Etude de la reaction chlorocarbene-acetals de cetenes : II. Stereoselectivite de la reaction

We have studied the stereoselectivity of the addition reaction of chloro and chloromethyl carbenoids with ketene alkylsilyl acetals. The best stereoselectivity was generally observed with the dimethyl tertiobutylsilyloxy group. With the chlorocarbenoid, using an E ketene acetal we obtained in majority (8?0%) an E α,β-ethylenic ester and using a Z ketene acetal we obtained in majority (7?0%) a Z α,β-ethylenic ester. In the case of the chloromethyl carbenoid the two ketene acetal isomers led to the same E α-substituted α,β-ethylenic ester (8?8% of selectivity). With the chlorophenylcarbenoid, formation of 9?0% of E α phenyl α,β-ethylenic ester is observed.     

(Triisopropylsilyl)acetaldehyde acetal as a novel protective group for 1,2-diols

(Triisopropylsilyl)acetaldehyde dimethyl acetal (TIPS-ADMA) was synthesized from chlorotriisopropylsilane in three steps. Cyclic and acyclic 1,2-diols can be transformed to (triisopropylsilyl)ethylidene acetals (TIPS-AA). Removal of the acetal by LiBF₄ regenerates the starting diol in excellent yield even in the presence of an acetonide of 1,2-diol. The TIPS-AA group can survive under the deprotection conditions of the acetonide in acetic acid at 80 °C. Selective protection of 2,3- and 4,6-diols for O-methyl d-mannoside with TIPS-ADMA and selective deprotection of the acetals have been achieved.     

Die Struktur des Antibioticums Roridin H. Verrucarine und Roridine, 20. Mitt. [1]

Structure 1 has been established for roridin H (C₂₉H₃₆O₈), an antibiotic isolated from Myrothecium verrucaria and formerly namend verrucarin H [3]. Base catalysed hydrolysis of 1 gave the known terpene alcohol verrucarol ( 8 ; C₁₅H₂₂O₄) and myrothecinic acid ( 3 ; C₁₄H₁₈O₆), a previously undescribed dicarboxylic acid. The structure of 3 was determined by spectral methods and by chemical cleavage of the unusual acetal group of dimethyl hexahydromyrothecinoate ( 6 ) by hydrolysis with HCl in the presence of 2, 4-dinitrophenylhydrazine, producing the 2, 4-dinitrophenylhydrazone 13 of 3-methylglutaric acid semialdehyde 10 and methyl 6, 7-dihydroxy-octanoate ( 11 ). 13 was transformed in to dimethyl 3-methylglutarate ( 15 ). Cleavage of 11 with HIO₄ gave acetaldehyde and adipic acid semialdehyde ( 17 ) which was oxidized to adipic acid ( 19 ). The 220 MHz NMR spectra of roridin H ( 1 ) and dimethyl hexahydromyrothecinoate ( 6 ) allowed unequivocal assignment of the signals to the majority of the protons in the antibiotic.     

Indium(III) triflate catalyzed tandem azidation/1,3-dipolar cycloaddition reaction of ω,ω-dialkoxyalkyne derivatives with trimethylsilyl azide

The azidation reaction of dialkyl acetal derivatives with trimethylsilyl azide (TMSN₃) was efficiently catalyzed by 1-5 mol % of In(OTf)₃. The major product differed depending on the substrate structure and molar ratio of TMSN₃, that is, aliphatic acetals provided α-azido ether derivatives, while aromatic acetal (benzaldehyde dimethyl acetal) provided gem-diazide, respectively. Furthermore, novel tandem azidation/1,3-dipolar cycloaddition reaction using alkynyl acetal derivatives gave bicyclic triazolo-heterocyclic compounds, recognized as chemically modified aza-sugar analogues, in high yields under mild conditions.     

