关于磷鎓叶立德的水解和醇解反应的先前工作在其目前公认的机理的背景下进行了总结和综述。与叶立德水解以及盐和叶立德醇解有关的一些实验事实表明与这些机理相冲突。特别是,我们证明了水和醇的p K a值在有机介质中过高,无法引起叶立德的质子化。因此,我们建议水合或醇O-H键在叶立德P = C键上协同加成。为了支持这一点,我们提供了NMR光谱证据,表明不需要氢氧化hydroxide参与的叶立德和醇之间的平衡。我们报告第一个P-烷氧基磷烷可以通过NMR光谱进行表征,而无需在NMR时标上进行交换。二维NMR光谱技术已首次应用于对P-烷氧基磷光烷的表征。
Unequivocal Experimental Evidence for a Unified Lithium Salt-Free Wittig Reaction Mechanism for All Phosphonium Ylide Types: Reactions with β-Heteroatom-Substituted Aldehydes Are Consistently Selective for<i>cis</i>-Oxaphosphetane-Derived Products
作者:Peter A. Byrne、Declan G. Gilheany
DOI:10.1021/ja300943z
日期:2012.6.6
erythro-β-hydroxyphosphonium salt) in reactions involving aldehydes bearing heteroatom substituents in the β-position. The effect operates with both benzaldehydes and aliphatic aldehydes and is shown not to operate in the absence of the heteroatom substituent on the aldehyde. The discovery of an effect that is common to reactions of all ylide types strongly argues for the operation of a common mechanism in all Li
Titanium (IV) catalysis in the reduction of phosphine oxides
作者:Tristan Coumbe、Nicholas J. Lawrence、Faiz Muhammad
DOI:10.1016/s0040-4039(00)75855-2
日期:1994.1
triethoxysilane, or more conveniently polymethylhydrosiloxane, and catalytic titanium (IV) isopropoxide and provides a system for the efficient one-pot generation of phosphonium salts; the reduction occurs with retention of configuration at phosphorus.
Wittig Olefination Using Phosphonium Ion-Pair Reagents Incorporating an Endogenous Base
作者:Anna C. Vetter、Declan G. Gilheany、Kirill Nikitin
DOI:10.1021/acs.orglett.1c00133
日期:2021.2.19
Despite common perception, the use of strong bases in Wittig chemistry is utterly unnecessary: we report a series of novel ion-pair phosphonium carboxylate reagents which are essentially “storable ylides”. These reagents are straightforwardly prepared in excellent yields, and their fluxional nature permits clean olefination of a broad range of aldehydes and even hemiacetals.
Stereospecific Photoredox‐Catalyzed Vinylations to Functionalized Alkenes and C‐Glycosides
作者:Kumar Bhaskar Pal、Ester Maria Di Tommaso、A. Ken Inge、Berit Olofsson
DOI:10.1002/anie.202301368
日期:——
photo-catalyzed, transition-metal-free C−C cross-coupling reaction has been developed with 4-alkyl-dihydropyridines (DHPs) and vinylbenziodoxol(on)es (VBX, VBO) to synthesize di- and trisubstituted alkenes with complete E : Z selectivity. A diastereoselective C-vinylation of glycosides was also developed. Preliminary mechanistic studies indicate a concerted radical coupling pathway.