PERCHLORATES AS POWERFUL CATALYSTS IN MANY IMPORTANT ORGANIC TRANSFORMATIONS

For long times, metallic perchlorates have been considered dangerous compounds[1] in that they function as explosives and as incontrollable oxidizers. Therefore, the fear of the great hazard connected with their manufacture and uses had prevented an extensive use both in research laboratories and in industrial processes.[2] However, recently it has been cleared that this bad reputation is due to the mistaken association of metallic perchlorates with the oxidizing potential of perchloric acid and the pyrotechnic performances of NH4ClO4. In this conference, we report that Magnesium and Zinc perchlorates can be used as powerful Lewis acids in several organic transformations which are commonly employed both in laboratory and industrial processes. As depicted in the Scheme, perchlorates are able to promote a series of reactions such as: a) Acylation of alcohols[3,4] b) Fisher esterification[5] c) Synthesis of b–enamino esters[6] d) Protection of the amino group as N-Boc derivative[7] Moreover, they can act as specific catalysts for the development of a new organic transformations. In fact, the treatment of an alcohol or a phenol with Boc2O in the presence of Mg(ClO4)2 leads to the unexpected formation of the corresponding t-butyl ethers.[8] This represents the first general method to synthesize aromatic t-butyl ethers. In an analogous manner, the treatment of phenols with diethyl dicarbonate results in a very efficient method to produce difficulty available aryl ethyl carbonates. Several of the above mentioned transformations can be carried out in the absence of the solvent, and often the catalyst can be easily recovered and reused without an appreciable loss of activity. Acknowledgement Work carried out in the framework of the National Project “Stereoselezione in Sintesi Organica. Metodologie e Applicazioni” supported by MIUR, Rome, by the University of Bologna, in the framework of “Progetto di Finanziamento Pluriennale, Ateneo di Bologna”, and by National project FIRB “Progettazione, preparazione e valutazione biologica e farmacologica di nuove molecole organiche quali potenziali farmaci” References [1] Schumacher, J. C. Perchlorates-Their Properties, Manufacture and Uses, ACS Monograph Series, Reinhold: New York, 1960.Author. Title[J]. Name of the journal, Year, Volume(Issue): initial page and ending page (Optional). [2] Long, J. Chemical Health & Safety, 2002, 9, 12. [3] Bartoli, G.; Bosco, M.; Dalpozzo, R.; Marcantoni, E.; Massaccesi, M.; Rinaldi, S.; Sambri, L. Synlett, 2003, 39. [4] Bartoli, G.; Bosco, M.; Dalpozzo, R.; Marcantoni, E.; Massaccesi, M.; Sambri, L. Eur. J. Org. Chem. 2003, 4611. [5] a) Gooβen, L.; Döhring, A. Adv. Synth. Catal. 2003, 345, 943; b) Bartoli, G.; Boeglin, J.; Bosco, M.; Locatelli, M.; Massaccesi, M.; Melchiorre, P.; Sambri, L. Adv. Synth. Catal. 2005, 347, 33. [6] Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Melchiorre, P.; Sambri, L. Synlett 2004, 239. [7] Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Massaccesi, M.; Melchiorre, P.; Sambri, L. Synlett 2004, 1794. [8] Bartoli, G.; Bosco, M.; Locatelli, M.; Marcantoni, E.; Melchiorre, P.; Sambri, L. Org. Lett., 2004, 7, 427.