Novel enaminones as non-cytotoxic compounds with mild antibacterial activity: Synthesis and structure-activity correlations

Catalyst-free reactions of anilines with β-chloroenones: synthesis of α-chloroenaminones and 1,4-benzodiazepines

The Michael addition of anilines to β-chloroenones gives enaminones by the elimination of hydrochloric acid (HCl). These enaminones are transformed into α-chloroenaminones via in situ sp2 C-H functionalization. Anilines that are attached to an electron-donating group react more readily with β-chloroenone to give the corresponding products in excellent yields. A highly atom-economical method has been developed using dimethyl sulfoxide (DMSO) as a green oxidant and solvent. The desired α-functionalized enaminones are formed in good yields with excellent Z-selectivity. We have established the generality of this reaction with many substrates, and scaled-up reactions have been performed to showcase the practical applications. A catalyst-free double annulation of β-chloroenones with o-phenylenediamine has also been demonstrated for the synthesis of 1,4-benzodiazepine derivatives in moderate yields under mild reaction conditions.

Copper-Catalyzed Oxidative α-Double Bond Construction in α-Amino Carbonyl Compounds via Homocoupling with Arylamine Release

Herein, we present a copper-catalyzed method for oxidative α-double bond formation in α-amino ketone compounds using DTBP as the oxidant. This process, involving homocoupling of α-amino radicals and arylamine release, efficiently produces a series of enaminone skeletons. The strategy has a broad substrate scope and functional group tolerance. In particular, arylamines bearing electron-rich substituents exhibit a pronounced reactivity. This approach facilitates the synthesis of diverse enaminones, enabling the efficient construction of nitrogen-containing heterocycles.

CuCl2·2H2O/TBHP mediated synthesis of β-enaminones via coupling reaction of vinyl azides with aldehydes

A facile and efficient oxidative functionalization of vinyl azides with aldehydes furnishing a diverse array of β-acylated enaminones was developed. The cross coupling was accomplished in the presence of CuCl₂·2H₂O/TBHP and produced the desired β-acylated enaminones in a (Z)-stereo-selective and atom-economic manner, which make this protocol particularly attractive. In the transformation, the new C-C and C-N bonds were formed via a one-pot strategy including the process of radical addition and recombination.

A Reusable CNT-Supported Single-Atom Iron Catalyst for the Highly Efficient Synthesis of C-N Bonds

C-N bond formation is regarded as a very useful and fundamental reaction for the synthesis of nitrogen-containing molecules in both organic and pharmaceutical chemistry. Noble-metal and homogeneous catalysts have frequently been used for C-N bond formation, however, these catalysts have a number of disadvantages, such as high cost, toxicity, and low atom economy. In this work, a low-toxic and cheap iron complex (iron ethylene-1,2-diamine) has been loaded onto carbon nanotubes (CNTs) to prepare a heterogeneous single-atom catalyst (SAC) named Fe-N_x /CNTs. We employed this SAC in the synthesis of C-N bonds for the first time. It was found that Fe-N_x /CNTs is an efficient catalyst for the synthesis of C-N bonds starting from aromatic amines and ketones. Its catalytic performance was excellent, giving yields of up to 96 %, six-fold higher than the yields obtained with noble-metal catalysts, such as AuCl₃ /CNTs and RhCl₃ /CNTs. The catalyst showed efficacy in the reactions of thirteen aromatic amine substrates, without the need for additives, and seventeen enaminones were obtained. High-angle annular dark-field scanning transmission electron microscopy in combination with X-ray absorption spectroscopy revealed that the iron species were well dispersed in the Fe-N_x /CNTs catalyst as single atoms and that Fe-N_x might be the catalytic active species. This Fe-N_x /CNTs catalyst has potential industrial applications as it could be cycled seven times without any significant loss of activity.