RESUMO
The Balz-Schiemann reaction endures as a method for the preparation of (hetero)aryl fluorides yet is eschewed due to the need for harsh conditions or high temperatures along with the need to isolate potentially explosive diazonium salts. In a departure from these conditions, we show that various organotrifluoroborates (RBF3 - s) may serve as fluoride ion sources for solution-phase fluoro-dediazoniation in organic solvents under mild conditions. This methodology was successfully extended to a one-pot process obviating aryl diazonium salt isolation. Sterically hindered (hetero)anilines are fluorinated under unprecedentedly mild conditions in good-to-excellent yields. Taken together, this work expands the repertoire of RBF3 - s to act as fluorine ion sources in an update to the classic Balz-Schiemann reaction.
RESUMO
A reduction of various aryl, alkyl, and α,ß-unsaturated amides with phenylsilane, catalysed by a borinic acid, is reported. The unprecedented reaction was carried out under very mild conditions and led to useful amines. Furthermore, the reaction tolerates a variety of functional groups. Initial investigations implicated that an intermediate diarylhydroborane is involved in the reaction mechanism.
RESUMO
An efficient method has been developed for direct amide bond synthesis between carboxylic acids and amines via (2-(thiophen-2-ylmethyl)phenyl)boronic acid as a highly active bench-stable catalyst. This catalyst was found to be very effective at room temperature for a large range of substrates with slightly higher temperatures required for challenging ones. This methodology can be applied to aliphatic, α-hydroxyl, aromatic, and heteroaromatic acids as well as primary, secondary, heterocyclic, and even functionalized amines. Notably, N-Boc-protected amino acids were successfully coupled in good yields with very little racemization. An example of catalytic dipeptide synthesis is reported.
Assuntos
Amidas/síntese química , Dipeptídeos/síntese química , Temperatura , Amidas/química , Catálise , Dipeptídeos/química , Estrutura MolecularRESUMO
Pseudomonas aeruginosa (P.A.) is a human pathogen belonging to the top priorities for the discovery of new therapeutic solutions. Its propensity to generate biofilms strongly complicates the treatments required to cure P.A. infections. Herein, we describe the synthesis of a series of novel rotaxanes composed of a central galactosylated pillar[5]arene, a tetrafucosylated dendron, and a tetraguanidinium subunit. Besides the high affinity of the final glycorotaxanes for the two P.A. lectins LecA and LecB, potent inhibition levels of biofilm growth were evidenced, showing that their three subunits work synergistically. An antibiofilm assay using a double ΔlecAΔlecB mutant compared to the wild type demonstrated that the antibiofilm activity of the best glycorotaxane is lectin-mediated. Such antibiofilm potency had rarely been reached in the literature. Importantly, none of the final rotaxanes was bactericidal, showing that their antibiofilm activity does not depend on bacteria killing, which is a rare feature for antibiofilm agents.
Assuntos
Biofilmes/efeitos dos fármacos , Calixarenos/química , Pseudomonas aeruginosa/efeitos dos fármacos , Compostos de Amônio Quaternário/química , Rotaxanos/farmacologia , Linhagem Celular Tumoral , Hemólise/efeitos dos fármacos , Humanos , Testes de Sensibilidade Microbiana , Polieletrólitos , Pseudomonas aeruginosa/metabolismoRESUMO
Correction for 'Borinic acid catalysed peptide synthesis' by Tharwat Mohy El Dine et al., Chem. Commun., 2015, 51, 16084-16087.