Synthesis of 6,7‐Dihydropyrrolo[2,1‐c][1,3]thiazino[3,2‐a]pyrazine‐4(11bH)‐(thi)ones from 1,2‐Dithiolo‐3‐(thi)ones

• Published in: European journal of organic chemistry 2019-07, Vol.2019 (26), p.4149-4158
• Main Authors: Ogurtsov, Vladimir A., Karpychev, Yury V., Nelyubina, Yulia V., Primakov, Petr V., Koutentis, Panayiotis A., Rakitin, Oleg A.
• Format: Article
• Language: English
• Subjects: 1,2‐Dithiole‐3‐thiones (3‐ones); 3,4‐Dihydropyrrolo[1,2‐a]pyrazine; Cyclic imines; Heterocycles; Substitution reactions
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201900142

An efficient synthesis of 6,7‐dihydropyrrolo[2,1‐c][1,3]thi‐azino[3,2‐a]pyrazine‐4(11bH)‐(thi)ones from readily available 1,2‐di‐thiolo‐3‐(thi)ones and 3,4‐dihydropyrrolo[1,2‐a]pyrazine is reported. The S2 atom in both monocyclic and fused 1,2‐dithioles is selectively replaced by aminomethylene to afford fused, rigid six‐membered 1,3‐thiazines. The scope of this two‐step one‐pot reaction was investigated: 1,2‐dithiolo‐3‐ones were more reactive than the corresponding 1,2‐dithiole‐3‐thiones. Optimized reaction conditions and a mechanistic rationale for the ring transformation are presented. Both monocyclic and fused 1,2‐di‐thiolo‐3‐(thi)ones underwent addition of 3,4‐dihydropyrrolo[1,2‐a]pyrazine with selective extrusion of S2 atom and formation of 6,7‐dihydropyrrolo[2,1‐c][1,3]thi‐azino[3,2‐a]pyrazine‐4(11bH)‐(thi)ones. 1,2‐Dithiolo‐3‐one moiety was found more reactive than the corresponding 1,2‐dithiole‐3‐thione one.