Asian Journal of Organic Chemistry最新文献

A metal- and additive-free multicomponent reaction (MCR) for the synthesis of 3-oxazoline skeletons is reported. This protocol utilizes readily available α-hydroxyketones, ketones, and ammonium salts as substrates, thus overcoming the limitations of existing methods. The reaction exhibits broad substrate tolerance, including cyclic/acyclic ketones, heterocyclic analogs, and various substituted α-hydroxyketones, affording polysubstituted 3-oxazolines in moderate to high yields.

A general means to access segmentally deuterium-labeled alkyl chains for applications in mass spectrometry, neutron scattering, and related biochemical studies is reported, using a key nickel boride mediated reductive desulfurization of substituted thiophenes. This approach enabled the preparation of (3,3,4,4,5,5,6,6-²H₈)undecanoic acid and 1-amino(1,1,2,2,3,3,4,4-²H₈)nonane, using only recrystallization or distillation for purification. Both compounds featured segments of four deuterated carbon atoms with > 98.5% overall deuterium incorporation. To assess site-specific deuterium retention during desulfurization, we demonstrated the utility of molecular rotational resonance (MRR) spectroscopy, which revealed the degree, position, and magnitude of isotope scrambling in a key thiophene reductive desulfurization step and established the methods set forth herein as being suitable for the construction of mass spectrometric standards and applicable to the synthesis of any CH₃(CH₂)_a(CD₂)_b(CH₂)_cCOOH (3 ≤ a ≤ 13, 3 ≤ b ≤ 6, c ≥ 1) using only commercially-available materials. Our studies revealed extensive exchange of the hydrogen atoms on the thiophene carbons during saturation of the ring, ruling out an idealized schema of the reaction that is present in the literature. We further observed reagent-dependent levels of isotopic scrambling at the benzylic position during desulfurization, challenging the assumption of benzylic stereospecificity in nickel-mediated reductive desulfurization while affirming the reaction's applicability for segmental deuterium labeling.

An efficient iron-catalyzed C─H bond functionalization strategy has been developed for the direct sulfonylmethylation of benzofused ketones. This three-component reaction employs sodium sulfinates as the sulfonyl source and dimethylacetamide (DMA) as a versatile one-carbon synthon, enabling concurrent construction of C─C and C─S bonds. The protocol demonstrates broad functional group tolerance and proceeds under oxidative conditions using FeCl₃ and K₂S₂O₈. A variety of α-tetralones, 1-indanones, and related substrates were transformed into the corresponding α-sulfonylmethylated derivatives in moderate to good yields. Mechanistic studies suggest a radical pathway involving a key 2-methylidenecycloalkan-1-one intermediate, offering a practical and step-economical route to sulfone-containing scaffolds.

Herein, we report a visible-light-catalyzed protocol for the trifluoroalkylation of alkynyl sulfones/ allyl sulfones using readily available α-trifluoromethyl haloalkanes. This reaction is driven by DIPEA as a halogen-atom transfer (XAT) reagent, providing a new strategy to access valuable propargyl and homoallyl trifluoromethyl compounds via Csp─Csp³ or Csp³─Csp³ bond formation. Notably, the methodology effectively suppresses the undesired β-fluoride elimination of α-trifluoromethyl radicals, thus avoiding the formation of gem-difluoroalkenes. The transformation proceeds efficiently under mild conditions, affording the trifluoromethylated products in modest to excellent yields.

This study introduces a novel Schiff base ligand (L) and its metal complexes (L-Cu²⁺, L-Ni²⁺, and L-Zn²⁺), which exhibit remarkable antifungal and antibacterial activity against the plant pathogens Alternaria solani and Xanthomonas euvesicatoria, the causative agents of early blight and bacterial spot in tomatoes, respectively. At 250 µg/mL, all compounds demonstrated exceptional antimicrobial activity, achieving 100% inhibition of A. solani, surpassing the commercial fungicide's 91% inhibition. Additionally, the compounds produced substantial inhibition zones against X. euvesicatoria. They also showed scavenging of reactive oxygen species (ROS), indicating their potential to mitigate oxidative stress in plant cells. Phytotoxicity tests at 300 µg/mL confirmed that none of the compounds adversely affected tomato seed germination. The dual action of pathogen inhibition and ROS neutralization, combined with non-toxicity to plants, suggests that L and its complexes are promising candidates for crop protection. Across all assays, efficacy was ranked as L-Cu²⁺ > L > L-Zn²⁺ ≈ L-Ni²⁺, with the L-Cu²⁺ complex demonstrating superior overall performance.

