Synthesis and Catalytic Performance of Ni/SiO 2

A series of Ni/SiO2 catalysts with different Ni content were prepared by sol-gel method for application in the synthesis of 2-methyltetrahydrofuran (2-MTHF) by hydrogenation of 2-methylfuran (2-MF). The catalyst structure was investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (TPR). It is found that structures and catalytic performance of the catalysts were highly affected by the Ni content. The catalyst with a 25% Ni content had an appropriate size of the Ni species and larger BET surface area and produced a higher 2-MF conversion with enhanced selectivity in 2-MTHF

Synthesis and Catalytic Performance of Ni/SiO 2 for Hydrogenation of 2-Methylfuran to 2-Methyltetrahydrofuran

A series of Ni/SiO 2 catalysts with different Ni content were prepared by sol-gel method for application in the synthesis of 2-methyltetrahydrofuran (2-MTHF) by hydrogenation of 2-methylfuran (2-MF). The catalyst structure was investigated by Xray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and temperature programmed reduction (TPR). It is found that structures and catalytic performance of the catalysts were highly affected by the Ni content. The catalyst with a 25% Ni content had an appropriate size of the Ni species and larger BET surface area and produced a higher 2-MF conversion with enhanced selectivity in 2-MTHF

Special Issue on Ruthenium Complexes

The organic chemistry of ruthenium has been one of the most vigorously growing research areas over the past decades. Considerable effort has been extended towards the design and application of a broad series of ruthenium complexes, which culminated with the development by Ryoji Noyori (2001 Nobel Prize for Chemistry) of chiral ruthenium catalysts for stereoselective hydrogenation reactions [1], and the discovery by Robert H. Grubbs (2005 Nobel Prize for Chemistry) of well-defined ruthenium– benzylidene catalysts for olefin metathesis [2] [...

Recent Advances in Ruthenium Catalysts for Alkene Metathesis

Although ruthenium initiators currently available for alkene metathesis are endowed with many beneficial properties, there is still room for improvement and many research groups are actively pursuing the quest for the next generation of alkene metathesis catalysts. The present contribution aims at providing a critical survey of some of the most significant achievements accomplished toward this goal during the last few years. New ligands and complexes designed to achieve the appropriate balance between electronic and steric properties of the ruthenium active centres are depicted, and their stability, activity, and chemoselectivity are briefly discussed

Synthetic approach to ruthenium vinylidene complexes and their applications in metathesis catalysis

Convenient routes for synthesis of ruthenium vinylidene complexes have been described, the majority of which use alkynes along with a ruthenium source as the main starting materials. Their successful application as efficient precatalysts in synthesis of heterocyclic and carbocyclic compounds by ring-closing metathesis of alpha,omega-dienes and in the synthesis of polymers by ring-opening metathesis polymerization of cyclooctene, norbornene, 5-substituted norbornene and dicyclopentadiene are fully illustrated. Relevant aspects concerning the activity and stereoselectivity in metathesis reactions of this type of Ru complexes are highlighte

Exploring New Achievements in olefin metathesis catalysts. Part 1 - Highlights on N-heterocyclic carbene ruthenium complexes

Most important advances in ruthenium catalysts for olefin metathesis achieved during the last 4 years are briefly reviewed. The first part of the survey focuses on new catalytic precursors endowed with inventive N-heterocyclic carbene ligands which have proved highly proficient in a diversity of applications based on metathesis reactions. Part two extends the progress in other types of Ru initiators

Enabling Access to Diverse Bioactive Molecules Through Enyne Metathesis Concepts

This paper surveys recent advances in valorization of transition-metal-catalyzed enyne metathesis as key events in the total synthesis of naturally occurring compounds of biological and medicinal importance. Special attention is devoted to methodologies based on dienyne ring-closing metathesis (RCM) applied in tandem and sequential processes, on relay ring-closing metathesis (RRCM), ring-rearrangement metathesis (RRM), enyne cross-metathesis (CM) and enyne skeletal bond reorganization, all proceeding under metalcarbenes (Ru or Mo alkylidenes) or metal-salts (Pd or Pt) catalysis. The high potential of these procedures in constructing versatile scaffolds as essential structural cores of a diversity of bioactive natural products is highlighted. Inventive functionalizations by non-metathesis transformations intervening in the total synthesis of the targeted natural compounds, prior to (Michael addition, Wittig olefination, allylation etc.) or after (Diels-Alder cycloaddion, Heck and Suzuki-Miyaura reactions, Dess-Martin oxidation, dihydroxylation, epoxidation etc.) the pivotal metathesis step have also been included

Exploring new achievements in olefin metathesis catalysts. Part 2 - Compelling innovations in ruthenium complexes

This part of the survey introduces recent developments on de novo designed types of ruthenium complexes used as promoters in olefin metathesis reactions. Encompassing diversity-oriented initiators not illustrated in Part 1, in this second part of the review emphasis is placed on the leading role played by distinct ligands in an exquisite control of metathesis reactions

NHC-Ru complexes- Friendly catalytic tools for manifold chemical transformations

N-Heterocyclic carbenes are now commonly encountered in organometallic and inorganic coordination chemistry. The increasing attention they enjoy is due to their ability to act as ancillary ligands in a growing number of transition metal catalysts or even to play the role of nucleophilic reagents and catalysts in diverse organic transformations. As a fine addition to the NHC-Ru-alkylidenes, popular for their tremendous success in metathesis chemistry, an array of robust and stable Ru-NHCs has proven their utility in non-metathetical reactions. The present review surveys different classes of Ru-NHCs and their applications as efficient catalysts (or precatalysts) in several types of fundamental organic processes e.g. hydrogenation, hydrogen transfer, isomerization, cycloisomerization, cyclopropanation, hydrosilylation, allylation and deallylation, enol-ester synthesis, heterocycle synthesis, C-C alkyne coupling, Kharasch addition and ATRP. A special section is devoted to tandem processes some of which include concurrent or sequential metathesis steps. Relevant mechanistic and stereochemical aspects related to NHC-Ru catalysis will be highlighted. (c) 2006 Elsevier B.V. All rights reserved