Olefin cross-metathesis reactions

These examples illustrate the occurrence of metal contamination during mech-anochemical treatment of organic molecules without affecting the reactivity and yields, however wear in organic mechanosynthesis can also lead to incompatibility in a chemical sense, which especially holds for metal-catalyzed reactions. In a recently pubhshed demonstration of olefin cross-metathesis reaction conducted under ball-milhng conditions [33], the authors reported on an observation that the model metathesis reaction of styrene to produce stilbene proceeded with diminished... 

Wenzel AG, Blake G, VanderVelde DG, Gruhhs RH. Characterization and Dynamics of Substituted Ruthenacyclobutanes Relevant to the Olefin Cross-Metathesis Reaction. J Am Chem Soc. 2011 133(16) 6429-6439. 

For a review on olefin cross-metathesis reactions, see Connon S.J., Blechert S. (2003) Angew. Chem. Int Edit 42 1900. 

Ceneral Conditions for Olefin Cross Metathesis Reactions... 

This concept was refined by the research group of Li, who employed the thiol-yne reaction instead of the olefin cross-metathesis reaction as key step [60]. In this case, the carboxylic acid component served as anchor, whereby terminal alkynes were introduced by the remaining components (5-hexyn-l-al and propargyl isocyanoacetamide). Interestingly, thiol-yne addition of 3-mercaptopropionic acid to the pendant alkynes enabled not only the incorporation of further carboxylic acids, but also resulted in additional branching. Therefore, the second generation dendrimer, synthesized in three steps, exhibited 16 peripheral triple bonds. Moreover, this concept offers the opportunity to introduce structural diversity into the dendrimer architecture because the use of only one alkyne-functionalized compound in the Passerini-3CR still results in branching due to the thiol-yne reaction. Here, a structural sequence of employed phenylacetaldehyde and 2-nitrobenzaldehyde was demonstrated. 

Smith AB III, Adams CM, Kozmin SA, Paone DV. Total synthesis of (—)-cylindrocyclophanes A and F exploiting the reversible nature of the olefin cross metathesis reaction. J. Am. Chem. Soc. 2001 123 5925-5937. 

The housefly (Musca domestica) uses the hydrocarbon (Z)-9-tricosene (318 in Scheme 58) as the major component of its sex pheromone. Simple syntheses involve Wittig coupling 153, 154) or alkylation of a terminal alkyne and subsequent reduction 155, 156) to afford the desired Z-isomer in ca. 95% purity. Erucic acid 157, 158) or oleic acid 159, 160) have served as starting material of known Z stereochemistry. The transition metal-catalyzed olefin cross-metathesis reaction has been applied by Rossi 161) to synthesize (318) as a mixture of /Z-isomers together with the other possible Cis and C28 olefins (Scheme 58). 

Rossi, R. Simple synthesis of sex pheromones of the housefly and tiger moths by transition metal-catalyzed olefin cross-metathesis reactions. Chim. Ind. Milan 57, 242—243 (1975). 

Olefin cross metathesis starts to compete with traditional C=C bondforming reactions such as the Wittig reaction and its modifications, as illustrated by the increasing use of electron-deficient conjugated alkenes for the ( )-selective construction of enals and enoates. 

The synthesis and olefin metathesis activity in protic solvents of a phosphine-free ruthenium alkylidene bound to a hydrophilic solid support have been reported. This heterogeneous catalyst promotes relatively efficient ring-closing and cross-metathesis reactions in both methanol and water.200 The catalyst-catalyzed cross-metathesis of allyl alcohol in D20 gave 80% HOCH2CH=CHCH2OH. 

Table A. Functionalized homoallylic alcohols from olefin cross metathesis and subsequent allylboration reactions with benzaldehyde...

The chiral Mo-alkylidene complex derived from AROM of a cyclic olefin may also participate in an intermolecular cross metathesis reaction. As depicted in Scheme 16, treatment of meso-72a with a solution of 5 mol % 4a and 2 equivalents of styrene leads to the formation of optically pure 73 in 57% isolated yield and >98% trans olefin selectivity [26]. The Mo-catalyzed AROM/CM reaction can be carried out in the presence of vinylsilanes the derived optically pure 74 (Scheme 16) may subsequently be subjected to Pd-catalyzed cross-coupling reactions, allowing access to a wider range of optically pure cyclopentanes. 

Where there is no spacer group between the C=C bond and the functional group, productive self-metathesis does not occur, but cross-metathesis reactions with other olefins are still possible. Recent impressive examples of this are the cross-metathesis reactions of acrylonitrile (equation 19). The reaction occurs with a wide variety of R groups. For 15 different compounds the yield of the new nitrile after 3 h at room temperature is 40-90%, with the cis isomer always strongly preferred (75-90%). Only minor amounts of RCH2CH=CHCH2R are formed, and no NCCH=CHCN182. The fact that acrylonitrile... 

Heterochalcogenides, with chromium, 5, 312 Heterocoupling reactions in olefin cross-metathesis, 11, 181 Pd-catalyzed, alkynes, 8, 274—275 Heterocubanes, reactions, 3, 8 Heterocumulenes in insertion reactions, 1, 107 nickel metallacycle reactions, 8, 103-104 Heterocyclic compounds... 

The chiral Mo-alkylidene complex derived from AROM of a cyclic olefin may also participate in an intermolecular cross metathesis reaction. As depicted in Scheme 15, treatment of meso-67a with a solution of 5 mol% 4a and 2 equivalents of styrene leads to the forma-... 

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