Ruthenium-catalyzed reaction

Trost, B.M., Eredericksen, M.U., Rudd, M.T. (2005) Ruthenium-Catalyzed Reactions - A Treasure Trove of Atom-Economic Transformations. Angewandte Chemie International Edition, 44, 6630-6666. 

Mascarenas developed a synthetic method to 1,5-oxygen-bridged medium-sized carbocycles through a sequential ruthenium-catalyzed alkyne-alkene coupling and a Lewis-acid-catalyzed Prins-type reaction (Eq. 3.45). The ruthenium-catalyzed reaction can be carried out in aqueous media (DMF/H20 = 10 1).181... 

The alkylation of olefinic G-H bonds proceeds when conjugated enones are employed in the ruthenium-catalyzed reaction with alkenes, as shown in Equation (16).1 7 Among the acylcyclohexenes, 1-pivaloyl-l-cyclohexene exhibits a high reactivity and the presence of an oxygen atom at the allylic position in the six-membered ring increases the reactivity of the enones. Some terminal olefins, for example, triethoxyvinylsilane, allyltrimethylsilane, methyl methacrylate, and vinylcyclohexane, are applicable for the alkylation of the olefinic C-H bonds. Acyclic enones also undergo this alkylation. 

The hydroarylation of olefins is also achieved by using a ruthenium catalyst, TpRu(CO)(NCMe)(Ph) (Tp = hydridotris(pyrazolyl)borate) (Equation (34)).39 The reaction of benzene with ethene is catalyzed by the ruthenium complex to give ethylbenzene (TN = 51, TOF = 3.5 x 10 3mol 1 s-1 at 90 °G for 4h). The ruthenium-catalyzed reaction of benzene with propene gives the hydroarylation products with a 1.6 1.0 ratio of -propyl to isopropylbenzene, with 14 catalytic turnovers after 19 h. 

In addition to aryl halides and triflates, organometallic reagents can be utilized for the catalytic arylation reaction. The rhodium-catalyzed arylation of arylpyridines proceeds with the use of tetraarylstannanes (Equation (67)).83 The ruthenium-catalyzed reaction of aromatic ketones with arylboronates affords the ortho-arylated aromatic ketones (Equation (68)).84... 

Another example of a ruthenium-catalyzed reaction appeared in 1996 for the dimerization of PhCH2C=CH (193) [136]. The catalyst used for the reaction was Cp RuH3(PCy3) and the butatriene 194 was obtained as a single isomer in 93% yield with >95% selectivity however, the geometry of 194 could not be determined unambiguously (Scheme 3.95). 

From the results presented here, one could get the impression that such allenes with hydroxyl groups in the substituents will always form heterocydes in the presence of transition metal catalysts, but in the presence of other substrates even allenylcarbinols can react to give different products. Examples are the rhodium-catalyzed reaction of allenylcarbinol 78 and phenylacetylene 79 to 80 [42], the palladium-catalyzed reaction of 81 and pyrrolidine 82 to 83 [43] and the ruthenium-catalyzed reaction of 78 and 79 to 84, an isomer of the rhodium-catalyzed reaction of the same substrates mentioned above [44] (Scheme 15.19). 

SCHEME 38. Ruthenium-catalyzed reaction of tertiary amines and amides with TBHP... 

Small amounts of ethylene glycol have been reported as products after ruthenium-catalyzed reactions in NMP and toluene solvents at 2000 atm (39). However, observations of minor amounts of this product must be viewed with caution unless great care is taken in the experimental procedure. For example, it was earlier reported that a catalyst derived from Ru,(CO)l2... 

Studies of ruthenium-catalyzed reactions in carboxylic acid solvents have been reported by Knifton (171,172), but most of these experiments contain added salt promoters which greatly modify the catalytic behavior. These experiments will be considered in Section V, along with other Lewis base-promoted ruthenium systems. 

