Palladium-catalyzed Hydrocarboxylatiom Of Alkynes In Water And Homogeneous Carbonyl Esterification

The development of environmentally friendly and efficient synthetic methods is one of the main directions of current chemical research.Metal-organic catalytic chemistry shows a very good application prospect,so it becomes the key technology to achieve this goal.Because the reaction substrates and reaction types are extremely consistent with the current environmentally friendly research directions,the carbonylation reaction with the C1 component CO as the carbon source has attracted extensive attention.The carbonylation reaction can provide important chemical raw materials such as aldehydes,alcohols and carboxylic acid derivatives.These chemicals can be further transformed into various chemical products and daily necessities.In this thesis,we studied the hydrocarboxylation reaction and carbonyl esterification reaction of alkynes,respectively.In the study of the hydrocarboxylation of alkynes,the work was focused on the substrate adaptability and the cyclability of the catalyst with water used as the reaction solvent.In addition,in the study of the carbonyl esterification reaction of alkynes,dppf,which is easily available,was used as a ligand,and water is used as an additive instead of traditional acid.Meanwile,the two methods introduced in this article were conducted under relatively low pressure of CO,which has the potential for industrialization.1.α,β-Unsaturated carboxylic acids are important structural units of many natural products and bioactive compounds.These important carbonyl compounds are also very useful and versatile building blocks for the synthesis of many important heterocycles,such as furan,pyrrolidone,lactone,indolizine,dihydropyranone,γ-alkylene butene lactone,etc.In this paper,a water-soluble Pd catalyst（Pd/sulfoxantphos）was developed and successfully applied to the hydrocarboxylation of alkynes with CO and H₂O.Using water as the reaction solvent,the catalyst can catalyze the hydrocarboxylation of various symmetrical and asymmetric alkynes to obtain correspondingα,β-unsaturated carboxylic acids in excellent yields（50-99%）,high regioselectivity and stereoselectivity.The water-soluble palladium catalyst can be easily separated from the product,so the catalyst can be reused.It can still maintain high activity after being reused for 5 times.The Pd-H complex with catalytic activity was characterized by ¹H NMR.Deuterium labeling experiments show that the cleavage of O-H bond of H₂O has an important effect on the reactivity.2.Using Pd/dppf as a catalyst,it was successfully applied to the hydroesterification of alkynes.Using methanol as the solvent,the catalyst can catalyze the hydroesterification of symmetrical aryl alkynes and alkyl alkynes affording the correspondingα,β-unsaturated esters with excellent yield（80-90%）;the catalytic system has good compatibility with functional groups such as methyl,methoxy and halogen.When ethanol is used as the reaction solvent instead of methanol,the reaction yield was reduced.