Jian-Biao Liu, Xiehuang Sheng, Chuanzhi Sun
Mar 10, 2016
Citations
0
Influential Citations
34
Citations
Journal
ACS Catalysis
Abstract
The origin of site selectivity of quinoline N-oxide substrate in Ir(III)-catalyzed amidation with tosyl azide was investigated computationally. The reaction proceeds exclusively at the C8 position, instead of the C2 position, which has been reported previously in many other reactions. C2-Amidation is kinetically impossible under the reaction condition according to our calculations, with high apparent activation energy up to 51.1 kcal/mol. The high energetic span is caused by the deep-lying 5-membered amido insertion intermediate, in which a strong stabilization effect was observed due to nN → π*C═N delocalization. For C8-amidation, however, the 6-membered counterpart is relatively unstable, making the activation energy only about half the value of C2-amidation. Meanwhile, denitrogenation is found to be turnover-limiting in the reaction. The oxidation state changes of the Ir center during the stepwise C–N bond formation were investigated, and a considerably higher effective oxidation state was found in the...