Reaction of aluminacyclopentadienes with aldehydes affording cyclopentadiene derivatives

Aluminacyclopentadienes, prepared in situ from the reaction of AlCl3 and 1,4-dilithio-1,3-dienes at room temperature, reacted with aldehydes at room temperature to afford cyclopentadiene derivatives including tetrahydroindenes in good to excellent yields. Both aromatic and aliphatic aldehydes undergo this reaction.