Much less information is available about [2 + 2]-cycloadditions. These allow the formation of cyclobutane derivatives in the reaction between two alkenes, or that of cyclobutenes from alkenes and alkynes. The reaction can be achieved thermally via biradical intermediates,543 by photoreaction,544 and there are also examples for transition-metal-catalyzed transformations. An excellent example is a ruthenium-catalyzed reaction between norbomenes and alkynes to form cyclobutenes with exo structure ... 

The ruthenium-catalyzed reaction of amines with bis(2-hydroxyethyl) ether or bis(2-hydroxyethyl)amines gives N-substituted morpholines or piperazines, respectively. 

In (C5Me5)Rh(C2H3SiMe3)2-catalyzed C-H/olefin coupling the effect of the coordination of the ketone carbonyl is different from that in the ruthenium-catalyzed reaction [10], In the rhodium-catalyzed reaction all C-H bonds on the aromatic ring are cleaved by the rhodium complex without coordination of the ketone carbonyl. Thus, C-H bond cleavage and addition of Rh-H to olefins proceed without coordination of the ketone carbonyl. After addition of the Rh-H species to the olefin, a coordinatively unsaturated Rh(aryl) (alkyl) species should be formed. Coordination of the ketone carbonyl group to the vacant site on the rhodium atom leads... 

Ruthenium-catalyzed reactions involving diynes generally lead to the intramolecular oxidative coupling of the two C=C bonds. Bicyclic compounds can be synthesized in the presence of another unsaturated molecule. 

The ruthenium-catalyzed reactions by their diversity, selectivity, and interest for the production of fine chemicals, especially during the last decade, show that molecular ruthenium catalysts are not only versatile but that they have now become unavoidable tools in organic synthesis [127]. They also appear to be complementary to organic, enzyme, or other metal catalysts as they have the power to generate original activation pathways for the combination of a variety of simple and complex molecules. 

C-H bonds. In this section, among the transition-metal-catalyzed C-H/olefin coupling, ruthenium-catalyzed reactions will mainly be discussed. 

In contrast to the process catalyzed by platinum complexes the ruthenium-catalyzed reaction gives endo-dig cyclization in this case to provide seven-mem-bered ring products even though the exo-dig process would form the more favorable six-membered ring. In all reactions only a single product isomer is observed [116]. 

Ruthenium-Catalyzed Reactions Involving C-H Activation in Aqueous Media... 

This monograph is not intended to provide a comprehensive view of all ruthenium-catalyzed reactions, as it is an explosive growth field. For instance, ruthenium-catalyzed enantioselective hydrogenation, already detailed in several monographs, will not be treated here in spite of its high impact in organic synthesis. 

Abstract Ruthenium holds a prominent position among the efficient transition metals involved in catalytic processes. Molecular ruthenium catalysts are able to perform unique transformations based on a variety of reaction mechanisms. They arise from easy to make complexes with versatile catalytic properties, and are ideal precursors for the performance of successive chemical transformations and catalytic reactions. This review provides examples of catalytic cascade reactions and sequential transformations initiated by ruthenium precursors present from the outset of the reaction and involving a common mechanism, such as in alkene metathesis, or in which the compound formed during the first step is used as a substrate for the second ruthenium-catalyzed reaction. Multimetallic sequential catalytic transformations promoted by ruthenium complexes first, and then by another metal precursor will also be illustrated. 

In this review, we will focus on cascade and sequential catalytic transformations in which the first one is a ruthenium-catalyzed reaction. This will include ... 

While ESl-MS studies of systems catalyzed by other metals are less common, one report investigated a ruthenium-catalyzed reaction with naturally charged Ru-cluster intermediates. The... 

Chen initiated the study of ruthenium-catalyzed reactions in solution in 2000 by doping a charged norbornene derivative into a solution containing catalyst and normal norbornene (Fig. 12). Initially the ruthenium catalyst is neutral and invisible by ESI-MS but as the norbornene monomers are incorporated, the mass spectrum shows a series of resting states of the catalyst after n additions of the monomer. 

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