Bicyclic acetal polymerization mechanism

These results indicate that the polymerization mechanism of bicyclic acetals is as complicated as that of monocyclic acetals184-188 and dependent on the monomer structure and the polymerization conditions. 

The m ority of the stereochemical studies described in the above cited papers surest an S]s 2 mechanism of propagation. However, Hail observed in the polymerization of some bicyclic acetals (e.g. 2,6-dioxabicyclo[2.2.2)octane) the formation of a stereorandom polymer, indicating an Si>(l proems. The randomization proceeds at higher temperatures whereas at low temperatures, a stereoregular polymer is exclusively formed by an Si 2 process l... 

This review summarizes all the data we obtained on the synthesis and cationic ring-opening polymerization of bicyclic acetals and orthoesters, and discusses the relationship between ring-strain and poly-merlzablllty. This ties In with earlier work on the polymerlzabll-Ity of monocyclic and bicyclic lactams ( - ). A new mechanism for the propagation step In the polymerization of bicyclic orthoesters Is supported. 

High molecular weight stereoregular polysaccharides were prepared by the cationic polymerization of bicyclic acetals. Schuerch developed and reviewed this field comprehensively several times and described the mechanism of polymerization, synthetic scope of the method, and applications of these synthetic polysaccharides (97-100). 

Suraimoto and Okada reviewed the reaction mechanism of the ringopening polymerization of bicyclic acetals, oxalactones, oxalactames, and related heterocyclic compounds (103). 

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