Synthesis Of Phenanthrenes Based On Norbornadiene

Norbornene-mediated ortho-C-H functionalization of aryl halide(Catellani reaction),has been widely used in the synthesis of multifunctional arenes.The Catellani reaction has many advantages,such as easy availability of materials,simple operation,good selectivity,wide range of substrate,high tolerance of functional group and onepot difunctionalization.Norbornadiene has similar structure and properties to norbornene,which can also undergo retro-Diels-Alder reaction to effectively construct C=C bond.Norbornadiene has potential applications as a new type of "C2 synthon".Phenanthrene is a class of polycyclic aromatic compounds and an important motif in drug molecules.These compounds have broad-spectrum pharmacological activities and unique photoelectric properties and are widely used in medicine and photoelectric fields.The main methods of obtaining phenanthrenes include extraction from natural minerals and artificial synthesis.At present,the synthesis of phenanthrenes is mainly via cyclizations using alkyne or benzynes precursors as "C2 synthon".In this thesis,two new methods have been developed for the preparation of phenanthrenes using norbornadiene as " C2 synthon".1.Rhodium-catalyzed [4+2] cyclization of 2-biphenylboronic acid and norbornadiene was developed for the efficient synthesis of phenanthrenes.The electron effect of substituents had great influence on the reaction,and the substrates with electron-draw groups were relatively ineffective under the same conditions.The reaction features wide range of substrates,high reaction selectivity and good yields.2.A new Pd-catalyzed method for the synthesis of phenanthrenes via the [2+2+2]cyclization of aryl iodide,2-bromophenylboric acid and norbornadiene was developed,using tri(2-furyl)phosphine as ligand.The reaction involves a tandem Catellani reaction and retro-Diels-Alder reaction,using norbornadiene as " C2 synthon".Electron effect affects reaction unobviously and steric effect is more important to the reaction.The method has the advantages of simple materials,easy operation,good chemical selectivity,high functional groups tolerance and excellent yield.