Domino metathesis reactions transformation

The main reason for the rapid development of metathesis reactions on a laboratory scale (the reaction itself had been known for quite a long time) has been the development of active and robust second-generation ruthenium catalysts (6/3-14 to 6/3-16), which usually provide better yields than the first-generation Grubbs catalysts (6/3-9 or 6/3-13) (Scheme 6/3.2). This also reflects the huge number of domino processes based on ruthenium-catalyzed metathesis, which is usually followed by a second or even a third metathesis reaction. However, examples also exist where, after a metathesis, a second transition metal-catalyzed transformation or a pericyclic reaction takes place. 

As illustrated by the schemes above, metathesis reactions in domino processes have swiftly become an established tool in modern organic synthesis. Especially, RRM and domino dienyne metathesis have found extensive uses and will surely continue to catch the attention of synthetic chemists as elegant and atom-economic transformations that allow a quick enhancement of molecular complexity. Next to combinations of metathesis events only, the incorporation of non-metathesis steps into true domino processes has advanced to a remarkable level and will certainly provide even more opportunities in the years to come. 

There are many combinations possible of metathesis reactions that can be used in domino metatheses, increasing process complexity with the number of transformations included. Natural product syntheses with ring-closing metathesis (RCM)-cross-metathesis (CM) sequences are described in this section. Ene-ene and ene-yne-ene cascade reactions in a two-metathesis step process will also be discussed. 

The 1,3-dienes resulting from an enyne metathesis can often be coupled with Diels-Alder reactions in a domino transformation. Heating of benzyldimethylsi-lylacetylene with the styrenes 170 and N-phenylmaleimide in the presence of the... 

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