已经通过吡啶-2-硫代氧羰基(PTOC)竞争动力学方法在单个浓度点上确定了壬基从20种N-杂环卡宾和硼烷(NHC-硼烷)的络合物中提取氢的速率常数。速率常数的范围是从<1×10 4到8×10 4 M -1 s -1。它们几乎不依赖于卡宾核的电子性质,但是存在随着卡宾N取代基尺寸的减小而增加速率常数的趋势。已经鉴定出两种有希望的具有小的N取代基的新试剂(R = Me)。
已经通过吡啶-2-硫代氧羰基(PTOC)竞争动力学方法在单个浓度点上确定了壬基从20种N-杂环卡宾和硼烷(NHC-硼烷)的络合物中提取氢的速率常数。速率常数的范围是从<1×10 4到8×10 4 M -1 s -1。它们几乎不依赖于卡宾核的电子性质,但是存在随着卡宾N取代基尺寸的减小而增加速率常数的趋势。已经鉴定出两种有希望的具有小的N取代基的新试剂(R = Me)。
In this Communication, we report an unprecedented β‐regioselective radical inverse hydroboration (compared with ionic hydroboration) of α,β‐unsaturated amides with NHC‐BH3 enabled by photoredox catalysis. Density functional theory (DFT) calculations show that the unique photoredox cycle is a key factor to control the β‐regioselective radical hydroboration, by lowering the energy barrier in comparison
A versatile new method for the preparation of NHC boranes starting from two stable, readily available reactants―an heterocyclic salt and an amine or phosphine−borane―is reported. It uses a Lewis base exchange at boron and provides easy access to new NHC boranes, in particular B-substituted borane ones.
Ring Lithiation and Functionalization of Imidazol-2-ylidene-boranes
作者:Andrey Solovyev、Emmanuel Lacôte、Dennis P. Curran
DOI:10.1021/ol202516c
日期:2011.11.18
N,N′-Dialkyl and N,N′-diaryl imidazol-2-ylidene-boranes and trifluoroboranes are rapidly lithiated at C4 of the imidazole ring, and the resulting intermediates have been quenched with an assortment of electrophiles to provide ring-functionalized imidazol-2-ylidene-boranes. Further deprotonation and functionalization of C5 have been demonstrated. Deboronation of the products by treatment with triflic