, D.-L. An efficient and inexpensive catalyst system for Friedel–
Crafts alkylation of aromatic compounds with benzyl and allyl alcohols. Synth. Commun.
2004, 34, 3161.
21. Zhu, X.; Ganesan, A. Regioselective synthesis of 3-alkylindoles mediated by zinc triflate.
J. Org. Chem. 2002, 67, 2705.
22. Qin, H.; Yamagiwa, N.; Matsunaga, S.; Shibasaki, M. Bismuth-catalyzed direct substi-
tution of the hydroxy group in alcohols with sulfonamides, carbamates, and carboxa-
mides. Angew. Chem. Int. Ed. 2007, 46, 409.
23. Anastas, P. T.; Warner, T. C. Green Chemistry: Theory and Practice; Oxford University
Press: New York, 1998.
24. Clark, J.-H. Solid acids for green chemistry. Acc. Chem. Res. 2002, 35, 791.
25. Arlette, S.-C.; Paolo, L.; Carlo, B. Regio- and stereoselective ring opening of 2,3-diaryl
oxiranes by LiBr=Amberlyst-15: A new stereocontrolled access to 1,2-diaryl-2-bromo
alcohols. J. Org. Chem. 2005, 70, 1605.
26. Das, B.; Thirupathi, P.; Mahender, I.; Reddy, V. S.; Rao, Y. K. Amberlyst-15: An
efficient reusable heterogeneous catalyst for the synthesis of 1,8-dioxo-octahydrox-
anthenes and 1,8-dioxo-decahydroacridines. J. Mol. Catal. A 2006, 247, 233.
27. Das, B.; Majhi, A.; Banerjee, J.; Chowdhury, N. A convenient highly stereoselective syn-
thesis of allyl amides from Baylis–Hillman adducts using Amberlyst-15 as a heterogeneous
reusable catalyst. J. Mol. Catal. A 2006, 260, 32.

HETEROGENEOUS AMBERLYST-15-CATALYZED ALLYLATION
1823
28. Yadav, J. S.; Reddy, B. V. S.; Vishnumurthy, P. Amberlyst-15 as a novel and recyclable
solid acid for the coupling of aromatic aldehydes with homopropargyl alcohol.
Tetrahedron Lett. 2005, 46, 1311.
29. Meshram, H. M.; Reddy, P. N.; Sadashiv, K.; Yadav, J. S. Amberlyst-15-promoted
efficient 2-halogenation of 1,3-keto-esters and cyclic ketones using N-halosuccinimides.
Tetrahedron Lett. 2005, 46, 623.
30. Das, B.; Banerjee, J.; Ramu, R.; Pal, R.; Ravindranath, N.; Ramesh, C. Efficient, selective
deprotection of aromatic acetates catalyzed by Amberlyst-15 or iodine. Tetrahedron Lett.
2003, 44, 5465.