- Biomimetic Total Synthesis of Enterocin
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The first chemical total synthesis of the highly oxygenated polyketide enterocin has been accomplished. The key step of the synthesis was a late-stage biomimetic reaction cascade involving two intramolecular aldol reactions in which each step proceeded in 52 % yield (averaged) and which established four of the seven stereogenic centers. The pivotal precursor for the cascade reaction was assembled from three readily available building blocks. A chiral dithioacetal with two stereogenic centers originating from L-arabinose represented the core fragment to both ends of which the other building blocks were attached by aldol reactions. The remaining stereogenic center was installed by Davis oxygenation immediately prior to the key step.
- Bach, Thorsten,Koser, Lilla,Lechner, Vivian Miles
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Read Online
- Synthesis of DPA-triazole structures and their application as ligand for metal catalyzed organic reactions
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In this work, the use of DPA-triazole (DPA = dipicolylamine) molecules as ligands for metal catalyzed organic reactions has been investigated. A small library of ligands has been prepared by a CuAAC (click reaction) between propargyl-DPA and different azi
- Colombo Dugoni, Greta,Sacchetti, Alessandro,Urra Mancilla, Carolina
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- Practical acetalization and transacetalization of carbonyl compounds catalyzed by recyclable PVP-I
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A novel PVP-I catalyzed acetalizations/transacetalizations of carbonyl compounds has been developed processing with a mild and easy handling fashion. Different types of Acyclic and cyclic acetals were prepared from carbonyl compounds or their acetals successfully. Further applications of newly developed catalytic combination were testified. This protocol featured with simplicity of operation, mild reaction condition, short reaction time, recyclable of catalyst and broad substrates scope with excellent yields.
- Cao, Fu-Rong,Lu, Guangying,Ren, Jiangmeng,Wang, Di,Zeng, Bu-Bing
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- Preparation method of acetal or ketal compound
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The invention discloses a preparation method of an acetal or ketal compound. The preparation method comprises the following steps: oscillating aldehyde or ketone, alcohol and a catalyst at 60 DEG C, and carrying out post-treatment after the reaction is finished to obtain the acetal compound, wherein the catalyst comprises alpha-chymotrypsin, the aldehyde or ketone has a structure represented by acompound A, R1 and R2 are respectively and independently selected from aryl, H and alkyl, the alcohol has a structure represented by a compound B, and R3 is selected from saturated alkane. The preparation method provided by the invention is catalyzed by alpha-chymotrypsin, is mild in reaction condition, simple in operation process, low in cost and environment-friendly, and has popularization and application values.
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Paragraph 0049-0057
(2020/04/22)
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- α-Chymotrypsin-Induced Acetalization of Aldehydes and Ketones with Alcohols
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This is the first report of a simple and general method for acetalization of aldehydes via an α-chymotrypsin-induced reaction under mild conditions. A broad range of aromatic and heteroaromatic aldehydes have been acetalized under neutral conditions in good yields using a catalytic amount of chymotrypsin.
- Jiang, Guofang,Lan, Jin,Le, Zhanggao,Xie, Zongbo,Yang, Jiangnan,Zhu, Haibo
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p. 2121 - 2126
(2020/07/14)
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- A bifunctional metal–organic framework platform for catalytic applications
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DUT-71 (DUT – Dresden University of Technology), a copper paddle wheel based framework, was used as a platform for postsynthetic modification to introduce specific catalytically active sites and to enhance the catalytic activity for fine chemicals product
- Müller, Philipp,Bon, Volodymyr,Senkovska, Irena,Nguyen, Khoa D.,Kaskel, Stefan
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supporting information
p. 382 - 386
(2019/01/03)
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- Nickel-Catalyzed Chemoselective Acetalization of Aldehydes With Alcohols under Neutral Conditions
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A molecularly defined NiII-complex catalyzing the chemoselective acetalization of aldehydes with alcohols under neutral conditions is reported. The reaction is general, efficient and showed a wide substrate scope (including aliphatic aldehydes) as well as excellent functional group tolerance. Reusability of the present nickel catalyst is also demonstrated.
