Efficient and mild iron-catalyzed direct allylation of benzyl alcohols and benzyl halides with allyltrimethylsilane

Article abstract of DOI:10.1080/00397910903219393

An efficient and mild iron-catalyzed direct allylation of benzyl alcohols and benzyl halides with allyltrimethylsilane has been developed. The present reaction would provide an excellent alternative to published methods because of its excellent yields, sustainable catalyst, and mild conditions. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910903219393

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Efficient and Mild Iron-Catalyzed Direct
Allylation of Benzyl Alcohols and Benzyl
Halides with Allyltrimethylsilane
Jie Han a , Zili Cui a , Jianguo Wang a & Zhongquan Liu a
a Institute of Organic Chemistry, Gannan Normal University,
Ganzhou, China and Lanzhou University , Lanzhou, China
Published online: 17 Jun 2010.
To cite this article: Jie Han , Zili Cui , Jianguo Wang & Zhongquan Liu (2010) Efficient and Mild Iron-
Catalyzed Direct Allylation of Benzyl Alcohols and Benzyl Halides with Allyltrimethylsilane, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry,
40:14, 2042-2046, DOI: 10.1080/00397910903219393
To link to this article: http://dx.doi.org/10.1080/00397910903219393
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Synthetic Communications1, 40: 2042–2046, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903219393
EFFICIENT AND MILD IRON-CATALYZED DIRECT
ALLYLATION OF BENZYL ALCOHOLS AND BENZYL
HALIDES WITH ALLYLTRIMETHYLSILANE
Jie Han, Zili Cui, Jianguo Wang, and Zhongquan Liu
Institute of Organic Chemistry, Gannan Normal University, Ganzhou, China
and Lanzhou University, Lanzhou, China
An efficient and mild iron-catalyzed direct allylation of benzyl alcohols and benzyl halides
with allyltrimethylsilane has been developed. The present reaction would provide an excel-
lent alternative to published methods because of its excellent yields, sustainable catalyst,
and mild conditions.
Keywords: Allylation; benzyl alcohols; benzyl halides; iron catalysis
The development of direct carbon–carbon (C–C) bond construction that uses
low-cost, environmentally benign, and sustainable catalysts is a critical challenge
for organic chemists. Recently, catalytic systems using iron as the active catalyst have
received great attention, and some efficient iron-catalyzed systems have been
developed for C–C couplings.[1] Herein, we report an efficient and mild iron-catalyzed
direct allylation of benzyl alcohols and benzyl halides with allyltrimethylsilane.
Although few C–C bond constructions using benzyl alcohols have been
achieved because of the poor leaving ability of the hydroxide group, it remains very
attractive because it would be atom-efficient and environmentally benign, as water is
the only by-product.[2] In past years, some efficient methods have been explored to
prepare terminal olefins via direct allylation of benzyl alcohols with allyltrimethylsi-
lane using various catalysts, such as BF3,[3] bis(fluorosulfuryl)imide,[4] B(C6F5)3,[5]
InCl3,[6] InBr3,[7] BiCl3,[8] ZrCl4,[9] and H-montmorillonite.[10] However, many of
these systems suffer from hash reaction conditions[3–5,10] and relatively expensive
metal catalysts.[6–9] Therefore, development of more efficient and mild catalysts to
promote the direct allylation of benzyl alcohols remains attractive. We successfully
accomplished an efficient and mild catalytic allylation of benzyl alcohols and halides
with allyltrimethylsilane by using 5 mol% of FeCl3 ꢀ 6H2O as the active catalyst
(Scheme 1, Table 1). To the best of our knowledge, this is the first example of an
iron-catalyzed allylation of benzyl alcohols and halides with allylsilane. (It puzzled
us that a very low yield (5%) of the allylated product was obtained using benzhydrol
Received March 26, 2009.
Address correspondence to Zhongquan Liu, Institute of Organic Chemistry, Gannan Normal
University, Ganzhou 341000, China. E-mail: liuzhongquan@yahoo.cn
2042

