Organometallic Chemistry

Our research group has developed a strong expertise in the field of organometallic chemistry as a powerful and very versatile tool for organic synthesis.

ORGANOCUPRATES CHEMISTRY

Acylsilanes can be considred as synthetic equivalents of the corresponding aldheydes. The silyl group, in fact, can be easily removed by means fo fluoro ions and moreover, and it can serve in controlling the reaction stereochemistry. Synthesis of alfa- and beta-aminoacylsilanes as useful building blocks for the preparation of biologically active molecules.

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B. F. Bonini, , M. Comes-Franchini, M.Fochi, J. Gawwronski, G. Mazzanti, A. Ricci, G. Varchi Eur. J. Org. Chem. 999, 437-445.

Reactions with vinyl magnesium bromide/CeCl3/THF complex

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B. F. Bonini, M. Comes-Franchini, M. Fochi, G. Mazzanti, A. Ricci, G. Varchi Synlett 2000, 11, 1688-1690.

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B. F. Bonini, M. Comes-Franchini, M. Fochi, L. Lunazzi, A. Mazzanti, G. Mazzanti, A. Ricci, G. Varchi Synlett 2001, 995-998.

FUNCTIONALIZED GRIGNARDS

Grignard poly-functionalized reagents are very important organometallic reagents since they allow o conduct Grignard reactions at low temperature and in the presence of many subscetible functional grups.

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L. Boymond, M. Rottländer, G. Cahiez, P. Knochel, Angew. Chem. Int. Ed. Engl. 1998, 37, 1701.

1,4 Addition of functionalized aryl magnesium reagents to enones

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G. Varchi, A. Ricci, G. Cahiez, P. Knochel Tetrahedron 2000, 56, 2727-2731;
M. Röttlander, L. Boymond, L. Bérillon, A. Leprêtre, G.Varchi, S. Avolio, H. Laaziri, G. Quèguiner, A. Ricci, G: Cahiez, P. Knochel Chem. Eur. J. 2000, 6, 767-770

Synthesis of Anilne Grignard Reagents

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G. Varchi, A. E. Jensen, W. Dohle, A. Ricci, G. Cahiez, P. Knochel Synlett 2001, 4, 477-480

HETEOCYCLES SYNTHESIS THROUGH INRAMOLECULAR HYDROSILYLATION AND SILYLFORMYLATION

Heterocycles serve as diverse, versatile, and important skeletons or components in pharmaceutical drugs, agrochemicals, and new materials. Among a variety of methods for heterocycles synthesis, the transition-metal-catalyzed reactions are highly attractive, since these reactions can construct simple and complex heterocyclic structures directly from readily available starting materials. As recently proposed by Yamamoto [Yamamoto, Y.; Nakamura, I. Chem. Rev. 2004, 104, 2127], the catalytic construction of heterocyclic skeletons can be classified into two major processes: 1) carbon-carbon bond formation from the corresponding acyclic precursors (Fig. 1, a) and 2) C-Y bond formation from the corresponding acyclic precursors (Fig. 1, b). Both processes can take place in an inter or intramolecular manner, depending on the nature of the starting materials, and reaction partners.

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Intramolecular hydrosilylation of dimethylsiloxyallenes

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The first intramolecular hydrosilylation of dimethylsiloxyallenes catalyzed by rhodium complexes under carbon monoxide atmosphere was reported. The reaction gave a mixture of endo-dig and exo-dig cyclization products, with variable ratios depending on the catalyst species used as well as reaction conditions. Among the rhodium complexes examined, [Rh(COD)Cl]2 was found to be the best catalyst so far. Thus, the reactions catalyzed by [Rh(COD)Cl]2 in toluene at 70C and 8 atm of CO afforded the endo-dig products in excellent yields and regioselectivity regardless of the ring size.

Intramolecular re-iterative silylfomylation of diynes:

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Studies on the transformations of oxasilacyclopentane, obtained via desymmetrization of siloxydiyne, has been reported. Reduction with NaBH4 followed by Tamao oxidation and acetylation affords compound 43. Propargyl Grignard reagent addition, followed by silylation gave the corresponding siloxyalkyne, which underwent silylformylation to afford bis (oxasilacyclopentane). Bis (oxasilacyclopentane) was subjected to the reduction-Tamao-oxidation-acetylation sequence to yield a polyoxygenated product, which introduced another 3-keto-1,5-diol unit to through reiterative operation of propargylation-silylation-silylformylation-reduction-Tamao oxidation-acetylation, proving the validity of this protocol. Bis-oxasilaheterocyle should serve as intermediate for the next reiterative operation.