Environmentally friendly arylmethylation of aromatics with benzyl halides using envirocat EPZ10 as the catalyst

Article abstract of DOI:10.1007/s007060070069

The Friedel-Crafts arylmethylation of aromatics with benzyl halides or bis-(bromomethyl)-benzene in the presence of Envirocat EPZ10 affords selectively para-arylmethylated products in good yields. Isolation of pure products involving an eco-friendly procedure and recyclability of the catalyst are important features of this method.

Full text of DOI:10.1007/s007060070069

Monatshefte fuÈr Chemie 131, 913±915 (2000)
Environmentally Friendly Arylmethylation of
Aromatics with Benzyl Halides Using Envirocat
EPZ101 as the Catalyst
Ã
Babasaheb P. Bandgar and Suhas P. Kasture
Organic Chemistry Research Laboratory, School of Chemical Sciences, Swami Ramanand Teerth
Marathwada University, Vishnupuri, Nanded-431606, India,
Summary. The Friedel-Crafts arylmethylation of aromatics with benzyl halides or bis-
(bromomethyl)-benzene in the presence of Envirocat EPZ101 affords selectively para-arylmethy-
lated products in good yields. Isolation of pure products involving an eco-friendly procedure and
recyclability of the catalyst are important features of this method.
Keywords. Envirocat EPZ101; Arylmethylation; Eco-friendly; Catalyst; Friedel-Crafts reaction.
Introduction
The benzylation of aromatic rings under Friedel-Crafts conditions is of substantial
synthetic, industrial, and pharmacological signi®cance [1±4]. Using homogenous
catalysis employing Lewis acids like AlCl3 and FeCl3, signi®cant volumes of
solvent are required and unwanted by-products are formed. Moreover, catalysts
cannot be reused, and transalkylation, dealkylation, rearrangements, and poly-
alkylations are dif®cult to avoid [4]. Therefore, alternative synthetic ways are of
considerable interest [5].
In recent years there has been a considerable growth of interest in the catalysis of
organic reactions by inorganic reagents supported on high surface area inorganic
materials [6]. These reactions often proceed with greater selectivity than analogous
homogenous reactions. Envirocats, a new family of solid-supported reagents, have
constituted a signi®cant breakthrough in environmentally friendly chemistry [6].
These supported reagents are non-toxic and reusable powers of both Brùnsted and
Lewis acid characteristics [6]. We report herein the Friedel-Crafts arylmethylation of
phenol and anisole with various benzyl halides using Envirocat EPZ101 as a novel
catalyst.
Results and Discussion
The results of arylmethylation are summarized in Table 1. The treatment of
activated aromatic compounds like phenol and anisole with benzyl halides or bis-
Ã
Corresponding author

914
B. P. Bandgar and S. P. Kasture
a
Products were characterized by their physical constants [7], their IR and 1H NMR spectra, and by
b
comparison with authentic samples; isolated products

Friedel-Crafts Reactions Catalyzed by Envirocat EPZ101
915
(bromomethyl)-benzene in the presence of catalytic amounts of Envirocat EPZ101
afforded mainly the corresponding para-arylmethylated products (o: p ˆ 1:4). The
para-selectivity is impressive compared with that achieved employing aluminum
chloride [1±3]. In the synthesis of the pharmaceutical intermediate 4-chloro-40-
hydroxydiphenylmethane (entry 2), the use of Envirocat EPZ101 offers a
commercially feasible route; the catalyst can be reused for several cycles without
loss of activity.
Experimental
Envirocat EPZ101 was obtained from Contract Chemicals, England, and used without activation. IR
spectra were recorded on a Bomen MB 104 FT-IR spectrometer, 1H NMR spectra on a Perkin-Elmer
90 MHz instrument using TMS as an internal standard.
A mixture of 5 mmol benzyl halide, 100 mmol phenol or anisole, and 100 mg Envirocat EPZ101
was re¯uxed for the time speci®ed in Table 1. After completion of the reaction (TLC), the catalyst
was ®ltered off and washed with ether (2 Â 10 cm3). The solvent was removed under reduced
pressure, and the products were puri®ed by column chromatography (silica gel G, ethyl
acetate:petroleum ether ˆ 1:19).
Acknowledgements
We thank Contract Chemicals, England, for a generous gift of Envirocat EPZ101.
References
[1] Olah GA (1964) Friedel-Crafts and Related Reactions, vol 11, part 1. Wiley Interscience, New
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Dekker, New York
[3] Olah GA, Krishnamurti R, Prakash GKS (1991) In: Trost BM, Fleming I (eds) Friedel-Crafts
Alkylations in Comprehensive Organic Synthesis. Pergamon Press, Oxford
[4] For a pharmacologically important intramolecular Friedel-Crafts benzylation reaction see:
Yamamoto T, Fukumoto M, Sakaue N, Furusawa T, Tashiro M (1991) Synthesis 699
[5] Kadomari M, Taguchi SJ (1996) Chem Res (S) 240; Tsuchimoto T, Tobita K, Hiyama T, Fukuzawa
S (1996) Synlett 557
[6] Clark JH, Kybett AP, Macquarrie DJ (1992) Supported Reagents. VCH, New York; Clark JH,
Macquarrie D (1996) J Chem Soc Rev 303; Contract Chemicals, England (1994) Product
information
[7] Dictionary of Organic Compounds, 6th edn (1995) Chapman & Hall, London; Vogel AI (1975) A
Text of Practical Organic Chemistry, 3rd edn. ELBS, Longman, London
Received January 17, 2000. Accepted (revised) March 2, 2000
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