Thermally Induced Electrocyclic Reaction of Methylenecyclopropane Methylene Diketone Derivatives: A Facile Method for the Synthesis of Spiro[2.5]octa-3,5-dienes

Thermally induced electrocyclic reactions of methylenecyclopropane (MCP) methylene diketone derivatives afford a novel method for the synthesis of spiro[2.5]octa-3,5-dienes in moderate to good yields. Applying this methodology in a one-pot manner for the reactions of MCP aldehydes with 1,3-diketones, catalyzed by l-proline, also afforded the corresponding spiro derivatives.