Sequential Construction of Complex Pyrrole-Pyrrole or Pyrrole-Pyrazole Systems from 1,2-Diaza-1,3-butadienes - Attanasi, Orazio A; De Crescentini, Lucia; Filippone, Paolino; Guidi, Barbara; Perrulli, Francesca R; Santeusanio, Stefania (Synlett, 1999)