- Subaramanian, Murugan,Landge, Vinod G.,Mondal, Akash,Gupta, Virendrakumar,Balaraman, Ekambaram
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supporting information
p. 4557 - 4562
(2019/08/30)
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- Formation of Acetals and Ketals from Carbonyl Compounds: A New and Highly Efficient Method Inspired by Cationic Palladium
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The development of a new, highly efficient, and simple method for masking carbonyl groups as acetals and ketals is described. This methodology relies on the nature of the palladium catalyst to direct the acetalization/ketalization reaction. This new protocol is mild and proceed with a very low catalyst loading at ambient temperatures. The method has been extended to a wide variety of different carbonyl compounds with various steric encumbrances to form the corresponding acetals and ketals in excellent yields.
- Green, Shawn D.,Kindoll, Tyler,Lazaro-Martinez, Brenda,Mensah, Enoch A.,West, Jesse
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p. 1810 - 1814
(2019/09/09)
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- Antimony(v) catalyzed acetalisation of aldehydes: An efficient, solvent-free, and recyclable process
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A highly selective, solvent-free process for the acetalisation of aldehydes was achieved by the use of a readily accessible antimony(v) catalyst which we previously prepared in our lab as a tetraarylstibonium triflate salt ([1][OTf]). High yields of the acetals were achieved in the presence of stoichimetric amounts of either triethoxymethane or triethoxysilane. It was found that triethoxymethane reactions required longer time to reach completion when compared to triethoxysilane reactions which were completed upon mixing of the reagents. The products can be easily separated from the catalyst by distillation which enabled further use of [1][OTf] in additional calytic reactions (up to 6 cycles). Moreover, [1]+ also catalyzed the deprotection of the acetals into their corresponding aldehydes using only water as a solvent.
- Ugarte, Renzo Arias,Hudnall, Todd W.
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p. 1990 - 1998
(2017/06/09)
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- Phosphorylated Polyacrylonitrile Fibers as an Efficient and Greener Acetalization Catalyst
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A novel solid acid catalyst (PANEAPF) is developed by immobilization of phosphoric acid on polyacrylonitrile fiber through covalent bonding. Various characterization techniques such as elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), etc. are utilized to confirm the successful grafting and the stability of the fiber catalysts during application. PANEAPF shows high catalytic activity in the acetalization of aldehydes owing to the high utilization efficiency of its functionalized acid sites. In addition, the strong polarity micro-environment in the surface layers of PANEAPF make it highly suitable for catalytic application in both water and alcohol. Furthermore, the fiber catalyst can be applied to the acetalization of aldehydes in a continuous-flow process at room temperature, and shows excellent reactivity and superior recyclability (over 20 times). The many advantages of PANEAPF such as simple preparation, convenient regulation of acid amount, high durability, and eco-friendly process make it very attractive for fixed-bed reactors in the chemical industry.
- Xu, Gang,Cao, Jian,Zhao, Yali,Zheng, Lishuo,Tao, Minli,Zhang, Wenqin
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supporting information
p. 2565 - 2575
(2017/09/25)
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- Visible-light-induced acetalization of aldehydes with alcohols
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In this work, we have achieved a simple and general method for acetalization of aldehydes by means of a photochemical reaction under low-energy visible light irradiation. A broad range of aromatic, heteroaromatic, and aliphatic aldehydes have been protected under neutral conditions in good to excellent yields using a catalytic amount of Eosin Y as the photocatalyst. Our visible light mediated acetalization strategies are successful for more challenging acid-sensitive aldehydes and sterically hindered aldehydes. Notably, this protocol is chemoselective to aldehydes, while ketones remain intact.
- Yi, Hong,Niu, Linbin,Wang, Shengchun,Liu, Tianyi,Singh, Atul K.,Lei, Aiwen
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supporting information
p. 122 - 125
(2017/11/27)
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- Tropylium salts as efficient organic Lewis acid catalysts for acetalization and transacetalization reactions in batch and flow
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Acetalization reactions play significant roles in the synthetically important masking chemistry of carbonyl compounds. Herein we demonstrate for the first time that tropylium salts can act as organic Lewis acid catalysts to facilitate acetalization and transacetalization reactions of a wide range of aldehyde substrates. This metal-free method works efficiently in both batch and flow conditions, prompting further future applications of tropylium organocatalysts in green synthesis.
