One-Pot Synthesis of Substituted Indole N-Oxides: TiCl4-Mediated Baylis-Hillman Reaction of α-Oxo Cyclic Ketene-S,S-acetal with o-Nitrobenzaldehydes and Subsequent Intramolecular Cyclization - Pan, Wei; Dong, Dewen; Sun, Shaoguang; Liu, Qun (Synlett, 2006)