手性双季铵盐诱导下的硝基甲烷与查而酮的Michael反应

为了探讨手性含1,3-亚乙氧基链双季铵盐在立体选择性反应中的不对称诱导效果,研究了硝基甲烷与查而酮的Michael加成反应。     

A novel and highly efficient two-carbon ring expansion

[reaction: see text]. Dynamic gas-phase thermoisomerization (DGPTI) of medium- and large-ring 3-vinylcycloalkanones at 600-630 degrees C produces isomeric gamma,delta-unsaturated cycloalkanones expanded by two carbon atoms. A reaction mechanism involving an open-chain diradical intermediate, followed by intramolecular recombination under insertion of the vinyl group is proposed. Substituents on the vinyl moiety are transferred locospecifically to the ring-expanded ketones as corresponding beta- and gamma-substituents, respectively. The preparation of extraordinary cyclic allenes can be accomplished by DGPTI (540 degrees C) of 3-ethinylcyclododecanone.     

A simple and efficient method of thioacetal - and ketalization

AlCl₃ has been found to be an efficient reagent for promoting thioacetal- and ketalization of carbonyl compounds.     

A Metal-Metal Bonded Dinuclear Ruthenium Ketene Complex

We report the synthesis of metal-metal bonded dinuclear ruthenium ketene complex [CpRu(CO)]₂(μ-CH₂CO)(μ-CO), 3 , (Cp=η⁵-C₅H₅) which contains the unique structural feature, of a μ-η²(C,C) ketene group bridging two metal centers. Complex 3 is prepared by a rare intramolecular CO insertion to the methylene group of a Ru complex [CpRu(CO)₂]₂(μ-CH₂), 1 , in the absence of CO or any donor ligand. The cis and trans isomers of 3 originating from the arrangement of the Cp groups and the unsymmetrically bridging ketene group, are observed in the NMR spectra. Unlike a ketene complex without a metal-metal bond [CpRu(CO)₂]₂(μ-CH₂CO), 2 , complex 3 exhibits the chemistry of a ketene molecule and might be used as a stoichiometric ketene precusor in organic reactions.     

Ketene acetal monomers: Cationic photopolymerization

A study of the photoinduced cationic polymerization of a novel series of cyclic and acyclic ketene acetal monomers was carried out. It was observed that the cyclic monomers underwent facile cationic polymerization to give high molecular weight polymers while the acyclic ketene acetals did not. Thermally induced polymerization was also observed on standing catalyzed by glass surfaces. Photoinduced cationic polymerizations employing both diaryliodonium and triarylsulfonium salt photoinitiators were studied. It was observed that the position and type of substitutents in the cyclic ketene acetals was the major factor in determining the proportion of vinyl and ring-opening polymerizations that take place. © 1996 John Wiley & Sons, Inc.     

Ketene acetal monomers: Synthesis and characterization

A new, facile, and high-yield synthesis of ketene acetals derived from readily available and inexpensive starting materials has been developed. For example, an α,β-unsaturated aldehyde can be condensed with an alkane diol to afford a 2-vinyl substituted cyclic acetal. This latter compound can be converted to the desired cyclic ketene acetal by isomerization of the double bond in the presence of tris(triphenylphosphine)ruthenium(II) dichloride. Good to excellent yields of cyclic ketene acetals were obtained employing this method. The novel monomers were fully characterized by IR, NMR, and by elemental analysis. © 1996 John Wiley & Sons, Inc.     

Sulfhydrolysis of Acyl Ketene Dithioacetals: A Convenient Synthesis of β-Oxodithioesters

β-Oxodithioesters are obtained in good yields from acyl ketenedithioacetals on treatment with hydrogen sulphide in the presence of boron trifluoride eiherate in refluxing dioxane     

A Short and Simple Synthesis of Ketene Acetals

A novel and convenient synthesis of ketene acetals 1a-g in moderate to good yield has been achieved starting from acetonitrile by using Pinner reaction approach.     

A study on the michael addition of dialkylphosphites to methylvinylketone

The addition of dialkylphosphites to methylvinylketone giving dialkyl‐3‐oxobutylphos‐ phonates was studied applying different reagents, such as NaOR/ROH, NaOH/H₂O under PTC, DBU, and R₃Al (R = Me, Et) under different conditions to find the optimum choice regarding efficiency and selectivity. Possible extensions to a few other model compounds were also investigated. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:226–229, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20266     

α-乙酰基二硫缩烯酮的新合成方法

本文采用酸为催化剂，实施了具有代表性的各种烷硫基α,α-二乙酰基二硫缩烯酮的脱乙酰基反应，得到了一条简洁、通用的α-乙酰基二硫缩烯酮的合成路线.用浓硫酸作催化剂，以极高的产率(90%—100%)制得到相应的α-乙酰基二硫缩烯酮.同时，通过控制反应时间，还可以得到硫代乙酰乙酸酯类化合物.     

The Threshold Photoelectron Spectrum of Fulvenone: A Reactive Ketene Derivative in Lignin Valorization

Unveiling reaction mechanisms by isomer-selective detection of reactive intermediates requires advanced spectroscopic knowledge. We study the photoionization of fulvenone (c-C₅H₄=C=O), a reactive ketene species relevant in catalytic pyrolysis of lignin, which was generated by pyrolysis of 2-methoxy acetophenone. The high-resolution threshold photoelectron spectrum (TPES) with vacuum ultraviolet synchrotron radiation revealed well-resolved vibrational transitions, assigned to ring deformation modes of the cyclopentadiene moiety. The adiabatic ionization energy was determined to be 8.25±0.01 eV and is assigned to the ²A₂← ¹A₁ transition. A broad and featureless band arising at 9 eV is associated with the ²B₁← ¹A₁ excitation. A conical intersection is responsible for the ultrafast relaxation of the fulvenone cation from the into the state resulting in a featureless and lifetime broadened band. These insights will increase the detection capabilities for fulvenone and thereby help to elucidate reaction mechanisms in lignin catalytic pyrolysis.     

Quadruple domino organocatalysis: an asymmetric aza-michael/michael/michael/aldol reaction sequence leading to tetracyclic indole structures with six stereocenters

Quadruple domino/Wittig-one pot: An organocatalytic, asymmetric, three-component quadruple cascade, which leads to tetracyclic double-annulated indole derivatives, is described. The domino products were further derivatized by aldehyde olefination under one-pot conditions to obtain complex isoindolo[2,?1-a]indole derivatives bearing six stereogenic centers in a highly stereoselective fashion.     

A Mild Method for the Preparation of Functionalised,Unsymmetrical Ketene Acetals

A variety of functionalised β-iodoacetals have been prepared, and their elimination reaction to give ketene acetals conducted under mild conditions.