The Reaction of 1-Amino-2,3-diphenylcyclopropenium Ions with 1,3-Diketones to Afford 2,4-Cyclopentadien-1-ols: The Regioselective Ring-Opening of 1-Aminocyclopropene Intermediates

Article abstract of DOI:10.1246/bcsj.61.2891

1-Amino-2,3-diphenylcyclorpopenium tetrafluoroborates (4) reacted with cyclic or acyclic 1,3-dicarbonyl derivatives (5) such as 1,3-diketones, β-keto esters, or gem-diesters in the presence of triethylamine to give 2,4-cyclopentadien-1-ols in moderate to good yields.Some isolated cyclopropene intermediates were, upon heating, converted to the corresponding cyclopentadienols.The factors that influence on the reactivities of 4 and 5 (basicities of the amino groups of 4 and bulkiness of the substituents of 4 and 5) are discussed qualitatively.