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Various Aldehydes (various + aldehyde)
Selected AbstractsChemInform Abstract: Syntheses of Chiral 1,3-Disubstituted Tetrahydro-,-carbolines via CIAT Process: Highly Stereoselective Pictet,Spengler Reaction of D-Tryptophan Ester Hydrochlorides with Various Aldehydes.CHEMINFORM, Issue 35 2009Sen Xiao Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Synthesis, oxidation and dehydrogenation of cyclic N,O - and N,S -acetals.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 20074-oxadiazolines, O -acetals: 3-acyl-, Part III., Transformation of N Various aldehyde and ketone acylhydrazones are synthesized and, under acylating conditions, cyclized into 3-acyl-1,3,4-oxadiazolines. The scope and limitations of these cyclizations and the possible side reactions (e.g. formation of the open-chain N,O -acylhydrazinocarbinols) are dissected. For the first time, simple, convenient and efficient dehydrogenations of 3-acyl-1,3,4-oxadiazolines to oxadiazoles by treatment with potassium permanganate, or more conveniently, with ammonium cerium(IV) nitrate (CAN) are presented. CAN oxidation of 2,2-disubstituted 3-acyl-1,3,4-oxadiazolines, as well as that of aldehyde diacylhydrazones (open-chain isomers of 2,5-disubstituted 3-acyl-1,3,4-oxadiazolines) regenerates the parent carbonyl compounds. [source] Electro-Organocatalysis: Enantioselective ,-Alkylation of AldehydesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2010Xuan-Huong Ho Abstract The asymmetric organocatalyzed ,-alkylation of aldehydes via a cationic radical enamine intermediate was performed under environmentally benign electro-oxidation conditions without the use of chemical oxidants. To promote the desired ,-alkylation reaction of aldehydes, various aldehydes with xanthene or cycloheptatriene groups were exposed to electro-organocatalytic conditions to afford optically active ,-substituted aldehydes (,-alkylated aldehydes) in good yield. A reaction mechanism involving the cationic radical enamine was proposed based on the cyclic voltammetry (CV) results, DFT calculations, and control experiments. [source] Synthesis of ,-Amino Nitriles from Carbonyl Compounds, Amines, and Trimethylsilyl Cyanide: Comparison between Catalyst-Free Conditions and the Presence of Tin Ion-Exchanged MontmorilloniteEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2010Jiacheng Wang Abstract In the absence of catalysts, the three-component, one-pot synthesis of ,-amino nitriles proceeded using various aldehydes and ketones together with amines and trimethylsilyl cyanide (TMSCN) in high yields under neat conditions at room temperature. The addition order of the reagents had a significant influence on the yields of the desired ,-amino nitriles. In contrast, when tin ion-exchanged montmorillonite (Sn-Mont), prepared by the ion-exchange of sodium montmorillonite (Na-Mont) with a tin tetrachloride solution, was used as a catalyst, the reaction rates significantly increased compared with those without catalysts, and the range of the applicable carbonyl compounds was also extended: structurally diverse aromatic, aliphatic and heteroatom-containing carbonyl compounds, including sterically hindered ketones as well as aliphatic and aromatic amines, were converted into the desired ,-amino nitriles in good to excellent yields with short reaction times under mild conditions. Sn-Mont showed a better catalytic activity than proton or other metal ion-exchanged montmorillonites, supported SnO2 catalysts and the previously reported homogeneous or heterogeneous catalysts. The recovered catalyst was reused several times without loss of catalytic performance. Along with the expansion of the interlayer space of Sn-Mont, the strong Brønsted acid and Lewis acid nature of Sn-Mont derived from protons and SnO2 nanoparticles present in the interlayers of Sn-Mont likely played important and cooperative roles in the high catalytic activity. [source] Asymmetric Homoaldol Reactions with Cyclohex-2-enyl N,N -Diisopropylcarbamate: Kinetic Resolution, Elucidation of the Stereochemical Course and Applications in the Synthesis of Hexahydroisobenzofuran-4-(1H)-onesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2007Jochen