各种连接的α-硼基乙酸酯的碱性水解提供了未知化合物硼乙酸(BH 2 CH 2 CO 2 H)的第一连接衍生物。用N杂环卡宾,胺和吡啶配体(L)制备了四种一元酸(L-BH 2 CH 2 CO 2 H)和一种二元酸(L-BH (CH 2 CO 2 H)2)。稳定的酸通过X射线晶体学和酸度常数(p K a)测量来表征。它们是所有已知羧酸中酸度最低的。反过来,它们的共轭碱是所有羧酸盐中最强的。
Hydroboration of Arynes with N-Heterocyclic Carbene Boranes
作者:Tsuyoshi Taniguchi、Dennis P. Curran
DOI:10.1002/anie.201408345
日期:2014.11.24
Arynes were generated in situ from ortho‐silyl aryl triflates and fluoride ions in the presence of stable N‐heterocyclic carbeneboranes (NHCBH3). Spontaneous hydroboration ensued to provide stable B‐aryl‐substituted NHC‐boranes (NHCBH2Ar). The reaction shows good scope in terms of both the NHC‐borane and aryne components and provides direct access to mono‐ and disubstituted NHC‐boranes. The formation
Insertion of Reactive Rhodium Carbenes into Boron–Hydrogen Bonds of Stable N-Heterocyclic Carbene Boranes
作者:Xiben Li、Dennis P. Curran
DOI:10.1021/ja4056245
日期:2013.8.14
available rhodium(II) salts catalyze reactions between NHC-boranes (NHC-BH3) and diazocarbonyl compounds (N2CRCOR'). Stable α-NHC-boryl carbonyl compounds (NHC-BH2-CHRCOR') are isolated in good yields. The reaction is a reliable way to make boron-carbon bonds with good tolerance for variation in both the NHC-borane and diazocarbonyl components. It presumably occurs by insertion of a transient rhodium carbene
N-Heterocyclic Carbene Boryl Iodides Catalyze Insertion Reactions of N-Heterocyclic Carbene Boranes and Diazoesters
作者:Thomas H. Allen、Takuji Kawamoto、Sean Gardner、Steven J. Geib、Dennis P. Curran
DOI:10.1021/acs.orglett.7b01777
日期:2017.7.7
Boron–hydrogen bond insertion reactions of N-heterocycliccarbene (NHC) boranes and diazoesters can be catalyzed by NHC-boryl iodides and produce stable α-NHC-boryl esters. The conditions of the reaction resemble the previous rhodium-catalyzed transformations (only the catalyst is different); however, the mechanisms of the two reactions are probably very different. The new boryl iodide catalyzed method is adept
Facile Synthesis of α-N-Heterocyclic Carbene-Boryl Ketones from N-Heterocyclic Carbene-Boranes and Alkenyl Triflates
作者:Wen Dai、Steven J. Geib、Dennis P. Curran
DOI:10.1021/jacs.9b05547
日期:2019.8.7
experimental evidence supports a radical chain mechanism that involves: (1) addition of an NHC-boryl radical to the alkenyl triflate, (2) fragmentation to give the α-NHC-boryl ketone, SO2 and trifluoromethylradical, and (3) hydrogenabstraction by trifluoromethylradicalfrom the starting NHC-borane to return the NHC-boryl radical along with trifluoromethane. Reactions (1) and (3) are both new and evidently
Dynamic Behavior of N-Heterocyclic Carbene Boranes: Boron–Carbene Bonds in <i>B</i>,<i>B</i>-Disubstituted <i>N</i>,<i>N</i>-Dimethylimidazol-2-ylidene Boranes Have Substantial Rotation Barriers
作者:Krishnan Damodaran、Xiben Li、Xiangcheng Pan、Dennis P. Curran
DOI:10.1021/acs.joc.5b00324
日期:2015.5.1
Dynamic NMR spectroscopy has been used to measure rotation barriers hi five B,B-disubstituted 1,3-dimethylimidaol-2-ylidene boranes. The barriers are attributed to the sp(2)-sp(3) bond between C(1) of the N-heterocyclic carbene ring and the boron atom: Bonds to boron atoms bearing a thexyl (1,1,2-trimethylpropyl) group Show especially high barriers, ranging from 75-86 kJ mol(-1). 2-Isopropyl-1,3,5-trimethylbenzene is used as a comparable to help understand the nature and magnitude of the barriers.