ChemInform Abstract: Synthetic Application of the Alder-Bong Reaction: Stereoselective Construction of the Methanohydroazulene Framework.

ChemInform Abstract

The combined Diels-Alder/ene reaction of the dienone acetal (I) with the acetylenedicarboxylate (II) produces the regioisomeric cycloadducts (III) and (IV). The major product (III) is deacetalized and then subjected to boron trifluoride etherate induced rearrangement, forming the tricyclic dienone (VI). This methanohydrazulene derivative is also directly obtained from (III). Deprotection of the acetal (IV) results in double bond isomerization, yielding the tetracyclic enone (VII).