2,5‐Bis(2‐(diphenylphosphino)phenyl)‐1,3,4‐oxadiazole ligands and their Cu(I) complexes for Sonogashira coupling reaction

Abstract

Two diphosphane ligands -2,5-bis(2-(diphenylphosphino)-5-R)phenyl)-1,3,4-oxadiazole (L1, R = H, L2, R = OMe) and their binuclear complexes, L1Cu and L2Cu, were prepared and characterized. The molecular structures of L1Cu and L2Cu, as perchlorate salts, were established by X-ray crystallography, which showed them to be binuclear complexes with each Cu atom tetrahedrally coordinated by two P atoms and two N atoms. The ligands and their Cu(I) complexes catalyzed Sonogashira coupling reactions of iodobenzene with phenylacetylene in the presence of K 2 CO 3 under Pd-free conditions. Coupling reactions catalyzed by L1 or L2 with Cu(MeCN) 4 ClO 4 in situ exhibited better yields than those by the corresponding Cu(I) complexes L1Cu or L2Cu. Detailed studies showed L1 or L2 with Cu(MeCN) 4 ClO 4 to be suitable catalysts for the coupling reaction of terminal alkynes and aryl halides. The coupling reactions of aryl iodides with electron-withdrawing groups showed better results.

bis‐(Aminophenyl)ferrocene ligand for palladium free CuI catalyzed Csp2−Csp cross‐coupling reaction

“…Supporting information file includes the general experimental procedure, compound characterization data and the 1 H and 13 C NMR spectra of all the compounds.…”

“…[10] Thereafter, a number of ligands have been applied to promote the catalytic activity of copper salts for Sonogashira coupling. [8,9] Both phosphine [11][12][13] and non-phosphine ligands, such as phenanthroline, [14] DABCO, [15] β-diketone, [16] 8hydoxyquinoline, [17] rac-BINOL, [18] N,N'-dibenzyl-BINAM, [19] salicyclic acid, [20] (À )-sparteine, [21] TMEDA, [22] ethylene glycol, [23,24] pyrene [25] and DMEDA [26] are reported for this Csp 2 À Csp crosscoupling reaction using copper catalysts. Joshaghani used a combination of Ni(acac) 2 and CuI in presence of 2,6bis(diphenylphosphino)pyridine as ligand for palladium-free Sonogashira cross-coupling reaction.…”

Copper‐catalyzed C(sp2)–C(sp) Sonogashira‐type cross‐coupling reactions accelerated by polycyclic aromatic hydrocarbons

“…It has been known for decades that aryl halides can couple with copper(I) acetylides to afford arylacetylenes . Recently, it was found that copper(I) catalysts alone can also mediate the coupling reaction of aryl halides and terminal alkynes, such as Cu(I)/amino acid derivatives, Cu(I)/DABCO, Cu(I)/diamines, copper nanoparticles, supported copper complexes and other copper‐based catalytic systems . So far, most Sonogashira coupling reactions are still conducted in the presence of high loadings of copper (5–30 mol%) catalysts and ligands.…”

Organophosphate‐accelerated copper‐catalyzed C(sp2)–C(sp) Sonogashira‐type cross couplings

“…Nowadays, Pd/Cu–phosphine‐catalyzed Sonogashira cross coupling provides a straightforward access to C(sp)–C(sp 2 ) bond formation and the cross‐coupling products are widely used as precursors for the synthesis of pharmaceuticals, natural products and organic materials . One of the latest aspects of attention focuses on the efficiency of catalyzed cross coupling of aryl halides with terminal alkynes using copper catalysts, for copper is less toxic and far more economic than palladium. Since Miura and co‐workers reported that PPh 3 /CuI (10 mol%) catalyzed the Castro reactions of aryl iodides and terminal alkynes in 1993, there have been reported huge innovations of copper‐catalyzed C(sp 2 )–C(sp) coupling reactions, including those involving Cu(I)/diamines, Cu(I)/amino acid derivatives, Cu(I)/1,4‐diazabicyclo[2.2.2]octane, copper nanoparticles, supported copper complexes and other copper catalytic systems .…”