Homocoupling reaction of terminal alkynes catalyzed by a reusable cationic 2,2′-bipyridyl palladium(II)/CuI system in water

Abstract

A cationic 2,2¢-bipyridyl palladium(II)/CuI system was proven to be a reusable and highly efficient catalyst for the homocoupling of terminal alkynes at room temperature using water as a solvent in the presence of TBAB under aerobic conditions. For aromatic terminal alkynes, the reaction was performed either with or without I 2 as an oxidant; the addition of I 2 was required when aliphatic terminal alkynes were used as a substrate for the homocoupling reaction. In the presence of 0.0001-1 mol% palladium catalyst and 1 mol% CuI, a variety of terminal alkynes were homocoupled in good to excellent yields. The water-soluble catalytic system was separated from the organic products by extraction and the residual aqueous solution showed activity for reuse for several cycles without a significant decrease in activity.

Ligand Redox Non‐Innocence in Transition‐Metal σ‐Alkynyl and Related Complexes

“…[60] Similar observations of the efficacy of mixed Pd/Cu catalysts in alkyne homocoupling have been reported elsewhere. [63][64][65][66][67][68][69] Other mixed-metal catalyst systems for the oxidative homo-and heterocoupling of alkynes have been reported recently, including [Fe(acac) 3 ]/[Cu(acac) 2 ] [70] and an unusual Cu/Ni system in which Cu plays a role as a templating group for the assembly of the active nickel bis(alkynyl) moiety (Scheme 3), [71] NiCl 2 /CuI has also been shown to be an effective catalyst for the cross-coupling of alkynes to give substituted 1,3-diynes in a modification of the Hay process, which can also be tuned to give acceptable yields of hetero-cross-coupled products. [72] Mixed Pd II /Au I catalysts to effect the cross-coupling of aryl iodides with terminal alkynes have been described by Laguna and coworkers, although the rates of reaction are slower than with a copper(I) co-catalyst, [73] with further complications arising from the use of 2 equiv.…”

Chemicals from Alkynes with Palladium Catalysts

“…An example of the use of this methodology is the coupling of acetylene 296 to furnish 1,3-diyne 297 (Scheme 112). 370 In this case, the watersoluble catalyst system was separated from the organic products by extraction and the residual aqueous solution was active for reuse for several cycles without a significant decrease in activity. There are a few examples were NHC-palladium complexes have been used as catalysts in the homocoupling of terminal alkynes, as is the case of complexes 300 which have been used as catalysts (0.3 mol%) in the homocoupling of arylacetylenes, working in the presence of benzoquinone as oxidant in acetonitrile as solvent at 70 ºC, although the conversions were low to moderate.…”

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

“…After the 1a consumed, the solvent was removed under a reduced pressure. The product was filtered through a short silica column with petroleum ether (60e90 C) to remove palladium residue and then was purified with a silica column using petroleum ether (60e90 C) as eluent, giving 1,3-diyne product 2a in 92% yield (46.5 mg) as a white solid [1]. 1 All the homo-coupling products 2 were identified through their NMR and/or HRMS data as well as IR spectra.…”

“…Tetradeca-6,8-diyne-2,13-dione (2h)Colorless oil,1 H NMR (300 MHz, CDCl 3 ) d 2.55 (t, J ¼ 7.2 Hz, 4H), 2.28 (t, J ¼ 6.9 Hz, 4H), 2.14 (s, 6H), 1.76 (dt, J ¼ 7.2, 6.9 Hz, 4H); 13 C NMR (75 MHz, CDCl 3 ): d 207.9, 76.6, 65.9, 42.0, 30.0, 22.0, 18.4; IR (neat) 2940, 2147, 1711, 1428, 1355, 1222, 1158, 950, 731 cm À1 ; HRMS (ESI) calcd for C 14 H 8 O 2 (M þ Na) þ : 241.1199, found: 241.1199. 4.4.…”