A mercury mediated route to the mitosenes

A Mitsunobu type of coupling is used to prepare a complex phenyl allyl ether which undergoes a Claisen rearrangement. A synthetic route to a mitosene is achieved.     

The Claisen rearrangement of protonated allyl phenyl ether

Molecular protonated ions of allyl phenyl ether undergo a Claisen rearrangement both in the ion source and along the flight path. The rearranged ions undergo fragmentation, the predominat loss being ethene, and only a small contribution from loss of carbon monoxide is observed. Collision-induced dissociation spectra are used to verify the structures of the daughter ions. These spectra, together with other evidence of an acid-induced ortho rearrangement, allow a mechanism to be proposed for the ethene loss. In contrast, molecular protonated ions of propargyl phenyl ether lose exclusively carbon monoxide.     

Photo-impulsive reactions in the electronic ground state without electronic excitation: non-photo, non-thermal chemical reactions

Allyl phenyl ether has an absorption band in the ultraviolet region (λ < 400 nm); therefore, irradiation with few-optical-cycle ultraviolet pulses (λ = 360-440 nm) causes a transition to the ultraviolet band, which leads to an electronic state and a photo-Claisen rearrangement (radical reaction) in the electronic excited state. However, the reaction scheme of allyl phenyl ether under irradiation with few-optical-cycle visible pulses (λ = 525-725 nm) was determined to be same as that of the thermal Claisen rearrangement ([3,3]-sigmatropic rearrangement), which is symmetry-allowed in the electronic ground state. Photo-excitation with few-optical cycle visible pulses below the absorption band induces a photo-impulsive reaction in the electronic ground state without electronic excitation, of which the trigger scheme is different from that of photoreaction or thermal-reaction. The photo-impulsive reaction in the electronic ground state is highly possible as a novel reaction scheme.     

Claisen rearrangement of allyl phenyl ether and its sulfur and selenium analogues on electron impact

The electron impact (EI) mass spectrum of allyl phenyl ether (1) includes an ion at m/z 106 that is formed mainly by the loss of CO from the molecular ion, as supported by high resolution and MS/MS data. The formation of the [M - CO](+) ion from 1 can be explained in terms of the Claisen rearrangement of 1 after ionization in the ion source of the mass spectrometer. Similarly, allyl phenyl sulfide (2) and allyl phenyl selenide (3) showed characteristic ions corresponding to [M - CH(3)](+), [M - XH](+) (X = S or Se) and [M - C(2)H(4)](+.), and the formation of these ions are explained via Claisen rearrangement of 2 and 3 in the ion source of the mass spectrometer resulting in a mixture of rearrangement products. The formation of molecular ions of 2-allyl thiophenol and 2-allyl selenophenol as intermediates, that cannot be isolated as the neutrals from the solution phase Claisen rearrangement of 2 and 3, respectively, is clearly indicated in the gas phase. The mass spectra of the rearrangement products obtained from the solution phase reaction were also consistent with the proposal of formation of these products in the ion source of the mass spectrometer. The formation of characteristic fragment ions attributed to the Claisen rearrangement products are also evident in the collision induced dissociation spectra of the corresponding molecular ions. Copyright 2000 John Wiley & Sons, Ltd.     

Polymerization of allyl(vinyl phenyl) ethers and reactions of the resulting polymers

Solution polymerizations of allyl(o-vinyl phenyl)ether and allyl(p-vinyl phenyl)ether with cationic and radical initiators were investigated. Soluble polymers were formed in polymerizations with boron trifluoride etherate and with benzoyl peroxide. In polymerization with azobisisobutyronitrile the polymerization in dilute solution gave a soluble polymer, whereas that in concentrated solution gave a crosslinked, insoluble one. For informationon the polymerization behavior some infrared and ultraviolet spectroscopic investigations of the soluble polymers were made. From these results it appears that polymers with pendant allyl groups are formed in polymerization with boron trifluoride etherate at low temperature, and polymers containing pendant vinyl groups and allyl groups are obtained with the two types of radical initiator. Copolymerizations of these monomers with ethyl vinyl ether and styrene with the use of boron trifluoride etherate were sucessfully effected. Such reactions as Claisen rearrangement, crosslinking induced with radical initiators, and epoxidation with perbenzoic acid were examined for the polymers prepared in the polymerization with boron trifluoride etherate. Good results were obtained for the former two reactions. However, the latter was unsuccessful.     

Claisen rearrangement induced by low-energy collision of ESI-generated, protonated benzyloxy indoles

The Claisen rearrangement is a well-known process occurring in condensed phase. In the gas-phase protonated allyl phenyl ethers, propargyl phenyl ethers, and N-allyl aniline produced by positive ion chemical ionization undergo Claisen rearrangement. This reaction has been observed even in the case of odd-electron molecular ions. Phenyl allenyl ether molecular ions actually undergo Claisen rearrangement, producing intense [M - CO](+*) ions. In this investigation, the behavior of protonated benzyloxy indole and some of its derivatives, obtained in electrospray conditions, is described. Low-energy MS/MS experiments carried out on [M + H](+) species show CO loss and an unexpected water loss: both can be justified only by the occurrence of Claisen rearrangement. Deuterium labeling experiments confirm this mechanism. The influence of different substituents in the indole moiety is discussed.     

