Cascade Radical Annulation of 2-Alkynylthio(seleno)anisoles with Acetone or Acetonitrile: Synthesis of 3-Acetomethyl- or Cyanomethyl-Substituted Benzothio(seleno)phenes

Mechanisms of C(sp3)-H Functionalization of Acetonitrile or Acetone with Alkynes: A DFT Investigation

The mechanisms for the C(sp3)-H activation and addition reactions between acetonitrile (or acetone) and alkynes have been investigated with the M06-2X-D3/ma-def2-TZVP method and basis set. The SMD (solvation model based on solute electron density) model was applied to simulate the solvent effect. In the first and second reactions, 2-phenylbut-3-yn-2-ol reacted with acetonitrile and acetone, respectively. First, the C(sp3)-H activations of acetonitrile and acetone could be achieved by PhCOO• and t-BuO• radicals. Then, addition reactions converted 2-phenylbut-3-yn-2-ol into final products P1 and P2. Gibbs free energy surfaces of these two reactions suggest that blue lines would be the favorable paths with lower Gibbs energy barriers, and the terminal C atom of the C≡C bond is the best reactive site. Moreover, the analysis of the IRI (Interaction Region Indicator) reveals the Z- and E-configuration transformations. While in the third and fourth reactions, methyl(2-(phenylethynyl)phenyl)sulfane has interactions with acetonitrile and acetone via some paths, respectively. Gibbs free energy profiles show that the C10 atom, rather than the C11 atom, has priority, and the blue lines are favorable. Furthermore, the action mode of Na2HPO4 could reduce the energy barrier and benefit the reaction. vdW (van der Waals) interactions play an important role in the choice for the reactive site. In the fifth (or sixth) reaction, it happened between 1-(2-(methylthio)phenyl)-3-phenylprop-2-yn-1-one and acetontrile (or acetone) to yield the final product P5 (or P6). The computational results uncovered the blue line is the best path, and the choice for the reactive site depends on the vdW interactions, which reveals the origin of selectivity. In addition, the investigation for the byproducts have been carried out, and these can explain the reason that only the main product is produced. Both of those can agree with the experimental results. The localized orbital locator (LOL) isosurfaces, Laplacian bond order (LBO), electron density of the bond critical point (ρBCP), electron spin density isosurface graphs, and IRI graphs can be used to analyze the structure and reveal the reaction substances.

Radical-Triggered Bicyclization and Aryl Migration of 1,7-Diynes with Diphenyl Diselenide for the Synthesis of Selenopheno[3,4-c]quinolines

The translocation of an aryl group from selenium into carbon enabled by the cleavage of the C-Se bond is reported by using nitrogen atom-linked 1,7-diynes and diaryl diselenides as starting materials, leading to various selenophene derivatives in a regioselective manner. This method enables the construction of two C-Se bonds and two C-C bonds through sequential radical bicyclization and 1,2-aryl migration under metal-free conditions. Control experiments and mechanistic studies suggest that this reaction proceeds through the cleavage of the inert C(Ph)-Se bond, facilitating the aryl translocation process. This transformation enables the one-step conversion of simple diselenides into diverse selenopheno[3,4-c]quinolines via a radical-promoted process, holding significant potential for new seleniferous heterocycles.

Preparation of Difluoromethylated Benzothiophene by Visible-Light-Mediated Alkyne Difunctionalization Reaction

An efficient method for the preparation of difluoromethylated benzothiophenes via visible-light-mediated alkyne difunctionalization was developed. In this method, inexpensive sodium difluoromethanesulfinate (HCF2SO2Na) was used as the fluorine source, and a variety of benzothiophene derivatives were obtained in moderate to excellent yield under mild reaction conditions. Moreover, the reaction operation is simple and easy to scale up.

Photoinduced Radical Cyclization of 2-Alkynylthioanisoles with Disulfides without an External Photocatalyst

An efficient strategy for the synthesis of 3-arylthiobenzo[b]thiophenes via a photodriven radical cyclization of 2-alkynylthioanisoles with disulfide was developed. The reaction proceeded smoothly under visible-light irradiation without any external photocatalyst and generated the desired products in high yields with good functional group tolerance.

Assembly of 5H-dibenzo[a,d]cycloheptenes by a formal [5 + 2] annulation of ortho-aryl alkynyl benzyl alcohols with arenes

A new synthetic methodology for the synthesis of 5H-dibenzo[a,d]cycloheptenes from ortho-aryl alkynyl benzyl alcohols and arenes via a Tf₂O-mediated formal [5 + 2] annulation reaction has been achieved. From this transformation, structurally diverse 5H-dibenzo[a,d]cycloheptenes were achieved in moderate to good yields. This transformation probably involves an intermolecular Friedel-Crafts-type alkylation and a subsequent intramolecular 7-endo-dig cyclization in one pot, highlighting the high efficiency, regioselectivity, and step-economy of this protocol.

Access to Thienopyridine and Thienoquinoline Derivatives via Site-Selective C-H Bond Functionalization and Annulation

To develop of an effective synthetic methodology for biologically relevant thienopyridines, a concise and efficient protocol is described for the synthesis of a series of substituted thienopyridine and thienoquinoline derivatives with high selectivity using EtOCS₂K as the sulfur source. The reaction proceeds via metal-free, site-selective C-H bond thiolation and cyclization of the alkynylpyridine and alkynylquinoline substrates.

Concomitant Functionalization of Two Different Ketones by Merging Brønsted Acid Catalysis and Radical Relay Coupling

In previous literature, incorporation of functional groups at the α-position of unactivated carbonyl compounds was mainly restricted to one kind of corresponding precursors. Herein, we report the concomitant functionalization of...

C-centered radical-initiated cyclization by directed C(sp3)–H oxidative functionalization

C(sp3)–H functionalization is attracting constant attention. This review emphasizes C-centered radicals initiated cyclization strategies by directed C(sp3)–H oxidative functionalization since 2012.

Di-tert-butyl peroxide as an effective two-carbon unit in oxidative radical cyclization toward 7-methylazolo[1,5-a]pyrimidines

An unexpected oxidative radical cyclization with DTBP as the C2 cyclic unit enables the assembly of privileged 7-methylazolo[1,5-a]pyrimidines.

Chemoselective Ullmann Reaction of α-Trisubstituted Thioamides: Synthesis of Novel 2-Iminobenzothiolanes

New classes of unexplored benzo[b]thiolanes are synthesized from trisubstituted thioamides through copper-catalyzed intramolecular S-arylation of thioamides for the first time. This method provides good to excellent yields with fully controlled chemoselectivity. Unusually, iminobenzo[b]thiolanes are very stable under mild acidic conditions. A plausible mechanism is proposed for the chemoselective S-arylation process.