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Abstract :
: An example of using readily available, less reactive aryl bromides as arylating reagents in the Pd(II)-catalyzed intermolecular arylation of unactivated C(sp(3))-H bonds is described. This reaction was promoted by a crucial 8-aminoquinolinyl directing group and a K2CO3 base, enabling regiospecific installation of an aryl scaffold at the beta-position of carboxamides. A mechanistic study by DFT calculations reveals a C(sp(3))-H activation-led pathway featuring the oxidative addition as the highest energy transition state.
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GB/T 7714 | Wei, Yu , Tang, Huarong , Cong, Xuefeng et al. Pd(II)-Catalyzed Intermolecular Arylation of Unactivated C(sp(3))-H Bonds with Aryl Bromides Enabled by 8-Aminoquinoline Auxiliary [J]. | ORGANIC LETTERS , 2014 , 16 (8) : 2248-2251 . |
MLA | Wei, Yu et al. "Pd(II)-Catalyzed Intermolecular Arylation of Unactivated C(sp(3))-H Bonds with Aryl Bromides Enabled by 8-Aminoquinoline Auxiliary" . | ORGANIC LETTERS 16 . 8 (2014) : 2248-2251 . |
APA | Wei, Yu , Tang, Huarong , Cong, Xuefeng , Rao, Bin , Wu, Chao , Zeng, Xiaoming . Pd(II)-Catalyzed Intermolecular Arylation of Unactivated C(sp(3))-H Bonds with Aryl Bromides Enabled by 8-Aminoquinoline Auxiliary . | ORGANIC LETTERS , 2014 , 16 (8) , 2248-2251 . |
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Abstract :
We report here that mono-N-protected amino acids (MPAAs), an important environmentally compatible structural motif, enable acceleration of Pd(II)-catalyzed dehydrogenative Heck reactions between pyridines and electron-deficient arenes with simple alkenes, leading to diversely functionalized C3- or meta-selective alkenylated pyridines and benzenes via non-chelate-assisted C-H activation. A comprehensive theoretical study by DFT calculations discloses that the amino scaffold of the MPAA ligand facilely converts to an X-type ligand by an initial N-H activation, resulting in a relatively low activation barrier for the C-H cleavage of pyridine. Then a property reversal of the amino group from X-type to L-type ligand allows the alkene substitution to take place smoothly, while the carboxyl group enables the formation of an intramolecular hydrogen bond, significantly decreasing the activation barrier for the carbopalladation. The results of calculations and the kinetic isotopic effect measurement support a rate-limiting C H activation by a mechanism involving a concerted metalation/deprotonation pathway, with an endothermicity of 31.0 kcal/mol in the process.
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GB/T 7714 | Cong, Xuefeng , Tang, Huarong , Wu, Chao et al. Role of Mono-N-protected Amino Acid Ligands in Palladium(II)-Catalyzed Dehydrogenative Heck Reactions of Electron-Deficient (Hetero)arenes: Experimental and Computational Studies [J]. | ORGANOMETALLICS , 2013 , 32 (21) : 6565-6575 . |
MLA | Cong, Xuefeng et al. "Role of Mono-N-protected Amino Acid Ligands in Palladium(II)-Catalyzed Dehydrogenative Heck Reactions of Electron-Deficient (Hetero)arenes: Experimental and Computational Studies" . | ORGANOMETALLICS 32 . 21 (2013) : 6565-6575 . |
APA | Cong, Xuefeng , Tang, Huarong , Wu, Chao , Zeng, Homing . Role of Mono-N-protected Amino Acid Ligands in Palladium(II)-Catalyzed Dehydrogenative Heck Reactions of Electron-Deficient (Hetero)arenes: Experimental and Computational Studies . | ORGANOMETALLICS , 2013 , 32 (21) , 6565-6575 . |
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Abstract :
The exchange coupling energy for two magnetized monolayers embedded symmetrically in a metal and polarized in an arbitrary direction has been investigated in contact interaction approximation. Since the model can be solved exactly in particular for-free-electron case, the coupling energy contributed from both extended state electrons and bound state electrons is calculated rigorously. For weak interaction, it is found that the leading term in the power-series expansion of density of states can give a correct coupling energy compared with rigorous one while extended state electrons give a much larger coupling energy. Furthermore, the relevant problems such as phase shift, 90 degrees coupling and lattice effects have been discussed; an asymptotic expression of the interlayer coupling has been derived in a different way and used to calculate the exchange energy between magnetic layers in copper with Fermi surface obtained from de Haas-van Alphen effect.
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GB/T 7714 | Wang, SF , Wang, ZC , Zou, SC . Exchange coupling between two magnetized layers in a metal [J]. | ACTA PHYSICA SINICA-OVERSEAS EDITION , 1998 , 7 (7) : 529-540 . |
MLA | Wang, SF et al. "Exchange coupling between two magnetized layers in a metal" . | ACTA PHYSICA SINICA-OVERSEAS EDITION 7 . 7 (1998) : 529-540 . |
APA | Wang, SF , Wang, ZC , Zou, SC . Exchange coupling between two magnetized layers in a metal . | ACTA PHYSICA SINICA-OVERSEAS EDITION , 1998 , 7 (7) , 529-540 . |
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