Pericyclic Reactions of Free Cyclopentadienone

Article abstract of DOI:10.1021/ja00397a035

Evidence showing that the existence of free cyclopentadienone is needed in reactions of 4-tosyl-2-cyclopenten-1-one is presented.The methods involve the "Three-Phase Test" to detect reactive intermediates in solution.Cyclopentadienone is generated from an insoluble polymer-bound precursor and trapped by a second solid phase using Diels-Alder reactions.In such additions, the elusive ketone can act either as a diene or as a dienophile, according to reaction conditions.