New opinions on the amidoalkylation of hydrophosphorylic compounds

A new and milder version of the procedure for the synthesis of N-protected α-aminoalkylphosphorylic compounds by reaction of alkyl carbamates, aldehydes and hydrophosphorylic compounds in acetic anhydride/acetyl chloride and a new mechanism for this type of reaction are described. The isolation, for the first time, of N,N′-benzylidene- and N,N′-alkylidenebiscarbamates as intermediates from the reaction medium and studies of the direct reaction of pre-obtained biscarbamates and hydrophosphorylic compounds in acetic anhydride are reported. A new version of the mechanism for this reaction which includes an Arbuzov-type reaction is proposed.     

Solvent-free catalytic preparation of 1,1-diacetates from aldehydes using a Wells-Dawson acid (H6P2W18O62·24H2O)

Aromatic and aliphatic aldehydes are transformed in 1,1-diacetates (acylals) in mild conditions, by a treatment with acetic anhydride and a Wells-Dawson acid (H₆P₂W₁₈O₆₂·24H₂O). gem-Diacetylation proceeds in Ac₂O with a little as 1% mol Wells-Dawson acid at room temperature and under solventless conditions, obtaining very good to excellent yields (88-98%) of 1,1-diacetates (19 examples). Neither 4-dimethylaminobenzaldehyde nor ketones react under the same conditions.     

Kinetics and mechanism of the catalytic reaction between ozone and <Emphasis Type="Italic">para</Emphasis>-cresol in acetic anhydride

The kinetics of the liquid-phase catalytic oxidation of para-cresol with an ozone-air mixture in the presence of manganese(II) acetate is reported. In an acetic anhydride medium, para-cresol reacts with ozone as para-cresyl acetate, which is formed at the instant the solution to be oxidized is prepared. Under these conditions, the major oxidation products are para-acetoxybenzyl acetate (63.5%) and para-acetoxybenzylidene diacetate (13.7%). The effect of the managanese(II) acetate concentration on the traction selectivity with respect to the oxidation of the methyl group of the substrate is reported. A mechanism consistent with the experimental data available on this catalytic redox reaction is suggested.     

A stable intermediate: a new insight into the mechanism of Lewis acids-promoted formation of acylals from aldehydes

Treatment of m-nitrobenzaldehyde with acetic anhydride in the presence of Lewis acids, such as InBr₃, ZnBr₂, Cu(OTf)₂, gives a stable intermediate at the initial stage of reaction. Based on this new organic compound characterized by X-ray single crystal diffraction, a new mechanism for Lewis acids-promoted formation of acylals from aldehydes is proposed. Exchange reaction with different ratio of acetic anhydride to propionic anhydride, in the presence of Lewis acids, is studied.     

Ethylenediamine diacetate-catalyzed three-component reaction for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones and their spirooxindole derivatives

Ethylenediamine diacetate (EDDA)-catalyzed one-pot syntheses of biologically interesting 2,3-dihydroquinazolin-4(1H)-ones and their spirooxindole derivatives from isatoic anhydride, amines, and benzaldehydes or isatins via a three-component condensation in aqueous media have been described. This method is of great value because of high yields and ease of handling.     

An Efficient One‐Pot Synthesis of Bis Butenolides

3,3′,4,4′‐Tetramethyl‐5,5′‐dioxo‐2,2′‐bifuran‐2,2′(5H,5′H) diyl diacetate was obtained from the reaction between 2,3‐dimethyl maleic anhydride and acetic anhydride in the presence of zinc in toluene. This easy synthetic route gave bis butenolide in excellent yield.     

A sesquiterpene lactone fromAcroptilon repens

A new sesquiterpene lactone has been isolated from the epigeal part ofAcroptilon repens, with the composition C₁₉H₂₂O₆, mp 199–201°C, M⁺ 346, and it has been called acroptin (I). The treatment of (I) with acetic anhydride in pyridine gave a diacetate (II). The structure of (I) has been confirmed by the NMR spectra of (I) and (II). Details of the IR and NMR spectra of (I) and (II) are presented.     

