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Transition metal-catalyzed direct C–H bond functionalization enabled by transient ligands has become an attractive topic. Here we report a palladium-catalyzed site-selective arylation of β-C(sp3)–H bonds in aliphatic ketones with β-alanine as the transient ligand. [ABSTRACT FROM AUTHOR]

Copper-promoted direct carbonylation of unactivated sp 3 C-H and aromatic sp 2 C-H bonds of amides was developed using nitromethane as a novel carbonyl source. The sp 3 C-H functionalization showed high site-selectivity by favoring the C-H bonds of α-methyl groups. The sp 2 C-H carbonylation featured high regioselectivity and good functional group compatibility. Kinetic isotope effect studies indicated that the sp 3 C-H bond breaking step is reversible, whereas the sp 2 C-H bond cleavage is an irreversible but not the rate-determining step. Control experiments showed that a nitromethyl intermediate should be involved in the present reaction.

The direct cyanomethylation of unactivated sp 3 C-H bonds of aliphatic amides was achieved via palladium catalysis assisted by a bidentate directing group with good functional group compatibility. This process represents the first example of the direct cross-coupling of sp 3 C-H bonds with acetonitrile. Considering the importance of the cyano group in medicinal and synthetic organic chemistry, this reaction will find broad application in chemical research.

The pyridine-enabled cross dehydrogenative coupling of sp 2 C-H bonds of polyfluoroarenes and unactivated sp 3 C-H bonds of amides was achieved via a copper-promoted process with good functional group compatibility. This reaction showed great site-selectivity by favoring the sp 2 C-H bonds ortho to two fluoro atoms of arenes and the sp 3 C-H bonds of α-methyl groups over those of the α-methylene, β- or γ-methyl groups of the aliphatic amides. Mechanistic studies revealed that sp 3 C-H bond cleavage is an irreversible but not the rate-determining step, and the sp 2 C-H functionalization of arenes appears precedent to the sp 3 C-H functionalization of amides in this process.

Transition metal-catalyzed cross dehydrogenative coupling is an important tool for functionalization of the α Csp 3 -H bond of amines. Among this reaction category, copper-catalyzed selective C-C bond formation under atmospheric O 2 is of considerable research interest and significant progress has been achieved in recent years. In comparison, development of the intramolecular version of this transformation is still in its infancy. Furthermore, diastereoselective cyclization with this transformation has not been achieved. Here, we describe the highly diastereoselective intramolecular dehydrogenative cyclization of N , N -disubstituted hydrazones by a copper-catalyzed sp 3 C-H bond functionalization process. The reaction protocol utilizes O 2 as the oxidant and shows great functional group compatibility. Computational studies suggest that a 5-center/6-electron disrotatory cyclization mechanism is probably involved in the process for controlling the diastereoselectivity. This work represents the first example of a copper-catalyzed, direct intramolecular diastereoselective coupling reaction via an iminium ion intermediate. Additionally, it provides an environmentally friendly and atom efficient approach to access substituted pyrazolines, an important structural unit in many biologically active compounds.

A novel rhodium-catalyzed imination of sulfoxides using O-(2,4-dinitrophenyl)hydroxylamine is developed under mild conditions with good functional group tolerance. This method provides an efficient access to free NH-sulfoximines, an important structural unit in a variety of biologically active compounds.

A novel Pd-catalyzed decarboxylative cross-coupling of oxamic acids with potassium phenyltrifluoroborates has been realized under mild reaction conditions. This method provides an efficient access to N-mono- or N,N-disubstituted benzamides and benzoates., (This journal is © The Royal Society of Chemistry 2011)