Nitropyrazoles: XII. Transformations of the 4-Methyl Group in 1,4-Dimethyl-3,5-dinitropyrazole and Cyclization of the Transformation Products

A preparative procedure for the synthesis of 1,4-dimethyl-3,5-dinitropyrazole by nitration of 1,4-dimethylpyrazole was developed. The reaction of 1,4-dimethyl-3,5-dinitropyrazole with dimethoxymethyl- (dimethyl)amine (N,N-dimethylformamide dimethyl acetal) gave (E)-N,N-dimethyl-2-(1-methyl-3,5-dinitropyrazol- 4-yl)ethenylamine. Acid hydrolysis of the latter afforded (1-methyl-3,5-dinitropyrazol-4-yl)acetaldehyde, and the reaction with sodium nitrite in hydrochloric acid led to formation of 2-hydroxymino-2-(1-methyl- 3,5-dinitropyrazol-4-yl)acetaldehyde. The corresponding O-methyloxime and phenylhydrazone reacted with K₂CO₃ to give 6-methyl-4-nitropyrazolo[4,3-d]isoxazole-3-carbaldehyde O-methyloxime and 1-methyl-3-nitro-4-(2-phenyl-2H-1,2,3-triazol-4-yl)pyrazol-5-ol, respectively. Treatment of (1-methyl-3,5-dinitropyrazol-4-yl)-acetaldehyde with benzenediazonium chloride gave (1-methyl-3,5-dinitropyrazol-4-yl)acetaldehyde phenylhydrazone which underwent intramolecular cyclization with replacement of the 5-nitro group by the action of K₂CO₃ in acetonitrile; in the reaction with K₂CO₃ in ethanol, the 5-nitro group was replaced by ethoxy.     

内型2—（3,3—二甲基—2—降冰片基）丁醛及其衍生物的合成

以内型３，３－二甲基－２－降冰片基乙醛（１）与叔丁胺反应制得醛亚胺（２），依次和溴化乙基镁，碘乙烷反应制得内型２－（３，３－二甲基－２－降冰片基）丁醛的亚胺（４），再经水解得内型２－（３，３－二甲基－２－降冰片基）丁醛（５）。后者经与乙二醇缩醛化及氧化分别制得该醛的缩醛（６）及羧酸（７）。这些化合物均为新化合物，经纯化后进行了结构分析，并对其质谱进行了讨论。     

Simplified synthesis of carbohydrate‐functional siloxanes via transacetalation. I. Glucose‐functional siloxanes

Carbohydrate‐functional siloxanes (CHFSs) that exhibit high intermolecular interactions and good environmental friendliness have successfully been synthesized by acid‐catalyzed transacetalation between an acetal‐functional siloxane and glucose in dimethylformamide/dioxane mixed solvents. Activated clay has proven to be a good catalyst because of its high activity and its easy removal from the product. Acetal‐functional siloxanes as starting materials can be easily synthesized in good yields by hydrosilylation between Si? H‐functional siloxanes and acrolein diethyl acetal. This method has the following advantages: (1) the inexpensive materials used, (2) the simplified process employed, and (3) the high yield achieved. Because the carbohydrate moieties in these materials have the nature of strong intermolecular interactions and are highly hydrophilic, CHFSs exhibit very high bulk viscosities in comparison with the corresponding acetal‐functional siloxanes and good solubilities in polar solvents such as dimethylformamide and dimethyl sulfoxide. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3336–3345, 2003     

One-Pot Synthesis of Rufloxacin

Rufloxacin (MF-934) was prepared in one-pot synthesis in 61% yield by treatment of the 2,3,5-trifluoro-4-(4-methyl-1-piperazinyl)-benzoyl acetate, first with N,N-dimethylformamide dimethyl acetal, then with 2-aminoethanethiol, followed by cyclization and hydrolysis.     

Lipase-catalyzed resolution of anti-6-substituted 1,3-dioxepan-5-ols

Several anti-6-substituted 1,3-dioxepan-5-ols were kinetically resolved using an immobilized lipase (Amano PS–C II) in toluene in the presence of vinyl acetate at 30 °C. This approach provided, in some cases, the alcohol and the acetate in high enantiomeric purity, depending on the nature of the substituent (R = N₃, SePh, I, OBn) and the acetal group (unsubstituted or dimethyl). The role of the size of substituents is also discussed. Enantiopure anti-6-substituted 1,3-dioxepan-5-ols are useful building blocks.     

