19.02.2004 | Dieter Enders, Manfred Kroll, Gerhard Raabe, Jan Runsink, Molecules Online, 2004

. 1-Aza-2-zirconacyclopent-4-enes 3, prepared from a,b-unsaturated imines 2 were used as homoenolate-equivalents to generate 3-aza-1-oxa-2-zirconacyclohept-4-enes 4 via the diastereoselective insertion of prochiral, sterically demanding ketones. Hydrolysis of the zirconacycles using our ...

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19.02.2004 | Lubomír Floch, Juraj Kubán, Andrea Gogová, Peter Zálupsky, Tibor Jakubík, Nada Prónayová, Molecules Online, 2004

Triton B catalyzed Michael addition of nitromethane on esters of !,#-unsaturated acids 1 has been studied. The course and regioselectivity of the reaction is discussed in the view of structure of products 2a-g, 3a-g, 4g, f, 5g, f, assessed by GC/MS, NMR and IR spectroscopy and by MOPAC ...

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19.02.2004 | Milan Potácek, Molecules Online, 2004

The Joint 12th Symposium on the Chemistry of Heterocyclic Compounds (SCHHC) and the 6th Blue Danube Symposium on Heterocyclic Chemistry (BDSHC) Content Type Journal Article Pages 114-115 Authors Milan Potácek, Professor of Organic Chemistry, Chairman of 12th SCHHC and 6th BDSHC, ...

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19.02.2004 | Tibor Gracza, Luboš Remen, Peter Szolcsanyi, Volker Jäger, Thomas Hasenöhrl, Molecules Online, 2004

The general approach to optically active anhydroalditols, a class of compounds that have proven most versatile intermediates for C-nucleosides / C-glycosides syntheses is presented. Our entry into this field features the palladium(II)-catalyzed oxycarbonylation of unprotected enitols as key ...

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19.02.2004 | Jan Jurik, Pavel Kubácek, Molecules Online, 2004

The conformational motion of cyclohexene rings in six octahydrocarbazole N-derivatives was studied by EPR spectroscopy. Additionally the potential energy surface for the conformational change of one cyclohexene ring was calculated using the semiempirical method AM1. Content Type Journal ...

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19.02.2004 | Katrin Illgen, Christine Hartung, Rainer Herzschuh, Bärbel Schulze, Molecules Online, 2004

Cyclic sulfinamides, a new class of recoverable chiral sulfoxides, have been used for the control of numerous asymmetric reactions including aldol condensation [1,2] and the asymmetric synthesis of amines [3]. The present communication reports on the synthesis of stable ...

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19.02.2004 | Wolfgang Ritzberger-Baumgartner, Joachim G. Schantl, György Hajos, Molecules Online, 2004

The polar cycloaddition reaction of cationic heteroaromatic dienes, the triazoloisoquinolinium ion 1 and the tetramethoxycarbonylquinolizinium ion 4 with electron-rich dienophiles was studied resembling Diels-Alder reactions with inverse electron demand. This was also substantiated by ab ...

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19.02.2004 | Branko Stanovnik, Molecules Online, 2004

The use of N,N-dimethylforamide dimethyl acetal (DMFDMA) and t-butoxybis(dimethylamino)methane in the synthesis of 2-substituted 3-dimethylaminopropenoates and related compounds, as well as their applicability to the synthesis of various heterocyclic systems is shown. Content Type ...

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19.02.2004 | Lech Chmurzynski, Molecules Online, 2004

The potentiometric titration method has been used to study the equilibria of cationic heteroconjugation in systems formed by substituted pyridine N-oxides in the polar non-aqueous solvents; nitrobenzene, acetonitrile, acetone and methanol. For comparison, the systems with trimethylamine ...

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19.02.2004 | Nawaf I. Al-Maharik, Seppo A. Kaltia, Kristiina Wähälä, Molecules Online, 2004

. Optimized conditions are described for the regioselective mono-O-alkylation of daidzein 1a, genistein 1b, and biochanin A 1c with ethyl bromoacetate. Content Type Journal Article Pages 20-24 DOI 10.1007/s007830050072 Authors Nawaf I. Al-Maharik, Laboratory of Organic Chemistry, ...

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