A new palladium-catalyzed arylation process based on C-H activation has been developed. The utilization of pyridine-containing directing groups allows the beta-arylation of carboxylic acid derivatives and gamma-arylation of amine derivatives. Both primary and secondary sp3 C-H bonds, as well as sp2 C-H bonds, are reactive.

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[reaction: see text] Spontaneous self-associations of various tricyclic phenalenyl radicals lead reversibly to either pi- or sigma-dimers, depending on alkyl-substitution patterns at the alpha- and beta-positions. Thus, the sterically encumbered all-beta-substituted tri-tert-butylphenalenyl radical (2*) affords only the long-bonded pi-dimer in dichloromethane solutions, under conditions in which the parent phenalenyl radical (1*) leads to only the sigma-dimer. Further encumbrances of 1* with a pair of alpha, beta- or beta, beta- tert-butyl substituents and additional methyl and ethyl groups (as in sterically hindered phenalenyl radicals 3* - 6*) do not inhibit sigma-dimerization. ESR spectroscopy is successfully employed to monitor the formation of both diamagnetic (2-electron) dimers; and UV-vis spectroscopy specifically identifies the pi-dimer by its intense near-IR band. The different temperature-dependent spectral (ESR and UV-vis) behaviors of these phenalenyl radicals allow the quantitative evaluation of the bond enthalpy of 12 +/- 2 kcal mol(-1) for sigma-dimers, in which the unusually low value has been theoretically accounted for by the large loss of phenalenyl (aromatic) pi-resonance energy attendant upon such bond formation.

A strategy in which C-H activation reactions promoted by Pd(II) have been combined with beta-heteroatom elimination to create a catalytic cycle achieving the arylation of haloacrylates is reported. The catalytic cycle can be subdivided into four parts: (1) C-H activation; (2) the functionalization step, migratory insertion of the olefin into a metal-carbon bond; (3) beta-heteroatom elimination; and (4) exchange of metal halide (if X = halogen) for a less coordinating anion. In this catalytic cycle, the oxidation state of the metal does not change, and an oxidant is not required. The method is more functional group tolerant compared with the existing alkene-arene coupling methods based on electrophilic C-H activation.

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A simple and general method for arylation of carbon-hydrogen bonds in compounds containing directing groups has been developed. Anilides, benzylamines, benzoic acids, 2-aryl and alkylpyridines can be arylated in ortho-positions by using a combination of substrate, aryl iodide, silver acetate and catalytic palladium acetate. The use of a pyridine-containing removable auxiliary ligand allows the arylation of b-positions in carboxylic acid derivatives and g-positions in amine derivatives. Non-activated sp 3 carbon-hydrogen bonds are also reactive. A mechanistically distinct method for the alkenylation of anilides has also been developed.

Bi‐ und Triarylbildung mit hohen Umsatzzahlen: Substituierte Anilide wurden mit Aryliodiden unter Palladiumkatalyse ortho‐aryliert (siehe Schema). Dieses Verfahren gelingt in Gegenwart einer Vielzahl anderer funktioneller Gruppen (FGs). Sogar ein Iodsubstituent an der Anilideinheit und ein Bromsubstituent am Aryliodid stören nicht.

Polyphenyl derivatives Q 0700Anilide ortho-Arylation by Using C-H Activation Methodology. -A new anilide arylation reaction is developed, involving the reaction of anilides, e.g. (I), with aryl iodides (II) activated by AgOAc in the presence of Pd catalyst. The reaction proceeds with excellent regioselectivity and is tolerant to various functional groups including halogen and ester groups. Up to 1000 turnovers are achieved. -(DAUGULIS*, O.; ZAITSEV, V. G.; Angew. Chem., Int. Ed. 44 (2005) 26, 4046-4048; Dep. Chem., Univ. Houston, Houston, TX 77204, USA; Eng.) -Mischke 43-102