Home About us Contact
|
Home About us Contact | ||
|
|
||
Claisen Condensation (claisen + condensation)
Selected AbstractsChemInform Abstract: Ring Opening of Cyclic Vinylogous Acyl Triflates Using Stabilized Carbanion Nucleophiles: Claisen Condensation Linked to Carbon,Carbon Bond Cleavage.CHEMINFORM, Issue 37 2010David M. Jones Abstract Treatment of the cyclic triflates (I) and (VII) with carbanion nucleophiles provides acyclic alkynes bearing 1,3-diketone, ,-keto ester, ,-keto phosphonate, or ,-keto phosphine oxide moieties. [source] ChemInform Abstract: Claisen Condensation of N-Methylpyrrolidinone and ,-Chloronicotinic Esters.CHEMINFORM, Issue 20 2008Thomas Kaminski 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] Pyranopyrazoles III synthesis of 1H -pyrano[2,3- c]pyrazol-4-ones,JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2001Misbahul Ain Khan Various derivatives of title ring system were synthesized by Claisen condensation of 4 acetyl-5 -hydroxy-pyrazoles with appropriate esters, followed by acid-catalyzed ring closure. [source] The first synthesis of [2- 13C]phloroglucinolJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 10 2010Laura J. Marshall Abstract A fast and efficient synthesis of [2- 13C]phloroglucinol in six steps from acyclic, non-aromatic precursors is presented, with regioselective placement of a 13C-atom in the aromatic ring. The 13C-label was introduced by reaction of [13C]methyl iodide with methyl 4-chloroformyl butyrate. Cyclization via an intramolecular Claisen condensation, followed by aromatization gave [2- 13C]resorcinol. Following subsequent methylation of the hydroxyl groups, the third hydroxyl group was introduced using an iridium-catalysed C,H activation/borylation/oxidation procedure. Demethylation then yielded the desired [2- 13C]phloroglucinol. Copyright © 2010 John Wiley & Sons, Ltd. [source] Biosynthesis of the Myxobacterial Antibiotic Corallopyronin ACHEMBIOCHEM, Issue 9 2010Özlem Erol Abstract Corallopyronin A is a myxobacterial compound with potent antibacterial activity. Feeding experiments with labelled precursors resulted in the deduction of all biosynthetic building blocks for corallopyronin A and revealed an unusual feature of this metabolite: its biosynthesis from two chains, one solely PKS-derived and the other NRPS/PKS-derived. The starter molecule is believed to be carbonic acid or its monomethyl ester. The putative corallopyronin A biosynthetic gene cluster is a trans-AT-type mixed PKS/NRPS gene cluster, containing a ,-branching cassette. Striking features of this gene cluster are a NRPS-like adenylation domain that is part of a PKS-type module and is believed to be responsible for glycine incorporation, as well as split modules with individual domains occurring on different genes. It is suggested that CorB is a trans-acting ketosynthase and it is proposed that it catalyses the Claisen condensation responsible for the interconnection of the two chains. Additionally, the stereochemistry of corallopyronin A was deduced by a combination of a modified Mosher's method and ozonolysis with subsequent chiral GC analyses. [source] Enantiospecific Syntheses of Copper Cubanes, Double-Stranded Copper/Palladium Helicates, and a (Dilithium),Dinickel Coronate from Enantiomerically Pure Bis-1,3-diketones,Solid-State Self-Organization Towards Wirelike Copper/Palladium Strands,CHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2008Abstract Enantiomerically pure, vicinal diols 1 afforded in a two-step synthesis (etherification and subsequent Claisen condensation) chiral bis-1,3-diketones H2L(S,S) (3,a,c) with different substitution patterns. Reaction of these C2 -symmetric ligands with various transition-metal acetates in the presence of alkali ions generated distinct polynuclear aggregates 4,8 by diastereoselective self-assembly. Starting from copper(II) acetate monohydrate and depending on the ratio of transition-metal ion to alkali ion to ligand, chiral tetranuclear copper(II) cubanes (C,C,C,C)-[Cu4(L(S,S))2(OMe)4] (4,a,c) or dinuclear copper(II) helicates (P)-[Cu2(L(S,S))2] (5) could be synthesized with square-pyramidal and square-planar coordination geometry at the metal center. In analogy to the last case, with palladium(II) acetate double-stranded helical systems (P)-[Pd2(L(S,S))2] (6,7) were accessible exhibiting a linear self-organization of ligand-isolated palladium filaments in the solid state with short inter- and intramolecular metal distances. Finally, the introduction of hexacoordinate nickel(II) in combination with lithium hydroxide monohydrate and chiral ligand H2L(S,S) (3,a) allowed the isolation of enantiomerically pure dinuclear nickel(II) coronate [(Li,MeOH)2,{(,,,)-Ni2(L(S,S))2(OMe)2}] (8) with two lithium ions in the voids, defined by the oxygen donors in the ligand backbone. The high diastereoselectivity, induced by the chiral ligands, during the self-assembly process in the systems 4,8 could be exemplarily proven by circular dichroism spectroscopy for the synthesized enantiomers of the chiral copper(II) cubane 4,a and palladium(II) helicate 6. [source] | ||||||||||