1,3-Diynes synthesis by homo-coupling of terminal alkynes using a Pd(PPh3)4/Ag2O simple catalyst system

Highly selective cross-coupling reactions of 1,1-dibromoethylenes with alkynylaluminums for the synthesis of aryl substituted conjugated enediynes and unsymmetrical 1,3-diynes

A highly efficient method for the synthesis of aryl substituted conjugated enediynes and unsymmetrical 1,3-diynes via selective cross-coupling reactions of 1,1-dibromoethylenes with alkynylaluminums using the Pd(OAc)2-DPPE and Pd2(dba)3-TFP complexes as catalysts, respectively, has been successfully developed. Though the alkyl substituted conjugated enediynes and unsymmetrical 1,3-diynes were not obtained, this case is also remarkable as the same starting materials could selectively produce either aryl substituted conjugated enediynes or unsymmetrical 1,3-diynes in moderate to excellent yields (up to 99%) in the different Pd-phosphine catalytic systems.

Ligand-free Pd/Ag-mediated dehydrogenative alkynylation of imidazole derivatives

A variety of 2-alkynyl(benzo)imidazoles have been synthesized by dehydrogenative alkynylation of (benzo)imidazoles with terminal alkyne in NMP under air in the presence of Ag₂CO₃ as the oxidant and Pd(OAc)₂ as the catalyst precursor. The data obtained in this study support a reaction mechanism involving a non-concerted metalation deprotonation (n-CMD) pathway.

The regioselective synthesis of 2-alkynyl(benz)imidazoles was successfully achieved by Pd(ii)/Ag(i)-mediated dehydrogenative alkynylation of the corresponding (benz)imidazoles with terminal alkynes in an open vessel.

Linker-Directed Assembly of Twisted ortho-Phenylene-Based Macrocycles

o-Phenylene tetramers have been coassembled with linkers into macrocycles through imine condensation. Variation of linker connectivity and length allows both [1 + 1] and [2 + 2] macrocycles to be obtained, complementing (previously reported) [3 + 3] macrocycles. For the [1 + 1] macrocycles, linker length has a clear effect on o-phenylene geometry and macrocycle stability. For the [2 + 2] macrocycles, both homo- and heterochiral configurations are observed, suggesting limited communication of helix handedness in these systems.

The Homocoupling Reaction of Aromatic Terminal Alkynes by a Highly Active Palladium(II)/AgNO₃ Cocatalyst in Aqueous Media Under Aerobic Conditions

A new and efficient Pd(II)/AgNO₃-cocatalyzed homocoupling of aromatic terminal alkynes is described. Various symmetrical 1,4-disubstituted-1,3-diynes are obtained in good to excellent yields. This protocol employs a loading with relatively low palladium(II) in aqueous media under aerobic conditions.

Copper(i) chloride catalysed room temperature Csp–Csp homocoupling of terminal alkynes mediated by visible light

An eco-friendly approach to the C_sp–C_sp homocoupling of terminal alkynes (including electron-withdrawing groups) was achieved at room temperature via a copper(i) chloride catalysed process mediated by visible light.

Unexpected bond activations promoted by palladium nanoparticles

Thioether-phosphines, 1 and 2, were applied for the stabilisation of palladium nanoparticles (PdNPs) synthesised by a bottom-up methodology, using [Pd2(dba)3] as an organometallic precursor. For the phenyl containing ligand 1, small (d(mean) = 1.6 nm), well-defined and dispersed nanoparticles were obtained; however, ligand 2 involving a long alkyl chain led to agglomerates. NMR and GC-MS analyses throughout the synthesis of the nanomaterials revealed partial cleavage of ligands by C-S and C-P bond activations, and XPS spectra of the isolated nanoparticles indicated the presence of both thioether-phosphines and their fragments on the metallic surface. Reactivity studies of molecular palladium systems as well as on extended palladium surfaces pointed out that cluster entities are responsible for C-heteroatom activations, triggering structure modifications of stabilisers during the synthesis of PdNPs.

A facile copper(I)-catalyzed homocoupling of terminal alkynes to 1,3-diynes with diaziridinone under mild conditions

A novel and efficient Cu(I)-catalyzed oxidative homocoupling of terminal alkynes with diaziridinone as an oxidant is described. Various terminal alkynes can be transformed into the corresponding 1,3-diynes in good yields. The reaction process is base-free, operationally simple, and amenable to the gram scale.