- Lyons,Crocker,Enders,Nguyen
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supporting information
p. 3993 - 3996
(2017/09/08)
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- Carbon nitride supported palladium nanoparticles: An active system for the reduction of aromatic nitro-compounds
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Synthesis of carbon nitride supported highly dispersed ultrafine palladium nanoparticles has been reported for the reduction of aromatic nitro-compounds using hydrazine hydrate as a reducing agent. As a demonstration, the as-synthesized carbon nitride-palladium composite was shown to be a highly active and chemo-selective for the title reaction. Utilizing the optimized reaction conditions a set of aromatic nitro compounds have been converted to their corresponding amine derivatives with good to excellent yield ranging from 80% to 99%. The catalyst can be used for multiple times without affecting the catalytic performance and can also be stored for a long time at ambient condition maintaining the high catalytic efficiency.
- Nandi, Debkumar,Siwal, Samarjeet,Choudhary, Meenakshi,Mallick, Kaushik
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- Method for synthesis of acetal derivative by photocatalysis
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The invention discloses a method for synthesis of an acetal derivative by photocatalysis. The method consists of: in the presence of a photocatalyst, dissolving aldehyde and lower alcohol in an organic solvent, mixing the substances evenly, then carrying out reaction for 4-12h in an inert gas atmosphere and under a 300-600nm wavelength illumination condition, and then carrying out separation and purification, thus obtaining the acetal derivative. According to the invention, aldehyde, lower alcohol and the photocatalyst are employed to construct the acetal derivative by one step directly under room temperature illumination, the preparation method is simple, has mild conditions, and can prepare the target product high selectively; the raw materials are cheap and easily available, green and economical, also the method has very good substrate applicability, greatly expands the substrate range, and has very great application potential in biomedical synthetic intermediates.
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Paragraph 0059
(2017/04/19)
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- Zeolite nanofiber assemblies as acid catalysts with high activity for the acetalization of carbonyl compounds with alcohols
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Zeolite nanofiber assemblies (HNB-MOR) as efficient heterogeneous catalysts for the formation of a range of acetals in good yields. The mesoporosity of HNB-MOR benefits mass transfer, and the strong acidic sites on HNB-MOR facilitate acetalization activity. The catalyst can be reused 10 times without loss of activity.
- Liu, Taotao,Fu, Wenqian,Zheng, Xiang,Jiang, Jun,Hu, Maolin,Tang, Tiandi
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p. 18217 - 18221
(2014/05/20)
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- A facile and efficient protocol for esterification and acetalization in a PEG1000-D(A)IL/toluene thermoregulated catalyst-media combined systems
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A novel efficient and recyclable temperature-dependent biphasic catalyst and reaction media combined system comprised of PEG-1000 linked dicationic acidic ionic liquid and toluene was developed and applied in esterification of aromatic acids and acetalization of aromatic aldehydes with good to excellent yields. This system is characteristic of temperature-dependent reversible biphasic property, simple and facile recyclability, high catalytic activity and extensive substrate and reaction adaptability.
- Wang, Yinglei,Zhi, Huizhen,Luo, Jun
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- Highly efficient and chemoselective acetalization and thioacetalization of aldehydes catalyzed by propylphosphonic anhydride (T3P) at room temperature
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Propylphosphonic anhydride (T3P), a low toxic peptide coupling agent, has been demonstrated to be an efficient catalyst for the chemoselective acetalization and thioacetalization of aldehydes in the presence of ketones. Cyclic and acyclic acetals of diverse aldehydes were obtained in good to excellent yields at room temperature in the presence of a catalytic amount of T3P.
- Augustine, John Kallikat,Bombrun, Agnes,Sauer, Wolfgang H.B.,Vijaykumar, Pujari
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p. 5030 - 5033
(2012/11/07)
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- Bis(perfluorooctanesulfonyl)imide supported on fluorous silica gel: Application to protection of carbonyls
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The immobilization of bis(perfluorooctanesulfonyl)imide (HNPf2) on fluorous silica gel (FSG) and its utilization in protection of carbonyls have been investigated. This system is reasonably general and can be applied to converting several carbonyls to the corresponding acetals and ketals in good to excellent yields. There is no need for the use of anhydrous solvents or inert atmosphere. Recycling studies have shown that the FSG-supported HNPf2 catalyst can be readily recovered and reused several times without significant loss of activity.