Cidnp study of reactions of ketyls and dianions derived from benzophenone and fluorenone with acetic anhydride

A study is presented of ¹H and ¹³C CIDNP effects in the reactions of Na and Li salts of ketyls and dianions derived from benzophenone and fluorenone with acetic anhydride in tetrahydrofuran and dimethoxyethane. CIDNP effects were observed for products obtained by mixing of reactants both at high and at low field. Interpretation of the CIDNP effects (mixing at high field) indicates that in reactions of ketyls with acetic anhydride the primary step is O-acylation followed by spin-selective electron transfer between ketyl and O-acylated ketyl. At higher dilution or in the presence of strongly coordinating agents, heterolytic deprotonation of acetic anhydride by ketyl is also observed. CIDNP effects depend on the presence of ketyl which affects the relaxation of sterically accessible nuclei and also suppresses the intensity of ketone signals by rapid electron transfer. In reactions of dianions, electron transfer between dianion and acetic anhydride partly takes place, and the ketyl formed in this way reacts with a further molecule of acetic anhydride.     

Regioselective ortho-acetoxylation/methoxylation of N-(2-benzoylphenyl)benzamides via substrate directed C-H activation

A highly regioselective ortho-acetoxylation of N-(2-benzoylphenyl)benzamides has been achieved using a catalytic amount of Pd(OAc)₂ (10 mol %) and a stoichiometric amount of PhI(OAc)₂ in a mixture of acetic anhydride and acetic acid via C-H activation to produce the corresponding 2-acetoxybenzamides in good yields. ortho-Methoxylation has been accomplished using methanol under similar conditions.     

Synthesis of novel tricyclic isoindole derivatives

Novel 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindoles were prepared from the thermolysis of (3R,9bS)-5-oxo-2,3,5,9b-tetrahydrothiazolo[2,3-a]isoindole-3-carboxylic acids in acetic anhydride. The structure of 3-methylene-2,5-dioxo-3H,9bH-oxazolo[2,3-a]isoindole 6a was determined by X-ray crystallography.     

Regioselective ortho-nitration of N-phenyl carboxamides and primary anilines using bismuth nitrate/acetic anhydride

An efficient and one-pot synthetic method for the regioselective ortho-nitration of the N-phenyl carboxamides and primary anilines has been developed by using bismuth nitrate and acetic anhydride as the nitrating reagents. Reaction proceeds at room temperature and results in corresponding ortho-nitrated products in moderate to excellent yields. This method provides an operationally simple, regioselective, and efficient access to synthesize o-nitro anilines under the mild conditions.     

Silica-bonded S-sulfonic acid as a recyclable catalyst for chemoselective synthesis of 1,1-diacetates

A simple and efficient procedure for the preparation of silica-bonded S-sulfonic acid (SBSSA) by reaction of 3-mercaptopropylsilica (MPS) and chlorosulfonic acid in chloroform is described. This solid acid is employed as a recyclable catalyst for the synthesis of 1,1-diacetates from aromatic aldehydes and acetic anhydride under mild and solvent-free conditions at room temperature.     

Fe2(SO4)3·xH2O-catalyzed per-O-acetylation of sugars compatible with acid-labile protecting groups adopted in carbohydrate chemistry

Fully acetylated saccharides are inexpensive and very useful starting materials for the synthesis of many naturally occurring glycosides, oligosaccharides, and glycoconjugates. Ferric sulfate hydrate (Fe₂(SO₄)₃·xH₂O) was found to be a valuable Lewis acid promoter in the per-O-acetylation reaction of saccharides with acetic anhydride in 100% of conversion rate and 88-99% yields. Interestingly, the procedure is perfectly compatible with the presence of a variety of acid-labile protecting groups, such as isopropylidene, benzylidene, trityl, and TBDMS groups. The reactions were simply performed by stirring the mixture of a sugar with a slight excessive acetic anhydride in the presence of 2.0 mol % of Fe₂(SO₄)₃·xH₂O at rt and the pure products were obtained by a simple dilution of the reaction mixture with dichloromethane and washings with aqueous Na₂CO₃.     

