Ir-Catalyzed C–H Amidation Using Carbamoyl Azides for the Syntheses of Unsymmetrical Ureas

Ir(iii)/Ag(i)-catalyzed directly C-H amidation of arenes with OH-free hydroxyamides as amidating agents

A versatile Ir(iii)-catalyzed C-H amidation of arenes by employing readily available and stable OH-free hydroxyamides as a novel amidation source. The reaction occurred with high efficiency and tolerance of a range of functional groups. A wide scope of aryl OH-free hydroxyzamides, including conjugated and challenging non-conjugated OH-free hydroxyzamides, were capable of this transformation and no addition of an external oxidant is required. This protocol provided a simple, straightforward and economic method to a variety N-(2-(1H-pyrazol-1-yl)alkyl)amide derivates with good to excellent yield. Mechanistic study demonstrated that reversible C-H bond functionalisation might be involved in this reaction.

Comprehensive Theoretical Study of Cp*IrIII-Catalyzed Intermolecular Enantioselective Allylic C-H Amidation: Reaction Mechanism, Electronic Processes, and Regioselectivity

Density functional theory was used to elucidate the reaction mechanism of Cp*Ir^III-catalyzed intermolecular regioselective C(sp³)-H amidation of alkenes with methyl dioxazolones. All substrates, intermediates, and transition states were fully optimized at the ωB97XD/6-31G(d,p) level (LANL2DZ(f) for Ir). The computational results revealed that this amidation occurred through the Ir^III/Ir^V catalytic cycle, involving four important elementary steps: C-H bond activation, oxidative addition of methyl dioxazolone, reductive elimination, and proto-demetalation, and the first was the rate-determining step. The C-H bond activation showed good α- and branch-regioselectivity, decided by the distortion energy of 2-pentene and the interaction energy of the transition state, respectively. The oxidative addition of dioxazolone occurred in one elementary step with CO₂ disassociation. The reductive elimination showed good branch-regioselectivity determined by the distorted energy of the allyl group. In the proto-demetalation, hydrogen directly transferred from the oxygen atom to the nitrogen atom. Moreover, to clarify the effect of the substituted groups, selected 12 substrates were also discussed in this text.

Transient Directing Groups in Metal-Organic Cooperative Catalysis

The direct functionalization of C-H bonds is among the most fundamental chemical transformations in organic synthesis. However, when the innate reactivity of the substrate cannot be utilized for the functionalization of a given single C-H bond, this selective C-H bond functionalization mostly relies on the use of directing groups that allow bringing the catalyst in close proximity to the C-H bond to be activated and these directing groups need to be installed before and cleaved after the transformation, which involves two additional undesired synthetic operations. These additional steps dramatically reduce the overall impact and the attractiveness of C-H bond functionalization techniques since classical approaches based on substrate pre-functionalization are sometimes still more straightforward and appealing. During the past decade, a different approach involving both the in situ installation and removal of the directing group, which can then often be used in a catalytic manner, has emerged: the transient directing group strategy. In addition to its innovative character, this strategy has brought C-H bond functionalization to an unprecedented level of usefulness and has enabled the development of remarkably efficient processes for the direct and selective introduction of functional groups onto both aromatic and aliphatic substrates. The processes unlocked by the development of these transient directing groups will be comprehensively overviewed in this review article.

Synthesis, biological evaluation and molecular modeling of urea-containing MraY inhibitors

The straightforward synthesis of aminoribosyl uridines substituted by a 5'-methylene-urea is described. Their convergent synthesis involves the urea formation from various activated amides and an azidoribosyl uridine substituted at the 5' position by an aminomethyl group. This common intermediate resulted from the diastereoselective glycosylation of a phthalimido uridine derivative with a ribosyl fluoride as a ribosyl donor. The inhibition of the MraY transferase activity by the synthetized 11 urea-containing inhibitors was evaluated and 10 compounds revealed MraY inhibition with IC50 ranging from 1.9 μM to 16.7 μM. Their antibacterial activity was also evaluated on a panel of Gram-positive and Gram-negative bacteria. Four compounds exhibited a good activity against Gram-positive bacterial pathogens with MIC ranging from 8 to 32 μg mL-1, including methicillin resistant Staphylococcus aureus (MRSA) and Enterococcus faecium. Interestingly, one compound also revealed antibacterial activity against Pseudomonas aeruginosa with MIC equal to 64 μg mL-1. Docking experiments predicted two modes of positioning of the active compounds urea chain in different hydrophobic areas (HS2 and HS4) within the MraY active site from Aquifex aeolicus. However, molecular dynamics simulations showed that the urea chain adopts a binding mode similar to that observed in structural model and targets the hydrophobic area HS2.

C-H Amidation and Amination of Arenes and Heteroarenes with Amide and Amine using Cu-MnO as a Reusable Catalyst under Mild Conditions

An atom-economical and efficient route for the direct amidation and amination of aryl C-H bonds using our synthesized recyclable heterogeneous Cu-MnO catalyst is reported here. The direct C-H amidation was carried out using a simple amide without any preactivated coupling partner, and simple air was used as the sole oxidant. The reaction proceeds very smoothly with a broad range of substrates containing numerous functional groups in very good to excellent yields. Direct C-H aminations with a secondary amine were carried out under base-, ligand-, and external oxidant-free conditions in very good to excellent yields in very mild conditions. Both the amidation and amination can be scaled up on a gram scale with similar yields. The major advantage is that our catalyst is recyclable and reused several times without any significant loss of reactivity.