Metal-Free Cascade Radical Cyclization Of1,6-Enynes With Aldehydes

1,6-enyne compound has already been extensively studied in the synthesis of natural products and pharmaceutical molecules, particularly in the transition-metal-catalyzed cyclization of1,6-enynes because they take advantages of unprecedented efficiency, higher atom-economic, and more operational simplicity. However, there are many deficiencies in the transition-metal-catalyzed reactions, such as high costs and environment damage. Therefore, development of a novel, environmentally friendly, highly efficient is in huge demand. This paper mainly discloses a metal-free TBHP-mediated cascade radical cyclization of1,6-enynes with aldehydes for the construction of fluorene derivative through a free radical mechanism. The text is divided into three parts:Chapter1gives an overview on the reaction types of the1,6-enyne cyclization and the related mechanisms, and we also make a summary of the recent progress in1,6-enyne ring isomerization reaction under various conditions as well as its application in organic synthesis.Chapter2introduces an overview on the historical perspective of radical cyclization reactions and their applications in organic chemistry.Chapter3develops the metal-free cascade radical cyclization of1,6-enynes with aldehydes. The reaction proceeded well under optimized reactions conditions: PivOH (2.0equiv.) and TBHP (2.0equiv.), at120℃under argon in CH3CN for48h. A series of fluorene derivatives were obtained. reaction underwent addition and cyclization process, induced by radical initiators. Structure of the product were confirmed by1H NMR,13C NMR, IR and X-ray crystallographic analysis.This approach reported in this thesis is differene from the conventional transition-metal-catalyzed reactions. It is simple, environment-friendly and efficient.