Michael F. Greaney

Intramolecular Oxidative C?H Coupling for Medium-Ring Synthesis

An oxidative C-H coupling is described for medium-ring synthesis.

Nucleophilic catalysis of acylhydrazone equilibration for protein-directed dynamic covalent chemistry

Dynamic covalent chemistry uses reversible chemical reactions to set up an equilibrating network of molecules at thermodynamic equilibrium, which can adjust its composition in response to any agent capable of altering the free energy of the system. When the target is a biological macromolecule, such as a protein, the process corresponds to the protein directing the synthesis of its own best ligand. Here, we demonstrate that reversible acylhydrazone formation is an effective chemistry for biological dynamic combinatorial library formation. In the presence of aniline as a nucleophilic catalyst, dynamic combinatorial libraries equilibrate rapidly at pH 6.2, are fully reversible, and may be switched on or off by means of a change in pH. We have interfaced these hydrazone dynamic combinatorial libraries with two isozymes from the glutathione S-transferase class of enzyme, and observed divergent amplification effects, where each protein selects the best-fitting hydrazone for the hydrophobic region of its active site.

Insertion of Benzene Rings into the Amide Bond: One-Step Synthesis of Acridines and Acridones from Aryl Amides

Insertion of benzene rings into the amide bond using the reactive intermediate benzyne is described. Aromatic amides undergo smooth insertion when treated with O-triflatophenyl silane benzyne precursors, producing versatile aminobenzophenone products in good to excellent yield. The process is entirely metal-free and has been exemplified on the synthesis of biologically active acridones and acridines.

Direct arylations on water: synthesis of 2,5-disubstituted oxazoles balsoxin and texaline

An efficient two-step palladium catalysed synthesis of 2,5-disubstituted oxazoles is reported.

Direct arylations of 2H-indazoles on water.

The efficient palladium-catalyzed synthesis of a range of substituted 2H-Indazoles via C-H arylation is reported. Reactions are performed on water and provide a direct and mild route toward 2,3-diaryl indazoles of widespread biological significance.

Ruthenium-Catalyzed meta-Selective C-H Bromination.

The first example of a transition-metal-catalyzed, meta-selective C–H bromination procedure is reported. In the presence of catalytic [{Ru(p-cymene)Cl2}2], tetrabutylammonium tribromide can be used to functionalize the meta C–H bond of 2-phenylpyridine derivatives, thus affording difficult to access products which are highly predisposed to further derivatization. We demonstrate this utility with one-pot bromination/arylation and bromination/alkenylation procedures to deliver meta-arylated and meta-alkenylated products, respectively, in a single step.

Decarboxylative Cross-Coupling of Azoyl Carboxylic Acids with Aryl Halides

Decarboxylative cross-coupling of thiazole and oxazole-5-carboxylic acids with aryl halides is reported. Under a bimetallic system of catalytic palladium and a stoichiometric silver carbonate, a variety of (hetero)arylated azoles can be prepared in excellent yield.

Atom-economical transformation of diaryliodonium salts: tandem C-H and N-H arylation of indoles.

Arylation using diaryliodonium salts generates one equivalent of an iodoarene as a side-product, a significant waste of atom economy. Here, we show that diaryliodoniums can undergo Cu-catalyzed tandem C-H/N-H arylation, producing novel indoles that incorporate both aryl groups from the reagent.

Direct arylation of oxazoles at C2. A concise approach to consecutively linked oxazoles.

The synthesis of bis- and trisoxazoles via direct arylation is discussed. A variety of aryl groups can be installed at the 2-position of 5-aryl and 5-carboxy-substituted oxazoles under mild conditions using palladium catalysis on water. The direct arylation method can be extended to the synthesis of bis- and trisoxazoles if 2-triisopropylsilyl-4-iodooxazole is used as the electrophile in the arylation.

Decarboxylative C–H Arylation of Benzoic Acids under Radical Conditions

A decarboxylative radical cyclization reaction has been developed for the synthesis of fluorenones. The reaction uses Ag(I)/K2S2O8 to oxidatively decarboxylate an aroylbenzoic acid to an aryl radical, which undergoes cyclization to afford fluorenone products in good yield.