Palladium (0)-catalyzed C(sp)-H oxygenation with carboxylic acids

Ligand-Enabled Photoinduced Ruthenium Catalysis for Ortho-C─O Bond Formation at Room Temperature

Photoinduced ruthenium-catalyzed ortho-benzoxylation through organophosphine ligand is unveiled. The in situ generation of the organophosphine-ruthenium complex facilitates ligand-to-metal charge transfer (LMCT) under visible light, promoting the site-selective ortho-benzoxylation at room temperature. The broad scope of aryl, aliphatic, and heterocyclic carboxylic acids are key attractions of this methodology. EPR and UV-Vis analysis support a LMCT process between a photoexcited organophosphine and Ru-complex under blue-light irradiation. Comprehensive mechanistic investigation highlights the role of light, ligands, oxidants, the LMCT process, and the unique reactivity of the directing group.

Recent Progress in the Synthesis of Benzoxazin-4-Ones, Applications in N-Directed Ortho-Functionalizations, and Biological Significance

The development of efficient synthetic procedures to access fused N, O-heterocyclic skeletons has been a pivotal research topic in organic synthesis for several years. Owing to the applications of N, O-fused heterocycles in organic synthesis, material sciences, and medicinal chemistry, significant efforts have been dedicated to design novel methods for their construction. To this end, 1,3-benzoxazin-4-ones are privileged candidates for N, O-heterocyclic molecules often found in natural products, agrochemicals, and materials science applications. In this review, we aim to summarize the existing literature on the synthesis of 1,3-benzoxazin-4-ones from 2010 onwards. Moreover, 1,3-benzoxazin-4-ones have also been identified as an excellent native directing group for the ortho-functionalization via C-H activation, which is often a strenuous task requiring pre-functionalized substrates. In the latter part of this report, we compiled several interesting examples of N-directed functionalizations of 1,3-benzoxazin-4-ones. Additionally, to emphasize biological importance, recent developments on the anticancer evaluations of benzoxazine-4-one core are included. We believe that by harnessing the methodologies discussed herein, new possibilities could be unlocked for the synthesis of fused N, O-heterocycles, leading to the development of novel biologically active compounds and functional materials.

Rhodium-Catalyzed Azine-Directed C-H Amidation with N-Methoxyamides

Using N-methoxyamide reagents as an amide source, C-H amidation was realized at the ortho position of azine under the action of rhodium and boric acid. The method has mild reaction conditions, high atomic utilization, excellent yield, and wide adaptability to amidation reagents (both aromatic amides and fatty amides are applicable). Amide-substituted ketones can be obtained by a simple treatment and can be further transformed into bioactive substances. This provides a good supplement for the C-H bond amidation of aromatic rings.