... J. Heterocyclic Chem, 34, 413 (1997 ... 3e (Scheme 2). This mech- anism seemed very unlikely to us and led us to propose the mechanism shown in Scheme 3. Scheme 2 stoic NNHPII C015' IQ ——- "'g("r°" n,c S NOH Q 4a 5 J C5]-l_ ... 414 RL Robey, CA Alt, and EE Van Meter Vol. ...