Enantioselective Synthesis of 5-Trifluoromethyl-2-isoxazolines and Their<i>N</i>-Oxides by [Hydroxy(tosyloxy)iodo]benzene-Mediated Oxidative N-O Coupling
Biologically attractive trifluoromethyl-2-isoxazoline N-oxides were synthesized in good yields for the first time by the [hydroxy(tosyloxy)iodo]benzene-mediated oxidative N–O coupling of β-trifluoromethyl β-hydroxy ketoximes generated from trifluoromethyl β-keto alcohols. The present method allows the synthesis of previously unknown 5-trifluoromethyl-2-isoxazoline N-oxides and also provides an alternative
Cuts both ways: The title reaction consists of an addition/cyclization/dehydration sequence and affords the biologically important chiral 3,5‐diaryl‐5‐(trifluoromethyl)‐2‐isoxazolines 1 in excellent yields with high ee values. The flexibility of accessing either the S or R enantiomers of the products has been achieved by the appropriate choice of phase‐transfer catalyst (2).