Rh(III) -catalyzed C-H activation: a versatile route towards various polycyclic pyridinium salts
Ching-Zong Luo1, Parthasarathy Gandeepan, Jayachandran Jayakumar
1Department of Chemistry, National Tsing Hua University, Hsinchu, 30013 (Taiwan), Fax: (+86) 3572-4698.
Abstract:
An efficient and convenient method for the synthesis of highly substituted polycyclic pyridinium salts from the reaction of various 2-aryl-pyridines and 2-aryl-sp(2) -nitrogen-atom-containing heterocycles with alkynes through rhodium(III)-catalyzed CH activation and annulation under an O2 atmosphere is described. A possible mechanism that involves the chelation-assisted CH activation of the 2-aryl-pyridine substrate, insertion of the alkyne, and reductive elimination is proposed. This mechanism was supported by the isolation of a five-membered rhodacycle (I'). In addition, kinetic isotope studies were performed to understand the intimate reaction mechanism.
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