In Situ Alcohol Oxidation-Wittig Reactions Using Non-stabilised Phosphoranes
作者:Leonie Blackburn、Chengxin Pei、Richard J. K. Taylor
DOI:10.1055/s-2002-19755
日期:——
New procedures have been developed which allow the in situ alcohol oxidation-Wittig reaction using manganese dioxide to be employed with non-stabilised phosphoranes and stabilised phosphonate anions. A number of examples are described utilising benzylic, allylic and propargylic alcohols.
Direct oxidation of 2,4-alkadienoic esters with seleniumdioxide gave 5-alkyl-2-furancarboxylic esters along with 5-alkyl-2-selenophenecarboxylic esters. Ethyl 5-methylfurancarboxylate was converted to 5-hydroxymethyl-2-furancarbaldehyde, a component of honey, via ethyl 5-bromomethyl-2-furancarboxylate (5) in good yield. The compound 5 was converted to (5-ethoxycarbonyl-2-furyl)methyl dimethyldithiocarbamate
by ethyl (2E)-4-hydroxy-2-alkenoates. Ethyl 2-cycloalkylidene-2-phenylsulfinylacetates were found to be more susceptible to pyrolysis. The enoate esters (2) undergo migration of their carbon-carbon double bond and then [2,3]sigmatropic rearrangement to benzene-sulfenate esters, followed by thermolytic extrusion of a benzenesulfenic acid probably via ethyl (2E)-4-phenyl-sulfinyl-2-alkenoates to afford
A new synthesis of 5-alkyl-2-furancarboxylates and 5-alkyl-2-selenophenecarboxylates via the direct oxidation of 2,4-alkadienoic esters with selenium dioxide is described.
One-Pot O<sub>2</sub>-Oxidation and the Horner–Wadsworth–Emmons Reaction of Primary Alcohols for the Synthesis of (<i>Z</i>)-α,β-Unsaturated Esters
作者:Kaori Ando、Chika Takaba、Masahiro Kodama
DOI:10.1021/acs.joc.2c00763
日期:2022.8.5
primary alcohols giving Z-α,β-unsaturated esters 3. TEMPO-(CuCl or CuBr2)-(2,2′-bipyridine) (1:1:1) catalyzed O2 oxidation of primary alcohols in the presence of Z-selective Horner–Wadsworth–Emmons reagent 1b and K3PO4 or NaH gave 3 with Z/E = 84:16 to 96:4 in high yields. A stepwise reaction was also developed. After TEMPO-CuBr2-(2,2′-bipyridine)-K3PO4 (1:1:1:1) catalyzed O2 oxidation of alcohols in MeCN
我们开发了伯醇的一锅氧化/烯化程序,得到Z -α,β-不饱和酯3。TEMPO-(CuCl 或 CuBr 2 )-(2,2'-联吡啶) (1:1:1) 在Z选择性 Horner-Wadsworth-Emmons 试剂1b和 K 3 PO 4存在下催化伯醇的 O 2氧化或 NaH以Z / E = 84:16 至 96:4 的高产率得到3 。还开发了逐步反应。TEMPO-CuBr 2 -(2,2'-联吡啶)-K 3 PO 4 (1:1:1:1)催化O 2后在 MeCN 中氧化醇,所得混合物在 -78 °C 至 0 °C 下用1b和t -BuOK 的 THF 溶液处理,得到具有更高选择性的3 ( Z / E = 91:9 至 99:1)。