Synthesis of Unsymmetrical 1,3‐Diynes via Pd/Cu‐Catalyzed Cross‐Coupling of Terminal Alkynes at Room Temperature

A facile and practical synthetic route of unsymmetrical 1,3‐diynes via the PdCl/CuI catalyzed oxidative coupling of two different terminal alkynes has been developed by using 3‐(diphenylphosphino)propanoic acid as a ligand in the presence of oxygen. This system is suitable for not only aromatic alkynes but also heteroaromatic and aliphatic alkynes which were transformed into the corresponding unsymmetrical 1,3‐diynes in moderate to good yields at room temperature. Moreover, the unsymmetrical 1,3‐diynes were also obtained on a multi‐gram scale. Mechanistic studies suggest that oxygen plays a key role in the catalytic cycles.     

Magnetic copper ferrite catalyzed homo‐ and cross‐coupling reaction of terminal alkynes under ambient atmosphere

The application of non‐toxic and magnetically separable nano‐CuFe₂O₄ as an efficient catalyst for oxidative homo‐ and cross‐coupling reaction of terminal alkynes is described. A wide range of symmetrical and unsymmetrical 1,3‐diynes have been synthesized in moderate to good yields under ambient atmosphere. The nano CuFe₂O₄ can be recovered with a magnet and reused at least five consecutive cycles with no appreciable loss of its catalytic activity.     

Copper‐Catalyzed Aerobic Oxidative Transformation of Ketone‐Derived N‐Tosyl Hydrazones: An Entry to Alkynes

A novel strategy involving Cu‐catalyzed oxidative transformation of ketone‐derived hydrazone moiety to various synthetic valuable internal alkynes and diynes has been developed. This method features inexpensive metal catalyst, green oxidant, good functional group tolerance, high regioselectivity and readily available starting materials. Oxidative deprotonation reactions were carried out to form internal alkynes and symmetrical diynes. Cross‐coupling reactions of hydrazones with halides and terminal alkynes were performed to afford functionalized alkynes and unsymmetrical conjugated diynes. A mechanism proceeding through a Cu‐carbene intermediate is proposed for the C? C triple bond formation.     

端基炔烃的简单快速二聚反应

端基炔烃在无钯催化剂的条件下, 以乙腈为溶剂, 三乙胺为碱, 与氯化亚铜和二醋酸碘苯反应, 常温下短时间内得到高产率的二聚产物, 提供了一个简单快速合成共轭二炔烃的新方法. 比较了反应条件, 并提出了可能的反应机理.     

Zirconocene-mediated, high-yielding macrocyclizations of silyl-terminated diynes

A series of silyl-terminated diynes of varying lengths and substitution patterns have been prepared. These diynes undergo zirconocene coupling with selective formation of trimeric macrocycles from linear alkynes, while nonlinear diynes give cyclodimeric products. The length of the linear diynes can be increased for the preparation of macrocycles with large nanoscale cavities. Reaction of the zirconium-containing macrocycles with acid results in the synthesis of metal-free cyclophanes. All of these macrocycles were prepared in multigram quantities, in the absence of high-dilution conditions, to give products in > 75% yield that are easily purified as crystalline solids.     

Synthesis of diynes and tetraynes from in situ desilylation/dimerization of acetylenes

[reaction: see text]. An efficient method for the in situ desilylation/oxidative dimerization of (trialkylsilyl)acetylenes is described. This protocol avoids the complications encountered with sensitive diynes by eliminating the deprotection and isolation steps. Various aromatic and alkyl diynes and tetraynes can be synthesized in a straightforward manner in good yields (82-99%) from TIPS-protected acetylenes. This method facilitates the efficient synthesis of novel tetrayne-bridged acetylenic cyclophanes 6 and 7 in a direct manner.     

