钯催化的炔烃环三聚反应

综述了两种不同价态的钯(零价、二价)催化的炔烃环三聚反应及其最新研究进展, 重点讨论配体、溶剂、取代基等对反应的化学选择性和区域选择性的影响, 并对其中一种较新颖的[2＋2＋1]型环三聚反应、作用机理及所遇到的挑战给予介绍.     

Synthesis of extended triphenylenes by palladium-catalyzed [2+2+2] cycloaddition of triphenylynes

The synthesis of ortho-(trimethylsilyl)triphenylenyl triflates 7 is described. Fluoride-induced decomposition of these triflates leads to the generation of didehydrotriphenylenes (triphenylynes) 6. These arynes undergo [4+2] cycloadditions with dienes to afford the corresponding Diels-Alder adducts or palladium-catalyzed formal [2+2+2] cycloadditions to afford extended triphenylenes.     

一种温和高效的钯催化乙炔的环三聚

乙炔是石油化工的重要产品之一,乙炔分子中存在高活性的π电子体系,具有很高的反应活性。许多催化体系包括过渡金属催化剂、非金属催化剂等可以催化活泼的乙炔发生环三聚反应,得到重要的化工原料苯。作者首次利用氯化钯作为催化剂催化乙炔环三聚,在很温和的条件下高效率地实现了这一反应。     

超临界二氧化碳介质中溴化钯催化炔烃环三聚反应

研究了以超临界二氧化碳为反应介质溴化钯催化炔烃环三聚反应的新方法.研究结果表明:二氧化碳介质中使用溴化钯为催化剂可以顺利地催化炔烃发生环三聚反应,区域选择性生成含苯环芳香族化合物.     

Preparation of C3‐Symmetric Homochiral syn‐Trisnorbornabenzenes through Regioselective Cyclotrimerization of Enantiopure Iodonorbornenes

C₃‐symmetric homochiral (?)‐syn‐trisoxonorbornabenzene 1 possessing a rigid cup‐shaped structure was synthesized through a novel regioselective cyclotrimerization of enantiopure iodonorbornenes catalyzed by palladium nanoclusters. The yield of the cyclotrimerization was dependent on the stability of the palladium clusters, which was ascertained from the appearance and TEM images of the reaction mixtures. The efficient preparation of (?)‐syn‐ 1 was established in short steps, including the newly developed cyclotrimerization reaction. The thus‐prepared homochiral (?)‐syn‐ 1 can serve as a key intermediate for the synthesis of C₃‐symmetric homochiral cup‐shaped molecules with a helical arrangement of substituents. Introduction of several types of substituents was well demonstrated through palladium‐catalyzed coupling reactions with the corresponding phosphate and triflate of (?)‐syn‐ 1 .     

Novel Role of Carbon Dioxide as a Selective Agent in Palladium-Catalyzed Cyclotrimerization of Alkynes

Carbon dioxide was found as a selective agent to promote the palladium-catalyzed cyclotrimerization of alkynes in water. Both aryl and alkylacetylenes afforded the corresponding cyclotrimerization products regioselectively in high yields using PdCl2, CuCl2, and CO2 as the catalytic system. However, tert-butylacetylene bearing a bulky group gave a dimerization product. Mechanism of this reaction was also discussed.     

A Regioselective Method for the Synthesis of Benzene Derivatives:Palladium-Catalyzed Cyclotrimerization of Ethyl Propiolate

An NEt3-induced palladium complex PdL2Cl2 catalyzed cyclotrimerization reaction of ethyl propiolate(EP) is reported for the first time.The reaction proceeded readily in a regioselective manner under mild conditions to give cyclotrimerization product 1,2,4-triethyl benzenetricarboxylate as well as its 1,3,5-isomer in good yields.Influences of the ligands.NEt3,solvents,oxidants as well as temperature are studied.and a possible mechanism is also proposed.     

Catalytic generation of arynes and trapping by nucleophilic addition and iodination

A fair exchange: In the title reaction, alkynyllithium serves as an initiator for benzyne generation through an iodine-lithium exchange (see scheme; Tf=trifluoromethanesulfonyl). When performed in the presence of stoichiometric amounts of a nucleophile, the generated benzyne undergoes attack by lithio nucleophiles to generate aryllithium, which is then iodinated by iodoalkyne to give the iodoarenes 1.     

Cyclotrimerization of an aliphatic aldehyde catalyzed by acidic ionic liquid

Without any additional organic solvent, the cyclotrimerization of aliphatic aldehyde could be catalyzed by acidic ionic liquid. Under optimum reaction conditions (298 K, 1 h, a molar ratio of 60:1 of isobutyraldehyde to ionic liquid), the conversion rate and selectivity for cyclotrimerization of isobutyraldehyde were 93.0 and 100%, respectively. The liquid product formed a separate phase that was decanted and the solid product could be separated by extraction. The ionic liquid could be easily reused after removal of water under vacuum.