Bi(OTf)3-catalyzed acylation of p-quinones: a facile synthesis of acylated hydroquinones

p-Quinones undergo smooth acylation with acetic anhydride in the presence of 2 mol % of bismuth triflate under mild conditions to afford the corresponding 1,4-diacylated-2-acetoxylated hydroquinones in excellent yields with high selectivity.     

A new synthesis of benzo[b]thiophenes utilizing an interrupted Pummerer reaction

A convenient synthesis of 3-arylbenzo[b]thiophenes utilizing an interrupted Pummerer reaction of 2-(1-arylvinyl)phenyl ethyl sulfoxides is described. Thus, treatment of these sulfoxides, which were readily prepared from 2-sulfanylphenyl ketones or 2-fluoro-5-methoxybenzaldehyde, with acetic anhydride at 100 °C afforded 3-arylbenzo[b]thiophenes in reasonable yields.     

Silica-bonded N-propyl sulfamic acid as an efficient catalyst for the formylation and acetylation of alcohols and amines under heterogeneous conditions

A simple and efficient procedure for the preparation of silica-bonded N-propyl sulfamic acid (SBNPSA) by the reaction of 3-aminopropylsilica (1) and chlorosulfonic acid in chloroform is described. This solid acid is employed as a new catalyst for the formylation of alcohols and amines with ethyl formate under mild and heterogeneous conditions at room temperature with good to excellent yields. Also, SBNPSA catalyzed acetylation of various alcohols and amines with acetic anhydride at room temperature.     

Preparation of 3-substituted and 2,3-disubstituted-4,4,4-trifluoro-2-butenoic acids—Perkin condensation of activated aromatic ketones

The Perkin reaction of the activated aromatic ketones (2,2,2-trifluoroacetophenone and its 4′-phenyl-derivative) with various condensing agents (acetic anhydride, propionic anhydride, phenylacetic acid/acetic anhydride) gives the title compounds in good or moderate yields, and high E-stereoselectivity. For some derivatives an appreciable amount of the Z isomer was also formed. Several of the resulting butenoic acids and their methyl esters are synthesised and characterised for the first time.     

Kinetische Untersuchung der Oxydation von 1,2,4,5-Tetramethylbenzol in einem polaren Lösungsmittel

A kinetic study was made of the liquid-phase oxidation of 1.2.4.5-tetramethylbenzene in polar solvents. It was shown that the catalytic activity of the cobalt salt catalysts used varies as the hydrocarbon concentration decreases, a finding attributed to the anionic effects in the catalyst. The catalytic activity of the cobaltous salts of nicotinic and isonicotinic acid was found to be high at low durene concentrations. Of the bromine derivatives studied as promotors, N-bromoacetamide was found to be the most effective. The effect of the polar solvent on the kinetics of the oxidation of durene was also studied in media containing acetic acid, acetic anhydride and mixtures thereof. The relationship between the rate constant (k) in acetic anhydride and the rate constant (k ₀) in acetic acid is found to be the following: $$\lg k = \lg k_0 + 24.59\frac{{\varepsilon - 1}}{{2\varepsilon + 1}}$$ A tentative mechanism of the oxidation steps is advanced to explain the higher values of the rate constant in acetic anhydride.     

Convenient synthesis of 5-methylene-4-substituted-2(5H)-furanones

A synthesis of novel 4-(substituted)benzyl-5-methylene-2(5H)-furanones involving Stobbe condensation of substituted aldehydes with ethyl levulinate followed by treatment with acetic anhydride in the presence of sodium acetate, has been developed.     

Indium-mediated one-pot reductive conversion of nitroarenes to N-arylacetamides

N-Arylacetamides were prepared in excellent yields from nitroarenes in the presence of acetic anhydride, acetic acid and indium by a one-pot procedure.