Recent advances in transition metal-catalyzed reactions of chloroquinoxalines: Applications in bioorganic chemistry.

The importance of the quinoxaline framework is exemplified by its presence in the well-known drugs such as varenicline, brimonidine, quinacillin, etc. In the past few years, preparation of a variety of organic compounds containing the quinoxaline framework has been reported by several research groups. The chloroquinoxalines were successfully used as substrates in many of these synthetic approaches due to their easy availability along with the reactivity especially towards a diverse range of metal and transition metal-catalyzed transformations including Sonogashira, Suzuki, Heck type of cross-coupling reactions. The transition metals e.g., Pd, Cu, Fe and Nb catalysts played a key role in these transformations for the construction of various CX (e.g., CC, CN, CO, CS, CP, CSe, etc) bonds. These approaches can be classified based on the catalyst employed, type of the reaction performed and nature of CX bond formation during the reaction. Several of these resultant quinoxaline derivatives have shown diverse biological activities which include apoptosis inducing activities, SIRT1 inhibition, inhibition of luciferace enzyme, antibacterial and antifungal activities, cytotoxicity towards cancer cells, inhibition of PDE4 (phosphodiesterase 4), potential uses against COVID-19, etc. Notably, a review article covering the literature based on transition metal-catalyzed reactions of chloroquinoxalines at the same time summarizing the relevant biological activities of resultant products is rather uncommon. Therefore, an attempt is made in the current review article to summarize (i) the recent advances noted in the transition metal-catalyzed reactions of chloroquinoxalines (ii) with the relevant mechanistic discussions (iii) along with the in vitro, and in silico biological studies (wherever reported) (iv) including Structure-Activity Relationship (SAR) within the particular series of the products reported between 2010 and 2022.

Novel Synthetic Routes to Prepare Biologically Active Quinoxalines and Their Derivatives: A Synthetic Review for the Last Two Decades.

Quinoxalines, a class of N-heterocyclic compounds, are important biological agents, and a significant amount of research activity has been directed towards this class. They have several prominent pharmacological effects like antifungal, antibacterial, antiviral, and antimicrobial. Quinoxaline derivatives have diverse therapeutic uses and have become the crucial component in drugs used to treat cancerous cells, AIDS, plant viruses, schizophrenia, certifying them a great future in medicinal chemistry. Due to the current pandemic situation caused by SARS-COVID 19, it has become essential to synthesize drugs to combat deadly pathogens (bacteria, fungi, viruses) for now and near future. Since quinoxalines is an essential moiety to treat infectious diseases, numerous synthetic routes have been developed by researchers, with a prime focus on green chemistry and cost-effective methods. This review paper highlights the various synthetic routes to prepare quinoxaline and its derivatives, covering the literature for the last two decades. A total of 31 schemes have been explained using the green chemistry approach, cost-effective methods, and quinoxaline derivatives' therapeutic uses.