Reactions of Verbenol Epoxide with Aromatic Aldehydes Containing Hydroxy or Methoxy Groups in the Presence of Montmorillonite Clay

The reactions of (?)‐cis‐verbenol epoxide with a number of aromatic aldehydes containing OH and/or MeO groups in the presence of montmorillonite K10 clay have been studied. Several new O‐containing heterocyclic compounds with different frameworks, including compounds with a previously unknown octahydro‐2H‐4,6‐(epoxymethano)chromene framework, have been synthesized. Introduction of one donor substituent in the benzaldehyde molecule led to a decrease in the total yield of intermolecular by formed products, while the introduction of two and more substituents led to an increase in the yield of these products.     

Reactions of Allyl Alcohols of the Pinane Series and of Their Epoxides in the Presence of Montmorillonite Clay

The reactivity of allyl alcohols of the pinane series and of their epoxides in the presence of montmorillonite clay in intra‐ and intermolecular reactions was studied. Mutual transformations of (+)‐trans‐pinocarveol ((+)‐ 2 ) and (?)‐myrtenol ((?)‐ 3a ) were major reactions of these compounds on askanite–bentonite clay (Schemes 1 and 2). However, the two reactions gave different isomerization products, indicating that the reactivity of the starting alcohol (+)‐ 2 or (?)‐ 3a was different from that of the same compound (+)‐ 2 or (?)‐ 3 formed in the course of the reactions. (?)‐cis‐ and (+)‐trans‐Verbenol ((?)‐ 16 and (+)‐ 12 , resp.), as well as (?)‐cis‐verbenol epoxide ((?)‐ 20 ) reacted with both aliphatic and aromatic aldehydes on askanite–bentonite clay giving various heterocyclic compounds (Schemes 4, 5 and 7); the reaction path depended on the structure of both the terpenoid and the aldehyde.     

Axial base‐controlled catalytic activity,oxidative stability and product selectivity of water‐insoluble manganese and iron porphyrins for oxidation of styrenes in water under green conditions

A series of water‐insoluble iron(III) and manganese(III) porphyrins, FeT(2‐CH₃)PPCl, FeT(4‐OCH₃)PPCl, FeT(2‐Cl)PPCl, FeTPPCl, MnT(2‐CH₃)PPOAc, MnT(4‐OCH₃)PPOAc, MnT(2‐Cl)PPOAc and MnTPPOAc, in the presence of imidazole (ImH), F^?, Cl^?, Br^? and acetate were used as catalysts for the aqueous‐phase heterogeneous oxidation of styrenes to the corresponding epoxides and aldehydes with sodium periodate. Also, the effect of various reaction parameters such as reaction time, molar ratio of catalyst to axial base, type of axial base, molar ratio of olefin to oxidant and nature of metal centre on the activity and oxidative stability of the catalysts and the product selectivity was investigated. Higher catalytic activities were found for the iron complexes. Interestingly, the selectivity towards the formation of epoxide and aldehyde (or acetophenone) was significantly influenced by the type of axial base. Furthermore, Br^? and ImH were found to be the most efficient co‐catalysts for the oxidation of olefins performed in the presence of the manganese and iron porphyrins, respectively. The optimized molar ratio of catalyst to axial base was different for various axial bases. Also, the order of co‐catalyst activity of the axial bases obtained in aqueous medium was different from that reported for organic solvents. The use of a convenient axial base under optimum reaction catalyst to co‐catalyst molar ratio in the presence of the manganese porphyrin gave the oxidative products with a conversion of ca 100% in a reaction time of less than 3 h. However, the catalytic activity of the iron porphyrins could not be effectively improved by increasing the catalyst to co‐catalyst molar ratio.     

Synthesis of 5-(perfluoroalkylmethyl)-1,3-dioxolan-4-ones

Acid catalysed condensation of F-alkyl α-hydroxy acids with simple aldehydes or ketones gave F-alkyl 1,3-dioxolan-4-ones. When BF₃,OEt₂ was used as the catalyst, the condensation products were obtained in moderate to good yields and the “cis” isomers are largely favoured, while with HOTs/H₂SO₄ as catalyst, poor yields and lower stereoselectivities were observed.     

