An Environmentally Friendly Route for the Synthesis of Benzofurane Derivatives using Selective Ring Acylation of Resorci
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An Environmentally Friendly Route for the Synthesis of Benzofurane Derivatives using Selective Ring Acylation of Resorcinol ´ gai Æ Ja´nos Farkas Æ Sa´ndor Be´ka´ssy Æ Be´la A Eszter Ga´bor Æ Ma´ria Ferenczi Æ Franc¸ois Figueras
Received: 15 February 2007 / Accepted: 10 March 2007 / Published online: 14 July 2007 Springer Science+Business Media, LLC 2007
Abstract The synthesis of 2,2-dimethyl-2,3-dihydrobenzofuran-6-ol, an important intermediate for benzofurane derivatives having pharmaceutical activity, is achieved by an environmentally friendly pathway. Whereas the current synthesis method, based on resorcinol dimethylether, uses or produces harmful, corrosive and dangerous reagents/materials, the procedure proposed here achieves 60% preparative yield for the selective direct ring acylation of resorcinol with isobutyryl chloride, using a solvent-free reaction catalysed by solid acids. Keywords Clays Acylation Resorcinol Solvent-free reaction Benzofurane precursor
The environmentally friendly preparation of the key intermediate 1-(2,4-dihydroxyphenyl)-2-phenylethanone for the synthesis of Ipriflavone, an antiosteopenic drug, has been reported earlier [1]. In contrast with the classical reaction based on Lewis acids such as AlCl3, the chemoselective Friedel-Crafts ring acylation of resorcinol with phenylacetyl chloride was achieved in solvent-free conditions, using a solid acid catalyst, and the method could be scaled up. We present here the synthesis of the precursor 2 of 2,2dimethyl-2,3-dihydro-benzofuran-6-ol (1) (Scheme 1), another important compound from pharmacological point of view, obtained by an environmentally friendly way, from resorcinol and isobutyryl chloride.
1 Introduction 2 Strategy for an Environmentally Friendly Synthesis One of the bases of the modern chemical technologies is to avoid the formation of hazardous effluents, instead of eliminating (usually by further chemical treatment) these effluents already arised. This principle is the base of our activity on new and environmentally friendly synthetic methods, e.g. for the preparation of dihydroxyphenyl ketones, which are important intermediates for drugs and perfumery.
´ gai J. Farkas E. Ga´bor S. Be´ka´ssy (&) B. A M. Ferenczi Department of Organic Chemical Technology, Budapest University of Technology and Economics, Budapest 1521, Hungary e-mail: [email protected] F. Figueras Institut de Recherches sur la Catalyse, 2 Av. Albert Einstein, Villeurbanne 69626, France
2.1 Choice of the Synthesis Route Benzofurane derivatives such as e.g. Carbofurane are important antioxidants and efficient pesticides. These compounds play a significant role also as essential constituents of 5-HT1 antagonists (3) [2] (Scheme 2).
O
HO
O
1
HO
OH
2
Scheme 1 Retrosynthetic route for benzofuranol from resorcinol
123
S. Be´ka´ssy et al.
220 Scheme 2 Benzofurane derivatives having biological activity
Cl OH
X
1.) O
2.) SnCl 4
OH
OH
Ar
A B
OH
O
N
O
3 The synthesis of the structural isomers of 3 was necessary for the elucid
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