Aldehyde Acetate Research Articles

Highly efficient and chemoselective acetalization of carbonyl compounds catalyzed by new and reusable zirconyl triflate, ZrO(OTf)2

AbstractVarious types of aromatic aldehydes were efficiently converted to their corresponding 1,3‐dioxanes and 1,3‐dioxolane with 1,3‐propanediol and ethylene glycol, respectively, in the presence of catalytic amount of ZrO(OTf)2 in acetonitrile at room temperature. The catalyst can be reused several times without loss of its catalytic activity. Very short reaction times, selective acetalization of aromatic aldehydes in the presence of aliphatic aldehydes and ketones, very mild reaction conditions, reusability of the catalyst, and easy workup are noteworthy advantages of this method. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:131–135, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20523

Pyridinium Salts as New Organocatalysts for Acetalizations

An efficient pyridinium-salt-1-catalyzed acetalization of aldehydes and ketones has been described. Among different pyridinium salts, catalyst 1 proved to be the most efficient species, with partially remarkable short reaction times (1 min to 48 h) and low catalyst loadings (0.1-10 mol%). The catalyst is proposed to form alcohol adducts, along with HBr acting as Brønsted acid catalyst.

Analysis of pentacyclic triterpenes by LC–MS. A comparative study between APCI and APPI

The analytical performances of three atmospheric-pressure sources, electrospray (ESI), atmospheric-pressure chemical ionization (APCI), and atmospheric-pressure photoionization (APPI), were evaluated for the analysis of pentacyclic triterpenes in liquid chromatography-mass spectrometry (LC-MS). Among these sources, APPI and APCI are particularly well adapted to sensitive analyses of pentacyclic triterpenes by LC-MS. Detection parameters were optimized for both the sources, and the effects of three dopants (toluene, acetone and anisole) on the detection (sensitivity and ion fingerprints in MS spectra) were studied in detail for APPI-MS.The limits of quantification were measured under selected ion monitoring conditions, in the range of 0.005-0.015 mg l(-1) and 0.002-0.84 mg l(-1) in APPI and APCI, respectively, depending on the studied pentacyclic triterpene. Overall, APPI was found more sensitive than APCI in positive ion mode, whereas APCI shows the greatest sensitivity for acidic triterpenes in negative ion mode.Following this study, the developed LC-MS method was used for the characterization of pentacyclic triterpenes in three plant extracts. High amounts of betulinic acid, betulinic aldehyde and betulinic aldehyde acetate were observed in plane bark. The main component of birch bark is betulin and extracts of okoume resin exhibit high amounts of alpha- and beta-amyrin.

Novel Brønsted acidic ionic liquids based on benzimidazolium cation: Synthesis and catalyzed acetalization of aromatic aldehydes with diols

In this article, a new group of Bronsted acidic task-specific ionic liquids based on benzimidazolium cation was synthesized and used as environmentally benign catalysts for acetalization of aromatic aldehydes with diols. Hammett method had been used to determine the acidity order of these ionic liquids, which was consistent with the catalytic activities observed in acetalization reaction. Maximum substrate conversion of 98% and product selectivity of 100% were obtained using [PSebim]HSO4 as catalyst, which could be reused at least 10 times without obvious loss of catalytic activity.

Acetalization of carbonyl compounds with 2,2,4-trimethyl-1,3-pentanedio catalyzed by novel carbon based solid acid catalyst

The synthesis of 2, 4-diisopropyl-5,5-dimethyl-1,3-dioxane through the acetalization of isobutyraldehyde with 2, 2, 4-trimethyl-1,3-pentanediol (TMPD) catalyzed by the novel carbon based acid was first carried out. High conversion (≥98%) and specific selectivity were obtained using the novel carbon based acid, which kept high activity after it was reused 5 times. Moreover, the catalyst could be used to catalyze the acetalization and ketalization of different aldehydes and ketones with superior yield. The yield of several products was over 90%. The novel heterogeneous catalyst has the distinct advantages of high activity, strikingly simple workup procedure, non-pollution, and reusability, which will contribute to the success of the green process greatly.

ChemInform Abstract: Hypervalent Iodine‐Mediated Efficient Synthesis of Imidazoles.

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An Indium Layered MOF as Recyclable Lewis Acid Catalyst

By using the bent linker 4,4′-(hexafluoroisopropylidene)bis(benzoic acid) (H2hippb), whose central atom is an sp3 carbon, a new In(III) MOF has been obtained. The structure is described as thick layers with the bent geometry of the ligand leading to the formation of square-shaped channels, which run inside the framework layers. This microporous, thermally stable compound has been proved to be an efficient heterogeneous catalyst for acetalization of aldehydes. Differences in the catalytic activity when a compound with empty or filled channels is used demonstrate that the catalytic reactions take place inside the pores.

General Synthesis Route to Benanomicin‐Pradimicin Antibiotics

A general approach to the regio- and stereoselective total synthesis of the benanomicin-pradimicin antibiotics (BpAs) is described. Construction of the aglycon has been achieved by 1) the diastereoselective ring-opening of a biaryl lactone by using (R)-valinol as a chiral nucleophile and 2) the stereocontrolled semi-pinacol cyclization of the aldehyde acetal by using SmI(2) in the presence of BF(3)OEt(2) and a proton source to afford the ABCD tetracyclic monoprotected diol. This strategy enabled us to control the two stereogenic sites in the B ring (C-5 and C-6) and the regioselective introduction of the carbohydrate moiety. The ABCD tetracycle could serve as an ideal platform for the divergent access to various BpAs. The amino acid (D-alanine) was introduced onto the ABCD tetracycle. Glycosylation was promoted by the combination of Cp(2)HfCl(2) and AgOTf (1:2 ratio). Construction of the E ring followed by deprotection completed the first total synthesis of benanomicin A (2 a), benanomicin B (2 b), and pradimicin A (1 a). The route is flexible enough to allow the synthesis of other congeners differing in their amino acid and carbohydrate moieties.

