Palladium-Catalyzed C(sp²)–H Pyridocarbonylation of <i>N</i>‑Aryl-2-aminopyridines: Dual Function of the Pyridyl Moiety

An efficient synthesis of 11<i>H</i>-pyrido­[2,1-<i>b</i>]­quinazolin-11-one through palladium-catalyzed C­(sp²)–H pyridocarbonylation of <i>N</i>-aryl-2-amino­pyridines has been developed. The pyridyl group acts as an intramolecular nucleophile for the first time in C–H carbonylation reactions

A Metal-Free Tandem Demethylenation/C(sp²)–H Cycloamination Process of <i>N</i>‑Benzyl-2-aminopyridines via C–C and C–N Bond Cleavage

A mild, metal-free synthesis of pyrido[1,2-<i>a</i>]benzimidazoles starting with <i>N</i>-benzyl-2-aminopyridines, which employs PhI(OPiv)₂ as a stoichiometric oxidant, has been developed. The process is initiated by an unusual PhI(OPiv)₂-mediated <i>ipso</i> S_EAr reaction, followed by solvent-assisted C–C and C–N bond cleavage

Arylative Cyclization of 2‑Isocyanobiphenyls with Anilines: One-Pot Synthesis of 6‑Arylphenanthridines via Competitive Reaction Pathways

A transition-metal-free method for the synthesis of C6 phenanthridine derivatives by arylative cyclization of 2-isocyanobiphenyls with arylamines in one pot was developed. Mechanistic studies suggest that electrophilic aromatic substitution (S_EAr) of a nitrilium intermediate and homolytic aromatic substitution (HAS) of an imidoyl radical intermediate are two competitive reaction pathways involved in the annulation step

Palladium-Catalyzed Intramolecular C(sp²)‑H Imidoylation for the Synthesis of Six-Membered N‑Heterocycles

A new strategy for the construction of phenanthridine and isoquinoline scaffolds, starting from arenes containing a pending isocyanide moiety under palladium catalysis, has been developed. This process involves sequential intermolecular isocyanide insertion to an aryl palladium­(II) intermediate and intramolecular aromatic C–H activation as key steps. Alkyl palladium­(II) intermediate lacking β-hydrogen is also applicable to this reaction, generating unique bisheterocyclic scaffolds with three C–C bonds being formed consecutively

CuI-Mediated Sequential Iodination/Cycloetherification of <i>o</i>‑Arylphenols: Synthesis of 2- or 4‑Iododibenzofurans and Mechanistic Studies

An efficient synthesis of 2- or 4-iododibenzofurans through CuI-mediated sequential iodination/cycloetherification of two aromatic C–H bonds in <i>o</i>-arylphenols has been developed. Both the preexisting electron-withdrawing groups (NO₂, CN, and CHO) and the newly introduced iodide are readily modified for a focused dibenzofuran library synthesis. Mechanistic studies and DFT calculations suggest that a Cu(III)-mediated rate-limiting C–H activation step is involved in cycloetherification

Modular Synthesis of 1,2-Benzothiazines and 1,2-Benzothiazine 1‑Imines via Palladium-Catalyzed C–H/C–C Activation Reactions

In this study, a modular approach toward cyclic sulfoximines and sulfondiimines via palladium-catalyzed intramolecular C–H/C-C activation reactions was reported. Various 1,2-benzothiazines including bicyclic, tricyclic, highly fused ones, ones of the seven-membered ring, along with 1,2-benzothiazine 1-imines were accessed in good yields. KIE experiment demonstrated that the C–H bond cleavage at the position ortho to the sulfoximine group is not the rate-determining step in the coupling reaction

Regio- and Diastereoselective Hydrophosphination and Hydroamidation of <i>gem</i>-Difluorocyclopropenes

In this study, concise, efficient, and modular hydrophosphinylation and hydroamidation of gem-difluorocyclopropenes were disclosed in a mild and transition-metal-free pattern. Through this approach, phosphorus, and nitrogen-containing gem-difluorocyclopropanes were produced in moderate to good yields with excellent regio- and diastereoselectivity. Readily available gem-difluorocyclopropenes and nucleophilic reagents, along with inexpensive inorganic bases, were employed. Multiple synthetic applications, including gram-scale and derivatization reactions and modification of bioactive molecules, were subsequently elaborated