The Reactions of Hydrazines with α-Lactams.
Regiochemistry of Hydrazine Addition and Subsequent Ring Closure to N-Aminohydantoins or 1,2,4-Triazine-3,6-diones.
-A combination of NMR and IR spectroscopy together with X-ray is used to determine the structures of hydrazine-trapping products such as (III) or (IX) and to identify factors which control their cyclization to either N-aminohydantoins or 1,2,4-triazines. From present and previous results it can be generalized that monosubstituted hydrazines with bulky or conjugating groups react regiospecifically to 1-acylated-2-substituted products which cyclize preferentially to N-aminohydantoins, e.g. (IV) and (VII), which originally was assigned as a 1,2,4-triazone-3,6-dione. Simple monoalkylhydrazines react at the internal nitrogen to give intermediates, which cyclize to triazines such as (XIII). Moreover, 1,2-disubstituted hydrazines can give only six-membered heterocycles, while 1,1-disubstituted hydrazines afford only five-membered rings. The application of this chemistry can be used for the synthesis of particular heterocycles. -(HOFFMAN, ROBERT