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Reaction of Metal-Carbene Complexes with Cyclobutenediones: The First General C-C Bond Insertion Reaction for Fischer Carbene Complexes

Zora, Metin
Herndon, James W.
Alkylcarbene-chromium complexes react with cyclobutenediones to give 2-alkoxy-4-cyclopentene-1,3-diones in moderate yield, accompanied by varying amounts of 4-cyclopentene-1,3-dione derivatives which result from reduction of the initial product by the chromium byproduct. The reaction is general for a variety of cyclobutenedione derivatives with alkoxy, alkyl, or aryl substituents. The major products of the reaction between arylcarbene complexes and cyclobutenediones are 5-alkylidenefuranone derivatives. A mechanism involving oxidative addition of the acyl-acyl C-C bond, followed by carbene insertion and reductive elimination, is proposed.