Synthesis of [1,3]dithiole and spiro[1,3]dithiole thiopyran derivatives of the [1,2]dithiolo[1,4]thiazine ring system.
We report the synthesis of some new polysulfur-nitrogen heterocycles by cycloaddition reactions to readily available tricyclic condensed 1,2-dithiole-3-thiones. Thus, treatment of bis[1,2]dithiolopyrrole ketothione 1 with diacyl acetylenes gave the bis-aducts 2a-d. On the other hand, cycloaddition of bis[1,2]dithiolo[1,4]thiazine ketothione 3 with 1 equiv of acyl or diacyl acetylenes gave [1,3]dithiolylidenyl[1,2]dithiolo[1,4]thiazines 4a-f in fair to high yields. Catalysis by scandium triflate was used in the reactions that implied the less reactive dipolarophiles. Treatment of 3 with 2 equiv of DBA gave the bis-aduct 5a, and reaction of 4c with DMAD gave the mixed bis-adduct 5b. Cyclic voltammetry of selected examples showed irreversible processes that were influenced by the electrochemical activity of peripheral groups bonded to the heterocyclic system.
Departamento de Química, Facultad de Ciencias, Universidad de Burgos, 09001 Burgos, Spain.
Susana
S
Barriga
Pedro
P
Fuertes
Carlos F
CF
Marcos
Oleg A
OA
Rakitin
Tomás
T
Torroba