Metathesis, alkene olefin tandem

A tandem RCM-alkene isomerization sequence to form 5-, 6-, and 7-membered enol ethers was reported by Snapper and co-workers <02JA13390> (Scheme 36). In this process the RCM reaction is run under an atmosphere of 95 5 N2.TI2 to convert the intermediate ruthenium alkylidene into an olefin-isomerization catalyst. Note that alkene migration can convert isomeric metathesis products into the same 2,3-enol ether. A single example of the formation of a 6-membered tosyl enamide was reported in this manuscript. 

Olefin metathesis. Cross metathesis permits a facile access to allylsilanes and Z)-a,P-unsaturated nitriles. Furthermore, employing an alkene metathesis in tandem with asymmetric allylboration provides functionalized alkenes. ... 

This chapter is divided into six sections. The first three sections loosely reflect the role of alkene cross-metathesis (CM) in the general plan of the synthesis of natural products, which can be the functionaHzation of terminal olefins appending a side chain to the core of a complex compound, or couphng two fragments to build the entire skeleton of the target molecule. Afterwards, tandem processes involving CM will be presented, followed by a few examples ofene-yne and alkyne CM in natural product synthesis [1]. 

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