Photochemical ring expansion of 4-azidouracil: a route to 5H-1,3,5-triazepin-2,4-dione in the nucleoside series.
Under aqueous conditions, 4-azidouracil/tetrazolo[1,5-c]pyrimidin-5(6H)-one nucleosides undergo a very efficient photochemical nitrogen elimination and ring expansion to 1,3,5-triazepin-2,4-dione nucleosides whose structure has been confirmed by X-ray crystallography. In contrast, when the photolysis was attempted under anhydrous conditions in the presence of a nucleophile, a ring contraction reaction occurred, affording 2-oxoimidazolone nucleosides. A mechanism to account for the formation of ring expansion and contraction reactions and involving a carbodiimide intermediate is proposed which is reminiscent of the known photochemical behavior of 2-azidopyridines/tetrazolo[1,5-a]pyridines.
Institut de Chimie des Substances Naturelles, UPR 2301 CNRS, 1 Avenue de la Terrasse, 91190 Gif-sur-Yvette, France.
Frédéric
F
Peyrane
Michèle
M
Cesario
Pascale
P
Clivio
D001381:Azepines / Q000138:chemical synthesis*; D001386:Azides / Q000737:chemistry; D002234:Carbodiimides / Q000737:chemistry; D009705:Nucleosides / Q000138:chemical synthesis* / Q000737:chemistry; D010777:Photochemistry / Q000379:methods*; D011725:Pyridines / Q000737:chemistry; D012997:Solvents; D014498:Uracil / Q000737:chemistry; D014867:Water
D001381:Azepines; D001386:Azides; D002234:Carbodiimides; D009705:Nucleosides; D011725:Pyridines; D012997:Solvents; C401522:triazepinone; D014867:Water; D014498:Uracil