Becker Abstract Enantio-enriched cyclohex-2-enyl N,N -diisopropylcarbamate (5) is stereospecifically deprotonated by sec -butyllithium/(,)-sparteine (9) to form the configurationally stable lithium complex 7·9. A kinetic resolution of rac - 5 by n -butyllithium/(,)-sparteine (9) yielded (R)- 5 with up to 99,% ee. Electrophilic substitution with tin electrophiles proceeds in a anti -SE, fashion as shown by chemical correlations. The synthesized allylstannanes 10 undergo a highly stereospecific TiCl4 -mediated homoaldol reaction with various aldehydes, yielding syn -configured homoaldol products 12. These were transferred into all - cis -configured hexahydroisobenzofuran-4(1H)-ones 22 by BF3·OEt2 -mediated reactions with aldehydes. The configurations of several products were determined by X-ray structure analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis of Substituted , -(Hydroxymethyl)- , -iodoacrylates via MgI2 -Promoted Stereoselective Aldol CouplingHELVETICA CHIMICA ACTA, Issue 9 2004Han-Xun Wei The efficient and highly stereoselective syntheses of a variety of (Z)-configured, substituted , -(hydroxymethyl) - , -iodo-acrylates from prop-2-ynoate and various aldehydes was achieved. The synthetic protocol involves a simple one-pot coupling reaction under mild conditions, promoted by MgI2, which serves both as a Lewis acid and iodine source for a BaylisHillman -type reaction. All adducts were generated in good-to-excellent yields, the (Z)-isomers being formed in high selectivity (>98%). The conversion of methyl prop-2-ynoate into an active ,, -iodo allenolate' intermediate, which then nucleophilically attacks an aldehyde, is proposed as a plausible reaction mechanism. [source] Facile route for the synthesis of benzothiazoles and benzimidazoles in the presence of tungstophosphoric acid impregnated zirconium phosphate under solvent-free conditionsHETEROATOM CHEMISTRY, Issue 4 2009Hamid Aliyan Rapid and efficient condensation reactions of o -phenylenediamine and o -aminothiophenol with various aldehydes were carried out using tungstophosphoric acid impregnated zirconium phosphate in solvent-free conditions to afford the corresponding 2-substituted arylbenzimidazole and arylbenzothiazole derivatives in good to excellent yields. This procedure constitutes a simple and practical green synthetic method for 2-arylbenzimidazoles and 2-arylbenzothiazoles and their structural analogs. Furthermore, the catalyst can be reused for several times but it will be less active. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:202,207, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20534 [source] Asymmetric Synthesis of 2,3,4-Trisubstituted Functionalised Tetrahydrofurans via an Organocatalytic Michael Addition as Key StepADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010Dieter Enders Abstract The organocatalytic Michael addition of various aldehydes to (2E,4E)-ethyl 5-nitropenta-2,4-dienoate has been achieved under the catalysis of diphenylprolinol trimethylsilyl ether furnishing the products in good to excellent yields (61,94%) and high stereoselectivities (dr up to >98:2, ee=97 to >99%). Starting from these Michael adducts, 2,3,4-trisubstituted functionalized tetrahydrofurans are available in two steps by reduction of the aldehyde followed by an intramolecular oxa-Michael addition in good yields (54,76%) and stereoselectivities (dr up to >95:5, ee=97 to >99%). [source] A Novel Proline-Valinol Thioamide Small Organic Molecule for a Highly Enantioselective Direct Aldol ReactionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Bing Wang Abstract A new prolinethioamide compound 4, prepared from readily available natural amino acid L -proline and amino alcohol L -valinol, has been found to be an active catalyst for the direct aldol reaction of various aldehydes with acetone, cyclohexanone or cyclopentanone at 0,°C. Using only 2,mol% loading of this organocatalyst, the reaction could give high enantioselectivity with up to 96% enantiomeric excess for the reaction of 2-nitrobenzaldehyde with acetone. And as for the cyclohexanone, the excellent diastereoselectivity (anti/syn: 99/1) and enantioselectivity (99% ee) could be achieved when reacted with 