Synthesis of unsymmetrical benzil licoagrodione

A synthesis of unsymmetrical 1,2-diarylethane-1,2-dione is reported involving the intramolecular cyclization of anionic benzylic ester of the aryl benzyl ether followed by oxidation employing dioxirane. With the use of microwave irradiation, licoagrodione was prepared from Claisen rearrangement of the corresponding allyl phenyl ether 1,2-diketone readily available from the Lindlar's reduction of the corresponding alkyne derivative. Subsequent removal of protecting groups then furnished the desired product.     

Isomerization and Cleavage of Allyl Ethers of Carbohydrates by Trans- [Pd(NH3)2Cl2

Allyl ethers are widely used for the “temporary” protection of hydroxy groups in carbohydrates. The allyl group is conveniently removed by isomerization and subsequent cleavage of the labile prop-1-enyl group.² The rearrangement of allyl ethers to prop-1-enyl ethers is readily achieved by treatment with potassium t-butoxide in dimethyl sulfoxide, using tris(tripheny1phosphine)rhodium chloride, palladium on activated charcoal and by an ene reaction with diethylazodicarboxylate. acidic conditions, ozonolysis followed by alkaline hydrolysis, reaction with alkaline permanganate solution, or treatment with mercuric chloride in the presence of mercuric oxide. The isomerization of allyl ethers to prop-1-enyl ethers can also be carried out in the presence of palladium on carbon or complex bis(benzonitrile)palladium(11) chloride. Bruce and Roshan-Ali' showed that derivatives of allyl phenyl ether are smoothly cleaved by this complex. This has made it possible to remove the protecting group in a one-pot operation. We have now investigated the effect of palladium catalysts on the isomerization and cleavage of the allyl group in carbohydrate derivatives.     

Synthesis of Cyclopropyl Ethers and Cyclopropanols by Carbene Transfer – Acetolysis of Cyclopropyl p-Toluenesulfonates

The reaction of chloromethyl phenyl ether with butyllithium in olefins yields phenoxy-cyclopropanes. 1-Chloro-1-phenoxycyclopropanes can be prepared in a similar manner, though the yields are poor. Alkoxycyclopropanes are formed when dichloromethyl alkyl ethers are treated with methyllithium/lithium iodide in the presence of olefins. Cyclopropanols can be obtained in good yields by reaction of (β-chloroethoxy)cyclopropanes either with butyl- or ethyllithium or with bases. – As was shown by acetolysis experiments with cyclopropyl p-toluenesulfonates having a known steric configuration, the rearrangement of a cyclopropyl derivative into an allyl cation proceeds in accordance with the Woodward-Hoffmann-DePuy rule. The solvolysis of exo-bicyclo[n.1.0]alkyl p-toluene-sulfonates is assumed to proceed via “semi-open” intermediates, which are somewhere between an allyl cation and a cyclopropyl cation.     

Structure Effect of Imidazolium-Based Dicationic Ionic Liquids on Claisen Rearrangement

A large group of imidazolium-based dicationic ionic liquids (DILs) has been prepared in good yields. Thermal stability of all DILs has been determined. The effects of the reaction time, cation, imidazolium C₂–H acidity, and anion on the Claisen rearrangement of allyl phenyl ether have been investigated. Type of anion and the presence of the acidic C₂–H bond in the imidazolium moieties have proven to be essential for this reaction. The simple procedure and the possibility of avoiding the use catalysts and volatile organic solvents make this synthetic method environmentally benign and adaptable for large-scale applications.     

Reduction of aryl bromides with lithium aluminum hydride: Evidence for a radical mechanism

Reduction of $\text{0}$-bromophenyl allyl ether with LiAlH₄ yields phenyl allyl ether and 3-methyl-2,3-dihydrobenzofuran, thus suggesting the involvement of radical intermediates in the reduction.     

烯丙基乙基醚接枝聚硅氧烷气相色谱固定相的研究

合成了侧链为烯丙基乙基醚的聚硅氧烷气相色谱固定相,静态法涂柱,评价了其色谱性能.该固定相柱效高,易于涂渍,耐温达290℃,分离选择性好,适用于醇类和酯类的分离以及白酒样品的分析.     

