Journal of the American Chemical Society p. 7744 - 7751 (1986)
Update date:2022-08-04
Topics:
Bernasconi, Claude F.
Kanavarioti, Anastassia
The title reaction leads to the formation of the zwitterionic Michael adduct T+/- (PhCH(R2NH+)C(COCH3)2-) which is in rapid acid-base equilibrium with its anionic form T-(PhCH(R2N)C(COCH3)2-).Rate (k1, k-1) and equilibrium constants (K1) for nucleophilic addition and the pKa of the T+/- adducts were determined in 50percent Me2SO - 50percent water at 20 deg C.From an interpolation of the rate constants to K1 = 1 an intrinsic rate constant, log k0 = 0.3, was determined.This value deviates negatively by approximately 2.5 log units from a correlation of log k0 for amine addition to five olefins of the type PhCH=CXY, with log k0 for the deprotonation of the corresponding carbon acids CH2XY.Two major factors are believed to contribute to this depressed intrinsic rate constant or enhanced intrinsic barrier: (1) steric inhibition of resonance in T+/- with the steric effect developing ahead of C-N bond formation (this conclusion is supported by an X-ray crystallographic study of p-methoxybenzylideneacetylacetone which showes that steric hindrance to optimal ?-overlap in the adduct T+/- is already present in the substrate); (2) intramolecular hydrogen bonding in T+/-, which is inferred from abnormally high pKa values and whose development lags behind C-N bond formation.These effects are shown to be manifestation of the Principle of Nonperfect Synchronization.
View MoreZouping Mingxing Chemical Co.,Ltd.
website:http://www.zoutong.com.cn
Contact:86-543-2240068 2240067
Address:428 Daixi Third Road Zouping County Shandong Province China
Zipont chem(wuhan)Tech co.,Ltd
Contact:+86-27-87587198
Address:wuhan
Contact:+86 18616952870
Address:Area
website:http://www.guarson.com
Contact:+86-523-88059600,+86-13805268803
Address:Room B1006,Yafang Building,Jiangyan Avenue,Jiangyan District, Taizhou City,Jiangsu,China
Beijing Apis Biotechnology Co., Ltd.
Contact:86-010-67856775-8551
Address:NO.4PUHUANGYU ROAD,FENTAI DISTRICT, BEIJING, CHINA
Doi:10.1002/chem.201501823
(2015)Doi:10.1039/c1gc15701a
(2011)Doi:10.1002/jhet.5570450420
(2008)Doi:10.1039/b802833h
(2008)Doi:10.1002/anie.201811032
(2019)Doi:10.1039/b800217g
(2008)