Organic & Biomolecular Chemistry最新文献

Herein, we describe a stepwise 1,2-reductive dearomatization/selective C₃-nitration of quinoline and a subsequent catalytic enantioselective homoenolate addition reaction using a NHC catalyst strategy to construct N-acetyl 3,4-disubstituted tetrahydroquinoline in good yields with remarkably high diastereo- and enantioselectivities (dr >99 : 1, ee up to >99%). An efficient metal- and base-free method for 3-nitroquinoline synthesis from readily accessible quinoline has also been realized.

Photochromic molecules from the spiropyran family are renowned for their ability to undergo light-induced interconversion between a colorless spiro form and a colored merocyanine form. The photoswitching behavior of various spiropyrans has been explored earlier but the influence of electron-donating and electron-withdrawing groups on the indoline and [2H]-chromene rings remains unexplored. In this work, we synthesized four distinct photochromic spiropyran molecules featuring all possible combinations of electronic effects. Their photoswitching activity and switching kinetics were systematically analyzed using spectroscopic and kinetic techniques. Furthermore, the antibacterial properties of these spiropyran derivatives were evaluated to uncover potential structure-activity relationships. This study provides important insights into the design of spiropyrans with customized photochromic properties and associated bioactivity.

(±)-trans-3-(2-Phenylcyclopropyl)prop-2-yn-1-ol (5) undergoes O-directed rt free radical hydrostannation with 2 equiv. of Bu₃SnH or Ph₃SnH in PhMe to produce the α-cyclopropyl-β-stannylvinyl radicals 26 and 27, which rapidly ring-open to give the benzylic stannylhomoallenyl radicals 28 and 29. These, in turn, react with the excess stannane that is present to provide 21 and 23 as primary reaction products. The triphenylstannylallene 23 also undergoes a competitive Ph₃Sn˙ addition to its central allene carbon. This affords the allylically-stabilised radical 31c, which itself reacts with the stannane to produce (Z)-6-phenyl-2,3-bis(triphenylstannyl)hex-3-en-1-ol (24). EPR studies of the reaction of 5 with Ph₃SnH (1 equiv.) and cat. Et₃B/O₂ in PhMe at 250 K have failed to identify the radicals 27 and 29 in the reaction mixtures. Rather, a sharp dd is always observed whose multiplicity is consistent with it being the tris-Ph₃Sn-stabilised free radical 33. The latter is suggested to arise from a reversible O-directed Ph₃Sn˙ addition to 24. The radical 33 has ¹H^β values of 1.32 mT (13.2 G) and 0.57 mT (5.7 G) and a g of 2.0020.

This study introduces a novel strategy for utilizing amides as direct alkylating agents. The activation of amides with Tf₂O and 2-F-Py induces the migration of the alkyl group from the nitrogen of the amide to the nitrogen of 2-F-Py. Following a one-pot hydrolysis or reduction step, N-substituted 2-pyridones or tetrahydropyridines are generated in situ. A total of 34 related compounds were synthesized with high yields across various substrates. This methodology was further applied to the synthesis of key intermediates for C3a receptor inhibitors. Mechanistic studies indicate the formation of a pyridinium salt as a reactive intermediate in the process. Overall, this work presents a novel approach to the application of amides in synthetic chemistry.

A photocatalyst-free, metal-free visible light-promoted thiol-ene/oxidation tandem reaction for sulfoxide synthesis has been developed under mild conditions with air as oxidant. Broad substrate scope as well as gram-scale synthesis enables this environmentally friendly approach with potential for further synthetic applications.

The in situ generated aza-π-allylpalladium species, formed via the palladium-catalyzed decarboxylation of vinyloxazolidine-2,4-diones, were successfully used for the divergent reaction with 2-alkynylphenols and 2-alkynylanilines. Using Pd₂(dba)₃·CHCl₃ as the catalyst and Cu(OTf)₂ as the additive, a range of 2,3-disubstituted benzofurans and indoles were obtained in moderate to excellent yields. However, when PPh₃ ligand was added, a series of γ-O/N-substituted α,β-unsaturated amides were obtained in acceptable yields. This reaction demonstrates that vinyloxazolidine-2,4-diones are capable of undergoing palladium-catalyzed decarboxylative allylic functionalization with carbon, oxygen, and nitrogen nucleophiles.

Among the various heterocyclic organoselenium compounds, a new class of benzoselenazoles has received great attention due to their chemical properties and biological applications. The ever-growing interest in the five-membered benzoselenazole heterocycles amongst chemists has made commendable impact. These heterocycles are a prominent class of organic molecules that have emerged as potential therapeutic agents for the treatment of a wide range of diseases. Substantial progress has been made in elucidating the complex chemical properties of these heterocycles. Moreover, they have garnered significant importance in a wide range of biological applications. However, despite their biological activities, research on benzoselenazoles remains relatively limited, emphasising the need for further exploration in this area. Hence, considering the importance of benzoselenazoles, this comprehensive review compiles various synthetic procedures, highlighting the recent advances in their synthesis that have been disclosed in the literature. This review would offer chemists an array of information that will assist them in the development of more affordable and effective synthesis processes for benzoselenazoles. Therefore, it is believed that this review would provide relevant context on these achievements and will inspire synthetic organic chemists to use these effective technologies of such heterocycles for the future treatment of diseases caused by oxidative stress. The biological and pharmacological properties of these organoselenium heterocycles, which include their antioxidant, antitumor, and antibacterial activities and their application in Alzheimer's disease treatment and as pancreatic lipase inhibitors, are thoroughly summarized. Finally, this review provides some perspectives on the challenges and future directions in the development of benzoselenazoles as heterocyclic organoselenium compounds.

An unexpected cascade of N-acylation/intramolecular [4 + 2] cycloaddition/decarboxylation/isoxazole ring-opening reactions is observed in the course of the interaction between 3-(isoxazol-3-yl)allylamines and maleic or trifluoromethylmaleic anhydrides. This four-step sequence begins with the initial N-acylation of allylamines by the anhydride, followed by an intramolecular Diels-Alder reaction, which is accompanied by spontaneous decarboxylation, and ends with the opening of the isoxazole ring. As a result, an original approach to a pyrrolo[3,4-c]pyridine core was discovered. A test series of pyrrolo[3,4-c]pyridin-3-ones was investigated for anti-inflammatory activity and cytotoxicity, including the ability to inhibit NLRP3 inflammasome activation.

Herein, we report for the first time an additive- and catalyst-free dehydrogenative multicomponent reaction of arylglyoxal, malononitrile, and indoles for the one-pot synthesis of indole-linked β-cyano-enones in DMF medium. The reaction was performed at 100 °C in DMF, forming one C-C single bond and one CC double bond in a single-flask. Furthermore, we developed an efficient method for the synthesis of indolyl-2-pyrrolones having a hydroxyl group-containing chiral carbon center from the β-cyano-enones using trifluoroacetic acid and water as reaction medium. The β-cyano-enones were also further transformed into indolyl-1,2-diketones via a base-mediated reaction, which yielded indolyl quinoxalines upon reaction with o-phenylenediamine (OPD).

Indole scaffolds, which are important structural motifs in organic chemistry, have garnered sustained interest due to their prevalence in pharmaceuticals, agrochemicals, and natural products. This study establishes a novel umpolung activation strategy for γ-position functionalization of electron-poor alkenyl sulfoxides, generating allylidenesulfonium intermediates that are subsequently trapped by indoles, achieving the synthesis of 3-functionalized indoles. Further transformations and plausible mechanism were investigated.