Ring opening oligomerization

Fig. 15 Ring-opening oligomerization of vemonia oil. Reproduced from [114] by permission of The University of Southern Mississippi...

Silylpalladium complexes have attracted attention due to their relevance in the mechanism of Pd complex catalyzed reactions such as hydrosilylation of alkenes and dienes, bis-silylation of dienes and alkynes, carbosilylation of alkynes, cross-coupling of organic halides with disilanes, and ring-opening oligomerization and polymerization of cyclic disilanes and polysilanes. 

Le Borgne, A. Vincens, V Jouglard, M. Spassky, N. Ring-opening oligomerization reactions using aluminum complexes of Schiff s bases as initiators. Makromol. Chem., Macromol. Symp. 1993, 73, 37 6. 

HER 09a] Herbert D.E., Gilroy J.B., Chan W.Y. et al, Redox-active metallomacrocycles and cyclic metallopolymers photocontrolled ring-opening oligomerization and polymerization of silicon-bridged [l]fertocenophanes using substitutionally-labile lewis bases as initiators . Journal of American Chemical Society, vol. 131, pp. 14958-14968, 2009. 

Rulkens R, Ni Y, Lough AJ, Manners I (1994) Anionic ring-opening oligomerization and polymerization of silicon-bridged [l]ferrocenophanes characterization of short-chain models for poly(ferrocenylsilane) high polymers. J Am Chem Soc 116 797-798... 

The process of PC oligomerization in the presence of less alkaline catalyst system was also investigated by Keki et The ring-opening oligomerization of PC was... 

TFEO is by fai the most reactive epoxide of the series. However, ail the reported perfluoroepoxides undergo similar ring-opening reactions. The most important reactions of these epoxides ate those with the fluoride ion or perfluoroalkoxides. The reaction of PIBO and the fluoride ion is an example (27). It also illustrates the general scheme of oligomerization of perfluoroepoxides (eq 5). 

The direction of nucleophilic ring opening of unsymmetrical perfluoroepoxides has been shown to be a function of the nature of the nucleophile and the solvent (23,28). Although many oligomeric products have been prepared by this procedure and variations of it, no truly high polymers have been obtained... 

Scheme 3.4 Ring-opening polymerization of oligomeric PBT cyclics...

Imipenem (5.46) has not completely fulfilled such expectations [122], Indeed, this compound is unstable in both acidic and alkaline media. In weakly acidic solutions, imipenem undergoes complex oligomerization, a reaction initiated by the intermolecular attack of the carboxy group on the /3-lactam Fig. 5.17) and yields, finally, a diketopiperazine compound. In weakly alkaline solution, an intermolecular reaction between the /3-lactam and (iminome-thyl)amino group was observed Fig. 5.18). This reaction proceeds via an unstable dimer that breaks down to thienamycin (5.45) and a /3-lactam ring-opened compound bearing a Ai-formyl group [123],... 

Ready, J. M. Jacobsen, E. N. (2001) Highly active oligomeric (salen)Co catalysts for asymmetric epoxide ring opening Reaction, J. Am. Chem. Soc., 123 2687-2688. 

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