Azacarbene-catalyzed Activation And One-electron Oxidation Of Aromatic Ester Compounds And Research On The Biological Activity Of Pesticides

Pesticides played as an important role in modern agriculture.The use of pesticides is closely related to the stage of the agricultural development and the progress of science and technology.The development and application of new pesticides will bring tremendous changes to the mode of agricultural production and the usage of pesticides.Nowadays,new pesticides are highly demanded.They can provide the most fundamental technical support for the"zero growth"of the use of pesticides.N-Heterocyclic carbenes(abbreviated as NHC or carbenes)have been widely applied in various aspects.For example,carbene can react with metal to generate metal complexes,which is applied to homogeneous catalytic reactions.Also,it can be used in organic light-emitting diodes(OLED)via synthetic phosphorescent compounds.In can also be used in photochemical water decomposition,chemical sensors,dye-sensitive solar cells and oxygen sensors.At the same time,carbene has been used in the development of anti-cancer drugs,which is benefit human health.Besides,NHC as organocatalysts led to the development of new synthetically useful transformations.The ability of NHC to form a variety of reaction intermediates paved the way for the development of a variety of catalytic asymmetric bond formations,cycloadditions,annulations,and domino reactions.The purpose of this thesis is developing new chiral pesticides enabled by NHC catalytic asymmetric reactions.We not only explore new catalytic activation methods of NHC but also synthesize new chiral pesticides with the newly developed novel catalytic activation modes.Most importantly the target products are applied to the bioactivity test in order to search for new chiral pesticides.Through NHC organocatalytic reactions,the products of six membered lactone compounds and chiral?functional groups were efficiently synthesized in environmental and friendly.The first part focuses on NHC catalyzed[4+2]reaction.o-QDM is a highly active intermediate and widely used in organic synthesis,which is a significant reaction to construct six-membered ring.However,o-QDM intermediates are rarely reported in organocatalytic reactions.The activation of inert sp~3 carbons through NHC organocatalytic reactions involving o-QDM intermediates is a long-standing challenge.In order to address this problem,we introduce the electron negative heteroatom into the aromatic ring.At the same time,the sp~3carbon on the methyl group can be activated under the oxidation condition to form the o-QDM intermediates.However,the synthesis of the starting materials is difficult,and the substrates are only limited to the indolealdehydes.Subsequently we disclose the incorporation of a silicon atom to an aryl carboxylic ester substrate.The resulting C-Si bond can be activated via the addition of a carbene catalyst on a remote site.This strategy allows for efficient functionalization of the benzylic sp~3-carbons of aryl carboxylic esters.Therefore,we chose to use 2-silicon methyl benzoyl as the model substrate.NHC were used as the reaction catalysts and the o-QDM intermediates were formed without of any external oxidants.Then 2,2,2-trifluoro-1-phenylethan-1-one,methyl 2-oxo-2-phenylacetate and indigo derivatives used as the dienophiles to react with the o-QDM intermediate through[4+2]cycloaddition processes.The reaction bore a good substrate generality.Different substituents at various positions were well-tolerated,although the enantioselectivity of this reaction was not satisfied at this moment.The second part of the thesis involves the single-electron-transfer reaction via NHC catalysis.The free radical reaction may provide an effective synthetic method for the preparation of molecules that are challenging to be synthesized through traditional methods.The single-electron-transfer process provides a novel and efficient synthetic strategy in the field of organic synthesis.This field is still its infant stage,the reaction mechanism is not clear,and the reaction route is also limited.The content of this chapter is mainly focused on the exploration of a new type of chiral single-electron oxidant,using chiral single-electron oxidant to achieve the enantioselective control of the target product.From the screening of chiral oxidants and the optimization of reaction conditions,we discovered that the chiral oxidants can control the enantioselectivity of the desired product.The broad substrate scope of this transformation can also support our reaction designs of the new chiral oxidants.Enals bearing different substitution patterns were tolerated,with the corresponding product afforded in good yields and excellent enantioselectivities.However,the asymmetric?-hydroxylation of enals was achieved via a chiral NHC catalysis with a stoichiometric amount of achiral nitroarene oxidant in previous work by Rovis and Chi.We switched the chiral information to the oxidant,which is a complementary and interesting idea.It is obvious that the previous protocols were more useful in terms of atom-economy and cost(the chiral oxidant used in this present work must be used in stoichiometric amounts).The drawbacks existed in the stoichiometric use of chiral oxidants need to address.The development of the catalytic use of chiral oxidants is an important task future research.The third part of the work is about the biological activity of the various functional small molecules that had been synthesized via NHC-catalyzed reactions.Based on the previous asymmetric catalytic activation of NHC,we are committed to using N-heterocyclic carbene as an organic small molecule catalyst to catalyze and synthesize new green pesticide compounds with certain physiological activity and complete independent intellectual property rights.After synthesizing many molecules,we used the growth rate method and turbidity method to test the antibacterial effect of the compound on fungi and bacteria.According to several rounds of biological activity tests,we can see that the solubility of the compound has a great influence on the biological activity,and the biological activity of different compounds is also very different.In later research,we will select the best chiral drugs as lead compound,modify the structure of the drugs,and investigate the effect of enantioselective biological activity by introducing active functional groups.