Methylpentanediolborane: Easy Access to New Air- and Chromatography-Stable, Highly Functionalized Vinylboronates
摘要:
Methylpentanediolborane (MPBH) 1 can be prepared easily by reaction of hexyleneglycol with BH3/DMS or B2H6 generated from NaBH4 and I-2. MPBH hydroborates stereo- and regioselectively highly functionalized alkynes, including propargyl bromide and propionaldehyde acetal. MPBH compares favorably with pinacolborane in terms of reactivity. The obtained vinylboronic esters are air- and chromatography-stable.
作者:Paula Dominguez-Molano、Gerard Bru、Oriol Salvado、Ricardo J. Maza、Jorge J. Carbó、Elena Fernández
DOI:10.1039/d1cc05815k
日期:——
Exchange of boryl moieties between alkenylboranes and diboron reagents has been postulated as a stereospecific cross-metathesis pathway with concomitant formation of mixed diboron reagents. DFT calculations propose a mechanism for the stereocontrolled C(sp2)–B/B′–B′ cross-metathesis with both symmetric and non-symmetric diboron reagents.
Mechanistic Studies on the Heck−Mizoroki Cross-Coupling Reaction of a Hindered Vinylboronate Ester as a Key Approach to Developing a Highly Stereoselective Synthesis of a C1−C7 <i>Z</i>,<i>Z</i>,<i>E</i>-Triene Synthon for Viridenomycin
作者:Andrei S. Batsanov、Jonathan P. Knowles、Andrew Whiting
DOI:10.1021/jo0626010
日期:2007.3.1
Mechanistic studies of the Heck−Mizoroki reaction of a vinylboronate ester with electronically different (four-substituted) aryl iodides shows that electron donors accelerate the cross-coupling, demonstrating that the oxidative addition step is not rate determining and that there is development of some degree of positive charge in the rate determining step. These results were used as a basis to allow
The hydroboration of alkynes with bis(pinacolato)diboron (B2pin2) using H2O or untreated H2O as a solvent is a challenging task. This work reports the aqueous N-heterocyclic carbene (NHC)-catalyzed hydroboration of alkynes with B2pin2, in which a wide range of alkynes with different functional groups are tolerated. The proposed NHC active species are formed through a nonclassical strategy in contrast
使用H 2 O或未经处理的H 2 O作为溶剂,用双(频哪醇)二硼(B 2 pin 2 )对炔烃进行硼氢化是一项具有挑战性的任务。这项工作报道了水性 N-杂环卡宾 (NHC) 催化的炔烃与 B 2 pin 2的硼氢化反应,其中可以耐受多种具有不同官能团的炔烃。所提出的 NHC 活性物质是通过非经典策略形成的,这与涉及在碱存在下咪唑鎓盐去质子化的传统方法相反。所提出的 NHC 催化硼氢化过程可以使用未经处理的 H 2进行在没有外源碱的情况下,在空气气氛下以 O 作为溶剂。包括控制实验、傅里叶变换红外光谱和密度泛函理论计算在内的机理研究表明,原位产生的 NHC是真正的活性物质。此外,还分离并充分表征了原位生成的二硼-NHC加合物,该加合物充当NHC的储存库,对于NHC在水介质中的稳定性至关重要。
4,4,6-Trimethyl-2-vinyl-1,3,2-dioxaborinane: a superior 2-carbon building block for vinylboronate Heck couplings
作者:Andrew P. Lightfoot、Graham Maw、Carl Thirsk、Steven J.R. Twiddle、Andrew Whiting
DOI:10.1016/j.tetlet.2003.08.032
日期:2003.10
4,4,6-Trimethyl-2-vinyl-1,3,2-dioxaborinane is a superior reagent in terms of stability and reactivity in comparison to the vinylboronate pinacol ester, giving improved selectivity for Heck versus Suzuki coupling with both aryl iodides and bromides, and being easier to prepare and store. (C) 2003 Elsevier Ltd. All rights reserved.
Improved dimethylzinc-promoted vinylation of nitrones with vinylboronic esters
作者:Nageswaran PraveenGanesh、Cristina de Candia、Antony Memboeuf、György Lendvay、Yves Gimbert、Pierre Y. Chavant
DOI:10.1016/j.jorganchem.2010.07.009
日期:2010.10
Vinylboronic esters derived from 4,4,6-trimethyl-[1,3,2]dioxaborinane react with nitrones in the presence of dimethylzinc; nucleophilic addition of the vinyl group onto nitrones produces N-allylic hydroxylamines in fair yields. The sequence is compatible with various functional groups on the vinylic moiety. The mechanism and kinetic aspects are discussed on the basis of DFT calculations. (C) 2010 Elsevier B. V. All rights reserved.