Intramolecular Diels−Alder Reactions of 4-Vinylimidazoles

The synthesis of a variety of unsaturated ethers, esters, and amides derived from urocanic acid and their Diels−Alder reactions are reported.
Propargylic ethers and esters cyclize with reasonable efficiencies, but the related mono- and unactivated olefins did not cyclize. On the other
hand, the corresponding amines and amides, along with the doubly activated ester/amide derivatives participate in the cycloaddition reaction.