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Development of a Method for the Preparation of Ruthenium Indenylidene-Ether Olefin Metathesis Catalysts
Molecules 2012, 17(5), 6001-6010; doi:10.3390/molecules17056001
Article

Metathesis Transformations of Natural Products: Cross-Metathesis of Natural Rubber and Mandarin Oil by Ru-Alkylidene Catalysts

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 and
*
Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, CU, Coyoacán, México, D.F. 04510, Mexico
* Author to whom correspondence should be addressed.
Received: 16 March 2012 / Revised: 30 April 2012 / Accepted: 3 May 2012 / Published: 18 May 2012
(This article belongs to the Special Issue Olefin Metathesis and Its Application)
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Abstract

This study reports on the degradation of natural rubber (NR) via cross-metathesis with mandarin oil and d-limonene, an abundant compound in essential oils; that were used as chain transfer agents (CTAs) and green solvents. Reactions were performed in the presence of the ruthenium-alkylidene catalysts (PCy3)2(Cl)2Ru=CHPh (I) and (1,3-dimesityl-4,5-dihydroimidazol-2-ylidene) (PCy3)Cl2Ru=CHPh (II), respectively. Catalyst II bears an N-heterocyclic carbene ligand (NHC) bounded to the ruthenium atom, which has a strong basic character; therefore it is more active toward trisubstituted olefins in comparison with catalyst I. In both cases, isolated monoterpene-terminated isoprene oligomers were obtained as products of the cross-metathesis degradation of NR. In the presence of catalyst II molecular weight values around Mn × 102 and yields of 80% were obtained; whereas with catalyst I, the molecular weights of products were about Mn × 104 with yields ranging 70 to 74%. The composition and yield of NR degradation products were determined by GC/MS (EI) analysis and it was found that the oligomers obtained have primarily one vinyl group and one terpene-monocyclic group at the chain end, with isoprene units Am = 2, 3 y 4.
Keywords: metathesis degradation; natural rubber; mandarin oil; alkylidene-ruthenium catalysts metathesis degradation; natural rubber; mandarin oil; alkylidene-ruthenium catalysts
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).
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Martínez, A.; Gutiérrez, S.; Tlenkopatchev, M.A. Metathesis Transformations of Natural Products: Cross-Metathesis of Natural Rubber and Mandarin Oil by Ru-Alkylidene Catalysts. Molecules 2012, 17, 6001-6010.

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