Selective Dehydrocoupling of Phosphines by Lithium Chloride Carbenoids
作者:Sebastian Molitor、Julia Becker、Viktoria H. Gessner
DOI:10.1021/ja509381w
日期:2014.11.5
for the formation of phosphorus-phosphorus bonds through dehydrocoupling of phosphines is presented. The reaction is mediated by electronically stabilized lithium chloride carbenoids and affords a variety of different diphosphines under mild reaction conditions. The developed protocol is simple and highly efficient and allows the isolation of novel functionalized diphosphines in high yields.
structure CH3X (X = CN, COOC2H5, COCH3) afforded an adduct with the solvent molecule, Ar2PCH2X, in significant amount. This photoreaction is acknowledged as a convenient method to prepare functional phosphines.
Steady-state photolysis of an acetonitrile solution of triarylphosphine (Ar3P) was carried out using a xenon lamp. The major products resulting from photolysis under deoxygenated conditions and under air were diaryl(cyanomethyl)phosphine Ar2PCH2CN and triarylphosphine oxide Ar3P=O, respectively. Intrinsically, Ar3P in the excited state undergoes homolytic cleavage of a P–C bond; however, electron transfer to O2 is predominant under air. Reactivity of Ar3P in the excited state is readily controlled by the choice of atmosphere used in the reaction.
dibromodiphosphane (TipPBr)2 (1), a compound not accessible using classic Mg reduction. Surprisingly, when using DipPBr2 (Dip = 2,6-iPr3C6H3) in the PEt3 catalysed reductivecoupling the diphosphene (PDip)2 (2) with a PP double was formed selectively. In benzene solutions (PDip)2 has a half life time of ca. 28 days and can be utilized with NHCs to access NHC-phosphinidene adducts. To show that this
经典的四芳基二膦是通过卤代膦 R 2 PX 的Wurtz 型还原偶联合成的,或者最近通过膦 R 2 PH的脱氢偶联合成。已经报道了脱氢偶联反应的催化变体,但仅限于 R 2 PH 化合物。使用 PEt 3作为催化剂,我们现在表明,TipPBr 2 (Tip = 2,4,6- i Pr 3 C 6 H 2 ) 被选择性偶联以得到二溴二膦 (TipPBr) 2 (1),这是一种无法使用的化合物经典的镁还原。令人惊讶的是,当使用 DipPBr 2 (Dip = 2,6- i Pr3 C 6 H 3 ) 在PEt 3催化的还原偶联中选择性地形成双膦 (PDip) 2 (2) 与 PP 双。在苯溶液 (PDip) 中, 2的半衰期约为。28 天,可与 NHC 一起使用以获取 NHC-膦亚基加合物。为了表明该协议具有更广泛的适用性,我们展示了 Ph 2 PCl 和 Mes 2 PX (X = Cl, Br)
9-BBN and chloride catalyzed reduction of chlorophosphines to phosphines and diphosphines
作者:Iris Elser、Ryan J. Andrews、Douglas W. Stephan
DOI:10.1039/d1cc06439h
日期:——
in the presence of phenylsilane. Aryl-chlorophosphines afford primarily diphosphines (P2R4) while secondary phosphines predominate for alkyl-substituted precursors. Use of the combined catalysts leads to reduced reaction time and temperature, providing a rapid, scalable, and facile protocol for the preparation of diphosphines or secondary phosphines.
市售的路易斯酸、9-BBN 和路易斯碱性 [Et 4 N]Cl 用作在苯基硅烷存在下还原氯膦 R 2 PCl 的催化剂。芳基-氯膦主要提供二膦(P 2 R 4),而仲膦主要提供烷基取代的前体。使用组合催化剂可减少反应时间和温度,为二膦或仲膦的制备提供快速、可扩展且简便的方案。