6533b7d0fe1ef96bd125a1f2

RESEARCH PRODUCT

Cycloaddition Reactions with Vinyl Heterocycles

subject

description

Publisher Summary The Diels-Alder reaction is one of the most common and elegant methods for the construction of six-membered rings. Although the number of Diels-Alder cycloadditions with open-chain and alicyclic dienes is very large, the number of examples with aromatic heterocyclic compounds is relatively small. The introduction of a vinyl group as a substituent onto a heterocycle increases the number of possible reactions. This new possibility, however attractive for synthetic purposes, is successful only with π-excessive five-membered heterocyclic derivatives with a few exceptions. The chapter discusses the reactions of vinyl heterocycles with carbodienophiles. The endocyclic and exo-endo diene systems of 2-vinylfuran participate in cycloaddition reactions with dimethyl acetylenedicarboxylate (DMAD), and a 1:1 mixture of the diesters endocyclic product and exo–endo product is obtained when the reaction is carried out at room temperature. The overall yield is very low due to polymerization of the 2-vinylfuran. In contrast with reactions with other dienophiles, the reaction with DMAD resulted in reduced selectivity, probably due to equilibration of the more soluble adducts.