RESUMO
The first approach to pyrazole-containing helicenes via sydnone-aryne [3 + 2]-cycloaddition is described. An unprecedented regioselectivity in the cycloaddition step toward the more sterically constrained product was observed in the presence of extended aromatic scaffolds. DFT calculations enabled understanding the origin of this unexpected selectivity.
Assuntos
Reação de Cicloadição , Compostos Policíclicos/química , Compostos Policíclicos/síntese química , Sidnonas/química , Modelos Moleculares , Conformação MolecularRESUMO
We report the discovery of a new bioorthogonal click-and-release reaction involving iminosydnones and strained alkynes. This transformation leads to two products resulting from the ligation and fragmentation of iminosydnones under physiological conditions. Optimized iminosydnones were successfully used to design innovative cleavable linkers for protein modification, thus opening up new areas in the fields of drug release and target-fishing applications. This click-and-release technology offers the possibility of exchanging tags on proteins for functionalized cyclooctynes under mild and bioorthogonal conditions.
RESUMO
Copper-catalyzed cycloaddition of alkynes with 4-bromosydnones provides a convenient, mild, and regioselective method for the synthesis of a wide range of bromopyrazoles. The broad functional group tolerance of the cycloaddition reaction and further palladium-catalyzed cross-coupling reactions allowed the preparation of polyfunctionalized 1,4,5-pyrazoles that are otherwise difficult to obtain by conventional methods.
Assuntos
Alcinos/química , Cobre/química , Pirazóis/síntese química , Sidnonas/química , Catálise , Reação de Cicloadição , Estrutura Molecular , Pirazóis/química , EstereoisomerismoRESUMO
A simple and efficient method for constructing 4-arylidene-5-imidazolones was developed using a phosphine-catalyzed tandem umpolung addition and intramolecular cyclization of amidine pronucleophiles on arylpropiolates. The reaction offers a robust route to heterocycle analogues of the fluorescent protein chromophores.
Assuntos
Imidazóis/síntese química , Fosfinas/química , Catálise , Ciclização , Imidazóis/química , Proteínas Luminescentes/química , Estrutura MolecularRESUMO
The concept of chelation-assisted copper catalysis was employed for the development of new azides that display unprecedented reactivity in the copper(I)-catalyzed azide-alkyne [3+2] cycloaddition (CuAAC) reaction. Azides that bear strong copper-chelating moieties were synthesized; these functional groups allow the formation of azide copper complexes that react almost instantaneously with alkynes under diluted conditions. Efficient ligation occurred at low concentration and in complex media with only one equivalent of copper, which improves the biocompatibility of the CuAAC reaction. Furthermore, such a click reaction allowed the localization of a bioactive compound inside living cells by fluorescence measurements.
Assuntos
Azidas/química , Cobre/química , Catálise , Química Click , Reação de Cicloadição , Espécies Reativas de OxigênioAssuntos
Aminobenzoatos/química , Azóis/química , Imunoensaio , Cobre/química , Estrutura Molecular , Oxigênio/químicaRESUMO
A simple and efficient method for constructing sulfur heterocycles was developed using a phosphine-catalyzed tandem umpolung addition and intramolecular cyclization of bifunctional sulfur pronucleophiles on arylpropiolates. The reaction offers a promising route to synthetically useful as well as biologically active heterocycles under neutral conditions.
