Search results for "combinatorial"
showing 10 items of 1208 documents
A Versatile Synthesis of Fluorinated Uracils in Solution and on Solid-Phase.
2004
[reaction: see text] An efficient and convenient two-step synthesis of new fluorinated uracils is described. The first step involves the condensation of an ester enolate with a fluorinated nitrile to furnish fluorinated beta-enamino esters. In turn, these compounds react with organic isocyanates or isothiocyanates to give C-6 fluorinated uracils or thiouracils, respectively, in excellent yields. This synthesis has been successfully adapted to solid-phase conditions with high diversity, thereby facilitating the creation of small (thio)uracil libraries.
Poly(alkylidenamines) dendrimers as scaffolds for the preparation of low-generation ruthenium based metallodendrimers
2011
The aim of this article is to highlight the use of nitrile-functionalized poly(alkylidenamines) dendrimers as building blocks for the preparation of low-generation ruthenium based cationic metallodendrimers having in view potential biomedical applications. Air-stable poly(alkylidenamines) nitrile dendrimers, peripherally functionalized with the ruthenium moieties [Ru(η5-C5H5)(PPh3)2]+ or [RuCl(dppe)2]+, have been prepared, characterized and are being studied for their anticancer activity. The followed strategy is based on the biological advantages associated with low-generation dendrimers, the known activity of ruthenium compounds as anticancer drugs and the stability of these dendrimers at…
Electroorganic synthesis of nitriles via a halogen-free domino oxidation–reduction sequence
2015
A direct electroorganic sequence yielding nitriles from oximes in undivided cells is reported. Despite the fact that intermediate nitrile oxides might be formed, the method is viable to prepare benzonitriles without substituents ortho to the aldoxime moiety. This constant current method is easy to perform for a broad scope of substrates and employs common electrodes, such as graphite and lead.
Triazolopyridines. Part 28. The ring–chain isomerization strategy: triazolopyridine- and triazoloquinoline–pyridine based fluorescence ligands
2012
Abstract The ring–chain isomerization of [1,2,3]triazolo[1,5-a]pyridines or [1,2,3]triazolo[1,5-a] quinolines has been efficiently employed as a tool to provide tridentate fluorescent structures. Based on these scaffolds, a new family of highly fluorescent compounds has been synthesized and evaluated for the recognition of zinc or copper cations. In addition, the 1:1 Zn+2-L complex of a naphthalene triazolopyridine–pyridine derivative revealed high efficiency as sensor for anions providing large binding constants for nitrite and cyanide.
ChemInform Abstract: Facile Synthesis of 5-Benzamido-4-diazopyrazole Derivatives, a Class of Biologically Active Agents and Key Intermediates.
2010
Abstract By reacting l-R1-3-R2-5-(R3-substituted)benzamidopyrazoles with a great ex-cess of nitrous acid in acetic acid media, the related 4-diazoderivatives in 65–80% yields were obtained.
ChemInform Abstract: Asymmetric Tandem Reactions: New Synthetic Strategies
2010
The use of domino and multicomponent reactions in asymmetric synthesis is con- stantly increasing nowadays. This allows for the synthesis of complex molecules in a single synthetic sequence, usually with high atom economy. Herein, we report three examples of new asymmetric tandem reactions recently developed in our laboratories, giving rise to new families of enantiomerically enriched fluorinated and nonfluorinated heterocycles. Thus, 1,4-dihydropyridines (1,4-DHPs) bearing fluorinated substituents at C6 were assembled by means of a Hantzsch-type reaction; cyclic β-amino carbonyl derivatives were prepared using a cross-metathesis (CM)-intramolecular aza-Michael sequence; while fluorinated i…
Tandem gold self-relay catalysis for the synthesis of 2,3-dihydropyridin-4(1 H)-ones: combination of σ and π Lewis acid properties of gold salts.
2014
The dual ability of gold salts to act as π- and σ Lewis acids has been exploited in a tandem self-relay catalysis. Thus, triphenylphosphanegold(I) triflate mediated the intramolecular carbonyl addition of the amide functionality of homoprogargyl amides to a triple bond. The formation of a σ complex of the gold salt with the intermediate oxazine promoted a nucleophilic addition followed by a Petasis-Ferrier rearrangement. This tandem protocol, catalyzed by the same gold salt under the same reaction conditions, gave rise to the efficient synthesis of 2,3-dihydropyridin-4-(1 H)-ones, which contain a cyclic quaternary α-amino acid unit. The asymmetric version was performed by generating the sta…
Synthesis of 1-Palmitoyl-2-((E)-9- and (E)-10-nitrooleoyl)-sn-glycero-3-phosphatidylcholines
2019
Extensive investigation of nitrated phospholipids in connection with various biologically important processes requires reliable access to suitable material. A selective chemical synthesis introducing a defined nitrofatty acid at the sn-2 position of a 2-lyso sn-glycero-3-phosphatidylcholine was developed. Given that the nitroalkene moiety of both reactant nitrofatty acid derivative and the product esters is characterised by particular sensitivity to nucleophile addition and, depending on the intermediate, subsequent olefin isomerisation and retro-Henry-type reaction, a reliable two-step ester formation was introduced. The activation of the nitrofatty acid succeeded after reaction with trich…
Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds
2015
A new tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM–IMDAR protocols.
Role of the gem-Difluoro Moiety in the Tandem Ring-Closing Metathesis−Olefin Isomerization: Regioselective Preparation of Unsaturated Lactams
2006
Careful selection of the metathesis catalyst, solvent, and reaction conditions allows for the efficient and regioselective synthesis of isomeric fluorinated and nonfluorinated lactam derivatives II and III from precursor amides I through a ring-closing metathesis (RCM) reaction or a tandem RCM-isomerization protocol, respectively. The presence of the gem-difluoro moiety in the starting materials exerts a pivotal effect by directing the isomerization step, making the overall tandem transformation a regioselective process. The scope, limitations, and synthetic usefulness of this protocol are also discussed.