Reductive Cleavage of Heteroaromatic Naphthyl Ethers: Structural Effects on Reactivity

Maria de Lurdes S. Cristiano ,  Nuna Araújo ,  Paula Pena ,  Luís Frija 

Universidade do algarve (FCT-UALG), Campus de Gambelas, Faro 8005-139, Portugal


Naphthols and naphthyl derivatives are widely used in organic synthesis, as starting materials, protecting groups or synthetic intermediates [1] and show important applications in pharmaceutical and biotechnological industries [2, 3]. Tetrazoles and benzisothiazoles have been the subject of extensive investigations due to their important practical applications, in key areas such as medicine and agriculture [4]. Tetrazolyl and benzisothiazolyl ethers have demonstrated important synthetic applications, for instance as intermediate compounds in the transformation of alcohols [5]. Heterogeneous catalytic transfer hydrogenolysis of benzyloxy- aryloxy- and allyloxy-tetrazoles and -benzisothiazoles has been used in the hydrogenolysis of phenols and allylic and benzylic alcohols, and presents a practical and selective synthetic alternative to other methods [6]. Hydrogenolysis of the C-OH bond is achieved after conversion of the hydroxyl group into an ether with the electron-withdrawing tetrazole or benzisothiazole. Continuing our ongoing research program on the reactivity of tetrazolyl and benzisothiazolyl derivatives, we have now investigated the efficiency of tetrazole and benzisothiazole as leaving groups for heterogeneous catalytic reduction of the p-extended 1- and 2-naphthols and 2-naphthylic methanols over Pd/C, using a hydrogen donor or molecular hydrogen. An interpretation of the reactivity will be provided, based on their structural and electronic features and on comparative adsorption abilities onto the catalyst surface.

Acknowledgements: The authors are grateful to Fundação para a Ciência e Tecnologia (FCT- POCTI/P/FCB/33580/00) and FEDER for financial support. . N.C.P.A. and L.M.T.F. are grateful to FCT for Grants SFRH/BPD/20587/2004 and SFRH/BD/17945/2004.

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[6] a) M. L. S. Cristiano, R. A. W. Johnstone, P. J. Price, J. Chem. Soc. Perkin 1, 1996, 1453. b) N. C. P. Araújo, A. F. Brigas, M. L. S. Cristiano, L. M. T. Frija, E. M. O. Guimarães, R. M. S. Loureiro, Journal of Molecular Catalysis A: Chemical 2004, 215, 113. c) L. M. T. Frija, M. L. S. Cristiano, E. M. O. Guimarães, N. C. Martins, R. M. S. Loureiro, J. F. Bickley, Journal of Molecular Catalysis A: Chemical 2005, 242, 241.

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Presentation: oral at 18th Conference on Physical Organic Chemistry, Symposium 2, by Maria de Lurdes S. Cristiano
See On-line Journal of 18th Conference on Physical Organic Chemistry

Submitted: 2006-06-01 21:08
Revised:   2006-07-31 10:29
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