Non-gaseous Palladium-catalyzed Carbonylation Cross-coupling Reaction

Carbon monoxide is an important carbonyl source in the palladium-catalyzed carbonylation coupling reaction.However,it is high toxic,the experimental operation using steel cylinders is complicated,and its safety is difficult to be guaranteed.Therefore,the development and utilization of non-gas carbonyl sources has become an important research direction.Common carbonyl sources are divided into three categories.Organic small molecule CO equivalents contain higher percentages of CO and lower decomposition product toxicity.But there are poor atomic economy and severe release conditions which are difficult to be compatible with catalytic conditions.Carboxylic acid derivative CO substitutes have high CO utilization.They are often used in conjunction with double-chamber reactors to avoid incompatibility issues between the carbon monoxide in situ release system and the palladium-catalyzed carbonylation system.But their decomposition products are more toxic,the experimental operation is more complicated,and the experimental device is more expensive.Metal carbonyl complex CO release molecules carry multiple CO,have higher potential for CO release and better atomic economy.But the existing release conditions are severe and the effect of release metal species on the carbonylation reaction is not clear.Facing the current situation and challenges in the study of non-gas carbonyl sources,we believe that the metal carbonyl complex has the best release potential.However,it is difficult to further improve the carbonyl utilization rate due to the limitation of the existing release methods.Accordingly,in order to develop a new metal carbonyl complex release mechanism which can be applied in palladium-catalyzed carbonylation coupling reactions.The following experimental investigations have been made in this paper:(1)Based on literature research and experimental investigations,we have developed a new decarbonylation release mechanism for the oxidation of iron pentacarbonyl.Using air as an oxidant and alkali as a promoter,CO can be generated in situ under mild conditions.The reaction process of the oxidation of iron pentacarbonyl by oxygen was established by monitoring the composition and content of the reaction gas/liquid phase,calculating and analyzing thermodynamic and kinetic parameters,capturing and releasing intermediates,and characterizing metal solids.The results show that in this system,one pentacarbonyl iron can be decomposed to produce four CO and one CO2.The release conditions are mild and controllable,the amount of CO generated is large,the by-products do not affect the carbonylation coupling process.As a non-gas carbonyl source it has a broad application prospect.(2)The oxidative decarbonylation release mechanism of iron pentacarbonyl was used in the palladium-catalyzed Sonogashira carbonylation and cyclization with oiodoaniline and terminal alkynes.By exploring the effect of different bases on promoting the release of iron pentacarbonyl and the carbonylation process,we selected triethylamine to promote the release of CO from iron pentacarbonyl,and piperazine was used to pull hydrogen during the formation of acetylenone and its ring formation.A double-bases palladium-catalyzed carbonylation system with piperazine and triethylamine has been established.The system can be applied to aromatic,heter-aromatic,aliphatic terminal alkyne substrates and halogen-or alkyl-substituted 2-iodoaniline substrates.23 cases of quinolone products with different substituents were successfully synthesized,the yields were up to 92%.The experimental results prove that the CO release method for oxidating iron pentacarbonyl by oxygen is safe,efficient,and has a high carbonyl utilization rate,which can be well applied to the synthesis of quinolone compounds.(3)The oxidative decarbonylation release mechanism of iron pentacarbonyl was used in the palladium-catalyzed Suzuki carbonylation coupling reaction with iodoarene and organoboron reagent.By exploring the effect of different bases on promoting the release of iron pentacarbonyl and the carbonylation process,we selected triethylamine to promote the release of CO from iron pentacarbonyl,and potassium carbonate was used to extract hydrogen in the nucleophilic attack stage.A double-bases palladium-catalyzed carbonylation system with potassium carbonate and triethylamine has been established.The system can be applied to para-and meta-substituted iodene aromatic hydrocarbon substrates and phenylboronic acid substrates substituted with electron-rich and electrondeficient groups.18 cases of diaryl ketone products with different substituents were successfully synthesized,the yields were up to 99%.The experimental results prove that the CO release method for oxidating iron pentacarbonyl by oxygen is safe,efficient,and has a high carbonyl utilization rate,which can be well applied to the synthesis of diaryl ketone compounds.