Ring-closing olefin metathesis reaction

Scheme 8.16. Examples of the Ring-Closing Olefin Metathesis Reaction...

Grubbs applied his ring-closing olefin metathesis reaction to the synthesis of (lS,5R)-44 as shown in Scheme 67 [99]. The key-step was the cyclization of A to give C. The unreacted anti-isomer B could be recovered and equilibrated to a mixture of A and B. 

Advent of ring-closing olefin metathesis reaction has influenced the synthetic strategy of pheromones very much. For example, the racemate of a macrolide pheromone such as (5Z,13S)-5-tetradecen-13-olide (29) (aggregation pheromone of the flat grain beetle, Cryptolestes pusillus) could readily be synthesized as shown in Scheme 42 [67]. Unfortunately, ( )-29 prepared by this method was a mixture of c/s, trans-isomers (Z/E=69 31). (S)-5-Hexadecanolide (27) was also synthesized by means of ring-closing olefin metathesis as shown in Scheme 43 [68]. 

The butadiene ligand in the Group 4 metallocene complexes is very reactive towards olefins attached at the Cp rings. A typical example is the system 9 that instantaneously reacts further to yield 10 when generated from 8 (see Scheme 4). In contrast, the unsaturated (butadiene)ansa-metallocene complexes s-cis-13 and s-trans-13 are stable when prepared from 12 under similar conditions.15 Complex 12 was obtained by a ring closing olefin metathesis reaction from 11. 

Application of the ring-closing olefin metathesis reaction (RCM) for the preparation of car-bocyclic rings from the appropriately functionalized sugars is now well documented [81]. Recently it was applied for the synthesis of compound 122, which can be regarded as a (n,m)-anhydrosugar [81]. The intermediate diolefin 121 was prepared in a few standard steps from the corresponding dialdose 120 (O Fig. 28) [82]. 

Glycals can also be obtained from suitable substrates, by ring-closing olefin metathesis reactions. In a general approach to variously linked C-disaccharides, illustrated in O Scheme 48, nonreducing-end glycals are typical intermediates, finally subjected to hydroboration or dihy-droxylation to afford the desired C-analogs of O-disaccharides [238,239]. 

The use of ring-closing olefin metathesis reactions to perform model macroannulations in the context of the construction of the macrocychc D ring of madangamines was also explored. The required dienes 83-85,... 

Urbina-Bianco CA, Skibinski M, O Hagan D, Nolan SP. Accelerating influence of the gem-difluoromethylene group in a ring-closing olefin metathesis reaction. A Thorpe-Ingold effect Chem Commun. 2013 49(65) 7201—7203. 

Reetz, M.T., Becker, M.H., Liebl, M., Fiirstner, A., IR-thermographic screening of thermoneutral or endothermie transformations the ring-closing olefin metathesis reaction, Angew. Chem. hit Edit. 2000,39 1236-1239. 

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