Diels–Alder reactions. Part I. The dienophilic properties of cis- and trans-β-formylcrotonic acid and their derivatives

Abstract

Methyl trans-β-formylcrotonate (2) and 4-hydroxy-3-methylbut-2-en-4-olide (cis-β-formylcrotonic acid) gave Diels–Alder adducts with dimethylbuta-1,3-diene with preservation of the steric arrangement of the substituents on the dienophile. The dienophile (2) similarly gave adducts with the 1,2,4-trisubstituted diene, 6,6-ethylenedi-oxy-3-methylhexa-2,4-dienyl acetate, which might prove of value in the synthesis of kitol-like dimers of retinol.