Synthesis Of Benzocoumarin Catalyzed By Visible Light Catalysis

This thesis mainly introduces my research topics during my master’s degree period:Multiple C-H bonds activation coulped with photoredox catalysis:synthesis of functionalized benzocoumarins.Direct functionalization of inert C(sp~3)-H bonds is an attractive synthetic technology for preparation of pharmaceutically significant compounds in modern synthetic organic chemistry.Direct functionalization of C-H bonds in petroleum by-products affords an efficient and versatile technology for a range of organic transformations,including various C-X,C-O,C-N,and C-C bond formations.Over the past decades,many transition metal based catalysts have been verified to play an important role in this scenario via thermal pathways.However,considering environmental friendliness,simple operation,economic reaction and other factors,it is still a very important research topic in this field to prepare pharmaceutically significant compounds by means of direct C-H bond functionalization under mild reaction conditions.With this context,visible-light-enabled photocatalysis has been regarded as a powerful synthetic tool to address the above issues due to its simple operation,convenient reaction device and abundant solar energy.Benzocoumarins,as a frequently encountered class of oxygenous heterocycles,widely exist in many biologically meaningful natural products as well as agrochemicals and pharmaceuticals.For instance,some representative bioactive compounds,such as dioncolactone A,alternariol,ellagic acid,fissitungfine B and ravidomycin V,contain this core structural unit.In addition,the substituents on the benzocoumarin skeleton also play a key role in regulating its biological activities.Therefore,their important uses have encouraged enormous synthetic efforts to explore mild,efficient and straightforward methods toward their preparations.Up to now,important progress has been made,but we believe that there are still some shortcomings in the previous synthesis methods,such as harsh reaction conditions,many synthesis steps and many by-products.Therefore,we attempt to use visible-light-enabled photocatalysis as a powerful synthesis tool to achieve efficient synthesis of benzocoumarins through the activation of multiple inert C(sp~3)-H bonds.After carefully optimizing the reaction conditions,an efficient and green visible-light-catalyzed method for the preparation of a series of benzocoumarins was developed using readily available 2-methylbiphenyl as the starting materials under the synergistic interactions of organic dye photocatalyst 4Cz IPN-Br,tetrabutylammonium bromide,potassium carbonate and oxygen in the mixed reaction solvent of DCE/Me CN(1:1).In this method,the substrates containing different substituents(such as ester,cyano,trifluoromethyl,ketone carbonyl,methoxy,sulfonyl,halogen atoms,etc.)have good functional group compatibility.In addition,we found that this method is not only suitable for simple substrate structures,but also for 2-methylbiphenyl substrates with natural product structural fragments such as terpenoids,sugars and amino acids.This method can also easily convert them into corresponding complex benzocoumarin products,which means that the method has broad application value in the field of drug synthesis.In summary,this paper provides an environmentally friendly,simple operation and high atom utilization method for the preparation of benzocoumarins.