Alkane metathesis is one of the most challenging areas in the modern era because of the strong sp3 C-H bond. The transformation of a given alkanes to higher and lower alkanes is a value added process in many chemical and petrochemical industry. Using surface organometallic chemistry allowed the development of various supported catalysts to transform alkanes to homologues different chain length alkanes in the past decades. Employing precursor well-defined supported W catalysts, we develop an unprecedented synthesis of macrocyclic alkanes from the cyclooctane metathesis.1. Introduction Alkane metathesis has recently emerged to be a powerful transformation to convert lower alkanes to higher alkanes. In 1997, Basset et al. synthesized a novel silica-supported tantalum hydride by surface organometallic chemistry route which transforms acyclic light alkanes to a mixture of their lower and higher homologues.3This direct transformation of an alkane to new alkanes is illustrated by the general equation:2 CnH2n+2 � Cn-iH2(n-i)+2 + Cn+iH2(n+i)+2Subsequently, they have developed numerous supported catalysts in alkane metathesis, mainly low molecular alkanes.4Herein, we wish to report the unprecedented alkane metathesis of cyclic alkanes (cyclooctane and cyclodecane) operating with a multifunctional single-site catalyst.Macrocyclic alkanes are a class of molecules with high value interest in industry because they serve as building blocks in the synthesis of macrolides. Today, a facile access to various macrocyclic alkanes size remains a synthetic challenge. Thus, it was envisaged that cyclooctane metathesis would offer a rapid and facile access to these cyclic structures. In the following work, we employ a single multifunctional silica-supported catalyst 15for synthesis of wider distribution of macrocyclic alkanes .: Well-defined silica supported speciesWe have demonstrated that the cyclic alkane metathesis catalyzed by a multifunctional supported W single catalytic system lead to an unprecedented distribution of macrocyclic alkanes in the range of C12 to C40. The main advantage of our catalyst system is the fact that we used a W single catalyst able to promote different elementary steps. Furthermore, no polymeric products were detected. Future studies will be aimed at post functionalization of these macrocyclic alkanes.References  1. J. M. Basset, C. Coperet, D. Soulivong, M. Taoufik and J. T. Cazat, Accounts Chem Res, 2010, 43 , 323-334.2. C. Coperet, M. Chabanas, R. P. Saint-Arroman and J. M. Basset, Angew Chem Int Edit, 2003, 42 , 156-181.3. V. Vidal, A. Theolier, J. Thivolle-Cazat and J. M. Basset, Science, 1997, 276 , 99-102.4. C. Coperet, Chem Rev, 2010, 110 , 656-680.5. M. K. Samantaray, E. Callens, E. Abou-Hamad, A. J. Rossini, C. M. Widdifield, R. Dey, L. Emsley and J. M. Basset, J Am Chem Soc, 2014, 136 , 1054-1061.

Cyclic alkane metathesis via surface organometallic chemistry

248th National Meeting (2014)

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