Photochemical and Free Radical Initiated Reactions Of1,3‐dimethylthymine With Isopropanol

A photochemically induced reaction of1,3‐dimethylthymine (DMT) with isopropanol leads to the formation of four alcohol adducts. The products have been identified as the cis and trans isomers of5,6‐dihydro‐1,3‐dimethyll‐6‐(2‐hydroxy‐2‐propyl) thymine (I and II), 2.4‐diaza‐8‐hydroxy‐2.4,6.8‐tetramethylbicyclo[4.2.0]octan‐1,3‐dione (III), and5,6‐dihydro‐1,3‐dimethyl‐6‐(2‐oxo‐l‐propyl)‐thymine (IV). An acetone photosensitized reaction of DMT with isopropanol gives the same products in a similar relative yield distribution. In both of these reactions, cyclobutane dimers of DMT are produced as well. Free radical reactions of 2‐hydroxyisopropyl radicals with DMT, initiated by decomposition of di‐t‐butyl peroxide, leads to formation of only one of the cis and trans isomers described above. along with1,3‐dimethyl‐5‐(2‐hydroxy‐2‐methyl‐1‐propyl)uracil (V).