Journal of Organic Chemistry最新文献

A convenient, metal-free one-pot synthesis has been developed to access 1,3,4-oxadiazol-2(3H)-ones using hydrazines, carboxylic acids, and 1,1′-carbonyldiimidazole (CDI) as an activating agent in the presence of triethylamine (TEA). This method can access the desired heterocycles in moderate to excellent yields in a one-pot transformation from commercially available starting materials, representing a significantly simpler path to access these compounds compared with existing tactics. The substrate scope investigation demonstrated that this method is broadly applicable and scalable.

The new copper(II) catalyst [Cu(^QFOX)(CH₃CN)][OTf]₂ has been synthesized and found to be active for alcohol dehydration to give olefins at 120 °C with a 1% catalyst loading (^QFOX = di-2-quinolinyl-fused-oxazolidine). Benzylic, allylic, and tertiary alcohols are all dehydrated. In some cases, ethers are observed to be produced, but these are re-entrained into the catalytic cycle. Unactivated secondary alcohols are also dehydrated. Similar catalysts employing Mn^II, Fe^II, Co^II, and Ni^II were also synthesized but showed reduced dehydration activity compared to the copper(II) derivative. A Cu^I analog was also prepared but did not show improved dehydration activity.

A highly efficient, iron(III)-BPsalan complex-catalyzed asymmetric 1,3-dipolar cycloaddition of nitrones and α,β-unsaturated acyl imidazoles has been developed to afford isoxazolidine (31 examples) and isoxazoline derivatives (13 examples) in moderate to excellent yields (up to 99%) and excellent stereoselectivity (up to 99% ee and >20:1 dr). The reaction proceeds readily in acetone under air conditions, maintaining high efficiency and selectivity.

An effective strategy for enhancing the heat of detonation is to incorporate high-enthalpy backbone structures while maintaining an oxygen balance close to zero. This approach maximizes energy release while supporting favorable decomposition characteristics. Consequently, 3,4-bis(5-(trinitromethyl)-1,2,4-oxadiazol-3-yl)-1,2,5-oxadiazole 2-oxide (4) was synthesized, which combines three oxadiazole rings and two nitroform groups. A series of energetic salts (3, 5-7) corresponding to the dinitromethyl derivative of 4 were also studied. The structures of compounds 3 and 4 were determined through a single-crystal diffraction analysis. Notably, compound 3 exhibits pores situated between its molecules and is categorized as a hydrogen-bonded organic framework (HOF). This characteristic imparts compound 3 with a lower mechanical sensitivity, indicated by its impact and friction sensitivity (IS = 25 J, FS>360 N). Compound 4 exhibits a markedly enhanced theoretical heat of detonation (6949 kJ kg^– 1), surpassing that of CL-20 (6534 kJ kg^– 1) and achieving the highest heat of detonation among other structurally analogous compounds. This comparison highlights its potential as a valuable contributor to the synthesis of high-energy compounds with enhanced heat detonation characteristics.

Despite significant progress in carbohydrate chemistry, the stereoselective synthesis of 1,2-cis-glycosides remains a long-standing challenge. To address this issue, glycosyl donors-bearing acyl substituents remote from the anomeric center are increasingly employed. Yet the origin of their stereochemical influence remains unresolved, being alternately interpreted in the literature as arising from remote participation or, more rarely, from intrinsic electron-withdrawing effects. Here we show that the electron-withdrawing 4-O-pentafluorobenzoyl (PFB) group exerts a strong α-directing effect in both galactosyl and glucosyl donors, irrespective of the configuration at C-4. This behavior demonstrates that the observed α-selectivity arises not from remote participation but from the electron-withdrawing nature of the PFB substituent. Comparative studies with less electron-withdrawing acyl groups (Ac, Bz, pMeOBz) confirmed that 4-O-PFB possesses the strongest α-directing ability. In galactosyl donors, the 6-O-benzoyl group alone favored β-glycoside formation, yet in combination with a 4-O-PFB substituent, it acted cooperatively, thereby providing complete α-selectivity. This cooperative action of 4-O-PFB and 6-O-substituents was further demonstrated in the stereoselective synthesis of a penta-α-(1→6)-d-galactoside structurally related to the α-(1→6)-d-galactan main chain of Cryptococcus neoformans galactoxylomannan.

