Seven-membered cyclic ketal

We next became interested in the possibility of extending this to a seven-membered cyclic ketal. It was immediately recognized that if the yield of the cyclic compound were not nearly quantitative, the resulting polymer would be cross-linked. In our previous work (16) the cis- and trans-l,2-bis (hydroxymethyl)-cyclohexane were prepared. When either the cis- or trans-diol was condensed with 1,4-cyclohexanedione, a 92% yield of the corresponding model compound was obtained. 

Since the seven-membered rings formed so readily to produce the ketals, an investigation was undertaken to see if eight-membered cyclic ketals would form as readily. A model compound was prepared from 1,8-bis(hydroxymethyl) naphthalene and cyclohexanone in a nearly quantitative yield of the cyclic ketal containing the eight-membered ring. 

It thus appears that a wide variety of tetrols and cyclic diketones can be used to prepare a large variety of soluble polyspiroketals. It appears that the reaction can be made to go readily when the ketal contains either five-, six-, seven-, or eight-membered rings. Some of the polymers containing the five-, seven- and eight membered rings can, of course, be considered to be a hybrid between ladder polymers and spiro polymers. An effort will be made to see what other cyclic ketals are useful for the formation of spiro polymers and what other types of reactions besides the ketal formation will produce similar polymers. 

Enantiomerically pure functional polycarbonate was synthesized from a novel seven-membered cyclic carbonate monomer derived from naturally occurring L-tartaric acid [99]. The ROP catalyzed by Novozym 435 was performed in bulk, at 80 °C, for 48h to afford optically active polycarbonate with M = 15500 g/mol and PDI 1.7 (Scheme 4.17). Hydroxy group functionality in the carbonate chain was achieved by deprotection of the ketal group. The polycarbonates have potential in biomedical applications. 

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