The Preparation Of 2-[4,5-Dihydro-3-Aryl-5-Isoxazolyl]-Phenols From C(α),O-Dilithiooximes and Lithiated Hydroxyaryl Aldehydes

C(a), O-Oximes were dilithiated in excess lithium diisopropylamide, and the resulting intermediates were condensed with lithiated hydroxyphenyl aldehydes and related materials and cyclized with acid to afford 2-[4,5-dihydro-3-aryl-5-isoxazolyl]phenols, substituted 4,5-dihydroisoxazoles (2-isoxazolines).     

Preparation of 2-[1-Phenyl-1H-pyrazol-5-yl]benzoic Acids from Dilithiated C(α),N-Phenylhydrazones and Methyl Hydrogen Phthalate

Select C(α),N-phenylhydrazones were dilithiated with excess lithium diisopropylamide to their dianion-type intermediates followed by condensation with methyl hydrogen phthalate. The resulting C-acylated hydrazones were not isolated but acid cyclized directly to afford new substituted 2-(1-phenyl-1H-pyrazol-5-yl)benzoic acids.     

The Preparation of 1H-Pyrazole-5-propanoic and 1H-Pyrazole-5-butanoic Acids from Dilithiated C(α),N-Carboalkoxyhydrazones and Succinic or Glutaric Acid Anhydrides

C(α),N-Carboalkoxyhydrazones were dilithiated with excess lithium diisopropylamide, condensed with succinic or glutaric acid anhydride, and cyclized to 1H-pyrazole-5-propanoic or 1H-pyrazole-5-butanoic acids.     

A Convenient Route to (E)-α,β-Unsaturated Methyl Ketones

Aldehydes are converted into (E)-α,β-unsaturated methyl ketones in good yield and with a high E stereoselectivity using α,α-bis(trimethylsilyl) N-tert-butyl acetimine 3. The reaction was mediated by a catalytic amount of tetrabutylammonium fluoride (TBAF) under mild conditions. The disilylated reagent 3 is easily generated from N-tert-butylacetimine, lithium diisopropylamide (LDA), and chlorotrimethylsilane. The mechanism of the reaction is discussed.     

The Preparation of 1H-Pyrazole-1-carboxylic Acid, 1, 1-Dimethylethyl Esters from Dilithiated C(α), N-Hydrazones of Hydrazinecarboxylic Acid, 1, 1-Dimethylethyl Ester

C(α), N-Hydrazones of hydrazinecarboxylic acid, 1, 1-dimethylethyl ester [C(α), N-carbo-t-butoxyhydrazones] were metalated with excess lithium diisopropylamide, and the dianion-type intermediates were condensed with select aromatic esters followed by acid cyclization to substituted 1H-pyrazole-1-carboxylic acid, 1, 1-dimethylethyl esters (N-carbo-t-butoxypyrazoles).     

Enantioselective Hydrogenation of α,β-Unsaturated Cyclic Ketones by Double Asymmetric Induction Preparation of (R)-Muscone

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The Preparation of Substituted Hydroxyphenyl-pyridyl-ethanols and α-Hydroxyphenyl-α-methylpyridineethanols by the Condensation of 2-, 3-, or 4-Picolyllithium with Select Hydroxy-benzaldehydes and 4-Hydroxyacetophenone

2-, 3-, or 4-Picolyllithium was prepared in excess lithium diiso-propylamide and condensed with several hydroxy-benzaldehydes and 4-hydroxy-acetophenone to afford substituted hydroxyphenyl-pyridyl-ethanols and α-hydroxyphenyl-α-methylpyridineethanols. In two instances. 3-picolyllithium condensed with aldehydes to presumably form the hydroxyphenyl-pyridyl-ethanol, which underwent linear dehydration to the substituted pyridyl-ethylenyl-phenol.     

Synthesis of Eudesmanolides Possessing Denebutenolide and Endocyclic α,β-Unsaturated Butenolide from α-(-)-Santonin

A new and efficient method of double bond functionalization of eudesmanolide was carried out by rearrangement of epoxide with methoxide. which is important to synthesis of bioactive natural products containing denebutenolid (1) and endocyclic α, β -unsaturated butenolide (2).     

The Reaction of 1-Aryl-2-(4-nitrophenylsulfonyl)ethanones with α,β-Unsaturated Esters

1-Aryl-2-(4-nitrophenylsulfonyl)ethanones (1) reacted with one equiv. of α,β-unsaturated esters at 60°C to afford the tandem addition-rearrangement products (3), while at 75°C 1a reacted with two equiv. of methyl acrylate and gave an unexpected addition-rearrangement-addition-annulation product which is dimethyl 4-hydroxyl-1-(4-nitrophenyl)-4-phenyl-1,3-cyclohexyldicarboxylate (4). A mechanism is suggested.     

