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

Organic & Biomolecular Chemistry Pub Date: 2020-09-25 DOI: 10.1039/D0OB01788D

Abstract

Various α-aminooxy amides bearing a quaternary carbon at the α-position were prepared in good to excellent yields under mild reaction conditions from N-vinyl nitrones and α-bromohydroxamates. The N-vinyl nitrones tolerate a wide range of N-vinyl fluorenone nitrones and N-vinyl isatin nitrones. Mechanistic studies show that the reaction initially proceeds through [3 + 3] cycloaddition between N-vinyl nitrones and aza-oxyallyl cations generated from α-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 α-aminooxy amides is also realized under Fe/NH4Cl conditions. Furthermore, gram-scalable preparations of α-aminooxy amides are easily achieved.

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