Acyclic diene metathesis oligomers

Acyclic diene molecules are capable of undergoing intramolecular and intermolec-ular reactions in the presence of certain transition metal catalysts molybdenum alkylidene and ruthenium carbene complexes, for example [50, 51]. The intramolecular reaction, called ring-closing olefin metathesis (RCM), affords cyclic compounds, while the intermolecular reaction, called acyclic diene metathesis (ADMET) polymerization, provides oligomers and polymers. Alteration of the dilution of the reaction mixture can to some extent control the intrinsic competition between RCM and ADMET. 

Acyclic diene metathesis (ADMET) polymerization of divinyl benzene, shown in Scheme 37, using an extremely reactive tungsten alkylidene catalyst (Schrock s catalyst) yielded PPV oligomers with DP of 8 [153]. In this example ethylene is formed as a side product of metathesis, and its removal by the use of high vacuum helps drive the polymerization in the forward direction. 

A new acyclic diene metathesis polymerization method has been developed using 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene)benzylidene mthenium(II) dichloride as catalyst. This reaction catalyst was used for preparing oligomers and polymers containing amino acids or polypeptides. 

A number of recently reported synthetic methods include the formation of organic polymers with pendent cyclic or linear phosphazene side groups (reactions 7-9) and a process for the preparation of linear polymers in which phosphazene rings are linked together by organic oligomer chains using acyclic diene metathesis (ADMET) techniques (reaction 10). ... 

As has already been mentioned, divinyl silicon derivatives, similarly to monovinyl-substituted silicon compounds, are also completely inert to productive homometathesis, particularly as far as acyclic diene metathesis (ADMET) polymerization is concerned. However, we have shown in earlier reports that in the presence of ruthenium, rhodium and cobalt complexes containing or generating M-H and/or M-Si bonds, divinyl-substituted silicon compounds undergo de-ethenated (poly)condensation to yield a mixture of oligomers and cyclic unsaturated siloxanes, silazanes and caibosilanes, as shown in Scheme 2 [21-29]. 

Walba DM, Keller P, Shao RF, Clark NA, Hillmyer M, Grubbs RH (1996) Main-chain ferroelectric liquid crystal oligomers by acyclic diene metathesis polymerization. J Am Chem Soc 118(11) 2740-2741. doi 10.1021/ja953779z... 

Silicon-Terminated Telechelic Oligomers by Acyclic Diene Metathesis Chemistry... 

Ungar, G., Zeng, X., Brooke, G.M., and Mohammed, S. (1998) Structure and formation of noninteger and integer folded-chain crystals of linear and branched monodisperse ethylene oligomers. Macromolecules, 31,1875-1879. Wagener, K.B., Boncella, J.M., Nel, J.G. et al (1990) The key to successful acyclic diene metathesis polymerization... 

Scheme 11.9. Acyclic diene metathesis leading to the oligomers 20 and end capping to 21 by cross metathesis (cat Mo-alkylidene complex of the Schrock-type).

The synthesis of a,co-difunctional telomers by cross-metathesis between cyclic olefins and acyclic functionalized olefins is possible in the presence of functional-group-tolerant catalysts. Thus, cross-metathesis of dimethyl hex-3-enedioate with cycloocta-1,5-diene (Pinazzi 1980 Reyx 1982b, 1990), cyclopentene (Reyx 1986, 1987), or norbomene (Cramail 1991a) in the presence of the catalyst system WCV Mc4Sn allows the synthesis of a,m-difunctional oligomers, e.g. reaction (2). 

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