A mild and efficient copper-catalyzed trifluoromethylation reaction which involves the cyclization of oximes has been developed. This method provides a convenient access to a variety of useful CF3-containing 4,5-dihydroisoxazoles by constructing a C–CF3 bond and a C–O bond in one step.
An asymmetric synthesis of 5-halomethyl pyrazolines and isoxazolines which bear a tertiary stereocenter by catalytic halocyclization of β,γ-unsaturatedhydrazones and ketoximes is described. By using Brønsted acids of anionic chiral Co(III) complexes as catalysts, a variety of chiral 5-halomethyl pyrazolines and isoxazolines were obtained in good yields with high enantioselectivities (up to 99% yield
BF<sub>3</sub>·OEt<sub>2</sub>-mediated cyclization of β,γ-unsaturated oximes and hydrazones with <i>N</i>-(arylthio/arylseleno)succinimides: an efficient approach to synthesize isoxazoles or dihydropyrazoles
作者:Wei Yu、Shichao Yang、Pei-Long Wang、Pinhua Li、Hongji Li
DOI:10.1039/d0ob01388a
日期:——
A highly efficient BF3·OEt2-mediated cyclization of β,γ-unsaturatedoximes and tosylhydrazones with N-(arylthio/arylseleno)succinimides has been established for the construction of N-heterocycles in a one-step manner. This metal-free cyclization provides direct access to isoxazoles and dihydropyrazoles in good to excellent yields at room temperature. The mechanistic experiments support the formation
A palladium-catalyzed efficient synthesis of 5-methylisoxazoles via oxime-mediated functionalization of unactivatedolefins is described. The reaction affords a variety of 5-methylisoxazoles in moderate to good yields. To further demonstrate the utility of the method, the rapid synthesis of valdecoxib and oxacillin is reported.
Room temperature iron(<scp>ii</scp>)-catalyzed radical cyclization of unsaturated oximes with hypervalent iodine reagents
作者:Shichao Yang、Hongji Li、Pinhua Li、Jingya Yang、Lei Wang
DOI:10.1039/c9ob02424g
日期:——
Here, we disclose an iron(ii)-catalyzed I-O bond cleavage of Koser's hypervalent iodine reagents (HIRs) that initiated the radical cyclization of unsaturated oximes at room temperature. This strategy is successfully applied for the construction of the isoxazoline backbone in an efficient manner. In particular, the direct introduction of a TsO group into products facilitates their late-stage transformations