Research On Gold-catalyzed Coupling Reactions Of Terminal Alkynes

Gold catalysts are unique soft Lewis and n acids,which can be used as catalysts for the activation of C-C multibonds toward various types of reactions,such as the hydration,ammonification,alkoxylation,carboxylation,arylation reaction of alkyne could be catalyzed by gold.Terminal alkynes are widely used in organic synthesis.Alkynyl compounds are not only useful synthons in organic synthesis,but also found in a wide range of natural products,medicines,organic materials and optical materials.They are very important for the synthesis of heterocyclic compounds with biological and pharmacological activities.Research towards their synthetic methods is of great significance in organic synthesis.The dissertation mainly contains two researches:The homocoupling reaction of terminal alkynes catalyzed by gold and the cross coupling reaction of terminal alkynes with diselenide catalyzed by gold.They are summarized as follow:1.The homocoupling reaction of terminal alkynes catalyzed by gold was discussed.We choose phenylethyne as substrate to optimize the reaction conditions.Homocoupling reaction of the terminal alkyne was realized at room temperature when AuBr3(5 mol%)and DIPEA(5 mol%)were used as catalysts,while Selectfluor and CH3CN were used as an oxidant and a solvent respectively.The highest yield of the target product was obtained(92%)when the molar ratio of phenylethyne to selectfluour was 1:0.5.We attempted the coupling reactions of the aromatic terminal alkynes with different substituent under the above conditions,and the target products were obtained in good to excellent yields(62-93%).The effects of substituent on the reaction were also studied.In order to further extend the scope of reaction substrates,1-nonyne,3-butyn-l-ol and 1-ethynylcyclohexene were used,but we didn't obtain the corresponding product.However the coupling product was obtained when but-3-ynyl benzoate was used as a substrate.2.The cross coupling reaction of terminal alkynes with diselenide catalyzed by gold was discussed.We choose phenylethyne and diphenyl diselenide as substrates to optimize the reaction conditions.The cross coupling reaction of the terminal alkyne with the diselenide was realized at 80? when AuBr3(10 mol%)was used as a catalyst and K2CO3 as a base.The proper molar ratio of phenylethyne,diphenyl diselenide and K2CO3 was 1:0.5:1,while the highest yield of the target product was obtained(92%).Then a range of different terminal alkynes to react with diaryl diselenides under above conditions were discussed,giving rise to coupling productsts in good to excellent yields(69-98%).The reaction is of wide scope,both aromatic and alkyl alkynes can give satisfactory yields.The effects of substituent on the aromatic ring of alkyne on the reaction were also studied,it can be seen that influence of different substituents on the same position on the reaction yield is not obvious.The substituents on the para position of benzene ring of diselenide have a certain extent influence on the reaction.Furthermore,we attempted to synthesize alkynyl sulfide by using the same mathod,but didn't obtain the cross-coupling products.