Oxidation of Hydroxylamines to Nitrones Catalyzed by (Salen)Mn(III) complexes. Enantioselective Synthesis of a protected cis-Dihydroxypyrroline N-oxide with Jacobsen Catalyst

Oxidation ofN, N-disubstituted hydroxylamines to nitrones catalyzed by the Jacobsen catalyst occurs cleanly in the presence of hydrogen peroxide, sodium hypochlorite or iodosylbenzene as the stoichiometric oxidant. Meso 3,4-cis-isopropylidenedioxy-1- hydroxypyrrofidine gave the corresponding protected 3,4-cis-dihydroxypyrroline N-oxide in an enantioenriched fashion for the first time (up to 36% e.e.).