The Synthesis Of Five-member Heterocycles By Oxidative Coupling Reactions

Oxidative coupling reactions between two nucleophiles provide a more green and atom economic route for organic synthesis,which is widely applied in our daily life.Five-membered heterocycles,especially furan,pyrrole and thiophene are importance motifs found in naturally occurring compounds,pharmaceuticals and material science.At first,the paper briefly reviewed the most important and exciting applications of oxidative coupling reactions in the formation of five-membered heterocycles.Then the research work of the thesis was committed to the synthesis of five-membered heterocycles proceeded via oxidative coupling reactions.Meanwhile,X-ray absorption(XAS)and electron paramagnetic resonance(EPR)provided a powerful method to explore the mechanism and guided our design for the synthesis.1.The first example of DMSO served not only as a solvent but also as oxidant to promote the oxidation of Cu(?)to Cu(?)has been demonstrated.XAS and EPR evidence revealed a single-electron redox process that DMSO could oxidize Cu(?)to Cu(?).The novel discovery guided the rational design of copper-catalyzed oxidative cyclization of arylketones with styrenes to furans,providing a new way to the syntheses of multiaryl-substituted furans(MSF)from cheap and readily available starting materials.2.An efficient FeCl3-catalyzed intermolecular annulation of arylketones and styrenes for the selectively synthesis of mutiaryl-substituted dihydrofurans was reported.Various arylketone were well tolerated in this methodology to give the corresponding desired products in moderate to excellent yields.3.A series of terthienyl were synthesized.At first,iodine-mediated oxidative homocoupling of simple ketone for the creation of 1,4-diketones,then,Paal-Knorr condensation reaction,which is an effective route to prepare terthienyl derivatives was employed.This transition-metal-free protocol represents an extremely simple and and atom-economic way to construct alkly-substituted terthienyl from basic starting materials under mild conditions.Next,a ligand enabled Pd-catalyzed Suzuki-Miyaura coupling of haloterthienyls for the synthesis of various thiophene-based ?-conjugated oligomers including quinquethiophenes was demonstrated.An indolyl phosphine ligand plays an important role in this transformation.Thiopheneboronic acids were well applied,which might open up a window for the application of thiopheneboronic acids in the synthesis of thiophene-based ?-conjugated oligomers in material chemistry.4.?,?-unsaturated ketone compounds have been used in the past as intermediates in the syntheses of furan and constitute key skeletons in numerous biologically active and medicinally valuable compounds.Herein,we report the palladium-catalysed selective mono-a-alkenylation of acetone and ketones with alkenyl tosylates.In the presence of Pd/XPhos catalyst(0.1-1.0 mol%),the proposed system provided monoselective products in good yields and exhibited excellent substrate tolerance.Significantly,acetone was exploited as a simple carbon feedstock for the construction of small ?,?-unsaturated ketones.