Aqueous Wittig Reactions of Aldehydes with In Situ Formed Semistabilized Phosphorus Ylides

The Wittig reactions of three semistabilized phosphorus ylides generated in situ from the corresponding phosphonium salts with aldehydes in water without any organic cosolvent were investigated. Most of the olefination reactions completed within between 5 min and 4.5 h in refluxing water containing 1.5 equiv of LiOH and 1.4 M LiCl to afford the products in 65–100% yields. The E∶Z selectivity depended not only on the substituent attached to the benzene ring of the ylides but also on the substituent bound to the aromatic aldehydes. LiCl promotes the aqueous Wittig reactions and suppresses decomposition of the ylide or the corresponding phosphonium salt.     

原位生成的烯丙基磷叶立德与醛的化学反应性研究

介绍了我们小组最近有关原位生成的烯丙基磷叶立德与醛的化学反应性研究结果.在化学计量叔膦作用下,烯丙基碳酸酯或联烯酸酯经原位生成的烯丙基磷叶立德活性中间体,与醛发生高度立体选择性的三组分Wittig烯化反应和vinylogous Wittig烯化反应,该类反应为合成多取代1,3-二烯衍生物提供了简单、高效的新方法;在催化量叔膦作用下,γ-甲基联烯酸酯经烯丙基磷叶立德关键中间体与醛发生多个膦催化的环化反应,为五元、六元含氧杂环化合物的合成提供了原子经济性的方法.通过氘代实验和核磁跟踪等方法,对上述反应机理进行了初步探索.     

Catalytic Wittig Reactions of Semi‐ and Nonstabilized Ylides Enabled by Ylide Tuning

The first examples of catalytic Wittig reactions with semistabilized and nonstabilized ylides are reported. These reactions were enabled by utilization of a masked base, sodium tert‐butyl carbonate, and/or ylide tuning. The acidity of the ylide‐forming proton was tuned by varying the electron density at the phosphorus center in the precatalyst, thus facilitating the use of relatively mild bases. Steric modification of the precatalyst structure resulted in significant enhancement of E selectivity up to >95:5, E/Z.     

(R)-甘油醛缩丙酮的合成及Wittig反应选择性

D-(R)-甘油醛缩丙酮是近年来研究的很多的一种用来合成一些手性药物和具有光学活性的天然产物的重要前体.用Lew is酸无水ZnC l2作为催化脱水剂,D-甘露醇与丙酮缩合反应合成二异亚丙基缩合物,然后用NaIO4氧化断键制备D-(R)-甘油醛缩丙酮,该方法具有产率高、价廉、环境友好等优点.主要研究了(R)-甘油醛缩丙酮W ittig反应的立体选择性.     

微波促进立体选择性合成烯丙酸酯类高碳糖衍生物

在微波促进下, 利用酮糖(1)及糖酸内酯(4)与叶立德(2, Ph₃PCHCOOEt)的Wittig反应, 立体选择性地合成了糖基烯丙酸酯类化合物(3和5), 反应效率显著提高, 反应时间由原来的20 h缩短为10 min; 并且研究了不同反应溶剂对反应立体选择性的影响. 提供了一种高效、 简便合成含有烯丙酸酯类高碳糖衍生物的方法.     

N-乙氧羰基亚甲基苯甲亚氨酸乙酯与脂肪及醛的反应

在氨基酸合成方法研究中,我们已经报道了 N-乙氧羰基亚甲基苯甲亚氨酸乙酯及 N-氰甲基苯甲亚氨酸乙酯的烷基化和 Micheal 加成反应,从而合成了一系列碳链增长的α-氨基酸。本文报道亚氨酸酯(1)与脂肪醛(2)在固液相转移催化条件下的反应。产物经快速柱层析分离,得到一对非对映异构体——顺式和反式(口恶)唑啉酯(3～7),(口恶)唑啉酯在盐酸中水     

