Rh/bisphosphine−thiourea ligand (ZhaoPhos)‐catalyzed asymmetric hydrogenation of (Z)‐β‐substituted‐β‐boryl‐α,β‐unsaturatedesters was successfully developed, furnishing a variety of chiral β‐borylated carboxylic esters with high yields and excellent enantioselectivities (up to 99% yield and >99% ee). The gram‐scale asymmetric hydrogenation was performed efficiently in the presence of only 0.05 mol%
成功开发了Rh /双膦-硫脲配体(ZhaoPhos)催化的(Z)-β-取代的-β-硼基-α,β-不饱和酯的不对称加氢反应,提供了高收率的多种手性β-硼化羧酸酯优异的对映选择性(高达99%的收率和> 99%的ee)。在仅0.05 mol%(S / C = 2 000)催化剂负载的情况下,可以有效地进行克级不对称氢化反应,并具有完全转化率,99%的收率和99%的ee。此外,加氢产物很容易转化为其他通用的合成中间体,例如(S)-3-羟基-3-苯基丙酸甲酯和(S)-3-(呋喃-2-基)-3-苯基丙酸甲酯。
trans-Selective hydrocyanation of ynoates, ynones and ynoic acids catalyzed by nucleophilic phosphines
the presence of TMSCN and an alcohol additive are catalyzed by nucleophilicphosphines. The trisubstituted E-olefin products of anti-addition of hydrogen cyanide to the alkyne are produced with high regio- and stereoselectivity. The alcohol additive reacts with TMSCN to produce hydrogen cyanide in situ. Ynoic acids undergo the phosphine catalyzed hydrocyanation in the presence of TMSCN under aprotic
In the presence of phosphine catalyst and pinacolborane, ynones undergo 1,2-reduction while ynoates undergotrans-hydroboration. Mechanistic insights into the two competing pathways lay grounds for control of selectivity in these processes.
the selectivity by preventing or reducing the rates of Z- to E-product isomerization. Close reaction monitoring enables isolation of the Z-alkenes with high selectivities. The computational results suggest that the reactions could be highly Z-selective owing to the stereoselective formation of the E-P-hydroxyphosphorane intermediate.
A New Method for Synthesis of Methyl Arylpropiolates by Direct Heck Coupling of Aryl Iodide and Methyl Propiolate in Presence of K<sub>2</sub>CO<sub>3</sub>
作者:Thomas Eckert、Junes Ipaktschi
DOI:10.1080/00397919808005726
日期:1998.1
Abstract A protocol for the efficient direct cross coupling of esters of propiolic acid and of aryl iodides with a Pd(PPh3)2Cl2/copper(I) iodide catalyst system in the presence of K2CO3 has been developed.