Synthesis Of Esters And Alkynones With CO₂ And CO Catalyzed By Palladium Nanoparticles

With the gradual development of human society,the reserves of fossil fuels are decreasing.The exploitation and utilization of Cl resources have been only way to the sustainable development of human society.CO2 and CO have recently attracted much attention in organic synthesis as the main Cl source.In terms of current stage,the exploration of transformation from CO2 and CO into high value-added organic chemicals by chemical method has always been the goal in academia and industry.Therefore,it is very meaningful to develop some efficient chemical conversion methods for realizing resource utilization of CO2 and CO.In the first part,an efficient method for the selective synthesis of δ-lactone from CO2 and 1,3-butadiene was developed using palladium nanoparticles(PdNPs)generated in situ as the catalyst without any additional ligand.The highest yield(51%with 94%selectivity)was achieved using Pd(acac)2 as the precatalyst in the presence of TBAAc as both reducing and stabilizing agent in acetonitrile at 70 ℃.The TON of 1020 achieved in the present study is the highest to date as compared with literatures.The palladium nanoparticles could be easily recovered through a simple extraction process and reused three times without an obvious loss in activity.The TEM image showed the presence of(3.8±1.1)nm-sized palladium nanoparticles in the reaction mixture.In the second part,the PdNPs-catalyzed three-component coupling of either(chloromethyl)arenes or(chloromethyl)heteroarenes with allyltrimethoxysilane and CO2(carboxylative Hiyama coupling reaction)was studied,and α,β-unsaturated esters were obtained in 61%-88%yields.The additive TBAF played key dual roles,namely,as a stabilizer for the palladium nanoparticles and as an activator for the allylsilane reagent through the coordination of the F anion to the silicon atom.This protocol shows good functional group tolerance.The existence of palladium nanoparticles in the reaction mixture was confirmed by TEM.In the last part,the palladium nanoparticles-catalyzed carbonylative coupling of aryl iodides with terminal alkynes(carbonylative Sonogashira reaction)was studied,and a series of alkynyl ketones were obtained in satisfactory to good yields(71%-84%)when various aryl and alkyl alkynes were examined.This reaction proceeded under mild conditions and exhibited good functional group tolerance.