Jun-Long Niu

Copper-Mediated Direct Aryloxylation of Benzamides Assisted by an N,O-Bidentate Directing Group

Copper-mediated selective mono- or diaryloxylation of benzamides has been achieved by using 2-aminopyridine 1-oxide as a new and removable N,O-bidentate directing group. The reaction system shows a broad substrate scope and provides a straightforward way for the synthesis of mono- and diaryloxylated benzoic acids.

Cobalt(II)-Catalyzed C-H Amination of Arenes with Simple Alkylamines.

A new method of cobalt-catalyzed amination of arylamides with simple alkylamines is reported through C(sp(2))-H bond functionalization. For the first time, inexpensive cobalt is exploited as the catalyst in the amination of C(sp(2))-H bond using simple alkylamines.

Cobalt(II)-Catalyzed Decarboxylative C–H Activation/Annulation Cascades: Regioselective Access to Isoquinolones and Isoindolinones

A new cobalt(II)-catalyzed decarboxylative C-H activation/annulation of benzamides and alkynyl carboxylic acids has been described. Alkynyl carboxylic acids were first employed as the coupling partners using inexpensive Co(OAc)2·4H2O as the catalyst. This method enables a switchable cyclization to isoquinolones and isoindolinones with excellent selectivity. Moreover, a catalytic amount of Ag2O was adopted as co-catalyst and O2 (from air) as a terminal oxidant for the preparation of isoquinolones.

Chiral bis(imidazolinyl)phenyl NCN pincer rhodium(III) catalysts for enantioselective allylation of aldehydes and carbonyl-ene reaction of trifluoropyruvates.

Chiral NCN pincer rhodium(III) complexes with bis(imidazolinyl)phenyl ligands were found to be effective catalysts for the allylation of a variety of electronically and structurally diverse aldehydes with allyltributyltin, giving the corresponding optically active homoallylic alcohols in high yields with enantioselectivities of up to 97% ee. These complexes were also applied in the carbonyl-ene reaction of ethyl or methyl trifluoropyruvate with various 2-arylpropenes. With the aid of silver trifluoromethanesulfonate, the pincer rhodium(III) catalysts could catalyze the reaction to provide the corresponding chiral α-hydroxy-α-trifluoromethyl esters in good yields with high stereoselectivities (up to 95% ee).

Cobalt(II)-Catalyzed Oxidative C–H Arylation of Indoles and Boronic Acids

Co(II)-catalyzed C-H C2 selective arylation of indoles with boronic acids through monodentate chelation assistance has been achieved for the first time. The unique features of this methodology include mild reaction conditions, highly C2 regioselectivity, and employment of a Grignard reagent-free catalytic system. A wide range of substrates, including unreactive arenes, are well tolerated, which enables the construction of the coupling products efficiently. This new strategy provides an alternative and versatile approach to construct biaryls using inexpensive cobalt catalyst.

Synthesis, Characterization, and Crystal Structures of Heteroannular Cyclopalladated Ferrocenylimine-Pyridine Complexes

Two new heteroannular cyclopalladated ferrocenylimine-pyridine derivatives, 2a and 2b, were easily prepared by the reaction of chlorine-bridged binuclear palladium complexes, 1a and 1b, with pyridine in high yields. They were characterized by ESI-MS, H-NMR, and IR spectra. The detailed structures of complexes 2a and 2b were determined by single-crystal X-ray analysis. According to the crystal structure, the palladium atom is bound to the unsubstituted Cp ring, forming a new heteroannular pyridine-cyclopalladated large-membered metallocycle. Complex 2a exists as a dimer in the crystal due to intermolecular CH(CH˭N)···Cl hydrogen bonds, while 2b has a two-dimensional network structure formed by the intermolecular hydrogen bonds between the Cl atom with the adjacent C-H groups of Cp and pyridine.

CCDC 811901: Experimental Crystal Structure Determination

Related Article: Dan-Dan Shao, Jun-Long Niu, Xin-Qi Hao, Jun-Fang Gong, Mao-Ping Song|2011|Dalton Trans.|40|9012|doi:10.1039/c1dt10329f