A novel transformation of 1,2-dithiole-3-thiones into 1,3-thiazine-4-thiones

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

“…In 2008, we reported a new reaction of fused 1,2-dithiole-3thiones (e.g., compd 1a) with 3,4-dihydropyrrolo[1,2-a]pyrazine (2) that gave pyrazino [2,1-b] [1,3]thiazines 3. [1] A similar transformation was also be achieved in two distinct steps by first treating the monocyclic 1,2-dithiole-3-thione 1b with a sulfur extrusion agent such as a trimethylphosphite (1 equiv.…”

“…), to give a rare four-membered thiete-2-thione 4 in 92 % yield. [3] Interestingly, relatively few pyrazino [2,1-b] [1,3]thiazines have been reported. gave the fused 1,3-thiazine-4-thione 3l in 95 % yield (Scheme 1).…”

“…gave the fused 1,3-thiazine-4-thione 3l in 95 % yield (Scheme 1). Synthesis of pyrazino [2,1-b] [1,3]thiazines 3a and 3l from 1,2-dithiole-3-thiones 1 and through thiete-2-thione 4. [3] Interestingly, relatively few pyrazino [2,1-b] [1,3]thiazines have been reported.…”

“…[2] Nitrogen-bridged heterocycles find many uses in a wide range of applications and are important classes of compounds. Pyrazino [2,1-b] [1,3]thiazine core shown in red color. Nevertheless, this nitrogen-bridged bicyclic system is present as a substructure in various natural products, epicoccin A, [4] D, [5] E, [6] F, [6] I [5] and the structurally similar eutypellazines A, B, F, G, and H [7] that are all thiodiketopiperazine-type alkaloids ( Figure 1).…”

“…Nevertheless, this nitrogen-bridged bicyclic system is present as a substructure in various natural products, epicoccin A, [4] D, [5] E, [6] F, [6] I [5] and the structurally similar eutypellazines A, B, F, G, and H [7] that are all thiodiketopiperazine-type alkaloids ( Figure 1). Other non-natural compounds containing the pyrazino [2,1-b] [1,3]thiazine substructure also show biological activities. Synthesis of pyrazino [2,1-b] [1,3]thiazines 3a and 3l from 1,2-dithiole-3-thiones 1 and through thiete-2-thione 4.…”