Search results for "405"
showing 10 items of 3208 documents
Synthesis of Symmetric Ethers Using Monocationic and Dicationic Acidic Ionic Liquids
2018
A series of monocationic and dicationic -SO3H functionalized Brønsted acidic ionic liquids (BAILs) are synthesized using different amines int.al., N,N,N′,N′-tetramethylethylenediamine, 1-methylimidazole, pyridine and alkylating agents 1,3-propane- and 1,4-butanesultones. The Hammett acidity (H0) and thermal properties by TG-DSC techniques are investigated. These ionic liquids have been applied to catalyze the dehydration reaction of aliphatic long chain alcohols (1-heptanol, 1-octanol, 1-decanol) at 195 °C. The optimization of reaction conditions and use of dicationic ionic liquids allow to reach rather high yields of symmetric diheptyl ether and dioctyl ether. The reusability of ionic liqu…
Mild and efficient 64Cu labeling of perhydro-1, 4-diazepine derivatives for potential use with large peptides, proteins and antibodies
2020
Abstract DATA (6-Amino-1,4-diazapine-triacetate) and AAZTA (6-Amino-1,4-diazapine-tetracetate) chelators represent a novel approach representing hybrid-chelates: possessing significant cyclic and acyclic character. It is believed that flexibility of the acyclic part facilitates rapid complexation, whilst the preorganized cyclic part minimizes the energy barrier to complexation and inhibits decomplexation processes. So far, these chelators have been used exclusively with 44Sc and 68Ga only. Recent results with natCu predict high stabilities for Cu-AAZTA, yet no radioactive labeling of AAZTA or DATA with 64Cu or any additional radioactive isotope has been reported. We present the one pot synt…
Absolute Configuration Determination of 2,3-Dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles Using Chiroptical Methods at Different Wavelengths
2016
A correlation between the absolute configuration and chiroptical properties of nonracemic 1,6,7-trisubstituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles was studied. A series of 16 novel representatives were prepared by Cu-catalyzed [3 + 2] cycloadditions of racemic (Z)-2-benzylidene-5-oxopyrazolidin-2-ium-1-ides to tert-butyl (S)-(3-oxopent-4-yn-2-yl)carbamate, and their structures were determined by NMR, VCD, ECD, and X-ray diffraction. A clear correlation between the sign of specific rotation and configuration at position C(1) allows for easy determination of the absolute configuration of 1,6,7-trisubstituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazoles by ECD and NMR. While VCD, requirin…
Pyrene-fused bisphenazinothiadiazoles with red to NIR electroluminescence
2017
The synthesis and characterisation of two pyrene-fused phenazinothiadiazole derivatives with different substituents is described. Light-emitting diodes incorporating such derivatives display red to near-infrared electroluminescence with emission peaks at wavelengths as long as 721 nm, illustrating that pyrene-fused bisphenazinothiadiazoles can serve as deep red and NIR emitters.
Anodic Formation of Aryl Mesylates through Dehydrogenative Coupling Reaction
2018
Understanding the Intramolecular Diels-Alder Reactions of N-Substituted N-Allyl-Furfurylamines: An MEDT Study
2017
From One-Pot NH-Sulfoximidations of Thiophene Derivatives to Dithienylethene-Type Photoswitches
2019
Thiophene NH-sulfoximines have been synthesized using a one-pot NH-sulfoximidation reaction of thiophenes. The reactivity of the products was investigated, and the developed protocols were used for the synthesis of a new class of dithienylethene-type photoswitches containing a sulfoximidoyl group.
Efficient and stereodivergent electrochemical synthesis of optically pure menthylamines.
2011
Recent Advances in the Synthesis of Piperidines: Functionalization of Preexisting Ring Systems
2018
Abstract The present review focuses on strategies for the construction of piperidines which have appeared in the literature since 2003 through mid-2017. In a preceding chapter ( 2017AHC191 ), we summarized synthetic methods involving the construction of the piperidine ring from essentially acyclic starting materials in an intra- or intermolecular manner. The present chapter aims at giving a general overview of decoration or modification of previously generated pyridines or piperidines. The hydrogenation of preformed pyridine or pyridinium rings and introduction of substituents into fully saturated piperidines as well as ring expansion of pyrrolidines to piperidines are the most prevalent me…
Asymmetric Synthesis of Five-Membered Spiropyrazolones via N-Heterocyclic Carbene (NHC)-Catalyzed [3+2] Annulations
2016
A new synthetic strategy for the asymmetric synthesis of five-membered spiropyrazolones via N-heterocyclic carbene-catalyzed [3+2] annulations employing enals and unsaturated pyrazolones as substrates has been developed. The new protocol allows the flexible variation of all four substituents of the pharmaceutically important spiropyrazolones in moderate to very good yields and in most cases with excellent diastereoselectivities and good to excellent enantioselectivities.