A New Concise Strategy for Synthesis of Dibenzo[b,f]thiepins and Related Fused Symmetrical Thiepin Derivatives

A new strategy for preparation of dibenzo[b,f]thiepins and related fused systems in good overall yields is described, featuring ortho-metalation of aromatic or heterocyclic aldehyde acetals followed by treatment with bis(phenylsulfonyl) sulfide for construction of the required bis(aryl)- or bis(heteroaryl) sulfide precursors, which were thereafter subjected to deacetalization, and finally McMurry coupling as the ring-forming step.

Diastereoselective Prins-Type Reaction of Cycloalkenylcyclopropanol Silyl Ethers and α,β-Unsaturated Aldehyde Acetals

Electrophilic addition of 1-(1-cyclohexenyl)-1-cyclopropanol trimethylsilyl ether to alpha,beta-unsaturated aldehyde acetals under Lewis acidic conditions proceeds with good to excellent diastereoselectivity to afford spirocyclobutanones containing three contiguous stereocenters. A convenient entry to enantioselective syntheses is available by use of a nonracemic C2-symmetric acetal. Elaboration of the resulting adducts provides ready access to medium-sized carbocycles.

2,4,6‐Trichloro‐1,3,5‐triazine‐Catalyzed Chemoselective Transthioacetalization of Aldehyde Acetals and Oxathioacetals.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Indium Triflate Mediated Acetalization of Aldehydes and Ketones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Study on catalytic synthesis of 1,3-benzodioxoles by HY zeolite

The acetalization and ketalization of various aldehydes and ketones with catechol by using HY zeolite as catalyst were studied. Effect of the reaction time, mole ratio of reactants, and amount of catalyst on the yield of benzodioxoles were investigated. Results show that HY is an efficient catalyst for the acetalization and ketalization with high conversion and selectivity in mild conditions. The best reaction conditions: molar ratio of catechol to aldehydes or ketones is 1:1.4, catalyst amount is 3.5 g/l mol catechol, reaction time is 5 h. Under these conditions, the conversion and selectivity were over 50% and 97%, respectively.

2,4,6-Trichloro-1,3,5-triazine Catalyzed Chemoselective Transthioacetalization of Aldehyde Acetals and Oxathioacetals

A mild and efficient transthioacetalization of aldehyde acetals and oxathioacetals was carried out using 2,4,6-trichloro-1,3,5-triazine as a mild and inexpensive catalyst. Chemoselective transacetalization is impressive as aldehyde O,O- and O,S-acetals are converted into the corresponding S,S-acetals in the presence of ketones or their acetals and oxathiocetals in nearly quantitative yields.

Indium triflate mediated acetalization of aldehydes and ketones

Aldehydes and ketones are rapidly transformed into either acyclic or cyclic acetals at room temperature in high yields and in very short reaction times using catalytic quantities of indium triflate, in contrast to previous reports.

One‐Pot Synthesis of N‐Protected α‐Amino Aldehyde Acetals from Three‐Component Reaction of Fluoroalkanesulfonyl Azide, Vinyl Ether and Alcohol.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Isostructural strontium formate, fumarate and acetylendicarboxylate

There currently is a considerable interest in metal-organic polymeric materials inspired by their intriguing structural diversity and potential functions as microporous solids for molecular adsorptions, ion exchange, and heterogeneous catalysis. Benzene multicarboxylate ligands have been found to be useful building blocks in construction of organic-inorganic materials with desired topologies owing to their rich coordination modes. Particularly, in our previous studies [1, 2] on the indiummetal-organic frameworks (MOFs) with benzenpolycarboxylic acids, the obtained materials have proven to possess intriguing structural features as well as interesting catalytic properties both in hydrogenation of nitroaromatics, and oxidation of sulfide reactions [1], and in acetalization of aldehydes [2]. Herein, we present the synthesis and crystal structure of the new polymeric indium MOF obtained in the course of hydrothermal reaction of the InCl3 and 4,4 u(hexafluoroisopropylidene)bis(benzoic) acid, H2L, in the presence of pyridyl (Py). Its structure was determined by X-ray singlecrystal diffraction. Structurally speaking we can conclude that the metal/connector rate is 1:1, the polymeric structure being 2D layered framework. The material obtained is thermally stable up to ∼420C. Catalytic activity of the new MOF has been evaluated as well.

New Catalytic Methods for the Preparation of Acetals from Alcohols and Aldehydes

The acetalization of aldehydes has been studied with ethyleneglycol, 3‐chloro‐1,2‐propanediol, 1,2‐propanediol, and 1,2,3‐propanetriol using resin‐D72 catalyst in high yields under reflux and water separator conditions. The reaction is simple, efficient, and chemoselective and does not involve any other additive.

The synthesis of 2-hydroxymethyl derivatives of phenols

2-Hydroxymethylphenols have been prepared in good yield by reduction with sodium borohydride of the precursor aldehydes, obtained regiospecifically from reaction of phenols with paraformaldehyde in toluene containing stannic chloride and tri- n-butylamine. By contrast, reaction of phenols with either paraformaldehyde under anhydrous conditions or with aqueous formaldehyde results in formation of both the hydroxymethyl and the bishydroxymethyl derivatives. Cyclic acetals of the precursor aldehydes are readily accessible.

Acid‐Free, Organocatalytic Acetalization.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.