Intramolecular ring-closing metathesis

Diynes can be employed in intramolecular ring-closing metathesis. Several catalysts involving Mo and W have been investigated. These cyclizations can be combined with semihydrogenation to give macrocycles with Z-double bonds. 

Mohr B, Week M, Sauvage J-P, Gmbbs RH. High-yield synthesis of [2]catenanes by intramolecular ring-closing metathesis. Angew Chem Int Ed Engl 1997 36 1308-1310. 

The second molecule is not symmetrical but this is all right as it will be an intramolecular (ring-closing) metathesis so we can expect few cross-products. There are many ways to make the starting material alkylation of a ketone is probably the simplest though conjugate addition would have its advantages. The same catalyst can be used and very little would be needed. 

Grubbs and co-workers reported the first successful results of the inter-molecular cross-metathesis and intramolecular ring-closing metathesis with more reactive ruthenium catalyst for the a-functionalized olefins bearing ester, aldehyde, benzoyl or acetyl group. 

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