Clean Procedure for the Synthesis of α-Aminophosphonates Catalyzed by Biodegradable Ionic Liquid

Abstract

A biodegradable SO₃H-functionalized ionic liquid (IL) was prepared and used as the catalyst for a one-pot, three-component condensation synthesis of α-aminophosphonates from aldehydes, amines, and triethylphosphite/diethylphosphite at room temperature under solvent-free conditions or in aqueous media. The products could be simply separated from the reaction mixture and the catalyst could be recycled and reused for several times without noticeably reducing catalytic activity.     

Synthesis of carboxylic esters from aldehydes using metal carbonyl anions,part 2. Dimerization of aldehydes to carboxylic esters catalyzed by disodium pentacarbonylchromate,na2[cr(co)5]

Na₂[Cr(CO)₅] (1) was found to be an efficient catalyst for the dimerization of aldehydes to carboxylic esters. Several aromatic aldehydes including furfural gave the corresponding esters in good yields. This reaction also proceeded intramolecularly to give phthalide from phthalaldehyde. Compared with M₂[Fe(CO)₄] (M = Na, K), 1 was found to be a more efficient catalyst for this reaction. However, aliphatic aldehydes gave aldolcondensation products instead of the corresponding esters. In the reactions of p-substituted benzaldehydes with 1, the reactivity decreased with the increase of the electron-releasing ability of the substituents. However, even p-anisaldehyde, which hardly reacted with M₂[Fe(CO)₄], reacted with 1 to give the ester in moderate yield. The reaction mechanism, including the nucleophilic attack of the pentacarbonylchromate dianion on the carbonyl carbon, is discussed.     

Fe（HSO4）3： An efficient,heterogeneous and reusable catalyst for the synthesis of 14-aryl- or alkyl- 14H-dibenzo[a,j]xanthenes

Fe（HSO4）3 has been used as an efficient and recyclable catalyst for the one-pot synthesis of 14-aryl- or alkyl-14Hdibenzo[aj]xanthene derivatives by the reaction of 2-naphtol and aldehydes. Different types of aromatic and aliphatic aldehydes are used in the reaction and in all cases the products were obtained in good to excellent yields.     

ZIF‐8‐Nanocrystalline Zirconosilicate Integrated Porous Material for the Activation and Utilization of CO2 in Insertion Reactions

The conversion of CO₂ to useful chemicals, especially to atom economical products, is the best approach to utilize an excess of CO₂ present in the atmosphere. In this study, a metal‐organic framework (ZIF‐8) is integrated with nanocrystalline zirconosilicate zeolite to develop an integrated porous catalyst for CO₂ insertion reactions. The catalyst exhibits excellent activity for the CO₂ insertion reaction of epoxide to produce cyclic carbonate in neat condition without the addition of any co‐catalyst. The catalyst is stable and recyclable during the cyclic carbonate synthesis. Further, the catalyst also exhibits very good activity in another CO₂ insertion reaction to produce quinazoline‐2,4(1H, 3H)‐dione.     

Hydrosilylation and double silylation of carbonyl compounds with 1,1′-bis(dimethylsilyl)ferrocene using nickel- and platinum-catalysts

A series of ferrocene-based organosilicon compounds have been prepared via hydrosilylation or double silylation of carbonyl compounds with 1,1′-bis(dimethylsilyl)ferrocene using (C₂H₄)Pt(PPh₃)₂ or Ni(PEt₃)₄ catalysts. In general, while the platinum catalyst (C₂H₄)Pt(PPh₃)₂ preferentially produced cyclic double-silylated products, the Ni(PEt₃)₄ catalyst led to the hydrosilylated ferrocene products from aldehydes or ketones.     

Encapsulation of a binuclear manganese(II) complex with an amino acid-based ligand in zeolite Y and its catalytic epoxidation of cyclohexene

A Schiff base ligand was synthesized by the condensation of salicylaldehyde with l-tyrosine. Interaction of this ligand with Mn(II)-exchanged zeolite Y leads to encapsulation of the ligand within the zeolite and complexation of the metal. The encapsulated complex has been characterized by spectroscopic studies and chemical analyses. This material serves as a catalyst for the oxidation of cyclohexene to cyclohexene epoxide and 2-cyclohexene-1-ol using H₂O₂ as oxidant. The reaction conditions have been optimized for solvent, temperature and amount of oxidant and catalyst. The catalyst shows high activity and selectivity toward production of cyclohexene epoxide in acetonitrile at 60 °C with [H₂O₂]/[C₆H₁₀] = 2.5 molar ratio. Comparison of the encapsulated catalyst with the corresponding homogeneous catalyst showed that the heterogeneous catalyst had higher activity and selectivity than the homogeneous catalyst.     

