Abstract An efficient strategy for synthesizing of 3-substituted bis-isoxazole ether bearing 2-chloro-3-pyridyl under microwave radiation was reported. The reactive regioselectivity was improved by changing mainly the solvent and acid-binding agent. 3-(2-Chloropyridin-3-yl)-5-(((3-substituted phenyl isoxazol-5-yl)methoxy)methyl)isoxazoles were synthesized in 31–92% yields and were characterized by FT-IR, HRMS, 1 H and 13 C NMR spectroscopy. The single crystal of 3-(2-chloropyridin-3-yl)-5-(((3-(p-tolyl)isoxazol-5-yl)methoxy)methyl)isoxazole was obtained, and the structure of compound has also been determined by X-ray diffraction technique. Weak intra- and intermolecular C–H∙∙∙O interactions and a C–H∙∙∙π interaction link molecules into a three-dimensional network. The results showed that the synthesized compounds belonged to triclinic system, and their regioselectivity depended on the solvent and acid-binding agent. The merits of this method include the environmentally friendly, efficient, simple operation, and higher regional selectivity. Graphic abstract An efficient synthesis of 3-substituted bis-isoxazole ethers was developed via 1,3-dipolar cycloaddition reaction starting from 3-substituted phenyl-5-((prop-2-yn-1-yloxy))methyl)isoxazoles and ( Z )-2-chloro- N -hydroxynicotinimidoyl chloride using NaHCO3 as an acid-binding agent in THF solvent-dissolved trace water under catalyst-free microwave-assisted conditions.
Tongyun Zhang,Chengping Zhang,Xiaoxun Ma,Hengdao Quan
3,3,3-trifluoropropyne (HFY-2223tz) is a novel refrigerant with great physicochemical properties. Though preparation of HFY-2223tz from halogenated olefins is theoretically effective, it remains great challenges for dehydrohalogenation from halogenated olefins, limiting the detailed knowledge. Here, we established a facile investigation to explore the gas-phase dehydrochlorination reaction of 2‑chloro-3,3,3-trifluoropropene (HCFO-1233xf) over various halides (Na, K, Rb, Cs) supported active carbon (AC) catalysts. The CsF was concluded as the optimal active component with best dehydrochlorination selectivity and conversion of HCFO-1233xf. The CO 2 -TPD results illustrated that dehydrochlorination of HCFO-1233xf proceeded through E1cB mechanism. Mechanism study revealed the evolution of side-products including ( Z / E )-1,3,3,3-tetrafluoropropylene, 2,3,3,3-tetrafluoropropylene, ( Z / E )-1‑chloro‑3,3,3-trifluoroproene, and 3,3,3-trifluoroprop-1-ene, etc. However, observable deactivation of CsF catalyst was noticed, which, according to combined XRD and XPS results and density functional theory (DFT) calculations, was attributed to the F/Cl exchange between HCFO-1233xf and catalyst, leading to rapid fluorine consumption. This work thus provides basic knowledge about heterogeneous catalytic synthesis of HFY-2223tz from dehydrohalogenation of halogenated olefins.
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