An Efficient Synthesis of Silyl Dienol Ethers from α, β-Unsaturated Aldehydes and Ketones

α, β-Unsaturated aldehydes and Ketones when reacted with NaBr-Me₃SiCl-Et₃N in DMF at ambient temperature, yield silyl dienol ethers in high yields.     

An Efficient Method for α-Alkylation of γ-Butyrolactone

Alkylated lactone is a common structure and segment in many natural products and medicines. The examples of alkylating lactone system at -position, obtained by reaction with alkyl halide such as MeI, in the presence of strong base LDA or it抯 derivatives, are very few1a, 1b. When this method was applied to the aromatic compound, the self-condensation of g-butyrolactone could not be avoided. In our previous work we have reported the hydrogenation of ? -unsaturated carbonyl compounds by cat…     

Triphenylphosphine–Iodine: An Efficient Reagent System for the Synthesis of Nitriles From Aldoximes

A wide range of aldoximes were smoothly converted to the corresponding nitriles with triphenylphosphine–iodine.     

An Efficient Method for the Synthesis of Aliphatic α-Organothio Aldoximes

Theimportanceofthealiptlatica-organothioaldoxilnecompounds3inthepreparationofvariouspesticidesiswellestablished.Moleculescomprisingthea-organothiooximemoietyhavebeenreportedtoexhibitwiderangeofbiologicalactivities,Suchasinsecticidal.nematocidal,miticidalactivity1'2.Inthesynthesisofthecompounds3,thea-chlorinationofthecorrespolldingaliphaticaldoximeIisthekeystep.Inconventionalmethods.thealiphaticaldoximeIisa-chlorinatedbychlorine(CI=),thentheresultinghydroximeacidchloride2istreatedwithsodiumal…     

m-Iodosylbenzoic Acid: Recyclable Hypervalent Iodine Reagent for α-Tosyloxylation and α-Mesyloxylation of Ketones

m-Iodosylbenzoic acid–mediated reactions of various carbonyl compounds provided α-organosulfonyloxy carbonyl compounds in good yields. The final products could be easily isolated without any chromatographic purification by simple treatment of the crude mixture with an anionic exchange resin.     

Reaction of Olefins with Sulfuryl Chloride and Cyclic Ethers: An Efficient Synthesis of α-Chloroalkyl ω-Chloroalkyl Ethers

Olefins react with sulfuryl chloride in presence of cyclic ethers to form the corresponding α-chloroalkyl ω-chloroalkyl ethers     

An Efficcient Method for α—Alkylation of γ—Butyrolactone

This paper provides a simple ,convenient and mild condition method for α-alkylation of γ-Butyrolactone,Three types of (E)-α-alkenyl-γ-Butyrolactone compounds were synthesized by condensation of corresponding aldehydes and γ-Butyrolactone,suing MeONa and EtONa as base, Then the α-alkyl-γ-Butyrolactone were gained by redcing the former alkenyl compounds through catalytic transfer hydrogenation under Pd/C catalyst with sodium hypophoshite at room temperature.     

Reduction and Reductive Alkylation of α-tert-Butylthio Carbonyl Compounds. An Efficient Method for Stepwise α-Alkylation of Esters,Nitriles and Ketones Via the α-Tert-Butylthio Derivatives

An efficient and generally applicable method for stepwise α-alkylatton of esters, nitriles, and ketones via the α-tert-butylthio derivatives is described. The method involves reductive-protonation and reductive-alkylation of α-alkylthio α,α-bis-alkylated carbonyl compounds which are prepared by stepwise alkylation of the corresponding simple α-alkylthio carbonyl precursors. The reduction is conveniently performed by use of stoichiometric amounts of a dissolving metal, particularly lithium, affording correspondingly the α-mono-and the α,α-bis-alkylated carbonyl compounds in good yields.     

An Efficient Synthesis of Dicarbonyl (η5—Cyclopentadien—YL)Iron(II) Complexes of Two Cyclic Enol Ethers

An efficient synthesis of dicarbonyl(η⁵—cyclopentadienyl)iron—(II)—complexes of 2,3—dihydrofuran and 3,4—dihydro—2H—pyran from 3—bromo—2—methoxytetrahydrofuran and—pyran, respectively, is described.     

An Efficient Mg/SmI_2 Catalytic System for the Intermolecular Deoxygenative Coupling of Amides and Ketones

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Mild and Efficient Method for α-Thiocyanation of Ketones and β-Dicarbonyl Compounds Using Bromodimethylsulfonium Bromide–Ammonium Thiocyanate

An efficient and convenient method for α-thiocyanation of ketones and β-dicarbonyl compounds has been developed using a reagent combination of bromodimethylsulfonium bromide (BDMS) and ammonium thiocyanate in acetonitrile. The developed method is mild and gave good yield of the products at room temperature.     

Stannic Chloride–Iodine: An Efficient Reagent for Regioselective Synthesis of Furan–Fused Heterocycles

SnCl₄‐I₂‐mediated cyclization of ortho‐cyclohexenyl phenol and ortho‐cyclohexenyl enol derivatives of coumarin, uracil, dimedone, and pyrone at room temperature for 1 h give the linear cyclized products in 78–90% yield, which, on treatment with 10% Pd‐C at 250°C for 1–2 h, afford corresponding aromatized products in 80–84% yield.     

