Aqueous Sonogashira coupling of aryl halides with 1-alkynes under mild conditions: use of surfactants in cross-coupling reactions

Abstract

Aqueous Sonogashira coupling between lipophilic terminal alkynes and aryl bromides or iodides gave moderate to high yields at 40 C using readily available and inexpensive surfactants (2.0 w/v% in water) such as SDS and CTAB. The catalyst precursor was 2 mol% Pd(PPh 3 ) 2 Cl 2 , and included a 5 mol% Cu(I) co-catalyst for aryl iodide substrates. Aryl-bromide reagents were found to be inhibited by iodide and Cu(I). Studies under Cu(I)-free conditions reveal two competing pathways. A deprotonation pathway gives rise to the traditional Sonogashira product (3), while a carbopalladation pathway produces enyne, 5.The surfactant solution (SDS or CTAB) can be recycled up to three times for coupling between 1-octyne and 1-iodonapthalene in the presence of CuI before the yields decrease.

Influence of Base on a Surfactant‐Assisted Heterogeneous Sonogashira Reaction

“…Overall, the results here indicate that tertiary amines auxiliaries clearly enhance the surfactant assisted heterogeneous Sonogashira reaction, whereas the secondary and primary amines evaluated do not. This is despite the fact that secondary amines such as piperidine have been successfully utilized in homogeneous and heterogeneous palladium catalyzed Sonogashira reactions in aqueous media . It is therefore suggested that the success of the reaction is governed by the interaction of the base at the surface of the catalyst.…”

In Situ Generation of Alkynylzinc and Its Subsequent Negishi Reaction in a Flow Reactor

“…1‐Methoxy‐4‐(phenylethynyl)benzene (3ba): 1 H NMR (400 MHz, CDCl 3 ): δ = 7.52–7.50 (m, 2H), 7.47 (d, J = 8.8Hz, 2H), 7.35–7.30 (m, 3H), 6.88 (d, J = 8.8 Hz, 2H), 3.82 (s, 3H). 13 C NMR (100 MHz, CDCl 3 ): δ = 159.7, 133.1, 131.5, 128.4, 128.0, 123.6, 115.4, 114.1, 89.4, 88.1, 55.3.…”

“…1‐(Cyclohex‐1‐en‐1‐ylethynyl)‐4‐methoxybenzene (3gc): 1 H NMR (400 MHz, CDCl 3 ): δ = 7.28 (d, J = 8.8 Hz, 2H), 6.75 (d, J = 8.8 Hz, 2H), 6.10–6.08 (m, 1H), 3.72 (s, 3H), 2.16–2.04 (m, 4H), 1.63–1.50 (m, 4H). 13 C NMR (100 MHz, CDCl 3 ): δ = 159.2, 134.5, 132.9, 120.9, 115.9, 113.9, 89.9, 86.7, 55.3, 29.4, 25.8, 22.4, 21.6.…”

Heterogenized Cu (II) salen complex grafted on graphene oxide nanosheets as a precursing catalyst for the Pd‐free Sonogashira coupling

“…Common procedures for the Sonogashira coupling reaction apply costly palladium along with a metal co‐catalyst and a base . The most broadly utilized co‐catalysts are copper salts, zinc, tin, boron, aluminum, Ag 2 O and Ag (OTf) . Recently, palladium‐free catalysis has been surveyed, and cheap metals like iron and nickel have been used as catalysts as well, but the use of such metals creates some problems, including requiring copper as a co‐catalyst, complex ligands, zinc additives and tough reaction conditions .…”