Investigation of the importance of nitrogen substituents in a N–P chiral ligand for enantioselective allylic alkylation
摘要:
The synthesis of three chiral chelate nitrogen-phosphorus (S)-valine derived ligands with the potential fur stereogenic nitrogen donation is described. In palladium catalysed allylic substitution reactions the ligands induced varying enantioselectivities ranging From 92%, e.e. of the (R)-enantiomer to 83% e.e. of the (S)-enantiomer. Structural and spectroscopic investigations into the origin of this effect were conducted, but were inconclusive. However, the importance of the consideration of N-substituents in such systems is highlighted. (C) 2001 Elsevier Science Ltd. All rights reserved.
To discover broad spectrum antifungal agents, two strategies were applied, and a novel class of l-amino alcohol derivatives were designed and synthesized. 3-F substituted compounds 14i, 14n, 14s and 14v exhibited excellent antifungal activities with broad antifungal spectra against C. albicans and C. tropicalis, with MIC values in the range of 0.03–0.06 μg/mL, and against A. fumigatus and C. neoformans
Versatile Chiral Bidentate Ligands Derived from α-Amino Acids: Synthetic Applications and Mechanistic Considerations in the Palladium-Mediated Asymmetric Allylic Substitutions
to other amino groups in the amidine skeleton and the production of other types of ligands, are possible using the precursor compounds of 7a. Thus, novel chiral ligands 7c,d, 8, 11, and 13, which provide sterically and electronically different chiral circumstances, were prepared and used for the palladium-mediated asymmetric allylic substitutions of both acyclic and cyclic compounds. In these reactions
Whereas palladium-catalyzed reaction of N-arylsulfonyl-alpha-amino allenes with an aryl iodide (4 equiv) in the presence of potassium carbonate (4 equiv) in DMF at around 70 degrees C affords the corresponding 3-pyrroline derivatives, the reaction in refluxing 1,4-dioxane under otherwise identical conditions yields exclusively or most predominantly the corresponding 2-alkenylaziridines bearing an aryl
A rapid entry to amino acid derived diverse 3,4-dihydropyrazines and dihydro[1,2,3]triazolo[1,5-a]pyrazines through 1,3-dipolar cycloaddition
作者:Saurav Bera、Gautam Panda
DOI:10.1039/c4ob00639a
日期:——
synthesis of diverse 3,4-dihydropyrazines, 6,7-dihydro-[1,2,3]triazolopyrazines and 7,8-dihydro-[1,2,3]triazolodiazepines through intramolecular 1,3-dipolar cycloaddition fromaminoacid derived common intermediates with high yields is described. Moreover, one-pot access to optically active 3-aryl substituted 6,7-dihydro-[1,2,3]triazolo[1,5-a]pyrazines in the palladium–copper co-catalytic system has
通过分子内1,3-高效,通用和实用地合成各种3,4-二氢吡嗪,6,7-二氢-[1,2,3]三唑并吡嗪和7,8-二氢-[1,2,3]三唑并二氮杂pine描述了从氨基酸衍生的常见中间体以高收率进行偶极环加成。此外,在此方法中,还可以通过一锅获得光学活性的3-芳基取代的6,7-二氢-[1,2,3]三唑并[1,5- a ]吡嗪在钯-铜共催化体系中的应用。工作。容易获得的基材和操作简便性使该工艺适合于进一步探索。
Kinetic and NMR Spectroscopic Studies of Chiral Mixed Sodium/Lithium Amides Used for the Deprotonation of Cyclohexene Oxide
chiral amino ether has been studied by NMR spectroscopy. Three different mixed-metal amides were used as chiral bases for the deprotonation of cyclohexene oxide. The selectivity and initial rate of reaction were compared for sodium-amido ethers, lithium-amido ethers, and mixtures of sodium and lithiumamido ethers in diethyl ether and tetrahydrofuran, respectively. The mixed sodium/lithium amides are