Search results for "SELECTIVITY"
showing 10 items of 1148 documents
4 H ‐3,1‐Benzoxathiine aus Benzothiet und Carbonylverbindungen
1990
4H-3,1-Benzoxathiines from Benzothiete and Carbonyl Compounds The o-quinoid 8-π electron system 2, generated by thermal ring opening of benzothiete (1) undergoes [8π + 2π] cycloaddition reactions with electron-deficient carbonyl compounds 3. In accordance with the frontier orbital theory, 4H-3,1-benzoxathiines (4) are obtained in a regioselective manner.
Addressing selectivity criteria in binding equilibria
2012
Abstract Chemical systems, in particular those involving biological and environmental backgrounds, develop through selective processes which are determined by multiple equilibria. Several methods that have been developed to assess thermodynamic selectivity in binding equilibria, including the analysis of selectivity coefficients, the use of calculated species distribution diagrams, selectivity diagrams, and conditional stability constants, are reviewed in this paper with reference to examples mainly related to chemical systems of biological and/or environmental concern. Also the concept of binding affinity has been dealt with, since binding selectivity in equilibrium systems relates to the …
Efficient Stereoselective Synthesis of o-Functionalized P-Chirogenic Phosphines Applied to Asymmetric Catalysis
2015
The stereoselective synthesis of P-chirogenic o-halogenophenylphosphines and their use for the preparation of o-functionalized derivatives are reported. The key step of this synthesis is based on t...
Designing P*-chirogenic Organophosphorus Compounds: from Ligands to Organocatalysts
2015
The interest of organophosphorus compounds bearing chirality on the phosphorus atom has greatly expanded in last decade, due to the development of efficient stereoselective synthetic methods, using...
Cycloaddition von Benzothiet an 4‐substituierte Styrole
1989
Durch thermische Ringoffnung entsteht aus Benzothiet (1) ein 8-π-Elektronensystem 2, das mit den 4-substituierten Styrolen 3a–j die Cycloaddukte 4/5a–j bildet. Die Erhohung der Reaktivitat durch elektronenspendende oder elektronenanziehende Reste und die Einflusse auf die Regioselektivitat werden an Hand von Grenzorbitalbetrachtungen diskutiert. Cycloaddition of Benzothiete of 4-Substituted Styrenes By thermal ring opening benzothiete (1) generates an 8-π electron system 2, which forms the cycloadducts 4/5a–j with 4-substituted styrenes 3a–j. The enhancement of the reactivity by electrondonating as well as electron-withdrawing substituents and their influence on the regioselectivity are dis…
Untersuchungen zur Diastereoselektivität beim O ‐Angriff von Elektrophilen auf β‐Ketocarbonsäureester‐Enolate
1989
Aus den in reiner Form eingesetzten Z- oder E-Enolen 2a–c werden uber die Enolatstufe 3a–c die O-alkylierten, -silylierten oder -acylierten Produkte 4aa–ae, 4ba, bf und 4ca, cc, cf hergestellt. Im Gegensatz zu der vollstandigen Regioselektivitat hangt die Z/E-Diastereoselektivitat dabei von den Substituenten in 2/3, dem verwendeten Elektrophil und den Reaktionsbedingungen ab. Insbesondere bei weichen Elektrophilen kann sich das Z/E-Verhaltnis bei der Umsetzung 34 stark andern. On the Diastereoselectivity of the O-Attack of Electrophiles on Enolates from β-Ketocarboxylates The O-alkylated, -silylated or -acylated derivatives 4aa–ae, 4ba, bf, 4ca, cc, cf of the pure Z or E enoles 2a–c are gen…
Reaction of dirhodium and diruthenium paddlewheel tetraacetate complexes with nucleophilic protein sites: A computational study
2022
Abstract The biomolecular affinity of three paddlewheel dinuclear complexes Rh2(µ-O2CCH3)4(H2O)2, Ru2(µ-O2CCH3)4(H2O)Cl, [Ru2(µ-O2CCH3)4(H2O)2]+ for the binding at cancer-specific protein targets was determined by means of DFT approaches. Thermodynamics of axial ligand substitution reaction by models of suitable protein sites was investigated in order to assess the binding selectivity displayed by the paddlewheel complexes. Both Rh2(µ-O2CCH3)4(H2O)2 and Ru2(µ-O2CCH3)4(H2O)Cl resulted to react favorably with most of the examined models of the protein side chains, with higher exergodicity demonstrated in the reaction of Arg, Cys, His, Lys, Sec, thus showing a limited selectivity. On the other…
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...
Characterization and synthesis of O- and N-tosylated N,N-bis(2-aminophenyl)isophthalamide based ligands
2009
Abstract A synthetic strategy for the preparation of O - and N- tosylated N , N -bis(2-aminophenyl)isophthalamide based ligands is described. It was observed that selectivity in O - and N -tosylation could be achieved by performing the reaction at low temperatures in the presence of an appropriate base. The obtained O - and N -tosylated products were characterized by means of NMR and mass spectroscopy, and X-ray crystallography.
Cycloadditionen von 2H ‐Benzo[ b ]thiet und Verbindungen mit kumulierten Doppelbindungen
1994
Cycloaddition Reactions of 2H-Benzo[b]thiete and Compounds with Cumulated Double Bonds o-Thiobenzoquinone methide (2), generated by thermal ring opening of 2H-benzo[b]thiete (1), reacts with allene 3, ketene imine 7, the carbodiimides 9a-c, and the N-sulfinylamines 11a-c in highly specific [8π + 2π] cycloaddition processes to form novel types of heterocyclic systems 4, 8, 10a-c, and 12a-c with exocyclic double bonds. The 1:1 adduct 4 can add a further molecule of allene to yield the spiro compounds 5 and 6.