Macroporous Polymer Supports for Organic Synthesis

摘要

Highly cross-linked macroporous polystyrenes and microporous polystyrenes have been used as supports for Wittig reagents and for ester precursors to medium and large ring lactones and Beta-keto esters. Functionalization of the polymer with the bulky lithium dipehnylphosphide allows subsequent high yield Wittig reactions even with large aldehydes to form vitamin A derivatives and with large ketones such as a 3-keto steroid on a 20% cross-linked macroporous support. Reduced mobility of the polymer-supported reagent compared with a soluble analog enabled cyclization of 12-hydroxydodecanoic thiol ester in higher yield in the polymer than in solution at similarly high concentration. C-13 NMR spectral analysis was developed into a routine tool for analysis of insoluble polymer-supported reagents. The glass-to-gel transition temperatures of polymer-supported reagents were shown to be much lower than the temperatures at which useful syntheses are carried out. A new, safe, low-cost method for preparation of chloromethylated polystyrenes by phase transfer catalyzed chlorination of poly(p-methylstyrene) was discovered.