- Hong, Mei,Xiao, Guomin
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experimental part
p. 121 - 126
(2012/08/28)
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- A clean, palladium-catalyzed oxidative esterification of aldehydes using benzyl chloride
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A highly efficient, mild, simple and clean procedure is presented for the one-pot oxidation of aromatic and aliphatic aldehydes to their corresponding ethyl esters using benzyl chloride as the oxidant under palladium-catalyzed conditions. The reaction is complete in just 30 min under microwave irradiation and inert conditions are not required to obtain good to excellent yields (65-93%) of isolated products.
- Heropoulos, Georgios A.,Villalonga-Barber, Carolina
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scheme or table
p. 5319 - 5322
(2011/10/31)
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- Oxidation reactions using polymer-supported 2-benzenesulfonyl-3-(4- nitrophenyl)oxaziridine
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A thermally stable polymer-supported oxidant has been developed. Polymer-supported 2-benzenesulfonyl-3-(4-nitrophenyl)oxaziridine was applied to microwave-assisted reactions that occurred at high temperatures and was shown to oxidize alkenes, silyl enol ethers, and pyridines to the corresponding epoxides and pyridine N-oxides in excellent to good yields and with much shorter reaction times. It also enabled tetrahydrobenzimidazoles to be oxidatively rearranged to spiro fused 5-imidazolones in a more efficient manner. Recycling of the polymer-supported oxidant is also possible with minimal loss of activity after several reoxidations.
- Susanto, Woen,Lam, Yulin
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experimental part
p. 8353 - 8359
(2011/11/12)
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- A three-component reaction based on a remote-group-directed dynamic kinetic aza-Michael addition: Stereoselective synthesis of imidazolidin-4-ones
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(Figure Presented) In control: An α-amino amide reacted with an aldehyde and a Michael acceptor to form stable imidazolidin-4-ones with high stereoselectivity. A dynamic kinetic aza-Michael addition was discovered and applied to the three-component reacti
- Xu, Zhenghu,Buechler, Tyler,Wheeler, Kraig,Wang, Hong
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supporting information; scheme or table
p. 2972 - 2976
(2010/07/06)
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- ZWITTERIONIC PHOSPHONIUM SALTS
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A zwitterionic phosphonium salt of Formula I: wherein n is 0 or 1; R is H or SO3-; R' is selected from the group consisting of C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C3-C10 cycloalkyl, phenyl, substituted phenyl, benzyl and C1-C10 alkoxycarbonyl; R' is CX3 when n is O; and X is selected from the group consisting of F, Cl, Br and I. The zwitterionic phosphonium salts are useful reagents for the preparation of alkenes and acetals from the corresponding aldehyde.
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Page/Page column 22; 29
(2010/04/03)
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- Chemoselective protection of aldehydes in the presence of ketones using rupvp complex as a heterogeneous catalyst
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Ruthenium(III)-polyvinyl pyridine (RuPVP) complex was prepared by refluxing a methanolic solution of polyvinyl pyridine and trihydrated ruthenium trichloride. RuPVP catalyst was characterized by Fourier transform-infrared and diffential scanning calorimetry-thermogravimetry (TG). The catalyst was used for chemoselective protection of aldehydes in the presence of a ketonic carbonyl group.
- Kshirsagar, Siddheshwar W.,Patil, Nitin R.,Samant, Shriniwas D.
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experimental part
p. 407 - 413
(2010/04/04)
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- Carbon tetrabromide/sodium triphenylphosphine-m-sulfonate (TPPMS) as an efficient and easily recoverable catalyst for acetalization and tetrahydropyranylation reactions
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A solid complex, conveniently prepared from carbon tetrabromide and sodium triphenylphos-phine-m-sulfonate (TPPMS), can be used as an easily recoverable catalyst for the selective acetalization of aldehydes and tetrahydropyranylation of alcohols. The catalyst can be recovered by simple pre-cipitation with ether and can be reused at least 7 times without loss of catalytic activity.
