Lewis Acid Mediated Reactions of Zirconacyclopentadienes with Aldehydes: One-Pot Synthetic Route to Indene and Cyclopentadiene Derivatives from Aldehydes and Benzyne or Alkynes.

One-pot procedures for the preparation of highly substituted indenes, tetrahydroindenes, and cyclopentadienes have been developed by using a combination of zirconocene-mediated Cbond;C-bond-forming reactions with Lewis acid mediated activation of carbonyl groups. The carbonyl groups of aldehydes were deoxygenated in the reaction and behaved formally as a one-carbon unit. A variety of Lewis acids were checked and showed different reactivities in this reaction.