Ruthenium complexes allyl

Allylation of perfluoroalkyl halides with allylsilanes is catalyzed by iron or ruthenium carbonyl complexes [77S] (equation 119) Alkenyl-, allyl-, and alkynyl-stannanes react with perfluoroalkyl iodides 111 the presence ot a palladium complex to give alkenes and alkynes bearing perfluoroalkyl groups [139] (equation 120)... 

The isomerisation of aUylic alcohols to saturated ketones usually has a strong thermodynamic driving force. The ruthenium NHC complex 62 has been used to catalyse the isomerisation of allylic alcohol 59 which gives ketone 60 as the principal product along with some of the reduction product 61 [32]. The catalyst was water-soluble and the aqueous phase could be re-used for several runs (Scheme 11.15). NHC analogues of Crabtree s catalyst, [IrlPCyjKpyridineXcod)] PFg, were found to be less efficient for the isomerisation of allylic alcohols than... 

Ruthenium-carbenoid complex 1 catalyzed the isomerization of /3,7-unsaturated ethers to the corresponding vinyl ethers. This reaction is useful in the deprotection of allyl and homoallyl ethers (Scheme 39).65... 

Allyl phenyl ethers are activated by a ruthenium(O) complex, ultimately affording a z7/-benzopyran (Equation (186)).150... 

Kondo and Watanabe developed allylations of various types of aldehydes and oximes by using nucleophilic (7r-allyl)ruthenium(ll) complexes of type 154 bearing carbon monoxide ligands (Equation (29)).345 These 73-allyl-ruthenium complexes 154 are ambiphilic reagents and the presence of the carbon monoxide ligands proved to be essential to achieve catalytic allylation reactions. Interestingly, these transformations occur with complete regioselectivity only the more substituted allylic terminus adds to the aldehyde. 

The formation as well as the reactivity of (7r-allyl)ruthenium(ll) complexes bearing phosphine ligands have been described in a series of articles. However, the main drawback in these cases is the use of non-catalytic... 

The most plausible mechanism proceeds through oxidative addition of the aldehyde to an active Ru(0) species to form (acyl)(hydrido)ruthenium(ll) complex 155. Insertion of the less-substituted double bond of the 1,3-diene into the Ru-H bond occurs to generate an (acyl)( 73-allyl)ruthenmm(ll) intermediate of type 156. Successive regioselective reductive eliminations between the acyl and the 73-allyl ligands provide the desired product with regeneration of the... 

Blechert carried out a tandem reaction of enynes in the presence of olefins instead of ethylene (Scheme 21). Treatment of cyclopentenol derivative 58a with Ic in the presence of an alkene affords 59a. The five-membered ring in estrone 58b is cleaved by Ic to give 59 and an alkene part is introduced on the six-membered C ring. However, cycloalkenyl amine derivative 60 is treated in a similar manner in the presence of an allyl alcohol derivative to give pyrrolidine derivative 61, and in this case, an alkene part is introduced on the diene moiety. Presumably, ruthenium carbene complex XVI reacts with an alkyne part to produce the pyrrolidine ring with a regioselectivity opposite to the other cases. 

Dihydropyrroles have recently become readily available by ring-closing metathesis. For this purpose, N-acylated or N-sulfonylated bis(allyl)amines are treated with catalytic amounts of a ruthenium carbene complex, whereupon cyclization to the dihydropyrrole occurs (Entries 6 and 7, Table 15.3 [30,31]). Catalysis by carbene complexes is most efficient in aprotic, non-nucleophilic solvents, and can also be conducted on hydrophobic supports such as cross-linked polystyrene. Free amines or other soft nucleophiles might, however, compete with the alkene for electrophilic attack by the catalyst, and should therefore be avoided. 

Although mechanistically different, a successful kinetic resolution of cyclic allyl ethers has recently been achieved by zirconium catalysis [2201. Other metals such as cobalt [221], ruthenium [222], and iron [2231 have been shown to catalyze allylic alkylation reactions via metal-allyl complexes. However, their catalytic systems have not been thoroughly investigated, and the corresponding asymmetric catalytic processes have not been forthcoming. Nevertheless, increasing interest in the use of alternative metals for asymmetric alkylation will undoubtedly promote further research in this area. 

An example of a tethered arene complex of ruthenium(II) in which the auxiliary ligand is a a-bonded carbon atom is complex 80, which is formed by the action of AgBF4 and P(OMe)3 on the r 4-tetraphenylcyclobutadiene r 3-allyl complex 79 [Eq. (13)]. In the proposed mechanism, the allyl group migrates to the four-membered ring, which opens to generate an intermediate cation 81, the pendant arene of which coordinates to the metal.74... 

Chiral silver complexes bearing bidentate NHC ligands (24) have been synthesized. They are used in alkene metathesis and allylic alkylation reactions high diastereos- (g) electivity is observed induced by the chiral backbone on the prochiral biphenyl.27 Ruthenium-based complexes obtained from transmetalation with a Grubbs-Hoveyda complex exhibited high activities and enantioselectivities in ring-opening metathesis/ ... 

The coordination chemistry of optically pure, chiral phosphetanes has been studied with special attention to the preparation and characterization of complexes since they are suitable for asymmetric catalytic reactions. The optically active P-menthylphosphetanes showed similar reactivities with usual trivalent phosphines to afford stable palladium(n) and ruthenium complexes, under usual reaction conditions. Similarly, the Pd-allyl complex 28 <1997JOM(529)465> has been prepared from [(allyl)PdCl]2 and was characterized by X-ray crystallography. Reaction of the P(R),C(3 )-2-benzyl-3,3,4,4-tetramethyl-l-menthylphosphetane 64 with Ru3(C0)12/HC02H proceeds normally to give the formato bridged dimer 65 (Figure 11) <1998S1539>. 

The observation that the Ru(amidinate)C5Me5 complex could generate the first allyl ruthenium(IV) complex containing a nitrogen ligand led to the use of this complex as catalyst for simple allyl substitution of allylcarbonates [111]. Re-... 

Keywords Allylic substitution, Allylation, Allylic alkylation, Jt-Allyl complexes, Palladium, Molybdenum, Ruthenium, Iridium... 

The addition of substituted alkenes with electron-withdrawing groups to ruthenium acetylide complexes results in the formal [2 + 2] cycloaddition of the olefin to the acetylene moiety. Facile ring opening of the resultant ruthenium cyclobutene complex (103) generates the ruthenium butadienyl species (104). Subsequent displacement of a phosphine ligand leads to the Tj3-allylic product (105) [Eq. (93)] (90-92). The intermediate cyclobutene complex has been isolated in one instance for the monocarbonyl derivative 106 [Eq. (94)] (92). 

The systems described above all involve peroxometal species as the active oxidant. In contrast, ruthenium catalysts involve a ruthenium-oxo complex as the active oxidant [1]. Until recently, no Ru-catalysts were known that were able to activate H202 rather then to decompose it. However in 2005 Beller and co-workers recognized the potential of the Ru(terpyridine)(2,6-pyridinedicarboxylate) catalyst [63] for the epoxidation of olefins with H202 [64]. The result is a very efficient method for the epoxidation of a wide range of alkyl substituted or allylic alkenes using as little as 0.5 mol% Ru. In Fig. 4.26 details are given. Terminal... 

---