Metal-free Cross-Dehydrogenative Coupling of HN-azoles with α-C(sp3)-H Amides via C-H Activation and Its Mechanistic and Application Studies.

A metal-free one step coupling reaction between various N-azole rings and diverse α-C(sp3)-H containing amides has been developed under oxidative reaction conditions. Commercially available tetrabutyl ammonium iodide (TBAI) in the presence of terbutylhydroperoxide (TBHP), under neat reaction condition, efficiently catalyzed the coupling. Various azole types, such as 1H-benzotriazoles, 1H-1,2,3-triazoles, 1H-1,2,4-triazoles, 1H-tetrazoles, 1H-pyrazoles, and 1H-benzimidazoles, and α-C(sp3)-H containing amides, such as N,N-dimethylacetamide, N,N-dimethylbenzamide, N-methylacetamide, N,N-diethylacetamide, N-methylpyrrolidine, and pyrrolidine-2-one, were successfully employed for the coupling. A series of designed and controlled experiments were also performed in order to study the involvement of the different intermediates. Based on the evidence, a plausible mechanism is also proposed. These novel, simple, rapid, attractive, and straightforward transformations open the way of the construction of novel highly functionalized N-azoles via direct covalent N-H bond transformations onto N-C bonds. This approach allows to the synthesis of complex molecules requiring number of steps using classical synthetic ways. In addition, the range of α-C(sp3)-H containing amide substrates is virtually unlimited highlighting the potential value of this simple system for the construction of complex heterocyclic molecules, such as fused azoles derivatives.

Metal-Free, Phosphonium Salt-Mediated Sulfoximination of Azine N-Oxides: Approach for the Synthesis of N-Azine Sulfoximines.

Herein, we report a simple and metal-free method for the synthesis of N-azine sulfoximines by the nucleophilic substitution of azine N-oxides with NH-sulfoximines. The present method works at room temperature with wide functional group compatibility and gives several unprecedented N-azine sulfoximines. The reaction conditions were also found suitable with enantiopure substrates and furnished products without any racemization. It also finds an application in the sulfoximination of azine-based functional molecules such as 2,2'-bipyridine, 1,10-phenanthroline, and quinine.

Metal-Free Approach for the Synthesis of N-Aryl Sulfoximines via Aryne Intermediate.

A metal-free and operationally simple N-arylation of NH-sulfoximines with aryne precursors is reported. Transition metal-free reaction conditions and shorter reaction times are the highlights of the present method. The mild optimized condition was also found to be suitable with enantiopure substrates.

Iron-catalyzed cross-coupling of electron-deficient heterocycles and quinone with organoboron species via innate C-H functionalization: application in total synthesis of pyrazine alkaloid botryllazine A.

Here, we report an iron-catalyzed cross-coupling reaction of electron-deficient heterocycles and quinone with organoboron species via innate C-H functionalization. Iron(II) acetylacetonate along with oxidant (K2S2O8) and phase-transfer catalyst (TBAB) under open flask conditions efficiently catalyzed the cross-coupling of pyrazine with arylboronic acids and gave monoarylated products in good to excellent yields. Optimized conditions also worked for other heterocylces such as quinoxalines, pyridines, quinoline, and isoquinoline as well as quinones. In addition, we demonstrated as a first example its application for the synthesis of anticancer marine pyrazine alkaloid botryllazine A.