Solid-liquid phase-transfer catalysis polymerization

Applications to Phase-transfer Methods.—Dehmlow has published a review on advances in phase-transfer catalysis (PTC) which discusses the introduction of crown ethers into this area. The full details are now available of a study of alkyl-substituted azamacrobicyclic polyethers (78a) as PT catalysts. When the alkyl chains are C14—C20, such molecules are very efficient catalysts in both liquid-liquid and solid-liquid phase-transfer modes, which contrasts with the lower catalytic ability of the less organophilic unsubstituted cryptand (78b). Crown ethers immobilized on polymeric supports have been demonstrated to possess increased PTC activity in 5n reactions, up to that of the non-immobilized systems, when the connection to the polymer involves long spacer chains [e.g. (79)]. 

The use of solid-liquid phase transfer catalysis in the conjunction with bis(carbonylimidazolides) (i) bis(p-nitrophenylcarbonates) 10) as developed by Fre-chet for the synthesis of novel tertiary copolycarbonates. The instability of tertiary chloroformates renders tertiary polycarbonates inaccessible through conventional chloroformate monomers or intermediates. The bis(carbonylmiidazoiide) monomer was shown to polymerize with both tertiary (3) and secondary alcohols (lljy demonstrating the utility of the method in forming polycarbonates fi-om less reactive steri-cally hindered monomers. Most of the examples reported involved benzene dimethanol derivatives, or 1,4-butynediol, indicating that an adjacent site of unsaturation may activate the alcohol in the solid-liquid phase transfer reaction scheme. 

Two reportshave appeared in which it has been demonstrated that the polymeric insolubilized HMPA derivative (66) acts as a good catalyst for reactions between two liquid phases (i.e. liquid-solid-liquid triphase catalysis) such as the treatment of organic bromides with aqueous metal chlorides and iodides (for halide interconversion) or other nucleophiles. In contrast to the onium ions and crown compounds, (66) is a more efficient catalyst than its soluble equivalent (67) it can also be used with 18-crown-6 as an additional catalyst for solid-liquid phase transfer in the same reactions (Le. a solid-liquid-solid triphase mode). ... 

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