Arylation Of Pyridine N-oxides Research Articles

Arylation of pyridine N-oxides via a ligand-free Suzuki reaction in water

Abstract We report a practical and highly efficient protocol for the arylation of pyridine N -oxides with arylboronic acid through palladium-catalyzed Suzuki reaction in water. This ligand-free Suzuki reaction is performed in the presence of diisopropylamine and gives 2- or 3-arylated pyridyl N -oxide derivatives in good to excellent yields within 1 h.

ChemInform Abstract: Copper‐Catalyzed Direct C—H Arylation of Pyridine N‐Oxides with Arylboronic Esters: One‐Pot Synthesis of 2‐Arylpyridines.

The first example of the copper-catalyzed direct C–H arylation of pyridine N-oxides with arylboronic esters has been developed, leading to a wide range of 2-arylpyridines in a one-pot synthesis with moderate to good yields without an additional reductant. This transformation allows for rapid access to a variety of 2-arylpyridines using an inexpensive catalytic system that would be more difficult to access with traditional methods. Thus, this method represents a simple and practical procedure to access 2-arylpyridines.

Copper-catalyzed direct C–H arylation of pyridine N-oxides with arylboronic esters: one-pot synthesis of 2-arylpyridines

The first example of the copper-catalyzed direct C-H arylation of pyridine N-oxides with arylboronic esters has been developed, leading to a wide range of 2-arylpyridines in a one-pot synthesis with moderate to good yields without an additional reductant. This transformation allows for rapid access to a variety of 2-arylpyridines using an inexpensive catalytic system that would be more difficult to access with traditional methods. Thus, this method represents a simple and practical procedure to access 2-arylpyridines.

Synthesis of Asymmetrically Substituted Terpyridines by Palladium‐Catalyzed Direct CH Arylation of Pyridine N‐Oxides

The synthesis of asymmetrically substituted 2,2':6',2''-terpyridines is reported. First, palladium-catalyzed C-H arylation of pyridine N-oxides with substituted bromopyridines gave 2,2'-bipyridine N-oxides, which were further arylated in a second step to form 2,2':6',2''-terpyridine N-oxides. Yields of up to 77% were obtained with N-oxides bearing an electron-withdrawing ethoxycarbonyl substituent in the 4-position. Pd(OAc)2 with either P(tBu)3 or P(o-tolyl)3 was used as the catalyst. Cyclometalated complexes derived from Pd(OAc)2 and these phosphines were also effective. K3PO4 as the base gave better results than K2CO3. Subsequent deoxygenation with H2 and Pd/C as the catalyst gave the asymmetrically substituted 2,2':6',2''-terpyridines in near quantitative yield. This reaction sequence significantly reduces the number of steps required in comparison with known cross-coupling methods and therefore allows convenient and scalable access to substituted terpyridines.

Regioselective Arylation of Pyridine N-Oxides via Silver-Catalyzed C–H Activation

Regioselective Arylation of Pyridine N-Oxides via Silver-Catalyzed C–H Activation