Stereo- and regio-selectivity in the photosensitized dimerization of 1 3-dimethylthymine in solution

The effects of reaction pathway and temperature on stereo- and regio-selectivity of photocycloaddition of 1, 3‐dimethylthymine (DMT) which gives four cyclobutane type dimers in solution using acetone as the photosensitizer, are investigated by measuring the product distribution. It is demonstrated that the ground-state aggregation between DMT molecules mainly leads to (h-t) dimers, and the diffusion-controlled triplet dimerization is favorable to the formation of (h-h) dimers. Supported by National Natural Science Foundation of China (Grant Nos. 30000036, 20273066) and Special Fund for Doctoral Programme from the State Education Commission of China (2000035821)