Generation of Cyclic Ketene-N,X-Acetals (X = O, S) from 2-Alkyl-1,3-oxazolines and 2-Alkyl-1,3-thiazolines. Reactions with Acid Chlorides, 1,3-Diacid Chlorides and N-(Chlorocarbonyl) Isocyanate - Zhou, Aihua; Pittman Jr, Charles U (Synthesis, 2006)