Abstract:The novel Pd-catalyzed C(sp(2))-H/C(sp(2))-H cross-coupling of unactivated xanthines with unactivated arenes utilizing a combination of Ag(I) and O(2) as oxidants exclusively yields C-8 arylated xanthines in a single synthetic operation.
“…In addition to indoles and pyrroles,39 the dehydrogenative coupling of benzofurans37c and CH acidic heteroarenes, such as xanthines,40 has also been reported.…”
The use of coordinating moieties as directing groups for the functionalization of aromatic C-H bonds has become an established tool to enhance reactivity and induce regioselectivity. Nevertheless, with regard to the synthetic applicability of C-H activation, there is a growing interest in transformations in which the directing group can be fully abandoned, thus allowing the direct functionalization of simple benzene derivatives. However, this approach requires the disclosure of new strategies to achieve reactivity and to control selectivity. In this review, recent advances in the emerging field of non-chelate-assisted C-H activation are discussed, highlighting some of the most intriguing and inspiring examples of induction of reactivity and selectivity.
“…In addition to indoles and pyrroles,39 the dehydrogenative coupling of benzofurans37c and CH acidic heteroarenes, such as xanthines,40 has also been reported.…”
The use of coordinating moieties as directing groups for the functionalization of aromatic C-H bonds has become an established tool to enhance reactivity and induce regioselectivity. Nevertheless, with regard to the synthetic applicability of C-H activation, there is a growing interest in transformations in which the directing group can be fully abandoned, thus allowing the direct functionalization of simple benzene derivatives. However, this approach requires the disclosure of new strategies to achieve reactivity and to control selectivity. In this review, recent advances in the emerging field of non-chelate-assisted C-H activation are discussed, highlighting some of the most intriguing and inspiring examples of induction of reactivity and selectivity.
“…Neben Indolen und Pyrrolen,39 wurden unter anderem die dehydrierenden Kupplungen von Benzofuranen37c und C‐H‐aciden Heteroarenen, wie den Xanthinen,40 beschrieben.…”
Der Einsatz von koordinierenden Gruppen als dirigierende Gruppen ist eine zuverlässige Methode zur Kontrolle von Reaktivität und Selektivität bei der Aktivierung von Aryl‐C‐H‐Bindungen. Im Hinblick auf die Anwendbarkeit von C‐H‐Aktivierungen in der Synthese besteht derzeit ein großes Interesse daran, Reaktionen zu entwickeln, in denen völlig auf dirigierende Gruppen verzichtet werden kann und somit die Funktionalisierung einfacher Benzolderivate möglich wird. Dieser Ansatz erfordert jedoch neue Strategien zur Reaktivitäts‐ und Selektivitätskontrolle. In diesem Kurzaufsatz werden aktuelle Fortschritte in dem noch jungen Gebiet der nicht‐chelatvermittelten C‐H‐Aktivierung diskutiert, wobei einige inspirierende Beispiele zur Reaktivitäts‐ und Selektivitätsinduktion hervorgehoben werden.
Fragment-based drug design was used to identify Mycobacterium tuberculosis (Mtb) dihydrofolate reductase (DHFR) inhibitors. Screening of ligands against the Mtb DHFR enzyme resulted in the identification of multiple fragment hits with IC50 values in the range of 38-90 μM versus Mtb DHFR and minimum inhibitory concentration (MIC) values in the range of 31.5-125 μg/mL. These fragment scaffolds would be useful for anti-tubercular drug design.
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