Efficient synthesis of maleimides and carbazoles via Zn(OTf) 2-catalyzed tandem annulations of Lsonitriles and allenic esters - Yuanzhen Li; Haixia Zou; Jianxian Gong; Jing Xiang; Tuoping Luo; Junmin Quan; Guoxin Wang; Zhen Yang (Organic Letters, 2007)