Synthesis of Functionalized Pyridines via a Regioselective Oxazoline Promoted C-H Amidation Reaction

Rhodium-catalyzed C-H activation and three-component tandem annulation leading to isoquinolones

A rhodium-catalyzed C-H activation and three-component coupling of oxazolines, vinylene carbonate and carboxylic acids has been developed. Various isoquinolone products were constructed under redox-neutral conditions with satisfactory yields. It is worth noting that diverse bioactive carboxylic acids have been proven to be effective substrates, and their application in this protocol has expanded the range of isoquinolones with biologically relevant motifs. Multi-dimensional mechanism exploration experiments and derivatization reactions were studied in sequence to explore the details and application prospects of this transformation. It offers an alternative approach for the synthesis of useful isoquinolone derivatives.

Metal-Free Regioselective Direct C(4)-H Amination of Quinazoline with N-fluorobenzenesulfonimide

A facile C-H amination of quinazoline employing N-fluorobenzenesulfonimide (NFSI) as the amination source has been disclosed in the absence of any metal, oxidant or additive. The methodology shows a board range of quinazolines with different functional groups in moderate to good yields up to 87 %. Furthermore, gram-scale reaction, desulfonylation to amine and synthesis of pharmaceutical intermediate were also investigated, which demonstrates potential applications in medicinal chemistry. A plausible amination mechanism is proposed via F+ transfer accompanied by the removal of one molecule of PhSO2F. DFT studies with experimental work suggest that the mechanism via F+ transfer is more favorable than the free radical one.

Directing Group Strategies in Rhodium-Catalyzed C-H Amination

Construction of a carbon-nitrogen bond is one of the most prevalent operations in nature and organic synthesis. The resulting amino compounds are privileged structural fragments in natural products, pharmaceutical drugs,...

The copper-catalyzed synthesis of dihydrooxazoles from α,β-unsaturated ketoximes and activated ketones

The first copper-catalyzed [3+2]-type condensation reaction of α,β-unsaturated ketoximes with activated ketones has been described for the synthesis of dihydrooxazoles, especially trifluoromethyl-decorated dihydrooxazoles. Notable features of this method include its broad substrate scope, good functional group tolerance, and simple operation.

Synthesis, Characterization, and Catalytic Application of Palladium Complexes Containing Indolyl-NNN-Type Ligands

In this study, a series of N-heterocyclic indolyl ligand precursors 2-Py-Py-IndH, 2-Py-Pz-IndH, 2-Py-7-Py-IndH, 2-Py-7-Pz-IndH, and 2-Ox-7-Py-IndH (L¹H-L⁵H) were prepared. The treatment of ligand precursors with 1 equivalent of palladium acetate affords palladium complexes 1-5. All ligand precursors and palladium complexes were characterized by NMR spectroscopy and elemental analysis. The molecular structures of complexes 3 and 5 were determined by single crystal X-ray diffraction techniques. The application of those palladium complexes 1-5 to the Suzuki reaction with aryl halide substrates was examined.

Recent advances in quinazolinones as an emerging molecular platform for luminescent materials and bioimaging

This review summarized recent advances relating to the luminescence properties of quinazolinones and their applications in fluorescent probes, biological imaging and luminescent materials. Their future outlook is also included.

Rhodium(III)-catalyzed C4-amidation of indole-oximes with dioxazolones via C-H activation

A novel method for the Rh(iii)-catalyzed oxime-directed C-H amidation of indoles with dioxazolones has been developed. This strategy provides an exclusive site selectivity and the directing group can be easily removed. This transformation features a wide substrate scope, good functional group tolerance and excellent yields, and may serve as a significant tool to construct structurally diverse indole derivatives for the screening of potential pharmaceuticals in the future.

Rhodium-Catalyzed C(sp2)-H Amidation of Azine with Sulfonamides

Direct C-H amidation of azine with sulfonamide was developed for the first time. The reactions proceeded smoothly under benign conditions and gave the corresponding products with high selectivity. This approach shows high regioselectivity, wide substrate scope, and functional group tolerance. Additionally, this transformation can also be scaled up to the gram level. This strategy allows for the direct preparation of ortho-sulfonamide-substituted ketone products, thus providing a good complement to previous C-H amidation.

Rhodium(III)-Catalyzed Regioselective C(sp2)-H Functionalization of 7-Arylpyrazolo[1,5-a]pyrimidines with Dioxazolones as Amidating Agents

Rh(III)-catalyzed C-H functionalization of 7-arylpyrazolo[1,5-a]pyrimidines was developed wherein the pyrazolo[1,5-a]pyrimidine moiety is reported for the first time to direct the C-H bond activation. Various 7-arylpyrazolo[1,5-a]pyrimidines underwent smooth C-H amidation with alkyl-, aryl-, and heteroaryl-substituted dioxazolones to afford the products in moderate to good yields. Mechanistic studies suggest that a six-membered rhodacycle intermediate involving N1 might play a key role in the regioselective catalytic cycle.

Nickel-promoted C(2)–H amidation of quinoline N-oxides with N-fluorobenzenesulfonimide

The first example of nickel-promoted C–H amidation of quinoline N-oxides with NFSI.

A convergent strategy towards febrifugine and related compounds

We report a modular five step synthetic route to the febrifugines that employs 2-(chloromethyl)allyl-trimethylsilane as a conjunctive reagent for the coupling of the piperidine and quinazolinone groups. We also demonstrate the application of a recent Rh-catalyzed quinazolinone synthesis for the facile generation of febrifugine analogs.

Rhodium-catalyzed regioselective C8-H amination of quinolineN-oxides with trifluoroacetamide at room temperature

A facile and efficient amination of quinolineN-oxides at room temperature proceeds with high selectivity and is convenient on a gram scale.

Synthesis of 2-aminobenzaldehydes by rhodium(iii)-catalyzed C–H amidation of aldehydes with dioxazolones

Various aldehydes were directly amidated with dioxazolones to afford 2-aminobenzaldehydes through rhodium(iii)-catalyzed CHO-directed C–H activation.

Intermolecular Aryl C-H Amination through Sequential Iron and Copper Catalysis

A mild, efficient and regioselective method for para-amination of activated arenes has been developed through a combination of iron and copper catalysis. A diverse range of products were obtained from an operationally simple one-pot, two-step procedure involving bromination of the aryl substrate with the powerful Lewis acid iron(III) triflimide, followed by a copper(I)-catalysed N-arylation reaction. This two-step dehydrogenative process for the regioselective coupling of aromatic C-H bonds with non-activated amines was applicable to anisole-, phenol-, aniline- and acetanilide-type aryl compounds. Importantly, the arene substrates were used as the limiting reagent and required no protecting-group manipulations during the transformation.

Discovery of 2-(pyridin-2-yl)aniline as a directing group for the sp2 C–H bond amination mediated by cupric acetate

2-(Pyridin-2-yl) aniline was designed as a new, removable directing group in promoting C–H amination mediated by cupric acetate.

Recent developments in transition metal catalysis for quinazolinone synthesis

Quinazolinones are an important class of heteroaromatic compound, and they are prevalent in a variety of important bio-active scaffolds. Traditionally, their synthesis has been achieved via classical condensation procedures, however over recent years catalytic methodologies have emerged as effective alternatives. This review examines recent developments in the employment of catalytic approaches towards this highly important heterocyclic motif.