Ozonation of N-aryl-cyclic amines in organic solvents gave N-aryl-lactams regioselectively. In particular, 4-(4-aminophenyl)-morpolin-3-one, a key intermediate in the preparation of factor Xa inhibitors, was obtained in fair yields. The method represents an alternative approach for the lactamization of tertiary N-arylic substrates and is based on a "metal-free" introduction of the carbonyl function into the heterocyclic ring.
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