Expedient synthesis of β,β-disubstituted α-methylenepropionates
摘要:
Baylis-Hillman alcohols are excellent sources of the allylic halides ArCH=CH(CH2X)(CO2R) (X = Br. Cl: R-1= Me, Et. Bu'). The Z double bond isomers are attained in high isomeric purity (> 14: 1. ZIE). The halides are chemo- and regiospecifically transformed into the acrylates (ArCHR2)C(=CH2)(CO2R1) on treatment with Zn(R-2)(2) (R-2 =Me. Et, CH2TMS, CH(2)SiMe(2)Ome) or PrZnBr- in the presence of catalytic amounts of copper(1) salts (0.5-20 mol%) in high yield. (C) 2004 Elsevier Ltd. All rights reserved.
PPh 3 /CCl 4 system has been employed for the stereoselective synthesis of (Z)- and ( £ )-allyl chlorides from Baylis-Hillman adducts in excellent yields.
silica chloride, an eco-friendly heterogeneous catalyst, silica chloride–arenes, and silica chloride–saturated and unsaturatedalcohols as reagent systems are reported. These reactions furnished highly functionalized isomerized Baylis–Hillman derivatives in good yield. The efficiency and necessity of silica chloridecatalyst was compared with thionyl chloride. A plausible mechanism of the reaction is proposed
Mapping the Mechanism of Nickel-Ferrophite Catalysed Methylation of Baylis-Hillman-Derived S<sub>N</sub>2′ Electrophiles
作者:Andrew Novak、Maria José Calhorda、Paulo Jorge Costa、Simon Woodward
DOI:10.1002/ejoc.200801029
日期:2009.2
presence of ferrophite ligands has been investigated computationally and experimentally. The sense and degree of enantioselectivity attained is independent of both the leaving group and the isomeric structure of the initial allylic halide. DFT studies support the selective formation of a limited number of energetically favoured anti and syn π-allyl intermediates. The observed regio- and enantioselectivity
A new and convenient stereoselective synthesis of (Z)-2-(chloromethyl)alk-2-enoates has been achieved from Baylis–Hillman adducts by treatment with PPh3/Cl3CCONH2 at room temperature. The synthesis can proceed under mild and acid-free conditions to form the products in high yields.
Acetyl chloride–ethanol brings about a remarkably efficient conversion of allyl acetates into allyl chlorides
作者:Veejendra K Yadav、K Ganesh Babu
DOI:10.1016/j.tet.2003.09.063
日期:2003.11
AcCl-EtOH transforms primary and secondary allyl acetates into allyl chlorides that retain the olefinic bond in the more stable position. Whereas secondary allyl alcohols also react with almost the same efficacy as the acetates, the reactions of primary allyl alcohols that possess 1,2-disubstituted alkenes are very slow. The products are isolated in high state of purity simply by removal of the volatiles. (C) 2003 Published by Elsevier Ltd.