Reactivity of Tungsten-aryloxides with Hydrosilane Cocatalysts in Olefin Metathesis
نویسندگان
چکیده
This reaction allows for new olefins to be synthesized and used as raw materials in polymers, perfumes, drugs and agrochemical industrial products, also serving as the starting point for more complex organic molecules. Catalytic systems are based mainly on the metals W, Mo, Re and Ru. The metal-alkylidenes synthesized by Schrock, [Mo(CHR)(NAr)(OR f ) 2 ], Grubbs, [Ru(CHR)(PCy 3 ) 2 Cl 2 ], Herrmann and Dixneuf are particularly interesting catalysts for olefin metathesis. When a catalyst is not a metal-alkylidene, a cocatalyst is added to generate a metalcarbene, known as the active species for metathesis. The homogeneous system [WCl 6 ]/SnR 4 is extensively studied in the literature and is appropriate for non-functionalized and fuctionalized olefins. Tungsten-aryloxides [WCl 4 (OAr) 2 ] are useful because they can be easily synthesized from [WCl 6 ] and its corresponding phenol and offer good handling stability. Moreover, these compounds are very versatile, because their activity and stereoselectivity can be modified, by changing their ring substituents. Thus, electronegative groups increase the reduction potential of tungsten atoms, enhancing the catalytic activity of these compounds in metathesis. Furthermore, stereoselectivity can be achieved by placing bulky groups in 2,6 positions of the ring. In previous studies we investigated the catalytic activity of a new system based on [WCl 6 ] plus PMHS Reactivity of Tungsten-aryloxides with Hydrosilane Cocatalysts in Olefin Metathesis
منابع مشابه
Synthesis of cyclic olefin polymers with high glass transition temperature and high transparency using tungsten-based catalyst system
Novel cyclic olefin polymers (COPs) derived from bulky cyclic olefins, tricyclodipentadiene (TCPD) and tricyclo[6.4.0.19,12]-tridec-10-ene (TTE), with high glass transition temperature (Tg), excellent thermal stability, and high transparency, have been synthesized by ring-opening metathesis polymerization (ROMP) and subsequent hydrogenation. ROMP of TCPD and TTE was carried out successfully wit...
متن کاملLight-induced olefin metathesis
Light activation is a most desirable property for catalysis control. Among the many catalytic processes that may be activated by light, olefin metathesis stands out as both academically motivating and practically useful. Starting from early tungsten heterogeneous photoinitiated metathesis, up to modern ruthenium methods based on complex photoisomerisation or indirect photoactivation, this surve...
متن کاملZ-Selective Olefin Metathesis Processes and Cis/Syndioselective ROMP with High Oxidation State Molybdenum Alkylidenes
Chapter 1 Reaction of W(CCMe 3)Cl 3(dme) with one equivalent of (3,5-Me 2C6H3NCH 2CH 2)3N)Li3 affords yellow, crystalline W(CCMe 3)(N3N) in good yield. The reactivity of this new alkylidyne complex towards terminal alkynes was investigated. Two other new tungsten alkylidynes, W(CCMe 3)(pyr) 3 (pyr = 2,5-dimethylpyrrolide) and W(CCMe3)(Ph 2N)3 were prepared by the addition of three equivalents o...
متن کاملA general model for selectivity in olefin cross metathesis.
In recent years, olefin cross metathesis (CM) has emerged as a powerful and convenient synthetic technique in organic chemistry; however, as a general synthetic method, CM has been limited by the lack of predictability in product selectivity and stereoselectivity. Investigations into olefin cross metathesis with several classes of olefins, including substituted and functionalized styrenes, seco...
متن کاملA One-Pot Tandem Olefin Isomerization/Metathesis-Coupling (ISOMET) Reaction
A tandem catalytic reaction has been developed as part of a process to discover tungsten-based olefin metathesis catalysts that have a strong preference for terminal olefins over cis or trans internal isomers in olefin metathesis. This tandem isomerization/terminal olefin metathesis reaction (ISOMET) converts Cn trans internal olefins into C2n−2 cis olefins and ethylene. This reaction is made p...
متن کامل