A Kinetic Study on Michael-type Reactions of 1-(X-Substituted Phenyl)-2-propyn-1-ones with Amines: Effect of Amine Nature on Reactivity and Mechanism

Bulletin of the Korean chemical society

Eun-Ju Lee¹  So-Jeong Hwang¹  Ik-Hwan Um¹ 

关键词: Michael-type reaction;    Enaminone;    Br©ªnsted-type plot;    Hammett plot;    Yukawa-Tsuno plot;   

DOI  :  

学科分类：化学（综合）

来源: Korean Chemical Society

【 摘 要 】

Second-order rate constants have been measured spectrophotometrically for the Michael-type reaction of 1-(Xsubstituted phenyl)-2-propyn-1-ones (2a-f) with amines in H₂O at 25.0 �? 0.1 ∑C. A linear Br┆nsted-type plot is obtained with �?_nuc = 0.25 �? 0.02, a typical �?_nuc value for reactions which proceed through a stepwise mechanism with attack of amine on the electrophilic center being the rate-determining step. Secondary alicyclic amines are found to be more reactive than isobasic primary amines. The Hammett plot for the reactions of 2a-f with morpholine is not linear, i.e., the substrate with a strong electron-donating group (e.g., 4-MeO) exhibits a negative deviation from the Hammett plot. However, the Yukawa-Tsuno plot for the same reactions exhibits an excellent linear correlation with �? = 0.62 and r = 0.82. Thus, it has been proposed that the nonlinear Hammett plot is not due to a change in the rate-determining step but due to ground-state stabilization through resonance interactions.

【 授权许可】

Unknown