Sequential catalytic reactions ruthenium catalysts

As illustrated above sequential catalytic reactions, performed in the same flask, either by modifying the initial ruthenium complex to create a new catalyst, or by introduction of another metal catalyst have been developed with efficiency for the production of useful molecules or polymers. 

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. 

During the last decade, molecular ruthenium catalysts have attracted increasing interest for organic synthesis due to their ability to perform specific new reactions with a large panel of applications. Beside individual catalytic transformations, a variety of multi-step catalytic transformations in one pot have appeared. These transformations present practical and economic advantages as far as they are efficient, selective and proceed with atom economy. Ruthenium catalysis has entered this field with a variety of cascade and sequential catalytic transformations. 

Several examples of sequential isomerization/ring-closing metathesis for the preparation of heterocycles have also been performed by using two successive catalytic reactions catalyzed by two different ruthenium catalysts, but the second catalyst was introduced after completion of the first catalytic reaction. The isomerization was usually catalyzed by RuHCl(CO)(PPh3)3 [48], or RuCl2(= CHPh)(PCy3)(bis(mesityl)imidazolylidene) in the presence of trimethylsilyl vinyl ether [49], whereas a classical metathesis catalyst was subsequently introduced for the cyclization [48,49]. 

In the past decade, chemists have become more and more interested in ruthenium catalysts for organic synthesis, since ruthenium catalysts are able to perform specific new reactions with a large number of applications [54]. A variety of cascade reactions and sequential catalytic transformations have been developed based on this powerful catalyst system, which can promote several different types of reactions. 

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