- Huo, Congde,Chan, Tak Hang
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experimental part
p. 1933 - 1938
(2011/02/28)
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- Tetrafluoroboric acid adsorbed on silica gel as a reusable heterogeneous dual-purpose catalyst for conversion of aldehydes/ketones into acetals/ketals and back again
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Aldehydes and ketones can be protected as acetals and ketals by treatment with trimethyl orthoformate (TMOF) or triethyl orthoformate (TEOF) under the catalytic influence of tetrafluoroboric acid adsorbed on silica gel (HBF 4-SiO2). In the case of aldehydes or ketones with highly electrophilic carbonyl group, the reactions are carried out under solvent-free conditions. Aryl alkyl ketones, aryl styryl ketones, aldehydes with weakly electrophilic carbonyl groups, and aldehydes with substituents that can coordinate with the catalyst require the presence of the corresponding alcohol as solvent. For substrates that can be converted into acetals under neat conditions, the acetal formation takes place at a faster rate when the alcohol is used as the solvent. The catalyst can be recovered and reused/recycled four times (after reactivation after each use) without any significant decrease in its catalytic efficiency. The parent aldehydes/ketones are regenerated from the corresponding acetals/ketals in high yields by the treatment with water-alcohol in the presence of HBF4-SiO2 at room temperature for short times. Excellent selectivity was observed during inter- and intramolecular competition studies involving carbonyl substrates with varying electronic and steric environments. Selective acetal formation of benzaldehyde takes place in the presence of 4-(dimethylamino)benzaldehyde, thiophene-2-carboxaldehyde, 1-naphthaldehyde, 9-anthraldehyde, or acetophenone, but 3-nitrobenzaldehyde undergoes selective acetal formation in preference to benzaldehyde. In the case of 4-acetylbenzaldehyde, exclusive acetal formation of the aldehyde carbonyl group occurs. Georg Thieme Verlag Stuttgart.
- Kumar, Dinesh,Kumar, Raj,Chakraborti, Asit K.
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p. 1249 - 1256
(2008/12/22)
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- Nucleophilic phosphine-catalyzed [3+2] cycloaddition of allenes with N-(thio)phosphoryl imines and acidic methanolysis of adducts N-(thio)phosphoryl 3-pyrrolines: a facile synthesis of free amine 3-pyrrolines
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In this report, the dipolarophile imines with easily removable activating group O,O-diethyl(thio)phosphoryl have been investigated in the nucleophilic phosphine-catalyzed [3+2] cycloaddition reaction of electron-deficient allenes. Under the catalysis of a tertiary phosphine, N-(thio)phosphorylimines readily undergo the [3+2] cycloaddition reaction with ethyl 2,3-butadienoate or ethyl 2,3-pentadienoate, affording the corresponding N-(thio)phosphoryl 3-pyrrolines in moderate to high yields with good diastereoselectivity. Removal of the (thio)phosphoryl group from the adducts has been successfully achieved via the acidic methanolysis of the P-N bond, giving the free amine 3-pyrrolines in fair to good yields without severe aromatization. Thus, a facile synthesis of N-unsubstituted 3-pyrrolines is established from the phosphine-catalyzed [3+2] cycloaddition reaction of allenes with imines.
- Zhang, Bo,He, Zhengrong,Xu, Silong,Wu, Guiping,He, Zhengjie
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p. 9471 - 9479
(2008/12/22)
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- Perchloric acid adsorbed on silica gel (HClO4-SiO2) as an inexpensive, extremely efficient, and reusable dual catalyst system for acetal/ketal formation and their deprotection to aldehydes/ketones
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Perchloric acid adsorbed on silica gel (HClO4-SiO2) is reported as extremely efficient, inexpensive, and reusable catalyst for dual role for protection of aldehydes/ketones (with trialkyl orthoformates) as acetals/ketals and deprotection (with water-alcohol) to regenerate the carbonyl compounds in high yields at room temperature and in short times. Acetalization/ketalization of electrophilic aldehydes/ketones was carried out under solvent-free conditions. Weakly electrophilic aldehydes/ketones and aldehydes having a substituent that can coordinate with the catalyst, required the corresponding alcohol as solvent. Georg Thieme Verlag Stuttgart.
