Suzuki–Miyaura cross-coupling reaction on copper-trans-A₂B corroles with excellent functional group tolerance
2011
König, Michael | Reith, Lorenz Michael | Monkowius, Uwe | Knör, Günther | Bretterbauer, Klaus | Schoefberger, Wolfgang
The palladium-catalyzed Suzuki–Miyaura cross-coupling reaction has been investigated on meso-substituted trans-A₂B-corrole using tailored Pd-catalyst systems. We present the first examples of Suzuki–Miyaura cross-coupling reactions on meso-substituted trans-A₂B-corrole derivatives with neutral, sterically hindered, inactivated and heteroaromatic boronic acids and esters, alkenylboronic acids, as well as quickly deboronating aryl boronic acids and benzo-condensated five membered heterocyclic boronic acids. In addition, we established a high-yield procedure for the Suzuki–Miyaura cross-coupling reaction of corroles with neutral boronic acids. Due to the lability of the free-base corrole macrocycles, functionalization of the corrole periphery was performed with the corresponding Cu-metallated species. meso-Substituted trans-A₂B-corrole can hence be regarded as highly versatile platform towards more sophisticated corrole systems. X-ray structure analysis of a functionalized meso-substituted trans-A₂B copper corrole exhibited the typical features of such a Cu-complex: short N–Cu distances and a saddled corrole configuration. Moreover, we observed a sensitivity of the formal oxidation state of the coordinated copper ions towards Suzuki–Miyaura cross-coupling reaction conditions, where the central copper(III) ion approaches the characteristic features of a copper(II) species. This redox behaviour was examined by UV/vis absorption spectra, nuclear magnetic resonance (NMR) experiments and time-dependent density functional theoretical calculations.
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