Synthesis of trisubstituted isoxazoles via in situ trapping strategy from α-nitro carbonyl compounds and methyl ketones or terminal aryl alkenes

Divergent Annulation Modes of (Z)-4-Aryl-4-oxo-2-(pyridin-2-yl)but-2-enenitrile and Methyl Nitroacetate: Selective Access to 2-Acyl-4H-quinolizin-4-one, Isoxazole, and 2-Acylindolizine

Three different annulation modes of (Z)-4-aryl-4-oxo-2-(pyridin-2-yl)but-2-enenitrile in the reaction with methyl nitroacetate were discovered, allowing selective access to diverse heterocycles such as quinolizin-4-one, isoxazole, and indolizine with unique substitution patterns in good yields. Ease of operation, good chemical yields, and good functional group tolerance of our protocol enabled us to rapidly construct a number of synthetic analogs based on each scaffold under three reaction conditions.

Primary nitro compounds: progress in the synthesis of isoxazoles by condensation with aldehydes or activated ketones

Among the known strategies directed towards the synthesis of isoxazole derivatives, the reactions of aldehydes with primary nitro compounds deserve a comprehensive treatment, including the historical development as well as the more recent applications. The reactions of aldehydes with primary nitro compounds in a 1 : 2 molar ratio have been shown to lead to isoxazoline-N-oxides or isoxazole derivatives, via β-dinitro derivatives. Several modifications of the process allowed the formation of products bearing substituents at various positions of the heterocyclic ring with control of regioselectivity. Ketones are reported to react with primary nitro compounds, only if activated (β-diketones, α-nitroketones, or strained ketones), to give isoxazole derivatives. Symmetric 2,4-dinitroglutarates formed from aromatic aldehydes and nitroacetate undergo ring closure to form isoxazole derivatives or, according to reaction conditions, 5-hydroxy-6-oxo-4-aryl-6H-1,2-oxazine-3-carboxylates ("oxazinones"), by loss of alcohol instead of water. Isoxazole-4-carbaldehydes are obtained by the reaction of 3-oxetanone with primary nitro compounds.

Switching Over of the Chemoselectivity: I2-DMSO-Enabled α,α-Dichlorination of Functionalized Methyl Ketones

Precise control of the chemoselectivity of the halogenation of a substrate equipped with multiple nucleophilic sites is highly demanding and challenging. Most reported chlorinations of methyl ketones show poor compatibility or even exclusive selectivity toward electron-rich arene, olefin, and alkyne residues. This is attributed to the direct or in situ employment of electrophilic Cl₂/Cl⁺ species. Here, we reported that, even bearing those competitive residues, methyl ketones can still undergo dichlorination to afford α,α-dichloroketones in a chemo-specific manner. Enabled by the I₂-dimethyl sulfoxide catalytic system, in which hydrochloric acid only acts as a nucleophilic Cl^- donor, this straightforward dichlorination reaction is safe and operator-friendly and has high atomic economy, giving access to structurally diverse α,α-dichloroketones in good yields and with good functional-group tolerance.

Reactions involving aryl methyl ketone and molecular iodine: a powerful tool in the one-pot synthesis of heterocycles

The preparation of heterocyclic compounds has attracted great attention in organic chemistry because of their extensive application in the field of bioactive molecules, materials science, and natural products.

Surface Plasmon-Enhanced Optical Formaldehyde Sensor Based on CdSe@ZnS Quantum Dots

For the first time, a reproducible surface plasmon-enhanced optical sensor for the detection of gaseous formaldehyde was proposed, which was fabricated by depositing a mixture of CdSe@ZnS quantum dots (QDs), fumed silica (FS), and gold nanoparticles (GNs) on the surface of a silica sphere array to meet the urgent requirement of a rapid, sensitive, and highly convenient formaldehyde detection method. Because of the spectral overlap between QDs and GNs, plasmon-enhanced fluorescence was observed in the film of QDs/FS/GNs. When exposed to formaldehyde molecules, the enhanced fluorescence was quenched linearly with the increase of formaldehyde concentration in the range of 0.5-2.0 ppm. The reason is attributed to the nonradiative electron transfer from QDs to the carbonyl of formaldehyde molecules with the assistance of amino groups. Our results demonstrate that the designed sensors are capable of detecting ultralow concentration gaseous formaldehyde at room temperature with a fast response-recovery time and excellent selectivity, stability, and reproducibility. This work provides a simple and low-cost approach for optical formaldehyde sensor fabrication and shows promising applications in environmental detection.

Employment of α-nitroketones in organic synthesis

This review summarizes the recent developments of the reactions of α-nitroketones and the consequent formation of a variety of structural frameworks is discussed.

Synthesis and Characterisation of Novel 3-(4-Benzoyl-5-Phenylfuran-2-yl) Coumarins

Novel 3-(4-benzoyl-5-phenylfuran-2-yl)coumarin derivates were synthesised via a simple three-step reaction from salicylic aldehydes, ethyl 3-oxobutanoate and 1,3-diphenylpropane-1,3-dione. The synthesised compounds were characterised by NMR, MS and elemental analyses and single-crystal X-ray diffraction analysis.

Heterogeneous Cu/OMS-2 as an efficient catalyst for the synthesis of tetrasubstituted 1,4-enediones and 4H-pyrido[1,2-a]-pyrimidin-4-ones

Copper supported on OMS-2: a heterogeneous catalyst Cu/OMS-2 was prepared for the synthesis of tetrasubstituted 1,4-enediones and 4H-pyrido[1,2-a]-pyrimidin-4-ones under the same conditions with air as the oxidant.

Palladium-catalysed carbonylative α-arylation of nitromethane

A palladium-catalysed approach to α-nitroketones via carbonylative α-arylation of nitromethane is presented, thus providing easy access to key intermediates and important heterocycles.