Regioselectivity in cycloaddition reactions on solid phases

Abstract

A 1% crosslinked divinylbenzene-styrene copolymer, incorporating benzyl acrylate groups, reacted in normal Diels–Alder reactions with E-1-phenyl-1,3-butadiene or methyl E-2,4-pentadienoate to give their respective polymer-bound benzyl cyclohexenecarboxylates. Polymer-bound benzyl propiolate and polymer-bound benzyl phenylpropiolate reacted with benzonitrile oxide in a typical 1,3-dipolar addition reaction to give their respective polymer-bound isoxazoles. Cleavage of the polymer-bound Diels–Alder adducts and the polymer-bound 1,3-dipolar addition adduct derived from polymer-bound benzyl propiolate gave mixtures of ortho and meta regiomers similar to those produced in analogous reactions in solution. Cleavage of the polymer-bound 1,3-dipolar addition adduct, derived from polymer-bound benzyl phenylpropiolate, followed by esterification, gave a solitary adduct, 4-carbomethoxy-3,5-diphenylisoxazole, but an analogous solution 1,3-dipolar addition yielded a 1:1 ratio of the two possible regiomers.

The Current Status of Heterocyclic Combinatorial Libraries

“…Yedidia and Leznoff reported the solid phase synthesis of isoxazole derivatives via 1,3-dipolar cycloaddition. 153 A divinylbenzene-styrene copolymer was reacted with propiolic acid or phenyl propionic acid to give the polymer-bound propiolate and polymer-bound benzyl phenyl propiolate. The treatment of those derivatives with benzonitrile oxide, generated in situ from R-chlorobenzaldoxime, at 0°C in THF yielded the corresponding polymer-bound benzylisoxazoles.…”

The monoblocking of symmetrical diketones on insoluble polymer supports

“…Microanalyses werc pcrformed by Guelph Chemical Laboratories Ltd., Guclph, Ont. All other instrumentation and general procedures werc the same as described prcviously (34).…”

Recent Advances in Solid‐Phase 1,3‐Dipolar Cycloaddition Reactions

“…10 Dimerization of the nitrile oxides has limited the utility of nitrile oxide cycloadditions in solution. Typically, nitrile oxides are generated in situ, and the cycloaddition reaction occurs smoothly at room temperature.…”