Reductive Molybdenum‐Catalyzed Direct Amination of Boronic Acids with Nitro Compounds

The synthesis of aromatic amines is of utmost importance in a wide range of chemical contexts. We report a direct amination of boronic acids with nitro compounds to yield (hetero)aryl amines. The novel combination of a dioxomolybdenum(VI) catalyst and triphenylphosphine as inexpensive reductant has revealed to be decisive to achieve this new C?N coupling. Our methodology has proven to be scalable, air and moisture tolerant, highly chemoselective and engages both aliphatic and aromatic nitro compounds. Moreover, this general and step‐economical synthesis of aromatic secondary amines showcases orthogonality to other aromatic amine syntheses as it tolerates aryl halides and carbonyl compounds.     

Reagent‐Free C−H/N−H Cross‐Coupling: Regioselective Synthesis of N‐Heteroaromatics from Biaryl Aldehydes and NH3

An unprecedented synthesis of N‐heteroaromatics from biaryl aldehydes and NH₃ through reagent‐free C−H/N−H cross‐coupling has been developed. The electrosynthesis uses NH₃ as an inexpensive and atom‐economic nitrogen donor, requires no oxidizing agents, and allows efficient and regioselective access to a wide range of phenanthridines and structurally related polycyclic N‐heteroaromatic products.     

Low-Valent Titanium Induced Reductive Coupling of Nitriles with Nitro Compounds

The intermolecular and intramolecular reductive coupling of a cyano group with a nitro group induced by a low-valent titanium reagent prepared from TiCl₄/Sm was studied. Amidines and 2-aminoquinolines derivatives are preparied in good yields under mild conditions respectively.     

PAd2‐DalPhos Enables the Nickel‐Catalyzed C−N Cross‐Coupling of Primary Heteroarylamines and (Hetero)aryl Chlorides

Base‐metal catalysts capable of enabling the assembly of heteroatom‐dense molecules by cross‐coupling of primary heteroarylamines and (hetero)aryl chlorides, while sought‐after given the ubiquity of unsymmetrical di(hetero)arylamino fragments in pharmacophores, are unknown. Herein, we disclose the new “double cage” bisphosphine PAd2‐DalPhos ( L2 ). The derived air‐stable Ni^II pre‐catalyst C2 functions well at low loadings in challenging test C?N cross‐couplings with established substrates, and facilitates the first Ni‐catalyzed C?N cross‐couplings of primary five‐ or six‐membered ring heteroarylamines and activated (hetero)aryl chlorides, with synthetically useful scope that is competitive with Pd catalysis.     

Transition‐Metal‐Free C3 Arylation of Indoles with Aryl Halides

We report an unprecedented transition metal‐free coupling of indoles with aryl halides. The reaction is promoted by KOtBu and is regioselective for C3 over N. The use of degassed solvents devoid of oxygen is necessary for the success of the transformation. Preliminary studies implicate a hybrid mechanism that involves both aryne intermediates and non‐propagative radical processes. Electron transfer is also a distinct possibility. These conclusions were substantiated by EPR data, isotopic labeling studies, and the use of radical scavengers and electron transfer inhibitors.     

One-Pot Reductive Mono-N-alkylation of Aromatic Nitro Compounds Using Nitriles as Alkylating Reagents

Palladium catalysed transfer hydrogenation using cyclohexene as the donor is found to deprotect readily alcohol benzyl ethers and aliphatic benzyl esters. The phenol benzyl ethers and benzyl benzoates are stable under these conditions.     

Catalytic HgCl2—Samarium System Induced Reductive Coupling of Nitriles with Nitro Compounds

The intermolecular coupling of a nitro group with a cyano group mediated by a Sm(Hg) amalgam prepared from metal samarium powder and catalytic mercury dichloride was studied.     

Visible‐Light‐Driven Palladium‐Catalyzed Radical Alkylation of C−H Bonds with Unactivated Alkyl Bromides

Reported herein is a novel visible‐light photoredox system with Pd(PPh₃)₄ as the sole catalyst for the realization of the first direct cross‐coupling of C(sp³)−H bonds in N‐aryl tetrahydroisoquinolines with unactivated alkyl bromides. Moreover, intra‐ and intermolecular alkylations of heteroarenes were also developed under mild reaction conditions. A variety of tertiary, secondary, and primary alkyl bromides undergo reaction to generate C(sp³)−C(sp³) and C(sp²)−C(sp³) bonds in moderate to excellent yields. These redox‐neutral reactions feature broad substrate scope (>60 examples), good functional‐group tolerance, and facile generation of quaternary centers. Mechanistic studies indicate that the simple palladium complex acts as the visible‐light photocatalyst and radicals are involved in the process.     

Photoarylation of Iodocarboranes with Unactivated (Hetero)Arenes: Facile Synthesis of 1,2‐[(Hetero)Aryl]n‐o‐Carboranes (n=1,2) and o‐Carborane‐Fused Cyclics

Photoarylation of iodocarboranes with unactivated arenes/heteroarenes at room temperature has been achieved, for the first time, thus leading to the facile synthesis of a large variety of cage carbon mono(hetero)arylated and di(hetero)arylated o‐carboranes. This work represents a clean, efficient, transition‐metal‐free, and cheap synthesis of functionalized carboranes, which has significant advantages over the known methods.