- Kumar, Raj,Kumar, Dinesh,Chakraborti, Asit K.
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p. 299 - 303
(2007/10/03)
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- Copper(II) tetrafluoroborate as a novel and highly efficient catalyst for acetal formation
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Commercially available copper(II) tetrafluoroborate hydrate has been found to be a highly efficient catalyst for dimethyl/diethyl acetal formation in high yields from aldehydes and ketones by reaction with trimethyl/triethyl orthoformate at room temperature and in short period. Acetalisation was carried out under solvent-free conditions with electrophilic aldehydes/ketones. For weakly electrophilic aldehydes/ketones (e.g., benzaldehyde, cinnamaldehyde and acetophenone) and for aldehydes having a substituent that can coordinate with the catalyst, the corresponding alcohol was used as solvent.
- Kumar, Raj,Chakraborti, Asit K.
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p. 8319 - 8323
(2007/10/03)
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- Bronsted acidic ionic liquids as efficient and recyclable catalysts for protection of carbonyls to acetals and ketals under mild conditions
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A series of acidic ionic liquids have been used as efficient catalysts for the protection of various carbonyl compounds at room temperature. The features of mild conditions, satisfactory isolated yield, simple workup, and the recyclability of the catalyst were present in this process. Copyright Taylor & Francis, Inc.
- Du, Yuying,Tian, Fuli
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p. 2703 - 2708
(2007/10/03)
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- Sulfamic acid as a cost-effective and recyclable catalyst for protection of carbonyls to acetals and ketals under mild conditions
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An efficient H2NSO3H-catalyzed protection of various carbonyl compounds at room temperature was investigated. The features of mild conditions, cost-efficient catalyst, simple workup, and the recyclability of the catalyst were represented in this process.
- Gong, Weizhong,Wang, Bo,Gu, Yanglong,Yan, Liang,Yang, Liming,Suo, Jishuan
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p. 4243 - 4247
(2007/10/03)
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- A highly efficient and chemoselective method for acetalization of carbonyl compounds catalyzed by TiO2/SO42- solid superacid
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Various types of aldehydes and ketones could be converted to their corresponding diethyl acetals with triethylorthoformate in the presence of TiO2/SO42- solid superacid in good to excellent yield under mild reaction conditions.
- Ma, Yan-Ran,Jin, Tong-Shou,Shi, Sheng-Xun,Li, Tong-Shuang
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p. 2103 - 2108
(2007/10/03)
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- Tetrabutylammonium tribromide (TBATB) as an efficient generator of HBr for an efficient chemoselective reagent for acetalization of carbonyl compounds
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Acyclic and cyclic acetals of various carbonyl compounds were obtained in excellent yields under a mild reaction condition in the presence of trialkyl orthoformate and a catalytic amount of tetrabutylammonium tribromide (TBATB) in absolute alcohol. Chemoselective acetalization of an aldehyde in the presence of ketone, unsymmetrical acetal formation, shorter reaction times, mild reaction conditions, the stability of acid-sensitive protecting groups, high efficiencies, facile isolation of the desired products, and the catalytic nature of the reagent make the present methodology a practical alternative.
- Gopinath, Rangam,Haque, Sk. Jiaul,Patel, Bhisma K.
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p. 5842 - 5845
(2007/10/03)
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- 2,4,4,6-Tetrabromo-2,5-cyclohexadienone (TABCO) as a versatile, efficient, and chemoselective catalyst for the acetalization and transacetalization of carbonyl compounds, the preparation of acetonides from epoxides and acylals (1,1-diacetates) from aldehydes
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The efficient and chemoselective preparation of acetals and ketals from carbonyl compounds, transacetalization reactions, the conversion of epoxides to acetonides, and the preparation of acylals from aldehydes in the presence of catalytic amounts of 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TABCO) are described.
- Firouzabadi, Habib,Iranpoor, Nasser,Shaterian, Hamid Reza
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p. 2195 - 2205
(2007/10/03)
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- Tungsten hexachloride (WCl6), a highly efficient and chemoselective catalyst for acetalization of carbonyl compounds
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Various types of aldehydes and ketones could be converted chemoselectively to their corresponding 1,3-dioxanes or diethyl acetals in the presence of catalytic amounts of tungsten hexachloride (WCl6) in good to excellent yields in CH2Cl2 or under neat conditions, respectively.
