RESUMEN
The environmental benefits of molecular oxygen as the oxidizing agent in oxidation reactions that synthesize fine chemicals cannot be overstated. Increased interest in developing robust photocatalysts is stimulated by the fact that the current photocatalytic transformation boom has made previously inaccessible synthetic approaches possible. Motivated by enzymatic catalysis, employing a reusable phenalenyl-based photocatalyst, we have successfully developed oxidative dehydrogenation utilizing molecular oxygen as a greener oxidant. Under photoinduced oxidative dehydrogenation conditions, different types of saturated N-heterocycles and alcohols were successfully dehydrogenated. The versatility of this bioinspired protocol is demonstrated by the fact that a wide variety of N-heteroaromatics, such as quinoline, carbazole, quinoxaline, acridine, and indole derivatives, as well as aldehydes and ketones, were successfully synthesized. Detailed mechanistic studies validate the proposed mechanism. Fluorescence lifetime and CV experiments revealed the crucial role of water on the efficiency of the reaction. The present protocol also provides chemoselectivity and scalability, leading to superior results and allowing for the functionalization of bioactive molecules at a late stage in a sustainable manner.
RESUMEN
Herein, we have established a phenalenyl-based molecular scaffold which serves as a potent photoreductant utilizing the empty NBMO in the presence of a base to form a radical anion which, upon photoexcitation, behaves as a stronger reductant and accomplishes the cleavage of strong C-X (X = Cl, Br, I) bonds under milder reaction conditions. The base was found to be involved in a dual role of electron and hydrogen atom donor. Further, the aryl radical formed by the homolysis of C-X bonds in this technique was captured for the Csp2-Csp2 coupling with unactivated arenes. The photoreductant potency of the phenalenyl-based catalytic system was further extended to C-P as well as C-B bond formation reactions. EPR and lifetime studies reveal the formation of a persistent radical having a sufficient lifetime to take part in the reaction by the PET mechanism. Different spectroscopic techniques combined with DFT calculations were utilized for the characterization of active catalytic species and for the elucidation of plausible mechanistic pathways. This not only is the initial report of the application of phenalenyl as a photoreductant but also provides a completely metal-free (alkali and transition metal) approach for the challenging reductive functionalization of aryl halides at room temperature.
RESUMEN
The development of versatile and mild methodologies for C-N bond construction has always been a hot topic of interest in synthetic organic chemistry. In recent years, electrochemistry has emerged as a promising green and sustainable environmentally benign approach to carry out these transformations under mild conditions utilizing electrons as oxidizing/reducing agents. The current state-of-the-art in combining electrocatalysis with transition metal catalysis has gained significant attention. This hybrid synthetic methodology has increasingly become a common tool and offers many potential advantages compared to direct electrolysis. This review comprehensively highlights recent developments in the merging of transition metal catalysis in electro-organic synthesis for the facile construction of C-N bonds. In this review major emphasis is given to mechanistic investigations and their synthetic applications of this hybrid catalysis.
RESUMEN
Herein, we have developed a new class of organic photocatalysts that can mimic transition metals for several oxidative and reductive organic cross-coupling transformations. Due to its wide potential window in both the oxidation and reduction ranges, cinnoline exhibits dual catalytic activity under visible light illumination, acting as both a photoreductant and photooxidant.
RESUMEN
An operationally simple process has been developed for the synthesis of unsymmetrical amines and α-amino carbonyl derivatives in the absence of a catalyst, ligand, oxidant, or any additives. Contrary to known reductive amination methods, this protocol is amenable to substrates containing other reducible groups. This process effectively results in consecutive cleavage and formation of C-N bonds. DFT studies and Hammett analysis provide useful insight into the mechanism. The role of noncovalent interactions as a stabilizing factor have been examined in the protocol. A wide range of alkyl-bromides have been coupled efficiently with a variety of dimethyl anilines to get unsymmetric tertiary amines with yields up to 90%. This methodology was further extended to the synthesis of α-amino carbonyl derivatives with yields up to 93%.