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.

Abstract

1,3-thiazines. -The 1-thia-3-aza-diene (I) undergoes a regio-and stereoselective [4 + 2] cycloaddition with allenes to yield cycloadducts (III)/(IV) and (VI) after elimination of dimethylamine. In the case of allenic ester (VII), the primary cycloadduct (VIII) is stable and can be isolated in high yield. -(ISHAR*, M. P. S.; KAPUR, A.; RAJ, T.; GIRDHAR, N. K.; KAUR, A.; Synthesis 2004, 5, 775-778; Dep. Pharm. Sci., Guru Nanak Dev Univ., Amritsar 143 005, India; Eng.) -Mais 32-179