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Cyclization Process (cyclization + process)
Selected AbstractsChemInform Abstract: Iron-Catalyzed, Microwave-Promoted, One-Pot Synthesis of 9-Substituted Xanthenes by a Cascade Benzylation,Cyclization Process.CHEMINFORM, Issue 22 2010Xiaobing Xu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] ChemInform Abstract: Polysubstituted Quinolines from 2-Alkynylanilines and ,,,-Ynones Through a Sequential Conjugate Addition,Cyclization Process.CHEMINFORM, Issue 40 2009Roberta Bernini 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] 2-Aryl and 2-Heteroaryl Indoles from 1-Alkynes and o-Iodotrifluoroacetanilide Through a Domino Copper-Catalyzed Coupling,Cyclization Process.CHEMINFORM, Issue 8 2004Sandro Cacchi Abstract For Abstract see ChemInform Abstract in Full Text. [source] Stereodivergent Syntheses of Highly Substituted Enantiopure 4-Alkoxy-3,6-dihydro-2H -1,2-oxazines by Addition of Lithiated Alkoxyallenes to Carbohydrate-Derived AldonitronesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2005Matthias Helms Abstract Additions of lithiated alkoxyallenes to D -glyceraldehyde-based nitrones 1 and 2 did not provide the expected hydroxylamine derivatives. Instead, a novel [3+3] cyclization process furnished 4-alkoxy-3,6-dihydro-2H -1,2-oxazines 9,14 with excellent syn selectivities and in moderate to good yields. Through precomplexation of the nitrones the corresponding anti -configured 1,2-oxazines 9, 10 and 13 could be obtained with high stereoselectivity. The reactions of nitrones 3,6, derived from D -erythrose or D -threose, generally proceeded less diastereoselectively, but reasonable yields of anti -configured 1,2-oxazines such as anti - 17 and anti - 19 could be obtained under Lewis acid promotion conditions. This was also the case for reactions of the D -arabinose-derived nitrone 7, which provided the anti -1,2-oxazines 23 and 24 with excellent diastereoselectivity and in good yields. Bis-nitrone 8 and lithiated methoxyallene furnished a mixture of six compounds, among which the major componentwas the C2 -symmetric syn/syn -1,2-oxazine 29. The diastereoselectivities of these reactions are interpreted on the basis of Dondoni's model for reactions between organolithium compounds and nitrones. The mechanisms for formation of 1,2-oxazines and of side products are discussed. The method introduced here seems to be of broad applicability and an excellent tool for diastereoselective chain elongation of carbohydrate derivatives, affording stereodefined precursors of aminopolyols and other highly functionalized compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Thiophenol-Mediated 1,5-Hydrogen Atom Abstraction: Easy Access to Mono- and Bicyclic CompoundsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-13 2005Florent Beaufils Abstract A thiophenol-mediated method for cyclization of alkynes is described. The reaction cascade involves the intermolecular addition of a phenylthiyl radical to a terminal triple bond generating an alkenyl radical, followed by a 1,5-hydrogen atom transfer and a 5- exo- trig radical cyclization. This very efficient tin-free procedure allows one to prepare highly functionalized cyclopentane derivatives as well as fused bicyclic and spirocyclic compounds from easily available precursors. During this cyclization process, a phenylthio moiety is incorporated into the final cyclized products. This functionalization is particularly attractive for further transformation of the products. [source] Mapping the characteristics of the radical ring-opening polymerization of a cyclic ketene acetal towards the creation of a functionalized polyesterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2009Peter Plikk Abstract Radical ring-opening polymerization of cyclic ketene acetals is a means to achieve novel types of aliphatic polyesters. 2-methylene-1,3-dioxe-5-pene is a seven-membered cyclic ketene acetal containing an unsaturation in the 5-position in the ring structure. The double bond functionality enables further reactions subsequent to polymerization. The monomer 2-methylene-1,3-dioxe-5-pene was synthesized and polymerized in bulk by free radical polymerization at different temperatures, to determine the structure of the products and propose a reaction mechanism. The reaction mechanism is dependent on the reaction temperature. At higher temperatures, ring-opening takes place to a great extent followed by a new cyclization process to form the stable five-membered cyclic ester 3-vinyl-1,4-butyrolactone as the main reaction product. Thereby, propagation is suppressed and only small amounts of other oligomeric products are formed. At lower temperatures, the cyclic ester formation is reduced and oligomeric products containing both ring-opened and ring-retained repeating units are produced at higher yield. