Vilsmeier-Haack Reaction of α-Oxo Ketene Dithioacetals to α-Chlorovinyl/Ethynyl Ketene Dithioacetals - Dong, Dewen; Liu, Yingchun; Zhao, Yulong; Qi, Yimei; Wang, Zhuo; Liu, Qun (Synthesis, 2005)