通过在碱性条件下用戊烯(如β-萘酚,α-萘酚和取代酚)处理硝基烯烃的Morita-Baylis-Hillman乙酸酯,已开发出一种涉及S N 2'反应和分子内氧杂-Michael加成的级联过程。在大多数情况下,苯并呋喃类产品以单一的区域异构体形式形成,收率好至极佳。该方法已成功地用于抗真菌剂异戊呋喃的全合成。
An Efficient Friedel-Crafts/Oxa-Michael/Aromatic Annulation: Rapid Access to Substituted Naphtho[2,1-<i>b</i>]furan, Naphtho[1,2-<i>b</i>]furan, and Benzofuran Derivatives
naphthofurans and benzofurans are easily accessible by treatment of naphthols/substituted phenols with nitroallylicacetates through a substitution–elimination process promoted by cesium carbonate. Reactions between naphthols and aromatic/heteroaromatic‐substituted nitroallylicacetates gave the desired functionalized naphthofurans in high to excellent chemical yields (14–97 %). On the other hand, treatment of
通过碳酸铯促进的取代-消除过程,用硝基烯丙基乙酸酯处理萘酚/取代的苯酚很容易获得取代的萘呋喃和苯并呋喃。萘酚与芳族/杂芳族取代的硝基烯丙基乙酸酯之间的反应以高至极好的化学收率(14-97%)提供了所需的官能化萘呋喃。另一方面,用各种硝基烯丙基乙酸酯处理苯酚衍生物(即3-二甲氨基,3-甲氧基和3,5-二甲氧基苯酚)可得到相应的苯并呋喃,其化学收率中等至良好(24-91%)。该反应通过有趣的Friedel-Crafts S N 2'过程进行,然后进行分子内的氧杂-Michael环化和随后的芳构化。对数图(k/ ķ ħ)针对哈米特常数σ p表明良好的线性具有正ρ值,表明初始的Friedel-Crafts型S Ñ 2'处理过程构成的速率决定步骤。该方法已被用于以邻苯二酚和间苯三酚为亲核伴侣的各种新颖的C 2和C 3对称的双呋喃和三呋喃的合成。当使用烷基取代的硝基烯丙基乙酸酯体系时,反应性降低。这可能与这些底物的亲电子特性降低有关。
Regiospecific synthesis of arenofurans via cascade reactions of arenols with Morita–Baylis–Hillman acetates of nitroalkenes and total synthesis of isoparvifuran
作者:Tarun Kumar、Shaikh M. Mobin、Irishi N.N. Namboothiri
DOI:10.1016/j.tet.2013.04.023
日期:2013.6
A cascade process involving an SN2′ reaction and an intramolecular oxa-Michael addition has been developed by treating Morita–Baylis–Hillman acetates of nitroalkenes with arenols, such as β-naphthols, α-naphthols, and substituted phenols under basic conditions. The products, arenofurans, are formed as single regioisomers in good to excellent yield in most cases. The methodology has been successfully
通过在碱性条件下用戊烯(如β-萘酚,α-萘酚和取代酚)处理硝基烯烃的Morita-Baylis-Hillman乙酸酯,已开发出一种涉及S N 2'反应和分子内氧杂-Michael加成的级联过程。在大多数情况下,苯并呋喃类产品以单一的区域异构体形式形成,收率好至极佳。该方法已成功地用于抗真菌剂异戊呋喃的全合成。