Xiaochen Ji

Conversion of Pyridine to Imidazo[1,2-a]pyridines by Copper-Catalyzed Aerobic Dehydrogenative Cyclization with Oxime Esters

A rapid and environmentally friendly conversion of pyridine to imidazo[1,2-a]pyridines has been developed via copper-catalyzed aerobic dehydrogenative cyclization with ketone oxime esters.

Palladium‐Catalyzed Sequential Formation of CC Bonds: Efficient Assembly of 2‐Substituted and 2,3‐Disubstituted Quinolines

A series of substituted quinolines was prepared from arylamines, aldehydes, and terminal olefins (see scheme). The palladium-catalyzed sequential formation of C-C bonds proceeds smoothly with both electron-deficient and electron-rich olefins. When acrylic acid is used as terminal olefin, decarboxylation occurs to provide 2-substituted quinolines.

Copper-catalyzed formal C-N bond cleavage of aromatic methylamines: assembly of pyridine derivatives.

An efficient copper-catalyzed C-N bond cleavage of aromatic methylamines was developed to construct pyridine derivatives. With neat conditions and facile operation, the fragment-assembling strategy affords a broad range of 2,4,6-trisubstituted pyridines in up to 95% yield from simple and readily available starting materials. Interestingly, when pyridin-2-yl methylamine was employed as the substrate, α-alkylation reaction of ketones readily occurred to give β-(pyridin-2-yl) ketones instead of the 2,4,6-trisubstituted pyridines.

Palladium-Catalyzed Oxidative Coupling of Aromatic Primary Amines and Alkenes under Molecular Oxygen: Stereoselective Assembly of (Z)-Enamines

An efficient Pd-catalyzed oxidative coupling of aromatic primary amines and alkenes under molecular oxygen is disclosed. Under mild reaction conditions, it provides a rapid access to (Z)-enamine compounds with exceptional functional group tolerance and excellent regio- and stereoselectivity. This attractive route is of great significance due to its applicability to a wide range of aromatic primary amines, most of which could not be efficiently converted into enamines previously. Moreover, this protocol is scalable, and the resultant enamines could be conveniently transformed into a series of N-containing heterocyclics, thus illustrating its potential applications in synthetic and medicinal chemistry.

Palladium-catalyzed oxidative C-N bond coupling involving a solvent-controlled regioselective bromination process.

Stereoselective palladium-catalyzed oxidative C-N bond coupling reactions between aromatic amines and alkenes involving a solvent-controlled regioselective bromination process under 1 atm of oxygen atmosphere are disclosed, providing easy access to two different brominated enamines. The addition of hydrogen peroxide (30% aq) as a co-oxidant in the system is crucial for the dehydrogenative aminohalogenation under molecular oxygen (1 atm), and in such a case, the C-N bond coupling/electrophilic bromination reaction cascade is proposed. Furthermore, the different reaction media leads to a switched regioselectivity of the process.