3-nitrobenzaldehyde in water in the presence of this thioamide 4. This structurally simple catalyst is a highly efficient prolinethioamide derivative, and the terminal hydroxy group in this catalyst is a primary alcohol which is different from the previously reported prerequisite secondary or tertiary alcohol of prolinamides. Our results suggest a new strategy in the design of diversiform organic catalysts for direct asymmetric aldol reactions and related transformations. [source] An Improved Protocol for the Direct Asymmetric Aldol Reaction in Ionic Liquids, Catalysed by Onium Ion-Tagged ProlinesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2007Marco Lombardo Abstract Two onium ion-tagged prolines, imidazolium bis(trifluoromethylsulfonyl)imide-substituted proline 6 and butyldimethylammonium bis(trifluoromethylsulfonyl)imide-substituted proline 7, were synthesised and their catalytic activity in the direct asymmetric aldol condensation was studied in ionic liquids. For the reaction of acetone with various aldehydes, using 5,% of the catalyst, the yields of the aldols varied between 50,85,% while the ee values were in the 80,85,% range. Other ketones were studied too, the yields obtained in those cases being in the 35,78,% range while the enantioselectivities varied between 75,94,%. [source] Catalytic and Highly Enantioselective Reactions of ,-Sulfonyl Carbanions with Chiral Bis(oxazoline)sCHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2008Shuichi Nakamura Prof. Abstract The enantioselective reactions of lithiated benzyl trifluoromethyl sulfones with a substoichiometric amount of a bis(oxazoline) and various aldehydes is disclosed. The products were formed with excellent diastereo- and enantioselectivities. Fluorination of the sulfone with N -fluorobenzenesulfonimide and a stoichiometric amount of a bis(oxazoline) gave products with extremely high enantioselectivities (up to 99,%,ee; ee=enantiomeric excess). The enantioselective reaction was confirmed to proceed through a dynamic thermodynamic resolution pathway. [source] Bifunctional Enantioselective Ligands of Chiral BINOL Derivatives for Asymmetric Addition of Alkynylzinc to AldehydesCHINESE JOURNAL OF CHEMISTRY, Issue 2 2008Xiao-Wei ZOU Abstract Four analogous binaphthyl compounds (R) -3a - 3d containing (R)-3,3,-bis(2-pyridyl) groups were synthesized by the conjugation of (R)-2,2,-dimethoxy-1,1,-binaphthyl-3,3,-diboronic acid [(R)- 2] with 2-bromopyridine, 2-bromo-5-methylpyridine, 2-chloro-4-fluoropyridine and 2-chloro-3-(trifluoromethyl)pyridine via Pd-catalyzed Suzuki reactions, respectively. The application of the four chiral ligands in combination with Et2Zn and Ti(Oi -Pr)4 to the asymmetric addition of phenylacetylene to various aldehydes has been studied. The results show that (R)- 3a and (R)- 3b are not good catalysts for the alkynylzinc addition to aldehydes, (R)- 3d shows good enantioselectivity only for the alkynylzinc addition to aliphatic aldehydes, and (R)- 3c exhibits excellent enantioselectivity for phenylethynylzinc addition to both aromatic and aliphatic aldehydes. All the four chiral ligands produced the opposite configuration of the propargylic alcohols to that of the chiral ligands. [source] Polystyrene-supported N -sulfonylated amino alcohols and their applications to titanium(IV) complexes catalyzed enantioselective diethylzinc additions to aldehydesCHIRALITY, Issue 1 2007Xin-Ping Hui Abstract Crosslinked polystyrene-supported resins 4, 7a, and 7b containing N -sulfonylated ,-amino alcohol in 98, 20, and 40% loadings are prepared. Asymmetric diethylzinc additions to benzaldehyde employing titanium complexes of 10 mol % resins 4, 7a, or 7b are examined and the best performed 7a/Ti(O- i -Pr)4 catalytic system applies to various aldehydes to afford desired secondary alcohols in excellent enantioselectivities up to 95% ee. The resin 7a is reused five times, giving the product with enantioselectivities ,86% ee and an 81% ee is obtained when the resin is used the sixth time. The used resin 7a is refreshed with 1 M HCl and the asymmetric reaction employing the regenerated resin 7a gives the product in 88% ee. Chirality, 2006. © 2006 Wiley-Liss, Inc. [source] | ||||||||||||||||||||||