Synthesis of 6-Alkylidene-5,6-dihydro-4H-1,3-thiazine Derivatives via the Cyclization ofN-3-Bromo-3-alkenylthioamides
摘要:
AbstractBy the treatment of N‐3‐bromo‐3‐alkenylthioamides with sodium hydroxide in DMF‐H2O in the presence of tetra‐butylammonium bromide, series of 6‐alkylidene‐5,6‐dihydro‐4H‐1,3‐thiazine derivatives were prepared in moderate to good yields. The cyclization is supposed to proceed via both the intramolecular vinylic nucleophilic substitution and the elimination‐addition mechanisms (formation of acetylenic intermediates) in a competitive manner.