Search results for "combinatorial"
showing 10 items of 1208 documents
ChemInform Abstract: Modular One-Pot Synthesis of Tetrasubstituted Pyrroles from α-(Alkylideneamino)nitriles.
2008
2,3,4,5-Tetrasubstituted pyrroles have been prepared with high regioselectivity by a formal cycloaddition of α-(alkylideneamino)nitriles and nitroolefins followed by elimination of HCN and HNO2. The reaction allows the convergent construction of the pyrrole ring in four steps from a nitroalkane and three aldehydes.
A new method for the regioselective synthesis of β-enamino acid derivatives
1993
Abstract A mild, simple and efficient route to β-enamino imidazole carbonilic derivatives 3 by reaction of ketimines with N,N′ -carbonyl diimidazole in the presence of boron triflouride as catalyst has been developed. The conversion of 3 to esters has also been explored.
Facile synthesis of pyrazoles and pyrroles via thermolysis of tetrazolo[1,5-b]pyridazines, tetrazolo[1,5-a]pyrimidines and tetrazolo[1,5-a]pyridines
2000
Abstract A simple and high yielding preparation of pyrazoles and pyrroles is described. Thermolysis of tetrazolo[1,5- b ]pyridazines, tetrazolo[1,5- a ]pyrimidines and tetrazolo[1,5- a ]pyridines allowed easy ring contraction thus providing a facile preparation of cyanopyrazole and cyanopyrrole heterocycles. Since the cyano group is a versatile precursor of other functionalities, the reaction appears of particular interest for the construction of a variety of pyrazoles and pyrroles. The simple preparation of the starting tetrazole derivatives, the relatively mild conditions employed, and the very short reaction times make this versatile procedure of great synthetic utility and applicable bo…
Recent Advances in the Synthesis of Pyrazoles. A Review
2009
Pyrazole (Figure 1), a five-membered, two-nitrogen-containing heterocycle ring, is widely found as the core structure in a large variety of compounds that possess important agrochemical and pharmac...
Mechanochemical Syntheses of N-Containing Heterocycles with TosMIC
2021
A mechanochemical van Leusen pyrrole synthesis with a base leads to 3,4-disubstitued pyrroles in moderate to excellent yields. The developed protocol is compatible with a range of electron-withdrawing groups and can also be applied to the synthesis of oxazoles. Attempts to mechanochemically convert the resulting pyrroles into porphyrins proved to be difficult.
ChemInform Abstract: Water in Stereoselective Organocatalytic Reactions
2009
In this review, recent advances in asymmetric organocatalytic reactions carried out with variable amounts of water, from substoichiometric to a large excess (reaction medium), are discussed. We also summarize several proposed mechanisms for the different possibilities of the action of water both in the increased activity of the catalyst and in the asymmetric induction. Finally, the application of this catalytic methodology to the enantioselective synthesis of valuable compounds through enamine or iminium catalysis is presented.
ChemInform Abstract: Low-Loading Asymmetric Organocatalysis
2012
Asymmetric organocatalysis is now recognized as the third pillar of asymmetric synthesis. Recent years have witnessed increasing interest towards the use of highly active and stereoselective organocatalysts. This critical review documents the advances in the development of chiral organocatalysts which are systematically used in ≤3 mol% loading in all the sub-areas of the field, namely aminocatalysis, Bronsted acids and bases, Lewis acids and bases, hydrogen bond-mediated catalysis, phase transfer and N-heterocyclic carbene catalyses (194 references).
ChemInform Abstract: Syntheses of Sialyl Lewis A Glycopeptides - A Partial Sequence of the P-Selectin Ligand PSGL-1.
2000
ChemInform Abstract: Boron Functionalization of BODIPY by Various Alcohols and Phenols
2014
The synthesis of new B–O BODIPY derivatives functionalized with different alkoxy or diarylalkoxy derivatives is described. These compounds were synthesized from the reaction of different B–F BODIPY precursors with various alcohols and phenols, in the presence of AlCl3. Water-soluble dyes could be synthesized as well with this method, specifically by the introduction of polyethyleneglycol (PEG) groups. A photophysical study of the different compounds was performed, and showed that the B–O BODIPY derivatives exhibit rich fluorescence properties. Finally, the conjugation of the BODIPY core has been extended using two distyryl groups, hence providing NIR emitting BODIPY derivatives, in which on…