Synthesis of New Conjugated Diynes Containing Carbamate Groups, and Study of Their Properties

Carbamates of monoacetylene and diacetylene series were synthesized and characterized. A catalytic system CuI-pyrrolidine was applied for the first time to a synthesis of symmetrical diacetylenes by oxidative dimerization of terminal acetylenes. The comparative activity of diynes obtained was studied in the photoinitiated solid-phase topochemical polymerization. Diyne carbamates undergoing thermal polymerization were obtained for the first time.     

A straightforward synthesis of indole and benzofuran derivatives

A new methodology for the synthesis of indole and benzofuran derivatives has been devised. The starting materials, ortho-substituted aryl diynes, have been easily converted into new unsaturated bis-indolyl and bis-benzofuran derivatives and into 2-ethynylindole and 2-ethynylbenzofuran. Both these products have been further elaborated into more complex unsaturated indole-benzofuran and bis-benzofuran derivatives.     

CuI‐catalyzed homocoupling of terminal alkynes to 1,3‐diynes

A simple and efficient protocol for CuI‐catalyzed oxidative homocoupling reaction of terminal alkynes to symmetrical 1,4‐disubstituted 1,3‐diynes was reported. The reaction can be carried out in the open air, using NaOAc as a base in the absence of any other additives. A variety of terminal alkynes were converted to the corresponding 1.3‐diynes in good to excellent yields without any side product formation. Copyright © 2010 John Wiley & Sons, Ltd.     

A strictly "pair"-selective synthesis of conjugated diynes via Pd-catalyzed cross coupling of 1,3-diynylzincs: a superior alternative to the Cadiot-Chodkiewicz reaction

A strictly "pair"-selective synthesis of conjugated diynes via Pd-catalyzed cross coupling of 1,3-diynylzincs is described. This method, like the Cadiot-Chodkiewicz reaction, requires three steps for the synthesis of R(1)Ctbd1;CCtbd1;CR(2) from R(1)Ctbd1;CH, R(2)X, and HCtbd1;CH. However, the high "pair"-selectivity permitting high-yield production of the desired conjugated diynes without separation of symmetrical diynes promises to make the present protocol superior to the Cadiot-Chodkiewicz reaction in many cases.     

Rhodium-catalyzed convenient synthesis of functionalized tetrahydronaphthalenes

Convenient as well as convergent synthesis of functionalized tetrahydronaphthalenes has been accomplished under mild reaction conditions by the cationic rhodium(I)/H₈-BINAP complex-catalyzed [2+2+2] cycloaddition of 1,7-octadiyne derivatives with functionalized monoynes. The effect of the diyne tether lengths was investigated, which revealed that 1,6-heptadiyne and 1,7-octadiyne exhibit higher reactivity than 1,8-nonadiyne. Mechanistic studies indicated that the present rhodium-catalyzed [2+2+2] cycloaddition proceeds through the rhodacyclopentadiene intermediate generated by oxidative coupling of a diyne with rhodium. On the other hand, in the reactions of diynes and dimethyl acetylenedicarboxylate, the rhodacyclopentadiene intermediate generated by oxidative coupling of a diyne and a monoyne with rhodium would also be involved.     

An efficient synthesis of diynes using (diacetoxyiodo)benzene

A novel and facile method for synthesis of symmetrical conjugated diynes, using (diacetoxyiodo)benzene as oxidant under palladium-catalyzed conditions is presented, in which diynes are prepared in good yields in a short period of time at room temperature.     

Oxidative addition reactions and stereochemistry on rhodium/4,5-bis(2-oxazolinyl)xanthene complexes

The oxidative addition reactions on 4,5-bis(2-oxazolinyl)-(2,7-di-tert-butyl-9,9-dimethyl)-9H-xanthene (Xabox)/rhodium(I) complex were examined using chloroacetate and substituted diynes to give stereoselectively the corresponding methoxycarbonylmethyl-rhodium(III) complex and rhodacyclopentadiene complexes, respectively. The rhodacycle complex 7 catalyzed the cyclotrimerization of the diynes and alkynes to give arene derivatives.     