The quinoline skeleton is commonly found in active molecules, making its synthesis a major focus of the ongoing research. This study presents a photoinduced strategy for synthesizing 2-trifluoromethylthiolated quinoline derivatives. This one-pot process involves a radical cascade cyclization between 1-isocyano-2-vinylbenzenes and Phth-SCF₃. Notably, the transformation proceeds in the absence of transition metals or oxidants and shows excellent chemoselectivity and broad functional group compatibility.

4-Acetoxycyclopent-2-enone is a versatile precursor for constructing polycyclic scaffolds; however, tandem Michael reactions with bis-nucleophiles are often complicated by undesired secondary allylation. Existing asymmetric strategies toward tetracyclic lactams typically require excess reagents, underscoring the need for a more practical approach. Herein, we describe an efficient DBU-mediated tandem Michael addition strategy using masked bis-nucleophiles to access cis-fused [5,5] bicyclic intermediates and their transformation into tetracyclic lactams. Improved tandem Michael reactions were achieved by adding masked bis-nucleophiles to 4-acetoxycyclopent-2-enone. The use of masked bis-nucleophiles prevented the second allylation of the adducts, thereby enabling easy purification of the resulting bicyclic Michael adducts. This strategy afforded a series of cis-fused [5,5] bicyclic products in yields of 38–82% under homogeneous basic conditions mediated by DBU. Subsequent removal of the ester-masked groups, followed by palladium(II)-catalyzed keto α-arylation furnished the corresponding cis-fused tetracyclic lactams in yields of 22–72%. Furthermore, the effects of the solvent and phenyl substitution patterns on the intramolecular cyclization were studied systematically.

The quinolone scaffold is a key structural motif found in heterocycles exhibiting biological activities, coordination behaviors, and photosensitizing properties. Herein, we report the synthesis and photophysical characterization of Donor−π–Acceptor (D−π–A) systems incorporating the pyrroloquinolone core. By varying the electron-donating and electron-withdrawing substituents, we demonstrate the formation of charge-transfer (CT) fluorophores exhibiting Stokes shifts exceeding 6000 cm^–1 and red emission. While the absorption spectra are essentially unaffected by solvent polarity, pronounced positive solvatofluorochromism is observed. Fluorescence quenching is nevertheless noted in polar solvents such as acetone, acetonitrile, and ethanol. The photophysical behavior of the dyes is further rationalized through time-dependent density functional theory (TD-DFT) calculations.

We present the first report of direct electro-oxidation of the α-CH bond of β-ketoesters employing a multisite concerted electron–proton transfer (MS-CEPT) mechanism to access dimerized products through C(sp³)–C(sp³) bond formation. The sustainable approach utilized a graphite anode and a Pt cathode, employing acetonitrile and methanol solvents, NH₄PF₆ electrolyte, and NaH as a base at a constant potential of 1.8 V for 3 h. The MS-CEPT mechanism involved H⁺ transfer to the base (NH₃) associated through hydrogen bonding with the α-CH bond and simultaneous transfer of an electron to the electrode, representing the inaugural instance of nonpolar C–H bond functionalization in a direct electro-oxidative environment. UV–vis studies provided evidence for hydrogen bonding between carbonyl groups of β-ketoesters and methanol or NH₄⁺, resulting in polarization of the α-CH bond. NMR experiments demonstrated that this polarization led to H-bonding between the α-CH proton and in situ-generated NH₃, revealing preassociation between the substrate and the base, a primary requirement for the operation of the MS-CEPT mechanism. High electrochemical isotopic current ratio (H/D) (∼1.7) supported the H⁺ transfer event in the rate-determining step. Twenty-one examples having diverse substituents with average yields of 73% have been provided. Dimeric β-ketoesters were further utilized in the total syntheses of naturally occurring dihydrocubebin and epi-dihydrocubebin.