Palladium-free Suzuki–Miyaura cross-coupling at elevated pressures

Guo, Yanhe; Young, David J.; Hor, T. S. Andy

doi:10.1016/j.tetlet.2008.07.060

Cited by 40 publications

(15 citation statements)

References 23 publications

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“…Recently, Chirik and co‐workers reported early results in the coupling of aryl triflates with arylboron pinacol esters by using a cobalt PNP‐pincer‐based catalyst . We now report the cross‐coupling of aryl chlorides and bromides with activated arylboronic pinacol esters, using simple cobalt catalysts prepared in situ from commercially available precursors.…”

Section: Methodsmentioning

confidence: 91%

Cobalt‐Catalyzed Suzuki Biaryl Coupling of Aryl Halides

et al. 2017

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Readily accessed cobalt pre-catalysts with N-heterocyclic carbene ligands catalyze the Suzuki cross-coupling of aryl chlorides and bromides with alkyllithium-activated arylboronic pinacolate esters.P reliminary mechanistic studies indicate that the cobalt species is reduced to Co 0 during the reaction.The palladium-catalyzed cross-coupling of organoboronic acids or esters with organic halides or related substrates-the Suzuki reaction-is ap owerful and very widely exploited method for the formation of biaryl compounds (Scheme 1). [1] This reaction is used commercially for the production of arange of materials,including the sartan class of angiotensin inhibitors for the treatment of hypertension (e.g. Lorsartan) and Boscalid, abroad-spectrum agrochemical fungicide.[2]While palladium-based catalysts are ubiquitous in Suzuki cross-coupling reactions,there is agrowing impetus to replace them with more sustainable alternatives based on earthabundant metals (EAM). This is not only because of the fact that palladium, like all platinum-group metals (PGMs), is scarce and expensive,b ut also because of the relatively high toxicity of PGMs;asac onsequence of this toxicity there are strict regulations in place for the removal of PGMs to the low ppm level from active pharmaceutical intermediates.[3] Of the EAM alternatives to palladium for Suzuki biaryl coupling, first-row transition metals are particularly attractive,w ith nickel-based catalysts being the most well developed to date. [4,5] Iron-catalyzed Suzuki cross-coupling can be performed between avariety of organic halides and organoboron reagents, [6] but simple biaryl bond formation remains elusive and challenging. [6a, 7, 8] Recently,C hirik and co-workers reported early results in the coupling of aryl triflates with arylboron pinacol esters by using ac obalt PNP-pincer-based catalyst.[9] We now report the cross-coupling of aryl chlorides and bromides with activated arylboronic pinacol esters, [10,11] using simple cobalt catalysts prepared in situ from commercially available precursors.Ther esults shown in Table 1s ummarize selected [12] optimization studies using 4-chorotoluene and the activated phenylboronic ester 1a, [6b,c,e, 8] catalyzed by species formed in situ from cobalt(II) chloride with ar ange of different ligands and ligand precursors.No reaction was observed in the absence of added ligand (Table 1, entry 1) and little or no product 2a was obtained when mono,b i-, or tridentate phosphine ligands were tested Scheme 1. Palladium-catalyzed Suzuki biaryl coupling and selected products.

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Section: Methodsmentioning

confidence: 91%

Cobalt‐Catalyzed Suzuki Biaryl Coupling of Aryl Halides

et al. 2017

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“…In particular, using FeCl 3 /2-(diphenylphosphino)pyridine as catalyst (5 mol%), 97% conversion was observed after 48 h at 100 8C. [20] They suggested that the main influence of pressure on the iron-catalyzed reaction should be the acceleration of the reduction of the metal to a catalytically active oxidation state. Usually, in iron-catalyzed cross-coupling reaction, a reducing agent such as a Grignard reagent is required to reduce the iron salt to its low valent state as the catalytically active species.…”

Section: Entrymentioning

confidence: 99%

Retraction: Iron‐Catalyzed Suzuki–Miyaura Cross‐Coupling Reaction

Bézier

Darcel

2009

Adv Synth Catal

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Initially, the use of potassium fluoride 99% from Acros lead to complete conversion with aryl iodides and activated aryl bromides. With several batches of iron(III) chloride 99.99% the authors succeeded to reproduce those results and the blank tests without iron(III) chloride 99.99% did not lead to any conversion. Those tests were made several times with different substrates. However, attempts to repeat this work in two independent laboratories have been unsuccessful.Therefore, the authors decided to re-examine the reaction, and more particularly to use different types of KF from different suppliers. The results are reported in the following It clearly seems that this reaction is sensitive to the quality of KF and as the authors cannot reproduce such reactions even with KF of the same quality from the same supplier, this communication has to be retracted.

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“…[21][22][23][24][25][26] However, the iron-catalysed Suzuki biaryl cross-coupling reaction ( Figure 1(a); M = Fe) remains problematic, 27 with early reports proving unreproducible, 28,29 leading to subsequent retractions. Indeed, to the best of our knowledge, the only example of a Suzuki biaryl cross-coupling reaction that occurs under mild conditions 30 is obtained in the coupling of 2-halobenzyl halides with the activated boronic ester 1a, which gives the expected benzylarylated product 2 along with some of the biaryl coupled-side product 3. 31 We speculated that the biaryl bond-formation in this case may be due to the substrate 'directing' the activation of the aryl-X bond at the iron centre, as has been observed previously in the olefinassisted alkylation of aryl chlorides.…”

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confidence: 99%