Decarboxylative ipso Amination of Activated Benzoic Acids.

In the presence of a bimetallic Pd/Cu system with 1,10-phenanthroline as the ligand and either air or N-methylmorpholine N-oxide as the oxidant, electron-deficient benzoic acids undergo oxidative decarboxylative coupling with unprotected amines. This operationally simple aniline synthesis is widely applicable with respect to the amine and gives good yields, even on multigram scale. The orthogonality of this reaction to other Pd-catalyzed cross-couplings allows the concise synthesis of multisubstituted arenes by sequential C-C, C-Cl, and C-N functionalizations. Mechanistic investigations suggest the intermediacy of a hypervalent Pd species.

Transition-Metal-Free Synthesis of Biarylmethanes from Aryl Iodides and Benzylic Ketones.

An original metal-free procedure for the synthesis of biarylmethanes is disclosed herein. The reactions occur with high selectivity starting from aryl iodides and benzylic ketones in the presence of superbasic media (CsOH/DMSO). This procedure allows a straightforward access to a wide range of biarylmethane derivatives substituted with electron-withdrawing and -donating substituents.

Regiospecific ortho-C-H Allylation of Benzoic Acids.

A carboxylate-directed ortho-C-H functionalization has been developed and it allows the regiospecific introduction of allyl residues to benzoic acids. In the presence of a [Ru(p-cymene)Cl2 ]2 and K3 PO4 , benzoic acids react with allyl acetates at only 50 °C to give the corresponding ortho-allylbenzoic acids. The protocol is generally applicable to both electron-rich and electron-poor benzoic acids in combination with linear and branched allyl acetates. The products can be further functionalized in situ, for example, by double-bond migration, lactonization, or decarboxylation.

Carboxylic Acids as Directing Groups for C-H Bond Functionalization.

The selective transformation of C-H bonds is one of the most desirable approaches to creating complexity from simple building blocks. Several directing groups are efficient in controlling the regioselectivity of catalytic C-H bond functionalizations. Among them, carboxylic acids are particularly advantageous, since they are widely available in great structural diversity and at low cost. The carboxylate directing groups can be tracelessly cleaved or may serve as the anchor point for further functionalization through decarboxylative couplings. This Minireview summarizes the substantial progress made in the last few years in the development of reactions in which carboxylate groups direct C-H bond functionalizations with formation of C-C, C-O, C-N, or C-halogen bonds at specific positions. It is divided into sections on C-C, C-O, C-N, and C-halogen bond formation, each of which is subdivided by reactions and product classes. Particular emphasis is placed on methods that enable multiple derivatizations by combining carboxylate-directed C-H functionalization with decarboxylative couplings.

Transition-Metal-Free α-Arylation of Enolizable Aryl Ketones and Mechanistic Evidence for a Radical Process.

The α-arylation of enolizable aryl ketones can be carried out with aryl halides under transition-metal-free conditions using KOtBu in DMF. The α-aryl ketones thus obtained can be used for step- and cost-economic syntheses of fused heterocycles and Tamoxifen. Mechanistic studies demonstrate the synergetic role of base and solvent for the initiation of the radical process.

On the frontier between nucleophilic aromatic substitution and catalysis.

A study on the arylation of heteroatom nucleophiles by using activated haloarenes, with or without metal catalysts, is reported. A discussion concerning the involvement of traces of metals is presented, supported by an unexpected ''ligand'' effect in the absence of added metal catalysts. We believe that the frontier between nucleophilic aromatic substitution and catalysis will likely prove to be much harder to delimit than is generally thought.