Base-Promoted One-Pot Synthesis of Pyridine Derivatives via Aromatic Alkyne Annulation Using Benzamides as Nitrogen Source

A decade of pyridine-containing heterocycles in US FDA approved drugs: a medicinal chemistry-based analysis

Heterocyclic scaffolds, particularly, pyridine-containing azaheterocycles, constitute a major part of the drugs approved in the past decade. In the present review, we explored the pyridine ring part of US FDA-approved small molecules (2014-2023). The analysis of the approved drugs bearing a pyridine ring revealed that a total of 54 drugs were approved. Among them, the significant number comprised the anticancer category (18 drugs, 33%), followed by drugs affecting the CNS system (11 drugs, 20%), which include drugs to treat migraines, Parkinsonism disorders, chemotherapeutic-induced nausea, insomnia, and ADHD or as CNS-acting analgesics or sedatives. Next, six drugs (11%) were also approved to treat rare conditions, followed by five drugs that affect the hematopoietic system. The analysis also revealed that drug approval was granted for antibiotics, antivirals, and antifungals, including drugs for the treatment of tropical and sub-tropical diseases. Primary drug targets explored were kinases, and the major metabolizing enzyme was CYP3A4. Further analysis of formulation types revealed that 50% of the approved drugs were tablets, followed by 17% capsules and 15% injections. Elemental analysis showed that most approved drugs contained sulfur, while fluorine was noted in 32 compounds. Therefore, the present review is a concerted effort to cover drugs bearing pyridine rings approved in the last decade and provide thorough discussion and commentary on their pharmacokinetics and pharmacodynamics aspects. Furthermore, in-depth structural and elemental analyses were explored, thus providing comprehensive guidance for medicinal chemists and scientists working in allied science domains.

Meta-Selective Copper-Catalyzed C-H Arylation of Pyridines and Isoquinolines through Dearomatized Intermediates

C(sp2)-H functionalization offers an efficient strategy for the synthesis of various elaborated N-containing heteroarenes. Along these lines, oxazino pyridines that can be readily prepared from pyridines, have been introduced as powerful substrates in radical- and ionic-mediated meta-C-H functionalization. However, the regioselective meta-C-H arylation of pyridines remains a great challenge. Herein, a copper-catalyzed meta-selective C-H arylation of pyridines and isoquinolines through bench-stable dearomatized intermediates is reported. Electrophilic aryl-Cu(III) species, generated from readily accessible aryl I(III) reagents, enable the efficient meta-arylation of a broad range of pyridines and isoquinolines. The method also allows the meta-selective alkenylation of these heteroarenes using the corresponding alkenyl I(III)-reagents. Late-stage arylation of drug-derived pyridines and larger-scale experiments demonstrate the potential of this synthetic methodology.

Urea-Promoted Neat Synthesis of Fused Dihydroisoquinolines and Disubstituted Pyridines: A Mechanistic Observation with Molecular-Sensing Studies

An efficient and short synthesis of fused dihydroisoquinolines, diaryl substituted pyridine derivatives in good to high yields has been established by using an environmentally safe, solvent-metal-oxidant-free tandem approach. In this article, we discuss how the electrocyclic reaction is more pronounced in the solid phase in the presence of urea, whereas the typical aza-Michael addition is more prominent in presence of arylamine in the solution phase for 3-(2-formylcycloalkenyl)acrylic ester derivative substrates. The wide range of substrates and urea-promoted neat synthesis made our approach more significant in medical and also analytical science. Moreover, an isoquinoline alkaloid decumbenine B analogue has been synthesized by using our newly developed neat methodology. We have also investigated the photophysical properties of the synthesized fused dihydroisoquinoline derivatives. One of the synthesized molecules was used as a sensor for the selective detection of toxic picric acid. Therefore, the effective neat synthesis and molecular sensing applications of these compounds made our approach more exciting in the field of heterocyclic chemistry.