Ring-closing metathesis reaction benzene ring

Ring-closing metathesis was also used as a key step in the enantioselective synthesis of (+)-carissone, a eudesmane sesqueterpenoid, by Stoltz and co-workers. Reaction of enone 154 with 3 mol % of 4 in benzene gave the corresponding carbocycle 155 in quantitative yields. Seven additional steps were required to aceess (+)-earissone (not shown). 

Shibasaki and co-workers used a ring-closing metathesis approach to prepare seven-membered rings from electron-deficient olefins. Reaction of acyclic enol ethers 226 and 228 with 7 mol % of 3 in benzene provided cyclic enol ethers 227 and 229 in 88 and 93% yield, respectively. 

As discussed before, the strategy to synthesize catenanes is not necessarily restricted to olefin metathesis as the ring closing reaction. Any reaction which can be carried out under conditions where the hydrogen-bonded dimers exist should be appropriate. A first example was realized by the formation of anhydride linkages with dicyclohexylcarbodiimide as the reagent in benzene as the solvent [57], as schematically illustrated in Scheme 5.19. 

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