Zinc cation supported on carrageenan magnetic nanoparticles: A novel,green and efficient catalytic system for one‐pot three‐component synthesis of quinoline derivatives

This is the first report of supporting zinc cation on ƛ‐carrageenan/Fe₃O₄ magnetic nanoparticles. The structural and magnetic properties of this hybrid (Zn²⁺/ƛ‐carrageenan/Fe₃O₄ nanoparticles) were identified using various techniques. This green and efficient catalytic system was applied in the synthesis of biologically important quinolines. The products were obtained in good to high yields (52–95%) from a one‐pot reaction procedure involving aromatic aldehydes, enolizable aldehydes and aniline derivatives. Our method has many advantages such as mild reaction conditions, easy work‐up, use of a reusable magnetic catalyst and high yields of products.     

氯化亚锡催化“一锅法”合成N1-取代的3,4-二氢嘧啶-2(1H)-酮

以芳香醛、乙酰乙酸乙酯(甲酯)、单取代脲为原料,氯化亚锡为催化剂,在无溶剂、80℃条件下,通过三组分"一锅法"合成了一系列N1-取代的3,4-二氢嘧啶-2(1H)-酮衍生物。考察了催化剂用量和反应温度对产品收率的影响。通过IR、~1H NMR、~(13)C NMR和元素分析对目标产物结构进行确证,提出了可能的催化作用机理。本文的合成方法具有催化剂活性高、廉价易得和反应时间短、条件温和、产率高、绿色环保等优点。     

Nicotinic acid-supported cobalt ferrite-catalyzed one-pot synthesis of substituted chromeno[3,4-b]quinolines

One-pot synthesis of substituted chromeno[3,4-b]quinoline derivatives was developed by three-component reaction of aldehydes, dimedone or 1,3-cyclohexadione, and 4-aminocoumarin in the presence of nicotinic acid-supported cobalt ferrite [CoFe₂O₄@SiO₂@Si(CH₂)₃Cl@NA] as a novel magnetic catalyst in chloroform at reflux conditions. Nicotinic acid-supported cobalt ferrite was characterized via Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, scanning electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, and vibrating sample magnetometry. Moreover, the catalyst could be easily recovered by magnetic separation and recycled up to five times without significant loss of its catalytic activity. The products formed in excellent yields over appropriate reaction times under environmentally friendly conditions. High efficiency and easy isolation of the catalyst from products by simple magnetic attraction are some of the considerable advantages of this procedure.     

HAlMCM-41介孔分子筛催化1,3-苯并二噁茂烷合成的研究

研究了HAlMCM-41分子筛催化邻苯二酚与环己酮、丁酮、丙酮、丙醛、丁醛、异丁醛、戊醛、正己醛、正辛醛、苯甲醛、二苯甲酮等十余种醛(酮)的缩合反应. 考察了反应时间、酚与醛(酮)的配比、HAlMCM-41分子筛用量、硅铝比、催化剂重用次数等因素对邻苯二酚与醛(酮)反应的影响. 结果表明, 当邻苯二酚与醛(酮)物质的量比为1∶1.4, 催化剂用量为3.5 g/mol邻苯二酚, 反应4 h, 分子筛n(SiO₂)/n(Al₂O₃)为15时, 选择性一般在99.4%以上, 转化率也一般在85.6%以上, 因此, HAlMCM-41分子筛对邻苯二酚与醛(酮)的反应有较好的催化性能.     

