Oxidative Coupling Of Quinone And Olefins

The skeleton of the compound containing a quinone structure is widely present in many biologically active natural products and pharmaceutically active molecules,especially 2-substituted para-quinone structures such as the vitamin K series.Therefore,efficient and rapid preparation of such compounds has very important research significance.There have been many reports on the synthesis of such compounds.Although many methods have good reaction yields,most of them require precious metal catalysis and introduction of pre-functional groups,which are poor in chemical economy and atom economy.Therefore,it is still of interest to organic chemists to develop methods that are straightforward,efficient,and inexpen sive to synthesize such compounds.Olefins are an inexpensive and readily available chemical.In the synthesis of many drug molecules,olefins are often used as synthetic blocks for the introduction of functional groups.The conventional reaction mode of hydrocarbon functionalization has the characteristics of direct and simple reaction,high efficiency and good atomic economy.In addition,this kind of reaction also meets the requirements of green chemistry,especially in recent years,it has received very extensive attention and development.Based on the above understanding,this paper designs the coupling of the two by direct hydrocarbon functionalization of hydrazine to achieve the direct and rapid preparation of the 2-substituted fluorene compound.Firstly,this thesis studies the basic model of styrene and 1,4-naphthoquinone which are cheap and easy to obtain.By screening the reaction conditions such as oxidant,catalyst and reaction temperature,The optimal reaction conditions were determined as follows:（NH₄）₂S₂O₈ as the oxidant,copper bromide as the catalyst,the reaction solvent was H₂O/CH₃CN/acetone（2.1 mL,v:v:v=1:1:1）,and the reaction temperature was 110°C,reaction time is 4 h.Subsequently,the paper studied the types of olefins suitable for the reaction conditions,and the results showed that styrene and its derivatives,whether it is the positional effect of the substituents on the benzene ring（ortho-,meta-,para-）,or the electronic effect of the substituents（electron donating group,electron withdrawing group）,the reaction can obtain the target product in moderate to good yield（65%-75%）.For linear olefins and even cyclic olefins,the reaction can proceed smoothly with a slightly lower yield（60%-71%）than styrene.Moreover,the reaction has good functional group tolerance,such as a halogen-substituted terminal olefin and a hydroxyl-substituted terminal olefin,all of which can obtain a target product in a medium yield（60%or more）,and provide a new product reaction site for subsequent functional group conversion.In order to further explore the scope of application of the reaction system,this paper attempts to use 1,4-benzoquinone instead of 1,4-naphthoquinone.However,the main product of the reaction is a benzodihydrofuran structure rather than the desired2-substituted benzoquinone compound.Through the analysis of the reaction results,the main reason for this special result may be due to the high activity of benzoquinone,resulting in the formation of the 2-substituted benzoquinone cannot stay,further reduced ring closure to form a benzodihydrofuran structure.Based on this,the paper adopts the"two-step one-pot"method,and the resulting mixture is not purified,and then directly oxidized with FeCl₃ to open the ring of the benzene ring structure,thereby obtaining the target product.Finally,this study carried out an isotope labeling experiment to label the oxygen atoms in the reaction solvent water to determine the source of water in the reaction product,subsequently,a free radical trap experiment was carried out to prove that the reaction follows the free radical mechanism.This study proposes a possible reaction mechanism for this type of reaction:first,the olefin generates a free radical carbon cation intermediate under the oxidation of SO4^·-,and then reacts with water,deprotonates,it is then coupled with quinone to form new radicals,which form the final product under the oxidation of divalent copper.In this paper,a practical method for the rapid coupling of olefins and quinones by（NH₄）₂S₂O₈ mediated olefins,quinones and inexpensive metal catalyzed three-component oxidation of H₂O has successfully developed.The method obtains the target product in a moderate to good yield,has a wide range of substrates,good atomic economy,is environmentally friendly,simple and convenient,and provides a reference method for the synthesis of similar quinones.