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4587,4601, 2009 [source] Development of an efficient route to hyperbranched poly(arylene ether sulfone)sJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2005Patrick Himmelberg Abstract A two-step route to an AB2 monomer that underwent polymerization via nucleophilic aromatic substitution to afford hyperbranched poly(arylene ether sulfone)s (HB PAES) was developed. The synthesis of 3,5-difluoro-4,-hydroxydiphenyl sulfone (4) was accomplished by the reaction of 3,5-difluorophenylmagnesium bromide with 4-methoxyphenylsulfonyl chloride, followed by deprotection of the phenol group with HBr in acetic acid. The polymerization of 4 in the presence of 3,4,5-trifluorophenylsulfonyl benzene or tris(3,4,5-trifluorophenyl)phosphine oxide as a core molecule afforded HB PAES with number-average molecular weights ranging from 3400 to 8400 Da and polydispersity index values ranging from 1.5 to 4.8. The presence of cyclic oligomeric species, formed by an intramolecular cyclization process, was a contributing factor to the relatively low molecular weights. The degree of branching (DB) of the HB PAES samples was estimated by a comparison of the 19F NMR spectra of the polymer samples with those of a series of model compounds, and DB values ranging from 0.51 to 0.70 were determined. The glass-transition temperatures for the HB PAES samples were in the range of 205,222 °C, as determined by differential scanning calorimetry. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43:3178,3187, 2005 [source] Viscoelastic properties of polyacrylonitrile terpolymers during thermo-oxidative stabilization (cyclization)POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2008K. I. Suresh Abstract A study on the thermo-oxidative stabilization (cyclization) of polyacrylonitrile (PAN) terpolymers using dynamic mechanical thermal analysis (DMTA) is reported in this article. When the changes in viscoelastic properties were monitored in a rectangular tension mode, besides the tan , peak characteristic of the glass transition observed below 200°C, the copolymer and the terpolymer displayed a second peak above 200°C due to the cyclization leading to the formation of ladder structures. The initiation temperature of the cyclization process as well as the peak temperature is found to depend on the acid value and the composition of the precursor polymer. The results presented show that monitoring the changes in viscoelastic properties during cyclization provides insight into the material properties as a result of the chemical changes that are taking place. These observations were confirmed by structural characterization using IR spectroscopy, and the observed chemical changes agree with the literature studies, as due to the thermal cyclization process. Copyright © 2008 John Wiley & Sons, Ltd. [source] Ring conformations and intermolecular interactions in two fused dibenzoazocinesACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010Andrés F. Yepes 5-Acetyl-2-chloro-8,11-dimethyl-5,6,11,12-tetrahydrodibenzo[b,f]azocine, C19H20ClNO, (I), crystallizes as a single fully ordered isomer, but 14-acetyl-8,11-dimethyl-7,8,13,14-tetrahydrobenzo[f]naphtho[1,2- b]azocine,14-acetyl-8,9-dimethyl-7,8,13,14-tetrahydrobenzo[f]naphtho[1,2- b]azocine (74/26), C23H23NO, (II), exhibits threefold whole-molecule disorder involving both configurational and structural isomers. In (I) and in the predominant form of (II), the azocine rings adopt very similar conformations, forming boat-shaped rings having approximate twofold rotational symmetry. There are no direction-specific intermolecular interactions in the crystal structure of (I), but the molecules of (II) are weakly linked into chains by an aromatic ,,, stacking interaction. The compounds were made under green conditions using an acid-catalysed cyclization process having very high atom utilization. [source] A Fluorous, Pummerer Cyclative-Capture Strategy for the Synthesis of N-HeterocyclesCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2007Laura Abstract A fluorous, cyclative-capture strategy based on a new Pummerer cyclization process allows rapid access to tagged, heterocyclic frameworks. Convenient modification of the fluorous, heterocyclic scaffolds by using a variety of approaches including Pd-catalyzed cross-couplings is possible. Traceless, reductive cleavage of the fluorous-phase tag or oxidative cleavage and further elaboration, completes a strategy for the high-throughput, fluorous-phase synthesis of a diverse range of N-heterocycles. [source] | |||||||||||||