Synergistic and Selective Copper/ppm Pd-Catalyzed Suzuki–Miyaura Couplings: In Water, Mild Conditions, with Recycling

Abstract

Copper-catalyzed Suzuki−Miyaura couplings can be carried out exclusively on aryl iodides under very mild conditions, which is made possible by synergistic effects due to the presence of ppm levels of palladium as cocatalyst. The coupling requires a hemilabile P(O)-N ligand, together with the benefits of micellar catalysis using water as the recyclable reaction medium.

A flow split test to discriminating between heterogeneous and homogeneous contributions in Suzuki coupling

“…Thus, the SM coupling of aryl bromide with aryl boronic acids was reported to proceed efficiently at very low Pd loading (100 ppb) within short time (5 min) albeit at rather high temperature (150 • C). Later, other evidence for trace Pd catalysis of the SM coupling was also provided by the group of Lipshutz [33] with so called "Fe-ppm Pd nanoparticle" containing 320 ppb Pd. These reports point the hyperactive nature of very low level Pd species and show that their activity relies on the way they are generated in the medium.…”

The Hydrophobic Effect Applied to Organic Synthesis: Recent Synthetic Chemistry “in Water”

“…Among them, problematic dipolar aprotic solvents such as DMF and elevated temperatures are oftentimes required . A very mild alternative has been documented wherein ppm levels of palladium serve as co‐catalyst in TPGS‐750‐M/H 2 O at 45 °C (Scheme ) . This small amount of Pd helps to overcome, via transmetallation, the high energy barrier to form a Cu III intermediate resulting from insertion into an aryl iodide.…”

“…[67] These and several other fascinating and intriguing discoveries, as detailsa ssociated with the various topics in this review,a re presented herein. There are also many "firsts" in micellar catalysis appliedt oo rganic synthesis, such as:1 )new ligands designed for applications based on micellar catalysis in water; [17,19,23,38] 2) ppm level metal-catalyzed processes; [27,39,50,54,56] 3) new heterogeneous nanoparticles that catalyze av ariety of important, commonly utilized reactions; [27,39,49,50] 4) new hybrid micellar derivatives that incorporate reagents within their structure; [25,49,67,69] 5) industrially important developments on the use of micelles influenced by the presenceo fc o-solvents; [75][76][77][78] and 6) examples of one-pot tandem processes enabled by micellar conditions. [27,81,82,85,88,89] These and several relatede xamples from just the past few years further documentt he potentialo ft his blossoming technology,i llustrating new synthetic chemistry that is sustainable, environmentally responsible, and acknowledges that chemistry as practiced today must be changedt ob ei ns tep with the laws of Nature.…”

“…[53] Av ery mild alternative has been documented wherein ppm levelso fp alladium serve as co-catalyst in TPGS-750-M/H 2 Oa t4 5 8C( Scheme27). [54] This small amount of Pd helps to overcome, via transmetallation, the high energy barriert of orm aC u III intermediate resulting from insertion into an aryl iodide. Cu(OTf) 2 ,c omplexed by a P, N -ligand, in open air,l ed to biaryls in high yields.…”

Palladium (II)–Salan Complexes as Catalysts for Suzuki–Miyaura C–C Cross-Coupling in Water and Air. Effect of the Various Bridging Units within the Diamine Moieties on the Catalytic Performance

“…Hydrophilic palladacycles [ 30 ], complexes of tertiary phosphines [ 23 , 31 , 32 ], N-heterocyclic carbenes [ 33 , 34 , 35 ] and water-soluble complexes with salen ligands [ 2 , 36 , 37 ] have already been applied as catalysts in aqueous C–C cross-couplings. Alternatively, the reactants and the catalyst have to be incorporated into micelles formed by appropriate surfactants within the bulk aqueous phase [ 38 , 39 , 40 , 41 , 42 ]. Both methods allowed the design of outstandingly productive and robust catalytic procedures.…”