p-Substituted 1-chloro-3-phenyldiazirines (5), the putative intermediates of the reaction of N,N,N'-trichlorobenzamidines (10) with excess of bromide ions, react further to afford mixtures of 3-bromo- (4) and 3-chloro-3-phenyldiazirines (6). The 6:4 ratios inversely correlate with the Hammett σp and σp+ constants of the p-substituents. The formation of 4, proposed to proceed by anti-SN2‘ mechanism
对位取代的1-氯-3-苯基重氮(5)是N,N,N'-三氯苯甲m(10)与过量溴离子反应的推定中间体,进一步反应生成3-溴-(4)和3-氯-3-苯基重氮(6)。该6:4的比率用哈米特σ负相关p和σ p +的常数p -取代基。4的形成,建议通过反S N进行2'机理主要是吸电子的p-取代基。化合物6是具有给电子性p取代基的主要产物,它可以由5通过极性过渡结构12进行氯的[1,3]-σ位移而从5中产生。气相DFT(B3LYP / 6-31 + G *)对这两种机理的研究结果与实验一致。
Hammett Analysis of a Family of Carbene−Carbene Complex Equilibria
作者:Lei Wang、Robert A. Moss、Jack Thompson、Karsten Krogh-Jespersen
DOI:10.1021/ol200083a
日期:2011.3.4
p-X-substituted phenylchlorocarbenes (X = NO2, CF3, Cl, H, Me, and MeO) form π-type complexes with trimethoxybenzene in pentane. The carbenes and complexes are in equilibrium, and logarithms of the measured equilibrium constants are well correlated by Hammett σp constants with ρ = 2.48. The carbene complexes are characterized by UV−vis spectroscopy, and computational analysis is afforded by DFT calculations
p -X取代的苯基氯卡宾(X = NO 2,CF 3,Cl,H,Me和MeO)与戊烷中的三甲氧基苯形成π型络合物。卡宾和配合物处于平衡状态,测得的平衡常数的对数与Hammettσp常数(ρ= 2.48)具有很好的相关性。卡宾配合物的特征在于紫外可见光谱,DFT计算提供了计算分析。
Hammett analysis of absolute carbene addition rate constants
Absoluterateconstants were determined for the additions of 5 5-X-substituted ArCCl (X=CF3, Cl, H, CH3, CH3O) to tetramethylethylene, trimethylethylene, trans-pentene, and 1-hexene; good Hammett correlations were obtained with ϱ = +1.4 – 1.6.
reactions of phenylchlorocarbene and related carbenes with alkenes are summarized and systematized. The experiments described provide the basis for a detailed examination of carbenic reactivity-selectivity principles. The results of studies on the influence of temperature on the absolute rate constants for carbene reactions are consistent with the existence of transient carbene/alkene intermediates.
Absence of the ‘p-nitro effect’ in the photochemical reactions of 3-chloro-3-aryldiazirines in the presence of amines
作者:Hideo Tomioka、Fusao Haya、Kunihiko Suzuki
DOI:10.1039/c39880001090
日期:——
Photochemical generation of arylchlorocarbenes from 3-chloro-3-aryldiazirines in the presence of diethylamine afforded N,N,N′,N′-tetraethylbenzylidenediamines regardless of the nature of the aryl substituent.