Magnetic nanoparticle supported amine: An efficient and environmental benign catalyst for versatile Knoevenagel condensation under ultrasound irradiation

Amine functionalized silica coated Fe₃O₄ nanoparticles (SiO₂@MNP-A) were successfully prepared as a novel heterogeneous amine. The catalyst was characterized by XRD, FT-IR, TEM, magnetic measurement, elemental analysis and was found to be a magnetically separable and highly active catalyst for ambient Knoevenagel condensation of aromatic aldehydes and α-aromatic (heteroaromatic or polyaromatic)-substituted methylene compounds in water under ultrasonic irradiation to afford the corresponding products in good to excellent yields. Very interestingly, SiO₂@MNP-A successfully catalyze the reaction of the non-cyano substituted compound with benzaldehyde to achieve a key intermediate for the preparation of Atorvastatin calcium in green and atom-economic manner. In addition, the catalyst SiO₂@MNP-A can be reused for 8 times without any obvious loss of its activity. The role of ultrasonication in the Knoevenagel condensation was also discussed with the assistance of UV–vis spectrometry.     

Neat synthesis of octahydroxanthene-1,8-diones,catalyzed by silicotungstic acid as an efficient reusable inorganic catalyst

In this article, the first use of silicotungstic acid (H₄SiW₁₂O₄₀) as a catalyst for the synthesis of octahydroxanthene-1,8-diones by the reaction of 5,5-dimethylcyclohexane-1,3-dione (dimedone) with various aldehydes under thermal solvent-free conditions is described. The obtained results showed that the catalyst has a high catalytic activity, and the desired products were obtained in high yields. Moreover, the catalyst was found to be reusable, and a considerable catalytic activity still could be achieved after the fifth run. Easy work-up and avoidance of using harmful organic solvents are the other advantages of this simple procedure.     

Efficient one-pot synthesis of some new pyrimido[5′,4′:5,6]pyrido[2,3-d]pyrimidines catalyzed by magnetically recyclable Fe3O4 nanoparticles

The study is devoted to one-pot reaction of 1,3-dimethylbarbituric acid with aromatic aldehydes and ammonium acetate using Fe₃O₄ nanoparticles as efficient and magnetically recyclable catalysts. Aromatic aldehydes substituted with electron-withdrawing groups or none, reacted successfully with 1,3-dimethylbarbituric acid and ammonium acetate to give new pyrimido[5′,4′:5,6]pyrido[2,3-d]pyrimidine derivatives (can be also named as pyrido[2,3-d:6,5-d′]dipyrimidines) in high yields over relatively short reaction time. The Knoevenagel condensation products were isolated using aromatic aldehydes bearing electron-donating substituents. The catalyst could be efficiently used for four times without substantial reduction in its activity. The new products were characterized on the basis of FT-IR, ¹H NMR and ¹³C NMR spectral data.

     

CuPy2Cl2: A Novel and Efficient Catalyst for Synthesis of Propargylamines Under the Conventional Method and Microwave Irradiation

CuPy₂Cl₂ is an efficient catalyst for the preparation of propargylamines via three-component coupling reaction of aromatic aldehydes, amines, and aromatic alkynes stirred at 95 °C without using any solvent to afford the corresponding products in good yields. The reaction mixture was irradiated at 450 W in a microwave oven to furnish the expected products in excellent yields.     

Peptide‐Catalyzed Stereoselective Conjugate Addition Reactions of Aldehydes to Maleimide

The tripeptide H‐d Pro‐Pro‐Asn‐NH₂ is presented as a catalyst for asymmetric conjugate addition reactions of aldehydes to maleimide. The peptidic catalyst promotes the reaction between various aldehydes and unprotected maleimide with high stereoselectivities and yields. The obtained products were readily derivatized to the corresponding pyrrolidines, lactams, lactones, and peptide‐like compounds. ¹H NMR spectroscopic, crystallographic, and computational investigations provided insight into the conformational properties of H‐d Pro‐Pro‐Asn‐NH₂ and revealed the importance of hydrogen bonding between the peptide and maleimide for catalyzing the stereoselective C?C bond formation.     

Catalytic oxidation of α-pinene by transition metal using t-butyl hydroperoxide and hydrogen peroxide

The allylic oxidation of α-pinene 1 was investigated using various catalytic systems. By a proper choice of the latter, the reaction can be directed toward the selective synthesis of verbenol 2 or verbenone 3. High yield into verbenone was achieved under mild conditions with copper salts as catalysts and t-butyl hydroperoxide (TBHP) as oxidant. On the other hand, when Pd(acac)₂ was used with hydrogen peroxide, verbenol was obtained as the main product.