Copper Oxide Nanoparticle‐Catalyzed Chalcogenation of the Carbon‐Hydrogen Bond in Thiazoles: Synthesis of 2‐(Organochalcogen)thiazoles

Abstract

We present (homepage: www.ufsm.br) herein the application of copper nanoparticles/diorganyl dichalcogenides to promote the synthesis of 2‐(organochalcogen)thiazoles via direct carbon‐hydrogen bond activation in thiazoles. A systematic study of the catalytic system revealed that the presence and amount of base played an essential role in this reaction. The results revealed that electron‐donating and electron‐withdrawing substituents, in the aromatic ring bonded to the chalcogen atom of diorganyl dichalcogenides, required one equiv. of base, while when neutral substituents were present two equiv. of base were needed to deliver the products in similar yields.magnified image

Metal‐Free Preparation of Cycloalkyl Aryl Sulfides via Di‐tert‐butyl Peroxide‐Promoted Oxidative C(sp3)H Bond Thiolation of Cycloalkanes

“…[2] Recently, metal-catalyzed C–S bonds formation through C(sp 2 )–H bond activation has become an alternative and intriguing methods for preparation of sulfides due to its high atom-economy and efficiency. [3] However, the cleavage of C(sp 3 )–H bond leading to the C–S bond formation is less studied. Very recently, Xiang and co-workers reported a novel thiolation of C(sp 3 )–H bond adjacent to a nitrogen or oxygen atom (Scheme 1a and 1b).…”

Copper-catalyzed direct C–H arylselenation of 4-nitro-pyrazoles and other heterocycles with selenium powder and aryl iodides. Access to unsymmetrical heteroaryl selenides

“…The TM-catalyzed direct arylselenation of C-H bonds is one of the most efficient methods for the synthesis of unsymmetrical diaryl selenides. The to-date developed protocols involve the use of diselenides (palladium, 63 rhodium, 72 ruthenium 64,73 iron oxide, 74 silver, 75,76 and copper 65,66,77 catalyzed) or ArSeCl (ruthenium 78 catalyzed) as selenium source. There are also a few very recent examples of copper-catalyzed one-pot three-component procedures involving Se powder, which can be considered an obvious step in methodology development, since diselenides are easily obtained from aryl iodides and selenium powder in similar catalytic conditions.…”

Copper‐Iodide‐ and Diorganyl‐Diselenide‐Promoted Cyclization of 2‐Alkynylphenols: Alternative Approach to 3‐Organoselanylbenzo[b]furans

“…Traces of the 3‐(phenylselanyl)benzo[ b ]furan 3a were observed by GC–MS analysis of the crude reaction mixture. This result suggests that a C–H activation pathway cannot be completely ruled out …”