A palladium-promoted route to 3-alkyl-4-(1-alkynyl)-hexa-1,5-dyn-3-enes and/or 1,3-diynes

C(sp2)‐C(sp) and C(sp)‐C(sp) Coupling Reactions Catalyzed by Oxime‐Derived Palladacycles

“…However, the presence of external oxidants such as iodine [25] did not result in any significant improvement in rate or yield (compare entries 8 and 11). Other oxidants such as chloroacetone [23] seriously inhibited the reaction (Table 5, entry 12). Therefore, oxime-derived palladacycle 8a is a competent promoter of the palladium-catalyzed homocoupling reaction of terminal alkynes at room temperature achieving turnover numbers of up to 1000.…”

“…These derivatives are finding increasing applications as key structural elements of new materials with unusual electrical and optical properties, and are encountered in numerous natural and biologically active compounds. Since Rossi in 1985 optimized the homocoupling reaction of terminal alkynes as a synthetic method, employing palladium as catalyst in the presence of CuI as co-catalyst and chloroacetone as terminal oxidant, [23] diverse modifications of the procedure have appeared using different oxidants such as DMSO, [24] iodine [25] or (diacetoxy)iodobenzene. [26] Palladium(II) complexes bearing N-heterocyclic carbenes modified with phosphines of the type 7 (Figure 1), have also been found to promote the homocoupling of phenylacetylene in the presence of CuI as co-catalyst and TEA as solvent even in the absence of added oxidant.…”

Chemicals from Alkynes with Palladium Catalysts

“…352 The process was optimized for the coupling of arylacetylenes using Pd(PPh 3 ) 4 as catalyst (2 mol%) and CuI (8 mol%) as co-catalyst using chloroacetone as oxidant and in the presence of triethylamine as base, in benzene at room temperature. 355 364 In addition, there are examples where no stoichiometric oxidant has been added to achieve the homocoupling using the combination PdCl 2 (PPh 3 ) 2 (3 mol%)/CuI (3 mol%) as catalyst, the addition of more triphenylphosphine (9 mol%) being sufficient. 365 This is the case of the homocoupling of propargyl glycosides, although large amounts of PdCl 2 (PPh 3 ) 2 (10 mol%) and 1 equivalent of CuI have been necessary.…”

Safer and Greener Catalysts – Design of High Performance, Biodegradable and Low Toxicity Ionic Liquids

“…Although Sonogashira coupling reactions works well under mild conditions, the drawback of this reaction is that copper catalysts used can promote side reactions, such as Glaster-type homocoupling of acetylenes. [49][50][51][52][53] Ryu and co-workers have reported a palladium(II) catalysed efficient Sonogashira coupling in ionic liquid, without any copper co-catalyst. [54] The reactions with an aryl halides and alkyl/aryl acetylenes were carried out in [BMIM] [PF 6 ] as a solvent and diisopropylamine or piperidine as a base.…”