Metathesis tricyclohexylphosphine

Thus far, considerably more research has been directed towards RCM in water. The majority of metathesis catalysts decompose rapidly in the presence of water or oxygen, however, Grubbs s ruthenium based catalysts are quite robust. Replacement of the tricyclohexylphosphine ligands with water soluble phosphines has allowed their deployment in aqueous-organic biphasic processes although conversions are often not as good as those obtained in other solvents [18]. 

A closer look on the history of the development of catalyst 52 shows that this class of compounds was to some degree predestined for the application of NHCs. Complex 51 containing triphenylphosphines is an active catalyst for olefin metathesis. However, the substitution of the triphenylphosphines by more electron-donating and sterically more demanding tricyclohexylphosphines is accompanied by a significantly increased stability and catalytic performance " Thus, complexes of type 53 58,2S5 logical development with respect... 

They can be handled analogous to thermosetting resins, and thus the use of highly volatile comonomers, such as ethene or prop-ene is prohibitive. Instead, other vinyl monomers are used. A heat curable formulation uses a mixture of tetracyclododecene, 2-norbomene, 5-vinyl-2-norbomene, and divinylbenzene as reactive components (41). The mixture further contains 3,5-di-ferf-butylhy-droxyanisole as antioxidant and a hybrid catalyst system containing a zirconium based metathesis catalyst and a radical catalyst. The metathesis catalyst is benzylidene (l,3-dimesitylimidazolidin-2-yl-idene)(tricyclohexylphosphine)ruthenium dichloride and the radical catalyst is di-ferf-butyl peroxide. 

Recently, it was shown that bis(tricyclohexylphosphine)benzyhdene ruthenium dichloride (101) [120, 121] is also capable of catalyzing olefin metathesis on a sohd support [122], Thus, performing the reaction as ring-closing metathesis offers an-... 

Ring D (see Scheme 15) has been successfully appended to the tricyclic core by an olefin metathesis reaction (147). Treatment of 177, prepared largely by the method described in Scheme 11, with the ruthenium complex 178 (Cy3P = tricyclohexylphosphine) resulted in the ABCD ring system of the manzamines. 

Ring closure across substituents of 1,4-disubstituted p-lactams is a convenient route to both bicyclic and tricyclic systems. For instance, cyclization of 81 gives the carbacephem 82 in high yield in the presence of benzylidenebis(tricyclohexylphosphine)ruthenium dichloride through an enyne metathesis process <97CCI375>. The 4-formyloxy-P-lactam 83 gives the oxacephem 84 by the action of Lewis acids but here the 4-substituent is eliminated to form the intermediate cation 85 <97TA2553>. 

After having observed that the most active ruthenium-based catalyst systems for olefin metathesis also displayed a high efficiency in atom transfer radical polymerisation, we then became interested in comparing the role of the catalyst in those two different reaction pathways. Ruthenium alkylidene complexes 4-6 are unsaturated 16-electron species which formally allow carbon-halogen bond activation to form a 17-electron ruthenium(III) intermediate. Our preliminary results indicate that polymerisations occur through a pathway in which both tricyclohexylphosphine and/or imidazolin-2-ylidene ligands remain bound to the metal centre. 

Stability (Figure 11.7) [60]. RCM of the standard substrate 17 using this complex showed complete conversion in 15 min, while the complexes 10 and 2 showed 92 and 85% conversions, respectively, under the same conditions. Subsequendy, the groups of Wagener, Mol, and Fiirstner reported the synthesis and metathesis activity of the tricyclohexylphosphine containing 38 and phosphine-free 39 (an analog of complex 37) [61-63]. In the self-metathesis of 1-octene, catalyst 38 displayed TONs six times larger (TON >640 000) and initial TOFs 20 times faster than those of 10 at ambient temperature, and an even better performance at elevated temperatures [62]. 

Ring-opening metathesis polymerization of monomers 32a-c with Z)i5 (tricyclohexylphosphine)benzylidene ruthenimn(lV) dichloride (Grubbs catalyst) allowed for the isolation of polynorbomenes 33a-c as shown in Scheme 14. These polymerization reactions were carried out using a monomerxatalyst ratio of... 

Olefin Metathesis. Olefin metathesis is one of the most important and powerful reactions in organic synthesis. Many of the catalysts used for the reaction contain at least one tricyclohexylphosphine ligand, the so-called Grubbs type 1(1) and Grubbs... 

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