Iridium-Catalyzed Unreactive C(sp3)-H Amination with 2,2,2-Trichloroethoxycarbonyl Azide

Carbonyl-Assisted Iridium-Catalyzed C-H Amination Using 2,2,2-Trichloroethoxycarbonyl Azide

The carbonyl-directed, mono C-H amination of arenes has been achieved using [Cp*Ir(III)Cl₂]₂ as the catalyst and 2,2,2-trichloroethoxycarbonyl (Troc) azide as an aminating reagent. The amination proceeds smoothly with a variety of arylcarbonyl compounds, including alkyl and vinyl arylketones, secondary and tertiary aryl amides, and acetyl indoles. The resulting ortho-TrocNH arylcarbonyl compounds are easily transformed to the corresponding free arylamines, aryl carbamates, or aryl ureas. Taking advantage of the electrophilic nature of both Troc and carbonyl groups in ortho-TrocNH arylcarbonyl compounds, the subsequent cyclization with dinucleophilic reagents has also been demonstrated. This provides an efficient strategy for the construction of aryl-fused N-heterocycles.

A New Dioxazolone for the Synthesis of 1,2-Aminoalcohols via Iridium(III)-Catalyzed C(sp3 )-H Amidation

Vicinal aminoalcohols are widespread structural motifs in bioactive molecules. We report the development of a new dioxazolone reagent containing a p‐nitrophenyldifluoromethyl group, which 1. displays a good safety profile; 2. shows a remarkably high reactivity in the oxime‐directed iridium(III)‐catalyzed amidation of unactivated C(sp³)−H bonds; 3. leads to amide products which can be hydrolyzed under mild conditions. The amidation reaction is mild, general and compatible with both primary C−H bonds of tertiary and secondary alcohols, as well as secondary C−H bonds of cyclic secondary alcohols. This method provides an easy access to free 1,2‐aminoalcohols after efficient and mild cleavage of the oxime directing group and activated amide.

Thioether-Directed NiH-Catalyzed Remote γ-C(sp3)-H Hydroamidation of Alkenes by 1,4,2-Dioxazol-5-ones

A NiH-catalyzed thioether-directed cyclometalation strategy is developed to enable remote methylene C-H bond amidation of unactivated alkenes. Due to the preference for five-membered nickelacycle formation, the chain-walking isomerization initiated by the NiH insertion to an alkene can be terminated at the γ-methylene site remote from the alkene moiety. By employing 2,9-dibutyl-1,10-phenanthroline (L4) as the ligand and dioxazolones as the reagent, the amidation occurs at the γ-C(sp³)-H bonds to afford the amide products in up to 90% yield (>40 examples) with remarkable regioselectivity (up to 24:1 rr).

Iron-catalyzed stereoselective haloamidation of amide-tethered alkynes

In this work, by using N-methoxybenzamides as efficient acyl nitrene precursors, an iron-catalyzed formal cis-haloamidation of alkyne is reported. Without assistance of additives, the reaction worked well in the presence of 50 mol% FeCl3 or FeBr3, leading to a series of chloro/bromo-containing isoindolin-5-ones with high efficiency and wide reaction scope. In the reaction, the iron-facilitated haloamidation proceeds through a halo anion-participating concerted [3+2] cyclization to release the final products. The key intermediate ferric acyl nitrene A is generated in situ from a formal removal of MeOH.

Catalytic Decarboxylative C-N Formation to Generate Alkyl, Alkenyl, and Aryl Amines

Transition-metal-catalyzed sp² C-N bond formation is a reliable method for the synthesis of aryl amines. Catalytic sp³ C-N formation reactions have been reported occasionally, and methods that can realize both sp² and sp³ C-N formation are relatively unexplored. Herein, we address this challenge with a method of catalytic decarboxylative C-N formation that proceeds through a cascade carboxylic acid activation, acyl azide formation, Curtius rearrangement and nucleophilic addition reaction. The reaction uses naturally abundant organic carboxylic acids as carbon sources, readily prepared azidoformates as the nitrogen sources, and 4-dimethylaminopyridine (DMAP) and Cu(OAc)₂ as catalysts with as low as 0.1 mol % loading, providing protected alkyl, alkenyl and aryl amines in high yields with gaseous N₂ and CO₂ as the only byproducts. Examples are demonstrated of the late-stage functionalization of natural products and drug molecules, stereospecific synthesis of useful α-chiral alkyl amines, and rapid construction of different ureas and primary amines.

Unravelling nitrene chemistry from acyclic precursors: recent advances and challenges

Recent advances in nitrene chemistry from acyclic precursors are reviewed in this paper.