IRON-CATALYZED ALLYLATION OF BENZYL ALCOHOLS
2043
Scheme 1. Iron-catalyzed allylation of benzyl alcohols and halides with allyltrimethylsilane.
Table 1. Optimization of the typical reaction conditionsa
Entry
1
Catalyst (mol%)
FeCl3 (5)
Solvent
CH2Cl2
Isolated yield (%)
100
100
100b
84c
0
2
FeCl3 ꢀ 6H2O (5)
CH2Cl2
3
4
Fe2(SO4)3 (5)
FeCl2 (5)
CuBr2 (5)
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CHCl3
DCE
0
5
0
6
CuBr (5)
0
7
FeCl3 ꢀ 6H2O (2)
FeCl3 ꢀ 6H2O (1)
FeCl3 ꢀ 6H2O (5)
FeCl3 ꢀ 6H2O (5)
FeCl3 ꢀ 6H2O (5)
FeCl3 ꢀ 6H2O (5)
FeCl3 ꢀ 6H2O (5)
FeCl3 ꢀ 6H2O (5)
94
86
0
8
9
10
11
12
13
14
60
0
CH3CN
H2O
0
Hexane
THF
0
0
aReaction conditions: 1-phenyl-1-p-chlorophenyl methanol (0.5 mmol), allyltrimethylsilane (1.0 mmol),
rt, 0.5 h.
bAlcohol=allylsilane ¼ 1:3.
cAlcohol=allylsilane ¼ 1:1.
and allyltrimethylsilane catalyzed by 5% FeCl3, according to Ref. 8. However, we
obtained nearly quantitative yield of the desired product by using 5% FeCl3 under
a similar condition.)
EXPERIMENTAL
For the initial research, we select 1-phenyl-1-p-chlorophenyl methanol and
allyltrimethylsilane as standard substrates to optimize suitable conditions for this
substitution reaction (Table 1). The desired allylation product was obtained in quan-
titative yield using 5 mol% of anhydrous FeCl3 at room temperature in CH2Cl2
(entry 1). It is interesting that 100% isolated yield of the product was also obtained
by using 5 mol% of FeCl3 ꢀ 6H2O as catalyst (entry 2). The yield of product decreased

2044
J. HAN ET AL.
Table 2. Allylation of benzyl alcohols and halides with allyltrimethylsilanea
Entry
1
Benzyl alcohols or halides
Products
Time (min)
Isolated yield (%)
30
98
2
3
4
5
30
30
30
30
80
94
100
71
6
7
60
60
88
25
8
9
40
30
84
95
—
—
10
11
180
180
0
0
12
13
14
—
—
—
180
180
50
0
0
Mixture
15
16
30
30
93
91
aReaction conditions: benzyl alcohol or benzyl bromide (0.5 mmol), allyltrimethylsilane (1.0 mmol),
5 mol% FeCl3 ꢀ 6H2O (0.025 mmol), CH2Cl2, rt.

IRON-CATALYZED ALLYLATION OF BENZYL ALCOHOLS
2045
to 84% while the reaction was carried out with equal amount of alcohol and silane.
However, other iron salts and copper salts were inactive to this reaction (entries 3–6).
Decrease or increase of the catalyst dosage was less efficient than 5 mol% (entries 7
and 8). Further investigation of solvent effect showed that CH2Cl2 is a more effective
solvent (entries 9–14).
Various alcohols have been tested as substrates for the allylation reaction
(Table 2). It is seen from Table 2 that diaryl methanols gave good to excellent, even
quantitative, yields of the products (entries 1–4). 1,3-Diphenyl-allyl alcohol also gave
a good yield of the corresponding allylation product (entry 5). An excellent yield was
obtained by using 1,2,3,4-tetrahydro naphthalen-1-ol as the substrate (entry 6).
1-Phenyl ethanol gave a very poor yield of the product (entry 7), whereas 1-p-methyl-
phenyl ethanol gave 84% isolated yield (entry 8). 1-(5-Chloro-thiophen-2-yl)-ethanol
also gave excellent yield of the desired product (entry 9). However, hydroxy-phenyl-
acetic acid ethyl ester (entry 10), 1-phenyl-ethane-1,2-diol (entry 11), 2-phenyl-
ethanol (entry 12), and phenylmethanol (entry 13) were inactive in this system.
3-Phenyl-prop-2-en-1-ol gave a mixture under the condition in entry 14. It is
noteworthy that benzyl halides such as bromo-diphenyl-methane and iodo-diphenyl-
methane also gave excellent yields of the allylation products (entries 15 and 16).
In conclusion, this work demonstrates an efficient and mild iron-catalyzed
allylation of benzyl alcohols and halides with allyltrimethylsilane. Compared with
the systems reported before, the present method provides a better alternative because
of its sustainable catalyst and mild conditions. Extension of this system to other
substrates is under way in our laboratory.
ACKNOWLEDGMENT
We thank Gannan Normal University for financial support.
REFERENCES
1. For recent reviews of iron-catalyzed transformations, see (a) Bolm, C.; Legros, J.; Le Paih,
J.; Zani, L. Iron-catalyzed reactions in organic synthesis. Chem. Rev. 2004, 104, 6217; (b)
Enthaler, S.; Junge, K.; Beller, M. Sustainable metal catalysis with iron: From rust to a
rising star? Angew. Chem. Int. Ed. 2008, 47, 3317; (c) Sherry, B. D.; Furstner, A. The
promise and challenge of iron-catalyzed cross coupling. Acc. Chem. Res. 2008, 41, 1500;
For select recent examples of C–C bond formation catalyzed by iron, see (a) Martin,
R.; Furstner, A. Cross-coupling of alkyl halides with aryl Grignard reagents catalyzed
by a low-valent iron complex. Angew. Chem. Int. Ed. 2004, 43, 3955; (b) Iovel, I.; Mertins,
K.; Kischel, J.; Zapf, A.; Beller, M. An efficient and general iron-catalyzed arylation of
benzyl alcohols and benzyl carboxylates. Angew. Chem. Int. Ed. 2005, 44, 3913; (c) Lu,
Z.; Chai, G.; Ma, S. Iron-catalyzed highly regio- and stereoselective conjugate addition
of 2,3-allenoates with Grignard reagents. J. Am. Soc. Chem. 2007, 129, 14546; (d) Jana,
U.; Biswas, S.; Maiti, S. A simple and efficient FeCl3-catalyzed direct alkylation of active
methylene compounds with benzylic and allylic alcohols under mild conditions. Tetra-
hedron Lett. 2007, 48, 4065; (e) Wang, B.; Xiang, S.; Sun, Z.; Guan, B.; Hu, P.; Zhao,
K.; Shi, Z. Benzylation of arenes through FeCl3-catalyzed Friedel–Crafts reaction via
C–O activation of benzyl ether. Tetrahedron Lett. 2008, 49, 4310; (f) Liu, Z.; Wang, J.;
Han, J.; Zhao, Y.; Zhou, B. An efficient and mild iron-mediated synthesis of alkenyl