Different rare-earth salts can regulate asymmetric 6π or 4π cyclization of triaryldivinyl ketones at different temperatures. The asymmetric Nazarov reaction of triaryldivinyl ketones is realized under the catalysis of Tb(OTf)₃-Pybox complex in tetrachloroethene at relatively high temperature, affording methyl (1R,5S)-3,4,5-triaryl-2-oxocyclopent-3-ene-1-carboxylates in moderate to good yields with good to excellent enantioselectivities in most cases. The π-stacking interaction between substrates and the phenyl group of the best ligand plays an important role in determining the enantioselectivity. Both solvent and reaction temperature tune the periselectivity. Relatively high temperature favors the Nazarov reaction. The rare-earth ions also execute an important impact in controlling asymmetric pericyclic reactions of triaryldivinyl ketones.

β-nitro ketones represent highly significant compounds for their simultaneous nucleophilic and electrophilic reactive sites in 1,3-related positions. These molecules are commonly obtained via nitration of enones in aprotic apolar organic solvents (such as THF and CPME) with large excesses of nitrating agents and acetic acid. In this work the use of weakly acidic natural deep eutectic solvents (NADESs) – glycolic acid based-ones – is proposed as both green and catalytic reaction media for the nitration of enones giving β-nitro ketones. The NADESs mixtures employed were the ones formed by mixing glycolic acid with trimethylglycine, with choline chloride and with water. The reaction proceeded with stochiometric amounts of nitration agents and taking advantage from the catalytic behavior of the NADESs solvents; the scope was explored giving satisfactory yields.

For the preparation of novel 5-styryl-substituted 9-hydroxy-1H-phenalen-1-ones, a sequential Pd-catalyzed Heck vinylenation–Suzuki arylation one-pot strategy was established, providing efficient access to a library of donor–acceptor chromophores. These multifunctional conjugates are characterized by a planar, highly conjugated backbone extended through vinyl substitution at the 5-position. The obtained compounds were comprehensively investigated with respect to their electrochemical and photophysical properties. Cyclic voltammetry demonstrates that the reduction potentials remain largely unaffected by substituents, whereas the oxidation potentials show a pronounced dependence on the electronic nature of the aryl groups. UV–vis and fluorescence spectroscopy revealed bathochromic shifts of absorption and emission maxima for electron-donating substituents, while electron-withdrawing groups induce hypsochromic responses. Complementary Hammett correlations confirm the dominance of resonance effects, with the strongest linear relationships observed for the extended σ_p+ parameter, highlighting mesomeric stabilization as the decisive factor in modulating electronic transitions. Quantum-chemical (TD)DFT calculations reproduce the spectroscopic trends and provide detailed insight into orbital contributions and charge-transfer characteristics. Solvatochromic analyses further evidence the polar nature of the excited states, supporting a pronounced intramolecular charge-transfer character.

Herein, we report a traceless directing group assisted Rh(III)-catalyzed C─H cyclization cascade of indoles and (arylprop-2-yn-1-yl)malonates under redox-free reaction conditions, thus providing a concise access to structurally diverse functionalized pyridoindolones. This transformation proceed smoothly with a tolerance of various functional groups and moderate to good efficiencies. In addition, the practical and stereoselective construction of 2-alkenylated NH-indole scaffold could be accomplished within 30 min by utilizing simple aromatic alkynes. Furthermore, the synthetic value of this strategy was demonstrated by the readily accessible and divergent transformations of products. A preliminary mechanism was also proposed based on a series of deuterating and control experiments.

A metal-free, organophotocatalyzed three-component reaction between alkenes, 2,2,2-trifluoroiodoethane, and carboxylic acids was developed. This protocol simultaneously introduces a trifluoroethyl group and an ester moiety in a single step. Preliminary mechanistic studies suggest the reaction proceeds via a radical pathway.