Iron-catalyzed intramolecular acyl nitrene/alkyne metalation for the synthesis of pyrrolo[2,1-a]isoindol-5-ones

In this work, by using N-methoxybenzamides as efficient acyl nitrene precursors, an iron-catalyzed acyl nitrene/alkyne metalation is reported for the synthesis of pyrrolo[2,1-a]isoindol-5-ones.

Iridium-Catalyzed C-H Amination of Weinreb Amides: A Facile Pathway toward Anilines and Quinazolin-2,4-diones

C-H amination of arenes directed by weakly coordinating Weinreb amides has been achieved with an iridium catalyst and 2,2,2-trichloroethoxycarbonyl (Troc) azide as an aminating agent, providing a robust method of producing synthetic useful ortho-TrocNH aryl Weinreb amides. Taking advantage of the reactivity of Weinreb amide and Troc groups in the amination products, selective hydrolysis was achieved as an attractive process for the synthesis of ortho-NH₂ aryl Weinreb amides, which are the building blocks useful in the synthesis of bioactive compounds, and cascade aminocyclization with primary amines was successful and provided an efficient pathway for the construction of quinazolin-2,4-diones, which are present in various alkaloids and natural products.

Copper-catalyzed ortho-C(sp2)-H amination of benzamides and picolinamides with alkylamines using oxygen as a green oxidant

A versatile Cu-catalyzed direct ortho-C(sp2)-H amination of benzamides and picolinamides with alkylamines has been achieved. This method employs cheap and eco-friendly copper as a catalyst and oxygen as an oxidant, and also has the advantages of straightforward steps and excellent functional group compatibility. Further application of our approach was demonstrated by the synthesis of TCMDC-125116, SPHINX, and SRPIN340.

Recent trends in catalytic sp3 C-H functionalization of heterocycles

Heterocycles are a ubiquitous substructure in organic small molecules designed for use in materials and medicines. Recent work in catalysis has focused on enabling access to new heterocycle structures by sp³ C-H functionalization on alkyl side-chain substituents-especially at the heterobenzylic position-with more than two hundred manuscripts published just within the last ten years. Rather than describing in detail each of these reports, in this mini-review we attempt to highlight gaps in existing techniques. A semi-quantitative overview of ongoing work strongly suggests that several specific heterocycle types and bond formations outside of C-C, C-N, and C-O have been almost completely overlooked.

Theoretical studies on the N–X (X = Cl, O) bond activation mechanism in catalytic C–H amination

A favorable S_N2-type N–Cl bond cleavage mechanism are proposed for Rh-catalysed C–H amination, which also works for N–O bond cleavage in Rh, Ru, and Pd analogous systems. These results could provide new understanding of C–H amination.

Rhodium(iii)-catalyzed unreactive C(sp3)-H alkenylation of N-alkyl-1H-pyrazoles with alkynes

The first example of pyrazole-directed rhodium(iii)-catalyzed unreactive C(sp³)-H alkenylation with alkynes has been described, which showed a relatively broad substrate scope with good functional group compatibility. Moreover, we demonstrated that the transitive coordinating center pyrazole could be easily removed under mild conditions.

Design and Optimization of Thioglycosyl-naphthalimides as Efficient Inhibitors Against Human O-GlcNAcase

β-N-acetylhexosaminidases represent an important class of exoglycosidases and have emerged as the promising targets for drug and pesticide discovery. Among these, human O-GlcNAcase (hOGA) has been reported to be closely linked to several diseases such as Alzheimer's disease, diabetes, and cancer. Potent hOGA inhibitors with high selectivity are therefore of great significance for the regulation of the corresponding physiological processes. In this study, several classes of novel and readily available thioglycosyl-naphthalimides bearing the amide linker were designed and synthesized. To investigate their potency and selectivity, the inhibitory efficiencies toward hOGA and human β-N-acetylhexosaminidase B (HsHexB) were assayed. Especially, compounds 10a (K _i = 0.61 μM) and 16l (K _i = 0.72 μM) exhibited excellent inhibitory potency against hOGA and high selectivity (HsHexB, K _i > 100 μM). In addition, during the preparation of these thioglycosyl-naphthalimides, a new practical method was developed for the synthesis of ureido glycosides from trichloroethyl carbamates at room temperature and normal pressure without catalyst. Furthermore, the possible binding modes of hOGA with 10a, 10d, and 16j were studied using molecular docking and molecular dynamics simulations to explore the molecular basis for the potency of these thioglycosides. This work present here provides useful clues for the further structural optimization toward hOGA.