Thiazolium Salt Immobilized on Ionic Liquid: An Efficient Catalyst and Solvent for Preparation of α-Hydroxyketones

Aldehydes were efficiently converted to acyloins and benzoins using a new ionic liquid, 3-[2-(1-butyl-1H-imidazol-1,3-ium-3-yl)ethyl]-4,5-dimethyl-1,3-thiazol-3-ium dibromide 1 . This ionic liquid is introduced as a catalyst and a solvent. Acyloins and benzoins were easily isolated from the reaction mixture via simple extraction, and the ionic liquid could be recycled for further use. Also, α-hydroxy ketones with an aromatic and aliphatic substituent were prepared starting from aromatic and aliphatic aldehydes in the presence of ionic liquid 1 .     

An Efficient Synthesis of Tertiaryaminomethylphosphonates,A Versatile Precursor for Synthesis of Glyphosate and α—Aminomethylphosphonates

Reaction of simple dialkyl phosphites with symmetrical 1,3,5-trisubstituted hexahydrotriazines (HHTs) in the presence of benzyl chloride,afforded tertiaryaminomethylphosphonates in excellent yields. Glyphosate,α-aminomethylphosphonates and their derivatives can therefore be synthesized by this procedure conveniently.     

TiCl4, Dioxane—A Facile and Efficient System for De-O-Benzylation,De-O-Allylation,and De-O-Xylylation of Phenolic Ethers

Abstract

Simultaneous de-O-xylylation and reductive coupling was observed when 1 equiv. of the dialdehyde 2a/2b was treated with 5 equiv. of each TiCl₄ and Zinc which lead to the development of TiCl₄ in dioxane as a new system for the facile deprotection of phenolic ethers 4a–4d, 5a–5d, and 6a–6c.     

Tween-20: An Efficient Catalyst for One-Pot Synthesis of α-Aminophosphonates in Aqueous Media

Abstract

A green one-pot three-component synthesis has been developed for α-aminophosphonates by condensation of aldehydes, amines, and diethylphosphite by using nonionic surfactant Tween-20 as catalyst in aqueous media. The results showed that this synthetic route for α-aminophosphonates takes just 25–60 min for completion at 60 °C and affords 64%–91% yields depending on the nature of the amine substrates. The major advantages of this novel method are green reaction conditions with water as solvent, simple workup, less reaction times, and high to moderate yields.     

Silica Sulphuric Acid: An Efficient and Recyclable Catalyst for the Synthesis of β‐Acetamido Ketones in Single Pot

Abstract

An efficient method has been developed for the synthesis of β‐acetamido ketones by a multicomponent condensation route using sulphuric acid on silica gel as an inexpensive catalyst. Catalyst was recycled without loss of activity.     

Communication: Synthetic Studies on Sialoglycoconjugates 110: Efficient Assembly of α-Linked Tetrameric Sialoglycosides Coupled with Galactose and Lactose

Polysialoglycoconjugates, such as polysialylated ganglio-series gangliosides and N-CAM (neural cell adhesion molecule), are of interest because of their important physiological functions in association with neural cell development, differentiation, neuron network formation, and so on.^2-4 Chemical synthesis of these glycoconjugates provides an effective method to elucidate their biological significance in nature at the molecular level, providing not only genuine original glycoconjugates but also their derivatives and analogs designed for biological investigation. We have established⁵ an efficient method to construct dimeric and trimeric sialoglycosides by using the lactonated sialic acid derivatives as building blocks, and succeeded in the systematic synthesis of various polysialogangliosides such as GD3, GQ1b, GQlbα and, very recently, GT3.⁶ In this paper, as a part of our continuous synthetic approach directed toward the polysialoglycoconjugates, we report the first synthesis of α-linked tetrameric sialoglycosides coupled with a galactose and lactose residue.     

Darzens Reaction Promoted by KF/Alumina: A Novel Stereoselective Method for Rapid and Efficient Synthesis of trans‐α,β‐Epoxy Ketones

The Darzens condensation of α‐chloroacetophenone with various aromatic aldehydes mediated by potassium fluoride on alumina at room temperature resulted in formation of good to excellent yields of trans‐α,β‐epoxy ketones in short time periods.     

Solvent‐Free Williamson Synthesis: An Efficient,Simple, and Convenient Method for Chemoselective Etherification of Phenols and Bisphenols

Etherification of phenols with dimethyl‐ and diethylsulfates and benzyl chloride was performed efficiently in the presence of a suitable solid base, NaHCO₃ or K₂CO₃, under solvent‐free conditions. The reaction proceeded rapidly at low temperature, and the corresponding ethers were obtained with high purity and excellent yield. Selective etherification of electron‐poor phenols in the presence of electron‐rich ones and also selective mono‐etherification of bisphenols are the noteworthy advantages of this method. This method is environmentally friendly.