853918-46-4Relevant academic research and scientific papers
Lewis Acid-Catalyzed Selective Reductive Decarboxylative Pyridylation of N-Hydroxyphthalimide Esters: Synthesis of Congested Pyridine-Substituted Quaternary Carbons
Gao, Liuzhou,Wang, Guoqiang,Cao, Jia,Chen, Hui,Gu, Yuming,Liu, Xueting,Cheng, Xu,Ma, Jing,Li, Shuhua
, p. 10142 - 10151 (2019)
A practical and efficient Lewis acid-catalyzed radical-radical coupling reaction of N-hydroxyphthalimide esters and 4-cyanopyridines with inexpensive bis(pinacolato)diboron as reductant has been developed. With ZnCl2 as the catalyst, a wide range of quaternary 4-substituted pyridines, including highly congested diarylmethyl and triarylmethyl substituents, could be selectively obtained in moderate to good yields with broad functional group tolerance. Combined theoretical calculations and experimental studies indicate that the Lewis acid could coordinate with the cyano group of the pyridine-boryl radical to lower the activation barrier of the C-C coupling pathway, leading to the formation of 4-substituted pyridines. Moreover, it could also facilitate the decyanation/aromatization of the radical-radical coupling intermediate.
Organoborohydride-catalyzed Chichibabin-type C4-position alkylation of pyridines with alkenes assisted by organoboranes
Guan, Wei,Li, Runhan,Li, Xiaohong,Li, Yanfei,Wang, Ying,Xiong, Tao,Yin, Jianjun,Zhang, Ge,Zhang, Qian
, p. 11554 - 11561 (2020/11/23)
The first NaBEt3H-catalyzed intermolecular Chichibabin-type alkylation of pyridine and its derivatives with alkenes as the latent nucleophiles is presented with the assistance of BEt3, and a series of branched C4-alkylation pyridines, even highly congested all-carbon quaternary center-containing triarylmethanes can be obtained in a regiospecific manner. Therefore, the conventional reliance on high cost and low availability transition metal catalysts, prior formation of N-activated pyridines, organometallic reagents, and extra oxidation operation for the construction of a C-C bond at the C4-position of the pyridines in previous methods are not required. The corresponding mechanism and the key roles of the organoborane were elaborated by the combination of H/D scrambling experiments, 11B NMR studies, intermediate trapping experiments and computational studies. This straightforward and mechanistically distinct organocatalytic technology not only opens a new door for the classical but still far less well-developed Chichibabin-type reaction, but also sets up a new platform for the development of novel C-C bond-forming methods.
Nickel-catalysed para-CH activation of pyridine with switchable regioselective hydroheteroarylation of allylarenes
Lee, Wei-Chih,Chen, Chien-Hung,Liu, Cheng-Yuan,Yu, Ming-Shiuan,Lin, Yung-Huei,Ong, Tiow-Gan
supporting information, p. 17104 - 17107 (2015/12/01)
para-CH activation of pyridine with allylbenzene is described by Ni/Al cooperative catalysis in combination with a bulkier NHC ligand and a Lewis acid, leading to linear hydroheteroarylation products. Interestingly, the branch selectivity can be achieved by using the combination of a less sterically hindered amino-NHC ligand and AlMe3 through tandem reaction of facile alkene isomerization followed by a slow CH bond activation process.
