Synthesis of β-Amino Ketones and β-Amino Alcohols

Significance

Reductive ring opening of 3,5-di­substituted 2,3-dihydroisoxazoles using sodium borohydride in acetic acid followed by zinc in acetic acid gave the corresponding syn-β-amino alcohols with good yields and diastereoselectivity. The reaction can be performed in one pot. Treatment of the 3,5-disubstituted 2,3-dihydroisoxazoles with zinc and acetic acid gave the β-amino ketone in good to excellent yield. Lower yields were obtained when R¹ = Ph, due to the formation of an competing α,β-unsatured ketone. An anomalous result was observed with R² = Ph: treatment of the 2,3-dihydroisoxazole with zinc in acetic acid produced the anti-β-amino alcohol rather than the expected β-amino ketone.