The reaction of some secondary cyclic alpha-ketoenamines with electrop
hilic diazenes of the type Ar-N=N-COAr1 has been investigated. Aromati
c alpha-ketoenamines reacted with diazenes to afford the relevant 1,3,
4-oxadiazine derivatives, whereas aliphatic alpha-ketoenamines, under
the same conditions, directly the more stable ketoenamine adducts. 1,3
,4-oxadiazines, when heated in the presence of a catalytic amount of T
sOH, underwent ring opening, providing both addition and rearrangement
products by independent pathways. A possible mechanism for the format
ion of these latter compounds is proposed.