The In Situ Palladium Nanocatalyzed Carbonylation Of Aryl Iodides At Normal Temperature And Pressure

Palladium catalysed carbonylation reactions are now widely recognized as a very important tool in industrial and organic chemistry.Palladium-catalyzed carbonylative reactions of aryl halides compounds with the Cl building block carbon monoxide are becoming a valuable tool in the synthesis of biaryl ketones,aromatic aldehydes and aromatic acids.In this paper,a ligand-free in situ-generated palladium nanoparticles(Pd(OAc)2/PEG-400)system has been developed,that is,the generation of the palladium nanoparticles and the catalysis of reations proceed in the same time.In situ-generated palladium nanoparticles-catalyzed Suzuki carbonylation:hereinwe report the first examples of an efficient nanopalladium catalytic system for carbonylative Suzuki reactions of aryl iodides,carbon monoxide and arylboronic acids,without an additional ligand.Remarkably,this transformation proceeds smoothly at ambient temperature and pressure,which has also never been reported so far.The reaction of 4-iodonitrobenzene,carbon monoxide and phenylboronic acid was selected as a model reaction.We optimized base,catalyst,and solvent.The combination of Pd(OAc)2 and K3PO4/tBUCO2H in PEG-400 gave the best results.Under the optimised conditions,we employed aryl iodides as substrates with aryl boronic acids to afford biaryl ketones in 71%-95%isolated yields.Interestingly,the nanopalladium catalytic system is also suitable for double carbonylation of diiodobenzenes,affording desired products in 80-95%isolated yields.Meantime,we made a TEM analysis to prove that the reaction system is a nanocatalysis.Gratifyingly,the in situ formed catalyst can be recycled up to nine times with a 80%average yield.Finally,a preliminary mechanism was researched.Hg and CS2 poisoning experiments suggest that the active catalystis very likely to be homogeneous in nature.In the hydroxycarbonylation,4-iodonitrobenzene was selected as a model substrate.We optimized base,water,and catalyst,The combination of 2 mol%Pd(OAc)2,K2CO3,and 0.5 mL H2O in PEG-400 gave the best results.Under the optimised conditions,we employed aryl iodides as substrates to afford aromatic acids in 86%-95%isolated yields.Meantime,1,4-diiodobenzene can afford the product 4-iodobenzoic acid in 92%isolated yields.Gratifyingly,the catalytic system can be expanded to the preparation of esters by one-pot two-step reaction and give good isolated yields.In the reductive carbonylation,4-iodonitrobenzene was selected as a model substrate.We optimized reducing agent,base,and catalyst,The combination of 2 mol%Pd(OAc)2,Na2CO3/NaHCO3,and HSiEt3 in PEG-400 gave the best results.Under the optimised conditions,we employed aryl iodides as substrates to afford aromatic aldehydes in 84%-92%isolated yields.Interestingly,the nanopalladium catalytic system is also suitable for double reductive carbonylation of 1,4-diiodobenzene,affording desired product terephthalaldehyde in 62%isolated yield.