Macroporous Polymeric Supports for Organic Synthesis

摘要

Chemical reactions on insoluble polymer supports require transport of reagents from solution into the cross-linked polymer matrix. Most previous polymeric reagents have employed 1-2% cross-linked polystyrene, which sells greatly in organic solvents. Such polystyrene gels, however, are weak mechanically, preventing their large scale application, and are unable to retard reactions between two polymer-bound species sufficiently to allow many site-isolation syntheses. Our research has been directed toward the use of more highly cross-linked polystyrene supports for organic synthesis. Examples include the generation and trapping of ester enolates by acylation and alkylation at room temperature (rather than the usual -78C) in high yield with no self-condensation of the ester, and effective Wittig olefin syntheses with macroporous supports having up to 20% cross-linking. Molecules as large as a 3-ketosteroid and a C19 aliphatic ketone are able to penetrate the 20% cross-linked polystyrene in Wittig syntheses. Transport of large organic molecules into reactive sites of the polymer succeds in the presence of a good solvent when the polymer has been functionalized initially by a transport-sensitive chemical reaction. (Author)