Regio- and π-Facial Selective Cycloadditions Involving 2-Phenyl-4-dimethylamino-1-thia-3-azabuta-1,3-diene and Allenic Esters: An Efficient Route to Novel 6-Alkylidene-6H-2-phenyl-5-ethoxycarbonyl-1,3-thiazines - Ishar, M P S; Kapur, Ashish; Raj, Tilak; Girdhar, Navdeep K; Kaur, Amritpal (Synthesis, 2004)