Catalytic Enantioselective Synthesis of 3,4,5‐Trisubstituted Isoxazoline N‐Oxides and Regioselective Synthesis of 3,4,5‐Trisubstituted Isoxazoles

An efficient catalytic asymmetric synthesis of 3,4,5‐trisubstituted isoxazoline N‐oxides and regioselective synthesis of 3,4,5‐trisubstituted isoxazoles has been described. α‐Nitrocinnamates and α‐nitrobenzophenones were utilized as Michael acceptors respectively. Hydroquinine derived thiourea in combination with cesium carbonate was effective for the synthesis of isoxazoline N‐oxides whereas stoichiometric di‐isopropylethylamine (DIPEA) was the best choice for isoxazole synthesis. In both cases a range of aryl and heteroaromatic groups was tolerated.