Study On The Cyclization Reactions Of Ortho-quinones

As a class of important multifunctional synthons,ortho-quinones are widely used in the synthesis of natural products,the study of drug molecules,and the performance improvement of functional materials.Ortho-quinones have unique reactivity and potential,and its transformation and application have attracted much attention.Although a series of progress has been obtained based on the nucleophilic addition,tandem reaction,ring-opening reaction,and annulation of ortho-quinones,it is still in the preliminary stage.Further exploration of the green,high-efficiency,economical and novel transformation mode of ortho-quinones,the development of its application in new reactions and in-depth mechanism research are still hotspots and difficulties for organic chemists.Meanwhile,benzoheterocycles are kind of important molecular framework,which plays an irreplaceable role in the fields of bioactive molecules,AIE structural units and new sensors.Therefore,the development of a new reaction model for the construction of benzoheterocycles involving the participation of ortho-quinones not only broadens the application range of ortho-quinones and promotes the development of quinones chemistry,but also has important theories and application value in the fields of chemistry,chemical engineering,pharmaceuticals,pesticides,and functional molecules.Based on our intense research interest in the filed of ortho-quinones chemistry,we used ortho-quinones as a synthetic building block,with the concept of green sustainable development as the guiding ideology and aim to synthesize functional molecules with high efficiency,high selectivity and high step economy,we developed a green,efficient,economical and novel reaction mode involving ortho-quinones as a synthon,constructed three types of benzoheterocyclic compounds including benzodioxoles,benzoxazoles and7-hydroxybenzoxazoles.The specific research content includes the following three parts:In chapter two,we have developed the palladium-catalyzed [4+1] cyclization reaction of ortho-quinones and N-tosylhydrazones to efficiently construct a series of benzodioxoles derivatives.This palladium-catalyzed coupling of N-tosylhydrazones and ortho-quinones were involved the process of carbonyl ylides generation,aromatization,and intramolecular nucleophilic addition,and for the first time realized the construction of two C-O bonds on the same metal carbene carbon.The features of this method include simple operation,gram-scale preparation,and wide substrate applicability.In chapter three,we have achieved a highly chemselective metal-free [3+1+1]cyclization reaction of ortho-quinones,aldehydes and hydroxylamine hydrochloride to construct benzoxazole compounds.This reaction takes advantage of the cheap and readily available inorganic substance hydroxylamine hydrochloride as a nitrogen source,and overcomes the inadequacy of using organic amines as a nitrogen source to construct benzoxazole derivatives,conforming to the development concept of green chemistry.In addition,we obtained the key ortho-quinones oxime intermediate,and further confirmed the absolute configuration of the intermediate by X-ray single crystal diffraction.This method has demonstrated metal-free,simple operation,good functional group tolerance,inexpensive and readily available starting materials,which provides a novel and practical synthetic route for the construction of benzoxazole derivatives.In chapter four,through the C-H amination strategy,we have developed [2+1+1+1]four-component cyclization reaction of ortho-quinones,aldehydes,hydroxylamine hydrochloride and water to direct synthesis of different types 7-hydroxybenzoxazole compounds with high chemoselectivity and high yields.The new method of7-hydroxybenzoxazole compounds provide a powerful reference for the one-step construction of 7-substituted benzoxazole compounds and its further modification to synthesize more complex functional molecules.The reaction has the characteristics of mild conditions,metal-free,strong operability and wide substrate applicability.It is worth noting that the deuterium-abeling experiment proved that water acts as both the reaction solvent and the source of oxygen atoms in the benzoxazole skeletons.