α-烯基-β-环糊精毛细管电色谱整体柱的制备与评价

将烯丙基缩水甘油醚(AGE)和β-环糊精在碱性条件下作用得到带有α烯基的环糊精衍生物——4(3-烯丙氧-2-羟基)丙氧基-β-环糊精(PCD),利用这种衍生物和甲基丙烯酸甘油酯(GMA)为功能单体,在毛细管中通过原位聚合反应,一步法制备得到了新型β-环糊精聚合物毛细管电色谱手性整体柱.在毛细管电色谱(CEC)模式下,应...     

An isomerization—claisen rearrangement route to olefinic dicarbonyl starting materials for conjugate cyclization

Unsaturated dicarbonyl compounds which are useful in conjugate cyclization processes are synthesized by a route which makes use of a sequential isomerization and Claisen rearrangement of the allyl ether of a substituted allyl alcohol.     

Use of Allylbenzene and Allyl Phenyl Ether as Chain-Transfer Agents in Radical Polymerization

The performance of allylbenzene and allyl phenyl ether as chain-transfer agents in radical polymerization of styrene, methyl acrylate, butyl methacrylate, vinylpyrrolidone, and vinylcaprolactam was evaluated.     

微波对烯丙基芳醚的Claisen重排反应影响研究

5种烯丙基芳醚衍生物在无溶剂、无催化剂的条件下进行Claisen重排反应,采用了微波加热和常规加热方式,比较了同等温度下微波加热和常规加热反应速率的差异.结果表明微波加热可以显著提高烯丙基苯醚Claisen重排反应的速率.反应温度为190℃时,微波加热下反应速率可提高5～10倍.微波加热是一种无催化剂、高产率的Claisen重排反应的方法.     

Pd(II)-catalyzed aliphatic Claisen rearrangements of acyclic allyl vinyl ethers

Palladium (II)-catalyzed [3,3] sigmatropic rearrangement of acyclic allyl vinyl ethers delivers 2,3-anti disubstituted pentenal Claisen adducts with high diastereoselectivity. Reaction conditions for circumventing allyl vinyl ether cleavage that had previously plagued catalyzed rearrangement of α-unsubstituted vinyl ether substrates are described. Merging Pd(II) catalysis with the facile access to the Claisen substrates afforded by Ir(I)-catalyzed olefin isomerization provides an expedient procedure for realizing asymmetric anti-selective Claisen rearrangements.     

The mechanism of chain growth in oxidative polycondensation of phenols

A new mechanism of chain extension in oxidative polycondensation of phenols has been proposed. Between the two accepted mechanisms: quinol ether redistribution and quinol ether rearrangement, the second mechanism seems to be the most important for the chain growth. The first mechanism, quinol ether redistribution, preserves the system average degree of polymerization and assures a permanent equilibration of the polymeric chains, but has only a minor contribution to the molecular weight increase. The second mechanism, quinol ether rearrangement, proved to be the most important for chain extension and was interpreted as a repeated Claisen rearrangement (a particular case of a sigmatropic rearrangement), characteristic to allyl ethers of phenols. Experimental data proved that the above mentioned mechanisms probably take place simultaneously and the real growth of the molecular weight is a result of the cumulative contributions of both mechanisms.     

双苯甲酰胺冠醚固定相的合成及毛细管柱气相色谱性能的研究

合成了一种新型的双苯甲酰胺冠醚固定相:(1S,2S)-1-(对苯甲酰胺基)苯基-2-苯甲酰胺基-16-冠-5,其结构经红外光谱、核磁共振、质谱及元素分析数据证实。考察了这种固定相的柱效、热稳定性、极性及选择性等色谱特性。该类固定相对极性位置异构体分离效果良好。由于冠醚上引入苯甲酰胺取代基,因而对苯胺类及不经衍生化的碱性化合物能特殊选择性地分离。     

Claisen rearrangement of aliphatic allyl vinyl ethers in the presence of copper(II) bisoxazoline

The Claisen rearrangement of 1-methyl-2-isopropyoxycarbonyl-6-propyl allyl vinyl ether catalyzed by copper(II) bisoxazoline (Cu-box) has been investigated using density functional theory. Both the phenyl- and tert-butyl-substituted Cu-box systems have been studied. Three different reaction media (vacuum, CH2Cl2, CH3CN) have been considered. In vacuum, the phenyl Cu-box catalyzed reaction yields a (1R,6R) configured major product with a low selectivity. The solvent induces a higher selectivity and a reversal of the absolute configuration (1S,6S). However, the tert-butyl Cu-box catalyzed reaction yields (1R,6R) as the major product both in the gas phase and in the solvent with a good selectivity. Although chair-like TSs are lower in energy than boat-like TSs, the energy difference is small. This is because in the presence of the catalyst the distance between the allyl and vinyl parts of the substrate is relatively large, and thus the steric repulsion between them is smaller than would normally be expected for boat-like structures. The enantioselectivity of tert-butyl Cu-box originates from the steric interactions between the substrate and the catalyst, which are less important for the phenyl Cu-box where the enantioselectivity is determined by the solvent effects.