Dynamic Covalent Reactions Of Aromatic Imines And Thermodynamic Quantitative Reactivity Scales

Dynamic covalent chemistry plays an important role in the construction of functional materials,and the regulation of biomolecules through the feature of reversibility,responsiveness and adaptability.In addition,the reversible formation and exchange of dynamic covalent bonds is also to enhance structural diversity.In the thesis,aromatic imines derivedin situ from pyridine-2-carboxyaldehyde were investigated systematically for reactivity based universal dynamic covalent reactions toward a series of S-,N-,,O-mononucleophiles.For the first time,unified thermodynamic quantitative reactivity scales were established based on these reversible reactions.Finally,2-formylbenzoic acid and its derivatives were synthesized and their dynamic covalent reactions with 1-butylamine were investigated.The main contents are as following:1.Dynamic multicomponent covalent assembly reactions were conducted with pyridine-2-carbaldehyde(2-PA),different primary aromatic amines,and a series of S-,N-,O-mononucleophiles,such as 1-propanethiol,ethanol,diethylamine,piperidine,in order to control the eq.uilibrium through in situ generated imines 1.The relative nucleophilicity of substituted aromatic primary amines and S,N-,0-mononucleophiles affect the reaction path.The substituent effects on aromatic amines were further investigated by using the Hammett linear free energy relationship to analyze the eq.uilibrium constant of the reaction of imine 1 with S-,N-,O-mononucleophiles.The results show that the electron-donating group(EDGs)stabilize the imine 1 while the electron-withdrawing group(EWGs)stabilize the product 4.2.The kinetic reactivity scales have been studied widely while thermodynamic quantitative reactivity scales have not been reported.Based on the aforementioned dynamic multi-component covalent assembly from S-,N-,0-mononucleophiles,the dynamic covalent reactions between imine 1 and a series of structurally diverse alcohols,thiols,primary amines,secondary amines were investigated and employed as reference reactions.The nucleophilic parameters RN and their associated nucleophilic sensitive parameters SN as well as the electrophilic properties RE were obtained by using the least-squares method of log K-SN(Rn + RE)-The thermodynamic quantitative reactivity scales were thus established.Further more,the generality and predictability of the scales were verified through thiol Michael addition.3.The dynamic covalent reactions of 2-formylbenzoic acid and its derivatives with different eq.uivalents of 1-butylamine were investigated in detail.The 1H-NMR analysis indicated that the products were mainly composed of open imines or cyclic hemiaminals.The investigation of reaction mechanism is still in progress.