Synthesis of α-aminooxy amides through [3+3] cycloaddition and Sc(OTf)3-catalyzed double C-N bond cleavage in a one-pot reaction

Various alpha-aminooxy amides bearing a quaternary carbon at the alpha-position were prepared in good to excellent yields under mild reaction conditions fromN-vinyl nitrones and alpha-bromohydroxamates. TheN-vinyl nitrones tolerate a wide range ofN-vinyl fluorenone nitrones andN-vinyl isatin nitrones. Mechanistic studies show that the reaction initially proceeds through [3 + 3] cycloaddition betweenN-vinyl nitrones and aza-oxyallyl cations generated from alpha-bromohydroxamates to afford six-membered N,O-heterocycles, followed by double C-N bond cleavage in the presence of the Sc(OTf)(3)catalyst. A selective N-O bond cleavage of the obtained alpha-aminooxy amides is also realized under Fe/NH4Cl conditions. Furthermore, gram-scalable preparations of alpha-aminooxy amides are easily achieved.