An efficient route to highly functionalized benzene derivatives by rhodium-catalyzed dimerization of diynes

An intermolecular efficient dimerization of diynes via Rh-catalyzed cycloaddition is presented. This protocol allows for the expedient synthesis of structurally diverse benzene derivatives, which retain an alkyne unit for post-functionalization to realize molecules with potential medicinal value and extended molecular complexity. The transformation is carried out in toluene and employs Rh(COD)₂OTf₃ as the metal source. Diversely decorated diynes tethered by nitrogen atom and ester were compatible with these conditions and furnished substituted benzenes with excellent selectivity.     

First report of a nano‐Cu2O‐catalyzed protocol for homo‐coupling reaction of terminal alkynes in water/ionic liquid medium

A new, efficient and green protocol for the nano‐Cu₂O‐catalyzed homo‐coupling reaction of terminal alkynes has been developed, using water/ionic liquid as an environmentally friendly solvent. Moreover, the system also allows the synthesis of unsymmetric 1,3‐diynes by cross‐coupling of two different terminal alkynes. It is noteworthy that the nano‐Cu₂O‐catalyzed methodology is a good supplement to copper catalyst for the Glaser‐type homo‐coupling reaction. Copyright © 2016 John Wiley & Sons, Ltd.     

An alternative CuCl–piperidine‐catalyzed oxidative homocoupling of terminal alkynes affording 1,3‐diynes in air

CuCl with the use of a catalytic amount of piperidine as additive shows high catalytic activity for the oxidative homocoupling reactions of terminal alkynes in toluene at 60 °C in air to afford 1,3‐diynes in high yields. Copyright © 2009 John Wiley & Sons, Ltd.     

Copper‐catalyzed homo‐ and cross‐coupling reactions of terminal alkynes in ethyl lactate

The bio‐based chemical ethyl lactate (EL) has been discovered to be an excellent medium for the Glaser‐type homo‐ and cross‐coupling reactions of terminal alkynes. Good to excellent yields of conjugate diynes have been obtained under ligand‐free and mild heating conditions in the presence of CuI and molecular oxygen. Copyright © 2014 John Wiley & Sons, Ltd.     

Ligand-Free Synthesis of 1,4-Disubstituted-1,3-diynes by Iron/Copper Cocatalyzed Homocoupling of Terminal Alkynes

A simple and efficient protocol for Fe/Cu cocatalyzed oxidative homocoupling reaction of terminal alkynes to symmetrical 1,4‐disubstituted‐1,3‐diynes was presented. The results showed that both CuBr and FeCl₃ played crucial roles in the reaction. It is noteworthy that this protocol employs mild, efficient, aerobic and ligand free conditions. The alkynes, including aromatic, heteroaromatic and aliphatic alkynes, were transformed into the corresponding 1,3‐diynes in good to excellent yields.     

Palladium-catalyzed oxidative homocoupling reaction of terminal acetylenes using trans-bidentatable 1-(2-pyridylethynyl)-2-(2-thienylethynyl)benzene

Palladium-catalyzed oxidative homocoupling of terminal acetylenes, in air, occurred in the presence of 1-(2-pyridylethynyl)-2-(2-thienylethynyl)benzene as ligand, affording the corresponding conjugated diynes.     

Formal [4+2] Reaction between 1,3‐Diynes and Pyrroles: Gold(I)‐Catalyzed Indole Synthesis by Double Hydroarylation

Indole synthesis by a gold(I)‐catalyzed intermolecular formal [4+2] reaction between 1,3‐diynes and pyrroles has been developed. This reaction involves the hydroarylation of 1,3‐diynes with pyrroles followed by an intramolecular hydroarylation to give the 4,7‐disubstituted indoles. This reaction can also be applied to the synthesis of carbazoles when indoles are used as the nucleophiles instead of pyrroles.