Accroissement de la reactivite des phosphorines en tant que dienes et philodienes par complexation du phosphore

The 2-Phenyl-4,5-dimethylphosphorin P-W(CO)₅ complex reacts easily as a dienophile with 2,3-dimethylbutadiene through its 1,6-positions and as a diene with N-phenylmaleimide, dimethyl acetylenedicarboxylate and cyclopentadiene, through its 1,4-positions.     

Cyclic Acetal-Photosensitized Polymerization. XII. Photopolymerizations of Styrene and Methyl Methacrylate in the Presence of Polycyclic Acetals

Styrene (St) and methyl methacrylate (MMA) were photopolymerized in the presence of poly-2-vinyl-1,3-dioxolane (PVDO), poly-2-vinyl-4-hydroxymethyl-1,3-dioxolane (PVHDO), or the terpolymer of vinyl formal/vinyl acetate/vinyl alcohol (PVFAcA) at 30 or 40°C. The ability to accelerate the photopolymerization increased in the order PVFAcA < PVHDO < PVDO; the ability of pendent cyclic acetal was larger than that of cyclic acetals which are not pendent. Moreover, the promoting ability per cyclic acetal increased with the increase in the number of cyclic acetal cyclic acetal group in the molecule.     

Construction of Highly Substituted Nitroaromatic Systems by Cyclocondensation. Part I. Synthesis of 4-nitro-3-oxobutyrate

Methyl 4-nitro-3-oxobutyrate ( 1 ) is prepared by substitution of 4-bromo- and 4-iodo-3-oxobutyrate enol ether or enol acetate derivatives with nitrite and deprotection of the keto function (Schemes 2 and 3). A much more convenient access to 1 is, however, the nitration of acetoacetate dianion with alkyl nitrates (Scheme 4). Compound 1 is stable and storable, and can be handled safely. Its use in cyclocondensations is established by the reaction with acetylacetone (Scheme 5), affording 4,6-dimethyl-3-nitrosalicylate 48 in 70% yield. The halogen-substitution method for the synthesis of 1 gives also access to the crystalline (E)-enol ether 18 of 1 , as well as to its dimethyl acetal 25 , (Z)-enol acetate 32 , and (E)-enol acetate 33 . The 3-substituted 4-bromobutenoates 15, 16 and 26 have been prepared from 4-bromo-3-oxobutyrate 12 , a useful alternative to existing methods applying N-bromo-succinimide.     

Catalytic behavior of nanoparticle α-PtO2 for ethanol oxidation

Fusion method is used to prepare α-PtO₂ and has a special needle-like microcrystalline morphology, with a diameter of ca. 6 nm and a length of ca. 50 nm. The two Pt–O bonds of α-PtO₂ are different in strength and α-PtO₂ decomposes thermally to Pt⁰ in two steps. α-PtO₂ is a p-type oxide semiconductor with a band-gap of 1.84 eV. α-PtO₂ is easily reduced by ethanol, its reduction product, Pt⁰, can directionally catalyze the oxidation of ethanol to acetic acid in the presence of air, while acetaldehyde, acetal and ethyl acetate are intermediates.     

Scandium trifluoromethanesulfonate as a recyclable catalyst for efficient methoxymethylation of alcohols

Scandium triflate [Sc(OTf)₃] has been found to be a recyclable catalyst for mild highly efficient methoxymethylation of a variety of alcohols using formaldehyde dimethyl acetal (FDMA).     

Etude thermodynamique de la decomposition thermique des hydrates du chlorure de magnesium

The thermodynamic study of the different compounds of the system MgCl₂, H₂O, HCl allows to draw the stability diagram of the 8 solid phases into a three-dimensional space (temperature, total pressure and ratio of HCl and H₂O partial pressures). The evolution of the composition of solid and gaseous phases during an isobaric heating is described. The conclusions of this study are in good agreement with the experimental results obtained in laboratory and with the industrial requirements set for the different steps of the dehydration of MgCl₂.     

