The Ru-catalysed C2–H arylation of indoles and pyrroles by using boronic acids under oxidative conditions is reported. This reaction can be applied to tryptophan derivatives and tolerates a wide range of functional groups on both coupling partners, including bromides and iodides, which can be further derivatised selectively. New indole-based ruthenacyclic complexes are described and investigated as possible intermediates in the reaction. Mechanistic studies suggest the on-cycle intermediates do not possess a para-cymene ligand and that the on-cycle metalation occurs through an electrophilic attack by the Ru centre.

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A new, operationally simple approach is presented to access arynes and their fluoride-activated precursors based on Ru-catalyzed C−H silylation of arylboronates. Chromatographic purification may be deferred until after aryne capture, rendering the arylboronates de facto precursors. Access to various new arynes and their derivatives is demonstrated, including, for the first time, those based on a 2,3-carbazolyne and 2,3fluorenyne core, which pave the way for novel derivatizations of motifs relevant to materials chemistry.

Studies. -The procedure can be applied to a broad spectrum of indole substrates including tryptophan derivative (XIV). A wide range of functional groups including halogens is tolerated at the heterocyclic skeleton and the boronic acid. Generally, iPrOH is the solvent of choice but the system H 2O/THF is also efficient [cf. conditions B)]. Product (XIa) is transformed to ester (XIII) as an example for selective derivatization. Some pyrroles are also arylated. New indole-based ruthenacyclic complexes are prepared and used in the investigation of the catalytic cycle. -(SOLLERT, C.; DEVARAJ, K.; ORTHABER, A.; GATES, P. J.; PILARSKI*, L. T.; Chem. -Eur. J. 21 (2015) 14, 5380-5386, http://dx.doi.org/10.1002/chem.201405931 ; Dep. Chem., Uppsala Univ., S-751 23 Uppsala, Swed.; Eng.) -Lehmann 34-153

Pyrrole C-glycosylated in either the 2- or the 3-position could be prepared by the acid-catalyzed reaction between trichloroacetimidate glycosyl donors and pyrrole, or [Formula: see text]-phenyl-trifluoroacetimidate glucosyl donor and [Formula: see text]-TIPS pyrrole, respectively. Pyrroles carrying glucose, mannose, galactose and lactose in the 2-position, and glucose in the 3-position were obtained. The configurations of the products could be assigned using a combination of 1D and 2D NMR spectroscopy. A number of undesired background reactions yielding a variety of stereo- and regioisomers were identified; in several cases these could be eliminated. Glycosylpyrroles could be incorporated into mono- and diglycosylated dipyrromethanes, a diglycosylated BODIPY dye, and a monoglycosylated Zn(II) porphyrin without damaging the sugar unit.

This review discusses the preparation and orthogonal reactivity of boryl ortho-silyl(hetero)aryl triflates as precursors for arynes. These triflates undergo a wide variety of selective reactions of either the boronate or aryne component. Activation of the boronate group affords diverse (hetero)aryne precursors, whereas aryne activation and capture gives previously difficult-to-access arylboronates, all starting from the same set of common starting materials. Thus, the boronate and aryne functionality can be used for their mutual postfunctionalization with unprecedented flexibility.

Cyclo­metalated Ru complexes play a major role in catalytic transformation. The Ru cation is coordinated by a pyrimidyl-3H-indole ligand, as well as a para-cymene ligand and one aceto­nitrile mol­ecule.

Ak ey mechanistic finding … …i nt he pyrimidine-directed Ru-catalysed CÀHa rylation of indoles is that the catalyst loses its cymene ligand.T his is described in detail in the Full Paper by L. T. Pilarski and co-workerso np age 5380f f. The picture illustrates this by way of ar uthenium "magician" standing on ap yrimidine directing group and breaking the indole CÀHbond by casting aspell with his wand. With his other hand, the magician is raising ah at in the shape of the cymenel igand. An aryl boronic acid, floating nearby, represents one of the other reagents used in the reaction.