Application of Chitosan/Poly(vinyl alcohol) Stabilized Copper Film Materials for the Borylation of α, β-Unsaturated Ketones, Morita-Baylis-Hillman Alcohols and Esters in Aqueous Phase
A chitosan/poly(vinylalcohol)-stabilized copper nanoparticle (CP@Cu NPs) was used as a heterogeneous catalyst for the borylation of α, β-unsaturatedketones, MBH alcohols, and MBH esters in mild conditions. This catalyst not only demonstrated remarkable efficiency in synthesizing organoboron compounds but also still maintained excellent reactivity and stability even after seven recycled uses of the
Synthesis of Monoprotected 2-Alkylidene-1,3-propanediols by an Unusual SN2' Mitsunobu Reaction
作者:Andre B. Charette、Bernard Cote、Sylvie Monroc、Sylvie Prescott
DOI:10.1021/jo00126a046
日期:1995.10
A simple and efficient route to monoprotected (E)- and (Z)-2-alkylidene-1,3-propanediols is described. The key step involves an unusual regio- and stereoselective S(N)2' Mitsunobu reaction of substituted 3-hydroxy-2-methylenealkanoates which are readily available from a Baylis-Hillman reaction between methyl acrylate and an aldehyde. These allylic alcohols, when treated with PPh(3), a carboxylic acid, and DEAD in THF at temperatures ranging from -40 degrees C to 22 degrees C, produced the corresponding 2-alkylidene-3-hydroxypropanoate derivatives (or (E)-2-(hydroxymethyl)-3-substituted-2-alkenoate derivatives) in >70% with S(N)2':S(N)2 ratio of 22:1 to >50:1. It was found that weak and bulky carboxylic acids and low temperatures favor S(N)2' addition. The reaction conditions were effective for alkyl substituted derivatives, but the addition of Et(3)N to the Mitsunobu conditions was necessary to improve the S(N)2':S(N)2 ratios for the vinyl 19 and phenyl 20 derivatives. The monoprotected (Z)- and (E)-2-alkylidene-1,3-propanediols can be efficiently synthesized by a three-step sequence involving either a transesterification, protection, and DIBAL-H reduction (>80% overall yield) or by the chemoselective reduction, protection, and ester cleavage (67% overall yield).