2046
J. HAN ET AL.
halides via direct C–C bond formation of benzyl alcohols and aryl alkynes. Tetrahedron
Lett. 2009, 50, 1240; (g) Liu, Z.; Wang, J.; Zhao, Y.; Zhou, B. A mild and efficient
iron-catalyzed synthesis of alkenyl halides via direct addition of benzyl halides to arylalk-
ynes. Adv. Synth. Catal. 2009, 351, 371.
2. (a) Dau-Schmidt, J. P.; Mayr, H. Relative reactivities of alkyl chlorides under Friedel–
Crafts conditions. Chem. Ber. 1994, 127, 205; (b) Kabalka, G. W.; Yao, M.; Borella, S.;
Wu, Z. Substitution of benzylic hydroxyl groups with vinyl moieties using vinylboron
dihalides. Org. Lett. 2005, 7, 2865; (c) Kabalka, G. W.; Yao, M.; Borella, S. Generation
of cations from alkoxides: Allylation of propargyl alcohols. J. Am. Chem. Soc. 2006, 128,
11320; (d) Liu, Y.; Liu, L.; Wang, Y.; Han, Y.; Wang, D.; Chen, Y. Calix[n]arene sulfonic
acids bearing pendant aliphatic chains as recyclable surfactant-type Brønsted acid cata-
lysts for allylic alkylation with allyl alcohols in water. Green Chem. 2008, 10, 635.
3. Cella, J. A. Reductive alkylation=arylation of arylcarbinols and ketones with organosili-
con compounds. J. Org. Chem. 1982, 47, 2125.
4. Kaur, G.; Kausik, M.; Trehan, S. Bis(fluorosulfuryl)imide: A Brønsted acid catalyst for
the coupling of allylic and benzylic alcohols with allyltrimethylsilane. Tetrahedron Lett.
1997, 38, 2521.
5. Rubin, M.; Gevorgyan, V. B(C6F5)3-catalyzed allylation of secondary benzyl acetates with
allylsilanes. Org. Lett. 2001, 3, 2705.
6. (a) Yasuda, M.; Saito, T.; Ueba, M.; Baba, A. Direct substitution of the hydroxy group in
alcohols with silyl nucleophiles catalyzed by indium trichloride. Angew. Chem. Int. Ed.
2004, 43, 1414; (b) Saito, T.; Nishimoto, Y.; Yasuda, M.; Baba, A. Direct coupling reac-
tion between alcohols and silyl compounds: Enhancement of Lewis acidity of Me3SiBr
using InCl3. J. Org. Chem. 2006, 71, 8516.
7. Kim, S. H.; Shin, C.; Pai, A. N.; Koh, H. K.; Chang, M. H.; Chung, B. Y.; Cho, Y. S.
InBr3-catalyzed deoxygenative allylation of benzylic and allylic alcohols and acetates with
allyltrimethylsilane. Synthesis 2004, 1581.
8. De, S. K.; Gibbs, R. A. Bismuth(III) chloride–catalyzed direct deoxygenative allylation of
substituted benzylic alcohols with allyltrimethylsilane. Tetrahedron Lett. 2005, 46, 8345.
9. Sharma, G. V. M.; Reddy, K. L.; Lakshmi, P. S.; Ravi, R.; Kunwar, A. C. Direct
c-allylation of aryl-alkyl=glycosyl carbinols: Facile synthesis of c-linked carbo-b2-=c2-=d2-
amino acids. J. Org. Chem. 2006, 71, 3967.
10. Motokura, K.; Nakagiri, N.; Mizugaki, T.; Ebitani, K.; Kaneda, K. Nucleophilic substi-
tution reactions of alcohols with use of montmorillonite catalysts as solid Brønsted acids.
J. Org. Chem. 2007, 72, 6006.