Carbon Atom Insertion into Pyrroles and Indoles Promoted by Chlorodiazirines
作者:Balu D. Dherange、Patrick Q. Kelly、Jordan P. Liles、Matthew S. Sigman、Mark D. Levin
DOI:10.1021/jacs.1c06287
日期:2021.8.4
calculations supporting a selectivity-determining cyclopropanation step. Computations surprisingly indicate that the stereochemistry of cyclopropanation is of little consequence to the subsequent electrocyclicringopening that forges the pyridine core, due to a compensatory homoaromatic stabilization that counterbalances orbital-controlled torquoselectivity effects. The utility of this skeletal transform is
Direct Observation of Carbene and Diazo Formation from Aryldiazirines by Ultrafast Infrared Spectroscopy
作者:Yunlong Zhang、Gotard Burdzinski、Jacek Kubicki、Matthew S. Platz
DOI:10.1021/ja805922b
日期:2008.12.3
first band is assigned to phenyldiazomethane, and the second is assigned to singlet phenylcarbene. This assignment is consistent with DFT calculations. Diazo band integration reveals that photoisomerization from diazirine to diazo occurs within a few picoseconds of the laser pulse. The majority of carbene produced is also formed instantaneously.
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.