碰撞诱导的衍生自邻烷氧基苯甲酸的阴离子的解离提供了一种生产气态烯醇式阴离子的简便方法。最初损失CO(2)后产生的烷氧基苯基阴离子通过邻位异构体所特有的双氢转移机理消除了苯分子,从而形成了烯醇式阴离子。氘标记研究证实,苯损失中转移的两个氢原子起源于烷基链的位置1和2。氢原子从C-1位置的初始转移形成了苯基阴离子和羰基化合物,两者均以离子/中性络合物的形式紧密结合。通过消除中性羰基化合物,该络合物要么直接断裂以生成苯基阴离子,或通过从C-2位置转移氢原子并在此过程中消除苯分子而形成烯酸酯阴离子。与将氘原子从C-2位置转移相比,当氘原子从C-1位置转移时观察到的明显的主要动力学同位素效应表明,第一次转移是速率确定步骤。量子力学计算表明,苯的中性损失是热力学上有利的过程。在所使用的条件下,除了邻位特异性烯醇根阴离子外,仅邻位异构体的光谱在m / z 77处显示出苯基阴离子峰,在苯氧基阴离子中显示出m
Pentafluorophenyl Esters: Highly Chemoselective Ketyl Precursors for the Synthesis of α,α-Dideuterio Alcohols Using SmI<sub>2</sub> and D<sub>2</sub>O as a Deuterium Source
作者:Hengzhao Li、Yuxia Hou、Chengwei Liu、Zemin Lai、Lei Ning、Roman Szostak、Michal Szostak、Jie An
DOI:10.1021/acs.orglett.9b04383
日期:2020.2.21
We report the first highly chemoselective synthesis of α,α-dideuterio alcohols with exquisite incorporation of deuterium (>98% [D2]) using pentafluorophenyl esters as ketyl radical precursors, SmI2 as a mild reducing agent, and D2O as the deuterium source. This system tolerates a variety of functional groups, offering rapid entry to valuable α,α-dideuterated alcohol building blocks. More generally
Low-Energy Collision-Induced Dissociation Mass Spectra of Protonated <i>p</i>-Toluenesulfonamides Derived from Aliphatic Amines
作者:Jason B. Bialecki、Carl S. Weisbecker、Athula B. Attygalle
DOI:10.1007/s13361-014-0865-4
日期:2014.6.1
dominated by the peak at m/z 105 for the incipient phenylethyl cation, which rapidly isomerizes to the remarkably stable methylbenzyl cation. The peaks for the carbocations are weak or absent in the spectra of most of N-alkyl-p-toluenesulfonamides because alkyl carbocations, such as the decyl cation, rearrange to more stable secondary cations by 1,2-hydride and alkyl shifts. The energy freed is not dissipated
The convenient and regioselectivedeuteration of hydroxy groups on vicinal carbons was achieved by the combination of 5% ruthenium on carbon (Ru/C), hydrogen gas and deuterium oxide (D2O).
Ambulation of Incipient Proton during Gas-Phase Dissociation of Protonated Alkyl Dihydrocinnamates
作者:Sihang Xu、Yong Zhang、Ramu Errabelli、Athula B. Attygalle
DOI:10.1021/acs.joc.5b01390
日期:2015.10.2
m/z 167 and 168 ions obtained for di- and tri-deuterio isotopologues showed peak pairs at m/z 134, 135 and 135, 136, at 1:2 and 1:1 intensity ratios, respectively, confirming the benzenium ion intermediate achieves complete randomization before the proton transfer. Additionally, protonated higher esters of alkyl dihydrocinnamates undergo a cleavage of the O–CH2 bond to form an ion/neutral complex,
在气相中活化后,质子化的二氢肉桂酸烷基酯发生醇损失。然而,遵循的机理不是在烷氧基上质子化之后简单地除去链烷醇分子。氘化荷氢二氢肉桂酸甲酯的m / z 166离子质谱图在m / z 133和134处显示两个强度比为1:5的峰,以确认初始质子是可移动的。最初连接到羰基的质子迁移到环并随机化,然后环质子之一随后转移到烷氧基以消除醇。而且,质子化的二氢肉桂酸甲酯经历了一次以上的H / D交换。从m记录的光谱分别获得二氘和三氘同位素的/ z 167和168离子在m / z 134、135和135、136处分别以1:2和1:1的强度比显示峰对,确认苯并鎓离子中间体已完全完成质子转移前的随机化。此外,烷基二氢肉桂酸酯的质子化高级酯会经历O-CH 2键的裂解,形成离子/中性络合物,该离子/中性络合物在活化后会解离生成碳正离子和二氢肉桂酸,或重排生成质子化的二氢肉桂酸和烯烃。通过非特定的质子转移。
Ruthenium Catalyzed Deuterium Labelling of α-Carbon in Primary Alcohol and Primary/Secondary Amine in D<sub>2</sub>O
Primary alcohols and primary/secondary amines are labelled with D atom at α-position regioselectively by means of deuterium oxide and ruthenium catalyst.