One‐pot Cascade Reaction for the Synthesis of Phenanthridines via Suzuki Coupling/C−H Oxidation/Aromatization

Palladium-catalyzed C-H bond activation and decarboxylation for the assembly of indolo[1,2-f]phenanthridine

A direct and convenient strategy for the assembly of indolo[1,2-f]phenanthridine via a Pd-catalyzed tandem cyclization reaction is presented. The current strategy delivers a range of indolo[1,2-f]phenanthridine derivatives by utilizing readily available 1-(2-iodophenyl)-1H-indole and commercially available o-bromobenzoic acids as the starting materials. The reaction features the formation of two C-C bonds through Pd-catalyzed C-H bond activation and decarboxylation.

Recent Advances in DMSO-Based Direct Synthesis of Heterocycles

Besides serving as a low-toxicity, inexpensive and easily accessible solvent, dimethyl sulfoxide (DMSO) has also been extensively used as a versatile reagent for the synthesis of functionalized molecules. Dimethyl sulfoxide can not only be utilized as a carbon source, a sulfur source and an oxygen source, but also be employed as a crucial oxidant enabling various transformations. The past decade has witnessed a large number of impressive achievements on the direct synthesis of heterocycles as well as modifications of heterocyclic compounds by applying DMSO as a reagent. This review summarized the DMSO-based direct heterocycle constructions from 2012 to 2022.

Synthesis of Aza[n]helicenes (n = 4-7) via Photocyclodehydrochlorination of 1-Chloro-N-aryl-2-naphthamides

A series of aza[n]helicenes (n = 4-7) was synthesized using a photocyclodehydrochlorination of 1-chloro-N-aryl-2-naphthamides as a general synthetic procedure introducing the nitrogen atom to the third ring of the helicene framework. The effect of the nitrogen presence in the helicene skeleton on the physicochemical properties of the prepared aza[n]helicenes was studied and compared to those of the parent carbo-analogues. The insertion of a nitrogen atom into the outer edge of the helicene molecule has a severe impact on certain physicochemical properties such as optical rotation, electrostatic potentials, and intermolecular interactions. On the other hand, some other properties such as UV/vis, fluorescence, and phosphorescence spectra remained almost unaffected when compared to the parent carbohelicenes. A nitrogen atom can be also used for further derivatization, which can lead to further modification of helicene properties, as manifested here in the fluorescence changes induced by protonation.

Iron-catalyzed [3+2+1] annulation of 2-aminobenzimidazoles/3-aminopyrazoles and aromatic alkynes using N,N-dimethylaminoethanol as one carbon synthon for the synthesis of pyrimido[1,2-a]benzimidazoles and pyrimido[1,2-b]indazoles

A simple and efficient method for the synthesis of pyrimido[1,2-a]benzimidazoles and pyrimido[1,2-b]indazoles from 2-aminobenzimidazoles/3-aminoindazoles, alkynes and N,N-dimethylaminoethanol in a three-component [3+2+1] annulation catalyzed by FeCl3 has been established, where N,N-dimethylaminoethanol...

DMSO as a Dual Carbon Synthon and Water as Oxygen Donor for the Construction of 1,3,5-Oxadiazines from Amidines

A selective and efficient synthesis of diaryl 1,3,5-oxadiazines was established for the first time from simple and readily available amidines in wet DMSO. DMSO was employed as a dual carbon synthon and water offered the oxygen atom to construct the oxadiazine ring. The reaction involved two new C-N and two new C-O bond formations.

I2-Catalyzed Three-Component Consecutive Reaction for the Synthesis of 3-Aroylimidazo[1,2-a]-N-Heterocycles

A convenient one-pot, three-component reaction has been developed for the synthesis of 3-aroylimidazo[1,2-a]-N-heterocycles from aryl ketones and 2-amino-N-heterocycles using dimethyl sulfoxide as a methylene donor. The reaction proceeds smoothly catalyzed by I₂ in the presence of K₂S₂O₈ and affords the desired products in moderate to good yields. This protocol offers significant superiority in accessing biologically active 3-aroylimidazo[1,2-a]-N-heterocycles with various substitution patterns.