A Facile Synthesis of α-Phenylchalcogeno(S,Se) α,β-Unsaturated Esters from Ethyl α-Bromo-α-phenylchalcogeno Acetates

Ethyl α-bromo-α-phenylseleno acetate 1 and ethyl α-bromo-α-phenylthio acetate 2 react with aldehydes in the presence of dibutyltelluride to give α-phenylchalcogeno-α,β-unsaturated esters, with Z preferential stereochemistry.     

Ligand Control of Palladium-Catalyzed Site-Selective α- and γ-Arylation of α,β-Unsaturated Ketones with (Hetero)aryl Halides

This study describes the first palladium-catalyzed, site-selective α- and γ-arylation of α,β-unsaturated ketones with (hetero)aryl halides. A wide range of hetero(aryl)halides coupled with α,β-unsaturated ketones, and transformation into the arylated products proceeded with excellent to good yields. The site selectivity of the reaction is switchable by simply changing the phosphine ligand to access either α-arylated or γ-arylated products in good to excellent yields by using a low catalyst loading, and the method demonstrates good functional-group compatibility.     

Synthesis of β-Substituted-α-[(trimethylsilyl)oxy]acrylonitriles from α, β-Unsaturated Aldehydes

The condensation of trimethylsilylcyanide with α, β-unsaturated aldehydes, followed by DBU catalyzed isomerization of the intermediate 0-silylated cyanohydrins, constitutes a facile synthesis of β-substituted- α-[(trimethylsilyl)oxy]acrylonitriles.     

Oxidation of Aryl Alkyl Ketones To α-Acyloxy, α-(Camphorsulfonyloxy), or α-Hydroxy Derivatives Using Manganese(III) Acetate in Combination with Carboxylic Acids or (1S)-(+)-10-Camphorsulfonic Acid

The α-oxidation of aryl alkyl ketones using manganese(III) acetate in the presence of various carboxylic acids and (1S)-(+)-10-camphorsulfonic acid provided a convenient synthesis of α-acyloxy, α-(10-camphorsulfonyloxy), and α-hydroxy derivatives in good yield.     

A Facile Synthesis of (±)2-(4-Chlorophenyl)-α-Methyl-5-Benzoxazoleacetic Acid (Benoxaprofen)

A convenient four step procedure for the synthesis of benoxaprofen is described starting with 4-hydroxyphenylacetic acid.     

Nickel(0)-Catalyzed Enantioselective [3+2] Annulation of Cyclopropenones and α,β-Unsaturated Ketones/Imines

Ni⁰-catalyzed chemo- and enantioselective [3+2] cycloaddition of cyclopropenones and α,β-unsaturated ketones/imines is described. This reaction integrates C−C bond cleavage of cyclopropenones and enantioselective functionalization by carbonyl/imine group, offering a mild approach to γ-alkenyl butenolides and lactams in excellent enantioselectivity (88–98 % ee) through intermolecular C−C activation.     

Reaction of [HO(CH2)3]3P with α,β-Unsaturated Ketones Containing a Phenylpropanoid Backbone

Abstract

Interaction of 3,4-(MeO)₂-benzylideneacetone with [HO(CH₂)₃]₃P (THPP) was studied in CD₃OD by NMR to compare reactivity of a phenylpropanoid α,β-unsaturated ketone with a corresponding α,β-unsaturated aldehyde. In the presence of HCl, both the ketone and a related cinnamaldehyde first establish an equilibrium with the product formed by nucleophilic attack of the THPP at the C?O bond, [ArCH?CHCX(OD)PR₃]⁺Cl^?(X?H or CH₃, Ar?Ph or 3,4-(MeO)₂C₆H₃). The ketone salt then slowly transforms into [R₃PCH(Ar)CH(D)C(O)CD₃]⁺Cl^?, the phosphonium product of nucleophilic attack of THPP at the C?C bond, whereas the final product from the aldehyde is the (α-ether)phosphonium chloride [ArCH?CHCH(OCD₃)PR₃]⁺Cl^?. In aqueous media, in the absence of HCl, 4-HO-benzylideneacetone, which is similar to a lignin-type, α,β-unsaturated aldehyde model compound, interacts with THPP to afford a stable phosphonium zwitterion, in contrast to the previously studied aldehyde model, which forms dimeric, bisphosphonium products.     

Solvent-Free Preparation of 5-(α-D-Glucosyloxymethyl)furfural from Isomaltulose–Choline Chloride Melts

5-(α-D-Glucosyloxymethyl)furfural, a versatile building block from renewable resources, was prepared from isomaltulose–choline chloride melts by acid catalysis. In this solvent-free process, moderate yields were achieved under mild reaction conditions.     

Crystal Structure of cis-2-〔(P,P-Diethoxy)phosphono(m-nitro)benzyloxy〕-4-Phenyl-5,5-Dimethyl-1,3,2-Dioxaphosphorinane 2-Sulfide

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