Synthesis of asymmetric 3,5-diaryl-4H-1,2,6-thiadiazin-4-ones via Suzuki-Miyaura and Stille coupling reactions

Asymmetric 3,5-diaryl substituted 4H-1,2,6-thiadiazin-4-ones can be prepared from 3,5-dichloro-4H-1,2,6-thiadiazin-4-one (1) via a multi-step protocol: selective nucleophilic mono-chloro substitution gives either the mono-methoxy or benzyloxy substituted mono-chlorothiadiazinones that can be phenylated via Suzuki-Miyaura coupling. Subsequent BBr3 mediated dealkylation gives 3-hydroxy-5-phenyl-4H-1,2,6-thiadiazin-4-one (9) that can be activated by a modified Finkelstein halodehydroxylation via the triflate, enabling further arylation reactions using Suzuki-Miyaura or Stille coupling chemistry.