Efficient synthesis of isoxazoles and isoxazolines from aldoximes using Magtrieve™ (CrO2)
作者:Sandeep Bhosale、Santosh Kurhade、Uppuleti Viplava Prasad、Venkata P. Palle、Debnath Bhuniya
DOI:10.1016/j.tetlet.2009.04.073
日期:2009.7
Treatment of aldoximes 1 with Magtrieve™ (CrO2) in presence of dipolarophile 3 or 4, furnished a variety of isoxazolines 5a–u and isoxazoles 6a–q as 1,3-dipolar cycloaddition (1,3-DC) products (38 examples; 63–90% isolated yields). In situ formation of a nitrile oxide intermediate was confirmed through isolation of the dimerization product furoxane 2a in absence of any dipolarophile. The methodology
A palladium‐catalyzed direct arylation of isoxazoles with aryl iodides has been achieved. The CH bond at the 5‐position is activated selectively to give coupling products in moderate to good yields. This direct arylation was applied to the synthesis of a spiro‐type chiral ligand, which proved to be most effective to the palladium‐catalyzed tandem cyclization of a dialkenyl alcohol.
Decarboxylative C–H functionalization of isoxazoles with alkenes and sulfoxonium ylides proceeded in the presence of rhodium(iii) catalysts to afford alkenylation and acylation products, respectively.