Polymeric onium salts as catalysts in preparative organic chemistry

Ammonium and phosphonium quaternary salts immobilized on organic and inorganic polymeric matrices are reviewed in relation to their main catalytic applications in preparative organic chemistry. Attention is paid to the systems active in heterophase anion-promoted reactions recognizable in the modern breakthrough created in conventional organic chemistry by the chapter of “phase-transfer” catalysis for its multivalent practical potential. After a mention of early applications in synthetic chemistry performed in the presence of conventional anion-exchange resins, examples of the reports that started to appear in the literature since 1975 on the specific topic of the title have been presented. In particular a rationalization of the specific catalytic activity in phase-transfer reactions has been attempted in terms of the structural parameters directly related to the polymeric matrix. This should not be considered only as a merely inert carrier because of its potential of affecting the specific rate of the overall process under the chemical and stereochemical point of view and defining its morphological and chemical integrity.