Arylation ruthenium catalysis

Aromatic imines can be ortho-arylated and alkenylated using ruthenium catalysis (Equation (129)).1... 

Related co-cyclotrimerizations of two alkyne molecules with limited isocyanates have also been achieved using cobalt and nickel catalysts. With respect to intramolecular versions, two examples of the cobalt(I)-catalyzed cycloaddition of a,m-diynes with isocyanates have been reported to afford bicyclic pyri-dones only in low yields, although 2,3-dihydro-5(lff)-indolizinones were successfully obtained from isocyanatoalkynes and several silylalkynes with the same cobalt catalysis [19]. On the other hand, the ruthenium catalysis using Cp RuCl(cod) as a precatalyst effectively catalyzed the cycloaddition of 1,6-diynes 21 with 4 equiv. of isocyanates in refluxing 1,2-dichloroethane to afford bicyclic pyridones 25 in 58-93% yield (Eq. 12) [20]. In this case,both aryl and aliphatic isocyanates can be widely employed. 

As carboxylic acid additives increased the efficiency of palladium catalysts in direct arylations through a cooperative deprotonation/metallation mechanism (see Chapter 11) [45], their application to ruthenium catalysis was tested. Thus, it was found that a ruthenium complex modified with carboxylic acid MesC02H (96) displayed a broad scope and allowed for the efficient directed arylation of triazoles, pyridines, pyrazoles or oxazolines [44, 46). With respect to the electrophile, aryl bromides, chlorides and tosylates, including ortho-substituted derivatives, were found to be viable substrates. It should be noted here that these direct arylations could be performed at a lower reaction temperatures of 80 °C (Scheme 9.34). 

Scheme 17.4 C-H/C-X coupling of 2-phenylpyridine derivatives with aryl halides under ruthenium catalysis.

Aryl and heteroaryl amidines underwent oxidative C-H bond functionalization with alkynes with the aid of ruthenium catalysis [48]. In the presence of [RuCl2(p-cymene)]2/KPF5 as catalyst, the cyclization reactions led to the formation of a variety of 1-iminoisoindolines with high site selectivity, regioselectivity, and... 

The next quantum leap in catalysis after DuPhos has been the development of the ruthe-nium-diamine-bisphosphine catalysts (JST). This combination of ligands on ruthenium produces a highly active and enantioselective catalyst for the reduction of aryl ketones at mild conditions. Although this technology is relatively young, the potential is strong for many industrial processes that use this catalyst system. 

Ackermann L, Bom R, Alvarez-Bercedo P (2007) Ruthenium(IV) alkylidenes as precatalysts for direct arylations of alkenes with aryl chlorides and an application to sequential catalysis. Angew Chem Int Ed 46 6364-6367... 

Since the researcher normally looks to the chemistry of soluble complexes in designing polymer-bound catalysts, it is notable that some areas that have proven fruitful in homogeneous catalysis have been omitted from investigations using polymer-bound catalysts. One of these areas concerns the reactions of arenes. Benzene, for example, may be hydrogenated with homogeneous cobalt phosphite and ruthenium phosphine complexes, but the corresponding supported versions are not reported. Aryl halides may be carboxylated in the presence of a soluble palladium catalyst ... 

A chelation-assisted mthenium-catalyzed arylation of aldehyde 99 was accomplished in combination with a palladium complex [47]. This cooperative catalysis [48] proved applicable to organostannanes and aryl iodides as arylating reagents (Scheme 9.35). The direct arylation proceeded most likely through ruthenium-catalyzed C—H bond activation, subsequent transmetallation to palladium, and reductive elimination from a palladium intermediate. 

The possibilities for the formation of carbon—carbon bonds involving aromatic compounds have been enormously enhanced by the use of transition metal catalysts, and this area has been the subject of several reviews. Some of these concentrate on the applications of specific metals, and there have been surveys of the use of compounds of silver, copper and nickel,mthenium, and palladium in catalysis. The metalation of carbon-hydrogen bonds, preceding functionalization, may be aided by carboxylate ions, and this subject has also been reviewed. There is evidence here for concerted base-assisted deprotonation as shown in (10). In the carboxylate-assisted reaction of aryl ketimines with alkyl halides, a ruthenium-bonded intermediate (11) has been proposed, which subsequently adds the alkyl halide. " ... 

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