Access to 5-fluoroisoxazoles via the nitrosation of geminal bromo-fluoro arylcyclopropanes

3,4-Diarylisoxazoles─Analogues of Combretastatin A-4: Design, Synthesis, and Biological Evaluation In Vitro and In Vivo

“…A retrosynthetic analysis was carried out to obtain 5-chloro-3,4-diarylisoxazoles. According to the retrosynthetic scheme based on our previous approach to 5-chloro- and 5-bromoisoxazoles (Scheme ), , eligible compounds for the preparation of 5-chloro-3,4-diarylisoxazoles are 2-aryl-1,1-dichlorocyclopropanes, which are easily obtained in high yields from the corresponding styrenes. The resulting 2-aryl-1,1-dichlorocyclopropanes were further converted into 3-aryl-5-chloroisoxazoles 1 – 7 via nitrosation with NOSO 3 Cl (Scheme ).…”

Rearrangements of the Radical Cations of 3-Aryl-5-fluoroisoxazoles: Further Evidence for Existence of Benzocyclopropenyl Cation

“…Recently, we have synthesized a series of previously unknown 3-aryl-5-fluoroisoxazoles via the reaction of 2-aryl-1-bromo-1-fluorocyclopropanes with nitrosonium chlorosulfate . Since no reports are available in the literature on the mass spectral behavior of 3-aryl-5-fluoroisoxazoles, we examined the EI mass spectra of isoxazoles 1 – 9 .…”

“…11 ■ RESULTS AND DISCUSSION Recently, we have synthesized a series of previously unknown 3-aryl-5-fluoroisoxazoles via the reaction of 2-aryl-1-bromo-1-fluorocyclopropanes with nitrosonium chlorosulfate. 12 Since no reports are available in the literature on the mass spectral behavior of 3-aryl-5-fluoroisoxazoles, we examined the EI mass spectra of isoxazoles 1−9. Analyzing the spectra, we found some differences in the radical cation fragmentation pathways of 5-fluoroisoxazoles with that of 5-chloro-and 5-bromoisoxazoles.…”

Fluorine-Activated and -Directed Allene Cycloadditions with Nitrile Oxides and Imine Oxides: Synthesis of Ring-Fluorinated Isoxazole Derivatives

“…5-Fluoroisoxazoles are potential but less accessible scaffolds for pharmaceuticals and agrochemicals . 5,5-Difluoroisoxazoline 3b was efficiently aromatized to 5-fluoroisoxazole 8a in 87% isolated yield via 1,4-elimination of HF with Me 3 SiOEt/ n -Bu 4 NF (TBAF, Scheme ).…”

“…5-Fluoroisoxazoles are potential but less accessible scaffolds for pharmaceuticals and agrochemicals. 13 5,5-Difluoroisoxazoline 3b was efficiently aromatized to 5-fluoroisoxazole 8a in 87% isolated yield via 1,4-elimination of HF with Me 3 SiOEt/n-Bu 4 NF (TBAF, Scheme 4). 14 Furthermore, S N 2′-type reactions of allylic difluorides 3 would facilitate aromatization, accompanied by the introduction of substituents.…”