- Firouzabadi,Iranpoor,Karimi
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p. 2255 - 2263
(2007/10/03)
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- 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) as a highly efficient and mild catalyst for diethyl acetalization of carbonyl compounds
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Various types of structurally different carbonyl compounds in the presence of ethyl orthoformate (EtO)3CH could be efficiently converted to their diethyl acetals by using a catalytic amount (1-3 mol%) of DDQ under mild reaction conditions.
- Karimi, Babak,Ashtiani, Ashraf Miri
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p. 1199 - 1200
(2007/10/03)
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- W-bromosuccinimide (NBS) as a powerful and chemoselective catalyst for acetalization of carbonyl compounds under almost neutral reaction conditions
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Highly efficient and mild acetalization of various types of carbonyl compounds was achieved using NBS under almost neutral reaction conditions. Due to the neutrality of the medium this method is especially useful for the protection of acid sensitive substrates. Thieme Stuttgart.
- Karimi, Babak
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p. 1456 - 1458
(2007/10/03)
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- Zirconium tetrachloride (ZrCl4) catalyzed highly chemoselective and efficient acetalization of carbonyl compounds
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Zirconium tetrachloride (ZrCl4) is a highly efficient and chemoselective catalyst for the acetalization, and in-situ transacetalization of carbonyl compounds under mild reaction conditions.
- Firouzabadi, Habib,Iranpoor, Nasser,Karimi, Babak
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p. 321 - 323
(2007/10/03)
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- Solvent free protection of carbonyl group under microwave irradiation
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Protection of aldehydes and ketones as acetals or dioxolanes catalysed by PTSA or KSF clay was readily achieved from orthoformates, 1,2-ethanediol or 2,2-dimethyl-1,3-dioxolane without solvent under microwave irradiation.
- Perio, Bertrand,Dozias, Marie-Joelle,Jacquault, Patrick,Hamelin, Jack
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p. 7867 - 7870
(2007/10/03)
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- Selective Acetalization of Aldehydes with Trialkoxystibine using Allyl Bromide
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Trialkoxystibine has been found to be an effective reagent for selective acetalization of aldehydes with the aid of allyl bromide.
- Liao, Yi,Huang, Yao-Zeng,Zhu, Fang-Hua
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p. 493 - 494
(2007/10/02)
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- New Type of Aldol Condensations Catalyzed by Metal(II) Complexes of α-Amino Acid Esters and that with Cyclodextrin System
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The aldol condensation of p-nitrobenzaldehyde with acetone catalyzed by metal ccomplexes of α-amino acid esters proceeded under mild and neutral conditions to afford an enantiomeric excess aldol-type products, 4-hydroxy-4-(4-nitrophenyl)-2-butanone, along with same dehydrated products without any by-product.The most effective catalyst system was a zinc(II) complex of the tyrosine ethyl ester, Zn(II)-(TyrOEt)2 in MeOH.Complexes of the second-row transition metals were inadeguate for the reactions.Reactions at 30-40 deg C for 24 h were fovorable regarding the asymmetric induction.An H2O solvent was the best for aldol-type product formation without asymmetric induction.An assistand effect of cyclodextrins(especially, β-CD) on the catalysis of the Zn(II)-TyrOEt complex were thought to be observed.
- Watanabe, Ken-ichi,Yamada, Yoichi,Goto, Katsuhisa
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p. 1401 - 1406
(2007/10/02)
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- Photolysis of Alkoxyacetic Acids in the presence of Mercury(II) Oxide and Iodine
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Homolytic decarboxylation of a series of alkoxyacetic acids has furnished alkoxyalkyl alkoxyacetates when no substituents were present at the 2-position.Electron donating and withdrawing 2-substituents, with the exception of trichloromethyl, afforded products due to fragmentation of the alkoxyacetic acids.The reaction pathway is rationalised on the basis of the reactivity of the alkoxyalkyl iodide intermediates.
- Glover, Stephen A.,Golding, Stephen L.,Goosen, Andre,McCleland, Cedric W.
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p. 2479 - 2483
(2007/10/02)
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