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.     

Fast, ligand- and solvent-free copper-catalyzed click reactions in a ball mill

A new, ligand- and solvent-free method for the Huisgen 1,3-dipolar cycloaddition (click reaction) was developed using a planetary ball mill. Besides various alkynes and azides, a propargyl functionalized polymer was converted by mill clicking. Moreover, it was possible to carry out a click polymerization in a ball mill.     

Copper-, ligand- and solvent-free synthesis of ynones by coupling acid chlorides with terminal alkynes

A general and efficient copper-, ligand- and solvent-free synthesis of ynones by coupling of a wide range of acid chlorides with terminal alkynes catalyzed by palladium(II) acetate at room temperature is reported.     

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.     

Oxidative homocoupling of terminal alkynes under palladium-, ligand- and base-free conditions using Cu(II)-clay as a heterogeneous catalyst

Homocoupling of terminal alkynes to 1,3-diynes has been investigated with Cu(II)-modified clay under mild and operationally simple conditions without the use of any ligand or a stabilizing agent. The catalyst is robust, ecofriendly, efficient, furnishes good to excellent yields of the desired products and can be reused several times with negligible loss in catalytic activity.     

Zirconium-mediated cross-coupling of terminal alkynes and vinyl bromides: selective synthesis of cyclobutene and 1,3-diene derivatives

A diastereoselective synthesis of 1,3-butadiene or cyclobutene derivatives by a zirconium-mediated reaction of alkenyllithium compounds and vinyl bromides is reported. The key steps involve the generation of zirconocene-alkyne complexes from haloalkenes and subsequent coupling with alkenyl bromides. Thus, formally the process supposes the cross-coupling reaction between a terminal alkyne and an alkenyl bromide. Moreover, the use of butyl vinyl ether instead of vinyl bromide as the unsaturated system allows an alternative access to different 1,3-butadiene regioisomers.     

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.     

Efficient P,O chelate palladium(II)/AgNO3 cocatalyzed homocoupling of aromatic terminal alkynes in aqueous media under ambient atmosphere

A new and efficient protocol for the P, O chelate Pd(II)/AgNO₃ cocatalyzed oxidative homocoupling reaction of aromatic terminal alkynes in the synthesis of symmetrical 1,4-disubstituted-1,3-diynes was described in aqueous media under ambient atmosphere. The results showed that both NEt₃ and THF/H₂O (in 4:1 proportion) played crucial roles in the reaction. In contrast, this protocol employs a low palladium(II) complex loading and AgNO₃ as cocatalyst to obtain the homocoupled products in moderate to good yields.     

A solvent-free synthesis of 1-(4-chlorophenyl)pyrazolidin-3-one in a ball mill

An easy, solvent-free method for the synthesis of 1-(4-chlorophenyl)pyrazolidin-3-one has been achieved by grinding 4-chlorophenyl hydrazine and methyl acrylate in the presence of base in a ball mill. A systematic investigation of the reaction has been made in order to study the various factors affecting the reaction.     

A reusable CuSO4 · 5H2O/cationic 2,2′‐bipyridyl system catalyzed homocoupling of terminal alkynes in water

A reusable CuSO₄ · 5H₂O/cationic 2,2′‐bipyridyl system catalyzed the homocoupling reaction of terminal alkynes in water using I₂ as the additive in the presence or absence of tetrabutylammonium bromide, giving the 1,3‐diynes in good to high yields. After reaction, the residual aqueous solution could be reused several times. Copyright © 2011 John Wiley & Sons, Ltd.