One‐Pot Wittig Reactions in Aqueous Media: A Rapid and Environmentally Benign Synthesis of α,β‐Unsaturated Carboxylic Esters and Nitriles
作者:Jinlong Wu、Congyong Yue
DOI:10.1080/00397910600773684
日期:2006.10
Abstract One‐pot Wittigreactions of ethyl bromoacetate and bromoacetonitrile with aldehydes in the presence of PPh3 and LiOH in water were investigated. Most of the olefination reactions completed within 5–120 min in refluxing water containing 1.2 M LiCl to afford the olefin products in 71–97% yields with 100:0–55:45 ratios of E:Z isomers.
Synthetic studies related to diketopyrrolopyrrole (DPP) pigments. Part 1: The search for alkenyl-DPPs. Unsaturated nitriles in standard DPP syntheses: a novel cyclopenta[c]pyrrolone chromophore
methacrylonitrile give 4,4-bis(cyanoethyl) and 4,4-bis(2-cyanopropyl) derivatives, and cinnamonitrile, substituted cinnamonitriles and 3-(2-thienyl)acrylonitrile give deep red 3-aryl-5-cyano-4-hydroxy-2H-cyclopenta[c]pyrrol-1-ones. These ambident nucleophiles may undergo N- and either O- or C-alkylation according to the alkylating agent used.
4,5-二氢-5-氧代-2-苯基吡咯-3-羧酸乙酯的阴离子与丙烯腈和各种二烯的狄尔斯-阿尔德加合物的反应很少产生预期的DPP衍生物。与环己-3-烯腈的反应提供了一个值得注意的例外:所生成的环己烯基-DPP的热解产生了丁二烯和不纯的3-乙烯基-6-苯基-DPP,后者是热不稳定的。当上述阴离子与α,β-不饱和腈反应时,迈克尔加成反应占主导:丙烯腈和甲基丙烯腈产生4,4-双(氰基乙基)和4,4-双(2-氰基丙基)衍生物,以及肉桂腈,取代的肉桂腈和3-( 2-噻吩基)丙烯腈得到深红色的3-芳基-5-氰基-4-羟基-2 H-环戊[ c ]吡咯-1-酮。这些亲核试剂两可可经历Ñ-和根据所用烷基化剂的O-或C-烷基化。
Highly Z-selective synthesis of α,β-unsaturated nitriles using the Horner–Wadsworth–Emmons reaction
作者:Kaori Ando、Miho Okumura、Shigeo Nagaya
DOI:10.1016/j.tetlet.2013.02.020
日期:2013.4
A new HWE reagent, (o-tBuC6H4O)2P(O)CH2CN (2e), reacts with various types of aldehydes to give Z-α,β-unsaturatednitriles with 86% to >99% Z-selectivity. Especially, the reaction of 2e with bulkier aldehydes, both aromatic and aliphatic, gave the Z-olefins with extremely high selectivity. The combination of t-BuOK and 18-crown-6 (1 equiv) is the base of choice for aromatic aldehydes and t-BuOK is generally
一种新的HWE试剂(o - t BuC 6 H 4 O)2 P(O)CH 2 CN(2e)与各种类型的醛反应生成Z -α,β-不饱和腈,含量为86%至> 99%Z选择性。特别地,2e与较大的醛(芳族和脂族)的反应使Z-烯烃具有极高的选择性。的组合吨-BuOK和18-冠-6(1当量)是选择用于芳族醛的基极和吨-BuOK通常是选择用于脂族醛的碱。
Knoevenagel, wittig and wittig-horner reactions in the presence of magnesium oxide or zinc oxide.
Knoevenagel and Wittig-Horner reactions in solid-liquid systems, with magnesium oxide or zinc oxide as catalyst. When Wittig-Horner reaction is competitive with Knoevenagel reaction, the catalyst can be modified to give a highly selective reaction ; the addition of dimethylsulfoxide on MgO or heiamethylphosphoric triamide on ZnO gives more efficient catalysts for the Wittig-Homer reaction. The addition of a small
bearing cyanomethyl, acetamide, and N,N-dimethylacetamide groups were examined for Wittig type reactions. All three reacted to give the corresponding olefins. The reaction of the cyanomethyl reagent with aldehydes gave α,β-unsaturated cyanides with high Z-selectivity in the case of aliphatic aldehydes (Z:E=94:6 to 99:1). On the other hand, the reactions of the two amide reagents with aldehydes yielded