Synthesis Of Functional Imidazo[1,2-a]pyridines Derivatives And Polymers Based On Groebke-Blackburn-Bienaymé Reaction

Heterocyclic compounds are widely used in medicine,agriculture,and industry.Among them,heterocyclic compounds with stable?-conjugated systems,are often used as fluorescent molecules in many applications such as dyes,photoelectric materials,fluorescent probes,fluorescent sensors,and so on.As a unique type of important heterocyclic compound,imidazo[1,2-a]pyridines is involved in a wide range of biological active compounds and drug intermediates,which can be facilely synthesized through the Groebke–Blackburn-Bienayméreaction(GBB reaction)from amidines,aldehydes,and isocyanides.In view of the advantages of the GBB reaction such as stable and efficient reaction,simple reaction conditions,broad substrates,and functional group tolerance,in this thesis,we developed an efficient multicomponent polymerization based on GBB reaction,and synthesized a series of imidazo[1,2-a]pyridines-containing derivatives and polymers.In Chapter 2,a new multicomponent polymerization of diisocyandies,dialdehydes and2-aminopyridine was developed for the synthesis of new polymer structures containing imidazo[1,2-a]pyridines on the polymer main chain.The multicomponent polymerization enjoys the advantages of metal-free,mild reaction condition,high atom economy,and environmental friendliness,affording four kinds of imidazo[1,2-a]pyridines-containing polymers with high M_w of up to 32 400 g/mol in high yields of up to 98%through one-pot procedure.The aromatic fused heterocycle-containing polymers possess good solubility,high thermal stability,unique luminescent properties,unique fluorescence in solution,and acid/base-triggered reversible fluorescence response.This multicomponent polymerization hence provides an effective method for synthesizing functional polymer materials.In Chapter 3,five imidazo[1,2-a]pyridine derivatives with different substituteswere designed and efficiently synthesized through GBB reaction,and their structure-property relationship on the photophysical properties were investigated.Solvatochromism study and emission behavior in the aggregated states reveal that while 2-(4'-ethoxyphenyl)imidazo[1,2-a]pyridines shows no aggregation-induced emission(AIE)and excited-state intramolecular proton transfer(ESIPT)properties,2-(2'-hydroxyphenyl)imidazo[1,2-a]pyridines with phenol group exhibits both AIE and ESIPT properties.The compound with ethoxy substituent located at the ortho position of phenolic hydroxyl group shows only AIE properties,and the derivatives with bromine substituent at the ortho position or para position exhibit ESIPT property.Moreover,2-(4'-ethoxyphenyl)imidazo[1,2-a]pyridines shows reversible fluorescence response upon the stimuli with acid/base,however,the other four compounds with phenol group show no such responsive towards acid/base.In addition,through the selective detection of metal ions,These compounds were found to be able to selectively detect Cu²⁺and show fluorescence quenching with the detection limit of 7.02×10^-7 M.In summary,we have developed an efficient new multicomponent polymerization of diisocyandies,dialdehydes and 2-aminopyridine,and synthesized a series of imidazo[1,2-a]pyridine-containing derivatives and polymers.Their structure-property relationship on photophysical property was studied to help guide the future materials design.