A Convenient Synthesis of 2,4-Dioxo-1,2,3,4-tetrahydro-10H-pyrimido[5, 4-b][1,4]benzothiazines (Dihydro-5-thiaisoalloxazines) via Thermal Smiles Rearrangement of 6-(2-Aminophenylthio)-5-bromouracils
5]benzothiazepine 10 was obtained in high yield by the Smiles rearrangement of 6, trapping of the resulting thiolate ion with formalin and subsequent acid-catalysed cyclization. Treatment of 1,3-dimethyl-6-(2-aminophenylthio)uracil 5 with hot acetic acid gave 1,3-bis[(2-benzothiazolyl)acetyl]-1,3-dimethylurea 12. Upon heating 5 or N-acetyl derivative 6 in dimethylsulfoxide, 5-thiaisoalloxazine 3 was obtained
Synthese und Alkylierung von 10H-Pyrimido[5,4-b][1,4]benzothiazinen
作者:Helmut Fenner、Hellmuth H. Rössler、Rolf W. Grauert
DOI:10.1002/ardp.19813141207
日期:——
10H‐Pyrimido[5,4‐b][1,4]benzothiazine 8 entstehen durch Kondensation von Barbitursäuren 5 mit o‐Aminothiophenol (7) in DMSO über das Ylid 6. Ihre Struktur als 1,5‐Dihydro‐System entspricht der Thiaisoalloxazin‐Struktur 1b. Aus einem komplexen Gemisch der aus 8 entstehenden Alkylierungsprodukte werden mit Hilfe von UV/VIS‐, 1H‐NMR‐,IR ‐ und ESR‐spektroskopischen Daten Strukturen zugeordnet und mit den
Irradiation of 6-(2-azidophenylthio)uracils (2) with a high-pressure mercury arc lamp resulted in the almost exclusive formation of dihydro-10-thiaisoalloxazines (3), while thermolysis of (2) gave a mixture of (3) and dihydro-5-thiaisoalloxazine (4).
Pyrimido-1,4-benzothiazines and -1,4-benzothiazepines. I. Oxidative coupling and Pummerer rearrangement of pyrimido-1,4-benzothiazine and its sulfoxide.
作者:YOSHIFUMI MAKI、TOKIYUKI HIRAMITSU
DOI:10.1248/cpb.24.3135
日期:——
Pyrimido-(1, 4)-benzothiazinedione (I) underwent oxidative coupling with water, alcohols and morpholine at the 4α-angular position in the presence of iodine and base such as triethylamine or morpholine. The facile Pummerer rearrangement of its sulfoxide also give 4α-substituted derivatives. The mechanisms of these reaction are also discussed.
Pyrimido-1,4-benzothiazines and -1,4-benzothiazepines. II. Thermal and photochemical rearrangements of pyrimido-1,4-benzothiazine sulfonium ylides.
作者:YOSHIFUMI MAKI、TOKIYUKI HIRAMITSU
DOI:10.1248/cpb.25.292
日期:——
Thermolysis of pyrimido-1, 4-benzothiazine sulfonium ylides caused competitively [1, 2] and [1, 4] rearrangements, or β-elimination, depending upon the natures of the substituents in the ylide moiety. Ultraviolet irradiation of the methyl, ethyl and benzyl sulfonium ylides resulted exclusively in the [1, 2] rearrangement followed by ring expansion leading to pyrimido-1, 4-benzothiazepines. On the basis of some data, the reaction sequences of these rearrangements were discussed.