Synthesis and Diels-Alder reactions of (E)-6,6-dimethoxy-3-hexen-2-one

Article abstract of DOI:10.1139/v82-397

Treatment of 3,3-dimethoxypropanal (2) with (acetylmethylene)triphenylphosphorane (4) gives (E)-6,6-dimethoxy-3-hexen-2-one (5).Reaction of 5 with cyclopentadiene, 1,3-cyclohexadiene, anthracene, and 1,3-diphenylisobenzofuran gives Diels-Alder adducts, which on hydrolysis are converted to the corresponding keto aldehydes.Attempts to effect intramolecular aldol condensation of the latter were unsuccessful.Hydrolysis of the exo-acetyl adduct from 1,3-diphenylisobenzofuran with aqueous formic acid gives 4-acetyl-2,3,3a,4,5,9b-hexahydro-5,9b-diphenylnaphtho<1,2-b>furan-2,5-diol, via aldehyde formation and hydrolytic cleavage of the ether bridge.The adduct from cyclopentadiene under anhydrous acid conditions give 3-acetyl-9-methoxy-tetracyclo<4.3.0.0^2,4.0^3,7>nonane (27).