Unusual Peptidomimetic Reaction of 1,2-Diaza-1,3-butadienes: Straightforward Entry to 2,3,6-Triazabicyclo[3.2.1]oct-3-enes, 5-Oxo-4,5-dihydro-2-pyrazines, and 2-Carbonyl-2-oxopropylaminoacetates - Attanasi, Orazio A; De Crescentini, Lucia; Filippone, Paolino; Giorgi, Gianluca; Mantellini, Fabio; Mazzanti, Andrea (Synlett, 2006)