Browsing by Author "Liu, Cheng-Yuan"

Now showing 1 - 3 of 3

Nickel-catalysed para-CH activation of pyridine with switchable regioselective hydroheteroarylation of allylarenes
(2015-01-01)
Lee, Wei-Chih
;
Chen, Chien-Hung
;
Liu, Cheng-Yuan
;
Yu, Ming-Shiuan
;
Lin, Yung-Huei
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.
Nickel-mediated cross-coupling via C-O activation assisted by organoaluminum
(1970-01-01)
Liu, Cheng-Yuan
;
Wititsuwannakul, Taveechai
;
Hsieh, Chu-Han
;
Tsai, Chung-Yu
;
Wang, Ting-Hsuan
We report the alkylation and arylation cross-coupling of aryl ethers based on C-O bond activation using a nickel catalyst and organoaluminum reagents. Ni(cod)(2) in combination with 1,2-bis(dicyclohexylphosphino)ethane ligand in toluene solution at 130 degrees C are the best conditions. The naphthyl ether or methoxy pyridine derivatives are suitable substrates for alkylation and arylation reaction with a wider scope of aluminum reagents in good yields. Computational analysis on the pyridine substrate is provided to help delineate the mechanistic pathway and demonstrate the important aspects of the cooperative interaction bimetallic catalysis. First, the coordination of AlMe3 to the O atom of pyridine is essential for C-O activation. Second, the beta-H transfer from methoxy to pyridine could be discouraged through the use of bidentate phosphine as a ligand. Finally, excess AlMe3 reagent is critical for facilitating a reductive elimination process.
Selective C(8)-H Activation of Imidazopyridines Mediated by Cooperative Nickel-Aluminum Catalysis
(2016-09-01)
Liu, Cheng-Yuan
;
Chen, Ying-Ho
;
Chen, Chih-Hao
;
Yu, Ming-Shiuan
;
Tsai, Fu-Yu
A catalytic paradigm is described featuring a synergistic interaction between nickel, aluminum and different ligands to impart a rather remote C-H alkenylation of imidazo[1,5-a] pyridines at the C-8 position without the necessity of installing a directing group. The scope of the direct C-H activation reactions of various 5-aryl- and 3-arylimidazopyridines is established using different sterically hindered alkynes.