Search results for "Reaction"
showing 10 items of 6134 documents
ChemInform Abstract: Diastereodivergent Synthesis of Fluorinated Cyclic β3-Amino Acid Derivatives.
2016
The ability of 2-p-tolylbenzyl carbanions to behave as a source of chiral benzylic nucleophiles has been shown in its reaction with fluorinated imines. The process takes place with high levels of stereocontrol, rendering the corresponding amines as single diastereoisomers. Subsequent cross-metathesis followed by intramolecular aza-Michael reaction makes the synthesis of fluorinated homoproline derivatives bearing three stereogenic centers possible. Furthermore, the selectivity of the cyclization process can easily be tuned up in a diastereodivergent manner simply by changing the reaction conditions.
Dianions of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Juvocimene I
1996
Abstract Juvocimene I is prepared by a non ambiguous synthesis based on the regioselective alkylation of 4-methylhexa-2,4-dienoic acid, and Wittig olefination of the aldehyde corresponding to the alkylated acid.
ChemInform Abstract: Dianions of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Juvocimene I.
2010
Abstract Juvocimene I is prepared by a non ambiguous synthesis based on the regioselective alkylation of 4-methylhexa-2,4-dienoic acid, and Wittig olefination of the aldehyde corresponding to the alkylated acid.
ChemInform Abstract: Efficient Stereoselective Synthesis of Boron L-amino Acid Derivatives Using Wittig and Borylation Reactions
2015
The stereoselective synthesis of a new classes of boronato- or trifluoroborato aminoacids and peptides was described using Wittig and C-H iridium borylation as key reactions. A trifluoroborato-thio...
ChemInform Abstract: Mixed Dialkylaluminum Chlorides and Mixed Trimethylorganoaluminates in Chemoselective 1,4-Addition Reactions to Alkylidene Malon…
2010
Mixed alkyl-methyl- and aryl-methylorganoaluminum chlorides 6 were formed by reaction of methylaluminum dichloride with organolithium or Grignard compounds and used for chemoselective 1,4 addition of higher alkyl, aryl, alkenyl and alkinyl groups to alkylidine malonic esters 1 and 2. As an alternative, mixed trimethylorganoaluminates 7 can also be applied for these Michael addition reactions. For conjugate addition of alkenyl groups to alkylidene malonates 1 and 2, alkenyl diisopropylalanes 10 obtained from alkynes and diisopropylaluminum hydride proved the most efficient reagents. Using these novel mixed organoaluminum compounds, β-branched malonic (carboxylic) acid derivatives 3c, 8, 9 an…
ChemInform Abstract: Novel Prolinamide-Supported Polystyrene as Highly Stereoselective and Recyclable Organocatalyst for the Aldol Reaction.
2008
A new prolinamide derivative anchored to a polystyrene support has been straightforwardly prepared and employed as heterogeneous catalyst in the direct asymmetric aldol reaction with good results in terms of yield and stereoselectivity. The optimal reaction conditions were found when a 1:2 (v/v) water/chloroform mixture was used. This mixture was the best compromise between the good swelling properties of chloroform and the formation of a concentrated organic phase due to the presence of water. Noticeably, the enantioselectivities obtained employing acetone as ketone were, to the best of our knowledge, the highest achieved with a supported proline derivative. This catalyst can be easily rec…
ChemInform Abstract: Organocatalytic anti-Selective Mannich Reactions with Fluorinated Aldimines: Synthesis of anti-γ-Fluoroalkyl-γ-amino Alcohols.
2010
The asymmetric Mannich reaction between fluoroalkyl aldimines and aldehydes catalyzed by α,α-diphenylprolinol trimethylsilyl ether is reported. The corresponding Mannich adducts were reduced in situ to afford anti-β-alkyl-γ-fluoroalkyl-γ-amino alcohols in moderate yields and with very high diastereo- and enantioselectivities. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Entzündungshemmende wirkstoffe. XI. Ringschlußreaktion an 5-phenyl-2-thiobiuret
1988
Die Umsetzung von 5-Phenyl-2-thiobiuret (1) mil α-Chlorcarbonylverbindungen 2 fuhrt zu den N-Phenyl-N′-(2-thiazolyl)harnstoffen (3). Unter den neuen Verbindungen finden sich besonders die entzundungshemmende, anthelminthische und trichomonazide Wirksamkeit stark ausgepragt. The reaction of 5-phenyl-2-thiobiuret (1) with α-chlorocarbonyl compounds 2 leads to the structure type of N-phenyl-N1-(thiazolyl)urea (3). The new compounds exhibit particularly antiinflammatory, anthelminthic, and trichomonacidal activity.
ChemInform Abstract: Solution and Fluorous Phase Synthesis of β,β-Difluorinated 1-Amino-1-cyclopentane Carboxylic Acid Derivatives.
2009
An efficient protocol for the preparation of β,β-difluorinated 1-amino-1-cyclopentane carboxylic acid derivatives was developed. 2,2-Difluro-4-phenyl-3-butenoic acid 6 was used as substrate for the preparation of the starting vinyl difluoro imino esters 8. The key steps of this methodology rely on the chemo- and diastereoselective addition of allylzinc bromides over the iminic functionality of 8 and subsequent RCM reaction. This synthetic sequence was successfully applied to fluorous synthesis.
Chemistry of Enzyme Visualization
1994
The basic principle of enzyme visualization in situ is to present an enzyme with a solution containing an enzyme specific substrate. Demonstration of an enzyme is achieved if the catalytic action of the enzyme on this substrate produces a coloured reaction product. Often, however, the primary reaction products are colourless and require coupling with a visualizing agent to generate a coloured, preferably insoluble, final reaction product.