Intermolecular Reductive Cyclodimerization of Cyclic α,β-Unsaturated Ketones Promoted by a Low-Valent Titanium Reagent: A Facile Synthesis of Some New Spiro Compounds - Shi, Da-Qing; Dou, Guo-Lan; Li, Zheng-Yi; Shi, Chun-Ling; Li, Xiao-Yue; Jiang, Hong; Ni, Sai-Nan; Ji, Shun-Jun (Synthesis, 2007)