Studies On The Ring-Opening Rearrangement,Ring-Opening Alkynylation Of Cycloketoxime Esters And Acylation Of Arylphosphine Ligands

1.Study on Copper Catalyzed Ring-Opening Rearrangement and Ring-Opening Alkynylation of Cycloketoxime EstersIn recent years,more and more studies have shown that C-C cleavage can be achieved by using cheap copper instead of rhodium,palladium,nickel and other transition metals.Further researches also show that cross-coupling reactions of C-C,C-N,C-O,and C-S can be realized by using copper instead of iridium and ruthenium as visible-light-induced reaction catalysts.Therefore,copper-catalyzed reactions have become a reliable alternative strategy for organic reactions.While exploring the copper-catalyzed C-C bond activation to achieve the ring-opening rearrangement reaction of cyclobutanoxime esters,we also propose a new method to achieve Csp3-Csp Cross-Coupling including C-C bond cleavage and C-H bond activation is presented.This method uses copper as the catalyst,terpyridine as the ligand,and K2CO3 as the base to realize the cross-coupling reaction of cycloketoxime esters and terminal alkyne under room temperature with the addition of TBAI and the specific light.This transformation was applied to prepare a diverse set of alkynyl nitriles using readily available cyclobutanones and terminal alkynes,including some natural products and functional molecules.Both theory and experiment showed that the in situ generated copper acetylide complex is the real photocatalyst to promote the C-C bond cleavage of cycloketoxime esters via a radical process.2.Study on Rhodium Catalyzed Phosphorous-Directed AcylationAs common ligands for cross-coupling reactions,phosphines are widely used in organic synthesis.Based on the excellent properties of their parent scaffolds,it is desirable to modify the aryl phosphines in situ to obtain a series of ligands.In this paper,we applied visible light to the activation of C-H bonds of aryl phosphines,and successfully developed an acylation method of 2-diphenylphosphine biphenyl compounds under mild conditions using light promoted rhodium catalysis.After that,a series of acylation products were obtained by using amides with sterically distorted structures and the additional use of potassium fluoride.This method does not produce decarboxylation products and only a very small amount of di-substituted substitution by-products3.Study on the Mechanism of Rhodium Catalyzed Phosphorous-Directed AcylationIn order to explore the reaction mechanism of visible light and rhodium catalyzed acylation of 2-diphenylphosphine biphenyl compounds,we designed a series of experiments,DFT calculations and consulted some references,we found that:1)potassium fluoride participates in anion exchange process,resulting in a series of fluororhodium intermediates;2)the visible light can realize cod dissociation by ways of converting 1,5-cod to 1,3-cod,or transforming 1,5-cod from bidentate ligand into monodentate ligand.Finally,we proposed two possible reaction mechanisms based on these results and explored that we can use[Rh(CH2=CH2)2Cl2]2 instead of[Rh(cod)Cl2]2 as a new catalyst to realize the acylation of 2-diphenylphosphine biphenyl compounds under room temperature even without light.