| Abstract: | Photochemical cycloaddition of 6-azauracil derivatives to enol acetates yields hydrolytically labile bicyclic azetidines which decompose in good to excellent yield to 5-substituted-5,6-dihydro-6-azauracils. These compounds can in turn be oxidized by bromine to the 5-substituted-6-azauracil. This reaction sequence has also been applied to 2′,3′,5′-tri-o-benzoyl-6-azauridine resulting in a 60% overall yield of the functionalized nucleoside derivative. The three-step procedure reported here affords a simple method for carbon? carbon bond formation at the 5-position of 6-azauracil and may be applicable to other imines systems. |
