Cross-coupling of aryl bromides

By utilizing a solid support-based tetradentate A-heterocyclic carbene-palladium catalyst, cross couplings of aryl bromides with phenylboronic acid were achieved in neat water under air.121 A high ratio of substrate to catalyst was also realized. 

In 2001, Nolan described the palladium/imidazoilium salt-catalyzed coupling of aryl halides with hypervalent organostannanes.The imidazolium salt 36 in combination with Pd(OAc)2 and TBAF was found to be most effective for the cross-coupling of aryl bromides and electron-deficient aryl chlorides with aryl and vinyl stannanes. 

Zapf, A. Beller, M. Palladium/phosphite catalyst system for efficient cross coupling of aryl bromides and chlorides with PhB(OH)2. 

Pyrazole-tethered Schiff base ligands 62 promoted Suzuki cross-couplings of aryl bromides and chlorides with phenylboronic acid efficiently under mild conditions <05TL15>. Chromium-trioxide complex with 3,5-dimethylpyrazole 63 oxidation of cyclohexenecarbonitrile provided 3-oxocyclohex-1 -ene-1 -carbonitrile <05S3179>. 

Suzuki-Miyaura Cross-Coupling of Aryl Bromides and Chlorides with Boronic Acids at Low Catalyst Loadings... 

The impressive stability of Pd/NHC complexes and their activity in crosscoupling reactions is strongly supported by the recent report of Zhao et al. [49], who developed an environmentally benign protocol for the cross-coupling of aryl bromides with phenylboronic acids in water. The catalytic system is based on a tetradentate NHC ligand. 

Following a recent theoretical study that suggested the suitability of mixed carbene-phosphine chelates for the Pd-catalyzed Heck reaction [58], a car-bene-phosphine chelating ligand (Fig. 5) was prepared and its efficacy investigated in the cross-coupling of aryl bromides with n-butyl acrylate [59]. 

The cross-coupling of aryl bromides and alkynes was found to be catalyzed by Pd(0Ac)2/IMes-HCl/Cs2C03 in DMAc at 80 °C (Scheme 17). Undesired dimerization products were obtained when phenylacetylene was employed as the alkyne source. This side reaction was suppressed by using a more reactive substrate, l-phenyl-2-(trimethylsilyl)acetylene [65]. Worthy of note is that high yields of coupled products were achieved under Cu-free conditions. Addition of 2 mol% Cul increased the reaction rates, most notably with deactivated or sterically encumbered aryl bromides. The catalytic system has a limited... 

Reliable and practical procedures for the synthesis of arylacetylenes by Pd-catalyzed cross-coupling of aryl bromides with terminal acetylenes have been developed, which... 

Scheme 14.7 Ni-catalysed cross-couplings of aryl bromides with tertiary alkylmag-nesium halides. Ratio of retention product to isomerisation products in parentheses. The reaction was warmed to room temperature and stirred overnight (10 h).

DeVasher, R.B., Moore, L.R. and Shaughnessy, K.H. (2004) Aqueous-phase, palladium-catalyzed cross-coupling of aryl bromides under mild conditions, using water-soluble, stericaUy demanding alkylphosphines. J. Org. Chem., 69, 7919-27. 

Phosphapalladacycles stabilized by highly hindered phosphines showed very good catalytic activity in the copper-free cross-coupling of aryl bromides with phenylacetylenes in NEts with a maximum TON of 8000. 

Nickel-catalysed cross-coupling of aryl bromides with tertiary Grignard reagents has been performed in the presence of donor-functionalized A-heterocyclic carbenes. Bifunctional A-heterocyclic carbene ligands (e.g. 15) were shown to result in especially selective and efficient transformations. 

Scheme 13.18 General and efficient cross-coupling of aryl bromides and chlorides.

Zare A, Abi F, Moosavi-Zare AR, Beyzavi MH, Zolfigol MA (2013) Synthesis, characterization and application of ionic liquid 1,3-disulfonic acid imidazolium hydrogen sulfate as an efScient catalyst for the preparation of hexahydroquinolines. J Mol Liq 178 113-121 SilarskaE, TrzeciakAM, Pemak J, Skrzypezak A(2013) [ILJ pdCl ] complexes (IL = imidazolium cation) as efficient catalysts for Suzuki-Miyaura cross-coupling of aryl bromides and aryl chlorides. Appl Catal A Gen 466 216-223... 

Figure 2.10 A cross-section of results for the Pd cross-coupling of aryl bromides with thioacetates as reported by Park et al. [52].

The group of Goofien recently published an optimized protocol for the palladium-catalyzed cross-coupling of aryl bromides into trimethylsilyl arenes. They also optimized the reaction for different classes of aryl bromides such as electron-poor and electron-rich arenes (Scheme 5-170). The solvent of choice was DMPU (1,3-dimethyltetrahydropyrimidin-2(l//)-one). McNeill et al. extended the scope of this reaction for aryl chlorides with similar catalyst systems. ... 

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