High-valent [Sn(Br8TPP)(OTf)2] as a highly efficient and reusable catalyst for selective methoxymethylation of alcohols and phenols: The effect of substituted bromines on the catalytic activity

High-valent tin(IV)octabromotetraphenylporphyrinato trifluoromethanesulfonate, [Sn^IV(Br₈TPP)(OTf)₂], was used for selective methoxymethylation of alcohols and phenols with formaldehyde dimethyl acetal (FDMA) at room temperature. Different primary, secondary and tertiary alcohols as well as phenols were converted to their corresponding methoxymethyl ethers with FMDA in the presence of an electron deficient tin(IV) porphyrin. The catalyst was reused several times without significant loss of its activity.     

Acetal‐functionalized polymer particles useful for immunoassays. II. Surface and colloidal characterization

Monodisperse polymer colloids with dimethyl and diethyl acetal functionalities were synthesized by a two‐step emulsion polymerization process. The first step consisted of a batch emulsion homopolymerization of styrene (St). The dimethyl and diethyl acetal functionalities were obtained by batch emulsion terpolymerization of St, methacrylic acid (MAA), and methacrylamidoacetaldehyde dimethyl acetal (MAAMA) or methacrylamidoacetaldehyde diethyl acetal (MAADA) in the second step, onto the previously formed polystyrene latex particles. The latexes were characterized by TEM and conductimetric titration, in order to obtain the particle size distribution and the amount of carboxyl and acetal groups on the surface, respectively. The chemical stability of the functionalized surface groups during the storage time was analyzed. The hydrophilic character of the surface of the polymer particles was determined by means of nonionic emulsifier titration. The colloidal stability of the synthesized latexes was studied by measuring the critical coagulation concentration (CCC) against KBr electrolyte, and the existence of a hairy layer on the surface of the latex particles was analyzed by measuring the hydrodynamic particle diameter at several electrolyte concentrations. The surface functionalized groups remained stable for 2 years. The relative hydrophilic character and the colloidal stability were affected by the pH of the medium. On the other hand, the higher the surface charge, the larger the thickness of the hairy layer. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 501–511, 1999     

Synthesis of 2,3-disubstituted benzofurans by platinum-olefin-catalyzed carboalkoxylation of o-alkynylphenyl acetals

The PtCl2-catalyzed cyclization reaction of o-alkynylphenyl acetals 1 in the presence of 1,5-cyclooctadiene produces 3-(alpha-alkoxyalkyl)benzofurans 2 in good to high yields. For example, the reaction of acetaldehyde ethyl 2-(1-octynyl)phenyl acetal (1a), acetaldehyde ethyl 2-(cyclohexylethynyl)phenyl acetal (1c), and acetaldehyde ethyl 2-(phenylethynyl)phenyl acetal (1f) in the presence of 2 mol % of platinum(II) chloride and 8 mol % of 1,5-cyclooctadiene in toluene at 30 degrees C gave the corresponding 2,3-disubstituted benzofurans 2a, 2c, and 2f in 91, 94, and 88% yields, respectively.     

Syngas reactions XII. The selective preparation of acetaldehyde,alkanols, esters and acetic acid from synthesis gas

Several classes of commercially important oxygenates, including acetaldehyde, ethanol, methyl acetate, ethyl acetate and acetic acid as well as C₁–C₃ alcohol/acetate ester mixtures, may each be selectivelygenerated from synthesis gas through the application of novel classes of ruthenium-containing bimetallic catalysts particularly those of ruthenium and cobalt (Ru? Co). A particular feature of these versatile catalysts is that all precursors are iodidefree. Products are formed through a combination of carbon monoxide hydrogenation, methanol homologation, methyl acetate homologation and methanol carbonylation reaction sequences.     

Di-n-butyl acetal of bromoacetaldehyde

Summary The di-n-butyl acetal of bromoacetaldehyde was synthesized by reacting the dibutyl acetal of acetaldehyde with bromine, and its infrared spectrum was taken.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 1709–1711, September, 1964