Efficient Synthesis Of 3,4-diaryl Coumarin From Aryl Alkynyl Ester "One-pot Method"

3,4-Diaryl coumarins as one of important coumarin derivatives not only have various potential biological activities,but also have been applied in the field of luminescent materials.The existing synthetic methods to construct these compounds need either expensive precursors or multi-step synthesis.In order to solve these shortcomings,the stepwise one-pot synthetic strategy is considered as the effective pathway.Recently,the stepwise one-pot synthetic method with the combination of various approaches have been developed to expand the application of this strategy in organic synthesis.Herein,an efficient one-pot method involving visible-light-induced cyclization and Pd-catalyzed Suzuki cross-coupling processes to construct 3,4-diaryl coumarins is developed,and explore its AIE optical activity.The main research contents are as follows:1.Under the light on-off optimized conditions,a series of alkynoates and aryl boronic acids were well suitable for this catalytic system,and were successfully transformed into the corresponding products in moderate to high yields.Meanwhile,this synthetic system has good applicability for other Pd-catalyzed coupling reactions,such as Heck and Sonogashira reactions.This work provides a straight forward way to create valuable multi-substituted coumarins.(Scheme 1).(?)2.Based on the results of controlled experiments and previous research,a possible mechanism is proposed.The studied light "on-off" strategy is carried out through photocatalysis and thermocatalysis processes.After the photocatalytic cycle studied in our previous work,the main intermediate 3-bromocoumarin 5 undergoes a continuous Pd-mediated Suzuki reaction process.In addition,3,4,7-triphenylcoumarin can be produced by the Suzuki reaction of 3-bromo-4,7-diphenyl and Ph B(OH)2,and it can be produced by Pd-catalyzed C-H activation.According to spectroscopic studies,we found that some 3,4-diarylcoumarins may have AIE activity.This work provides a direct method for creating multi-substituted coumarins with potential AIE properties.