Part I: The Development of the Catalytic Wittig Reaction

We have developed the first catalytic (in phosphane) Wittig reaction (CWR). The utilization of an organosilane was pivotal for success as it allowed for the chemoselective reduction of a phosphane oxide. Protocol optimization evaluated the phosphane oxide precatalyst structure, loading, organosilane, temperature, solvent, and base. These studies demonstrated that to maintain viable catalytic performance it was necessary to employ cyclic phosphane oxide precatalysts of type 1 . Initial substrate studies utilized sodium carbonate as a base, and further experimentation identified N,N‐diisopropylethylamine (DIPEA) as a soluble alternative. The use of DIPEA improved the ease of use, broadened the substrate scope, and decreased the precatalyst loading. The optimized protocols were compatible with alkyl, aryl, and heterocyclic (furyl, indolyl, pyridyl, pyrrolyl, and thienyl) aldehydes to produce both di‐ and trisubstituted olefins in moderate‐to‐high yields (60–96 %) by using a precatalyst loading of 4–10 mol %. Kinetic E/Z selectivity was generally 66:34; complete E selectivity for disubstituted α,β‐unsaturated products was achieved through a phosphane‐mediated isomerization event. The CWR was applied to the synthesis of 54 , a known precursor to the anti‐Alzheimer drug donepezil hydrochloride, on a multigram scale (12.2 g, 74 % yield). In addition, to our knowledge, the described CWR is the only transition‐/heavy‐metal‐free catalytic olefination process, excluding proton‐catalyzed elimination reactions.     

Phase-Transfer Catalyzed Additions. VI. Reaction of N-Diphenylmethyleneaminoacetonitrile with Aromatic Aldehydes

The phase-transfer catalyzed reaction of N-diphenylmethyleneaminoacetonitrile with aromatic aldehydes affords 4-aryl-3-cyano-1,1-diphenyl-2-aza-1,3-butadienes (3) in good yields.     

S-甘油醛缩丙酮的合成及其Wittig反应

以L-抗坏血酸为原料合成了S-甘油醛缩丙酮;研究了S-甘油醛缩丙酮的Wittig反应立体选择性.     

Wittig反应在天然产物合成中的应用

综述了近十年来Wittig反应、Wittig－Horner反应及其它类型Wittig反应在天然产物合成中的应用。参考文献33篇。     

改良的Wittig 反应

本文对改良的Wittig反应进行了综述,并讨论了膦酸酯类与羰基化合物反应的各种机理。还介绍了此反应在有机合成上的应用。     

二苯基甲基烯丙基型膦烷与醛的Wittig反应的立体化学研究

利用3-甲氧基羰基-2-稀丙基二苯基甲基膦叶立德与醛(脂肪醛、芳香醛、杂环醛)的Wittig反应合成了5-取代-2,4-戊二烯酸甲酯(ABA酯类似物),研究了碱对Wittig反应立体化学的影响,发现了该类型季鏻盐的Wittig反应具有很好的4E选择性,并提出了可能的反应机理.     

Combretastatin A-4 全合成中的光化学Wittig反应

在天然产物Combretastatin A-4全合成的关键步骤——Wittig反应中,引入紫外(254nm)辐射,结果使得Wittig反应的产率从原有的65％提高到83．6％。特别是其产物的Z-式立体异构体选择性大大提高,从原来的Z／E之比为3．6提高到11．5,笔者推测这种光化学反应是按双自由基机理进行。     

利用Wittig反应制备乙烷类液晶

以4-（反式4’-正烷基环己基）环己酮和氯甲醚三苯基磷盐为起始原料,经Wittig反应、水解、转型、Wittig反应和氢化反应合成了1-（3,4-二-氟苯基）-2-[反式4’-（反式4＂-正烷基环己基）环己基]乙烷类液晶,其结构经^1H NMR,^13C NMR及MS确证。纯化总收率约30％。     

含氟磷亚胺化合物的合成及其氮杂-Wittig反应的初步研究

以氟烷基叠氮化合物为原料,合成了含氟磷亚胺化合物,并对其氮杂-Wittig反应进行初步研究,通过^1H NMR,^19F NMR,IR,MS及元素分析对化合物的结构进行了表征。     

Asymmetric Dearomative Fluorination of 2-Naphthols with a Dicarboxylate Phase-Transfer Catalyst

A linked dicarboxylate phase-transfer catalyst enables smooth asymmetric dearomative fluorination of 2-naphthols with Selectfluor under mild conditions to give the corresponding 1-fluoronaphthalenone derivatives in a highly enantioselective manner. This reaction, which is compatible with a range of functional groups, is the first example of catalytic asymmetric fluorination of 2-naphthols, and is expected to be useful in the synthesis of bioactive molecules.     

Synthesis of Nonsymmetric Divinylarenes by a Heck/Wittig Reaction Combination

A protocol for a one-pot Heck reaction/Wittig olefination to divinylarenes has been developed.     

Application of Wittig Reaction in Synthesis of Novel Pyridine Dicarboxylic Acid Derivatives with High Ligand Activity

A series of novel conjugated molecules with two pyridine dicarboxylic acid units have been synthesized by a Wittig reaction of corresponding alkyltriphenylphosphonium salts with aromatic aldehydes. The novel pyridine dicarboxylic acid derivatives with high ligand activity were completely characterized from their mass and ¹H NMR spectra. The E-configuration of these alkenes was confirmed by infrared spectroscopic data.