Abstract
A thymine and acridine conjugate (1), containing a benzylic carbon of thymine and an electron-rich aromatic ring (acridine) within the same molecule, was synthesized. Treatment of 1 with N-bromosuccinimide (NBS) in anhydrous chloroform in the presence of azobisisobutylnitrile produced a dibromo-substituted thymine–acridine conjugate (7) as a major product, in which the bromination was only observed on the acridine ring. Nuclear Overhauser effect (NOE) difference spectroscopy revealed that the actual bromination substitution was on C-2 and C-7 of acridine. Our results suggest that electrophilic aromatic substitution, not the expected benzylic radical reaction, takes place predominantly even when 1 is subjected to the NBS reaction condition, which favors radical processes. In addition, such selectivity is clearly solvent dependent.
ACKNOWLEDGMENTS
We are grateful for support of this research by University of the Pacific and the National Science Foundation (MRI-0722654). We also thank Mr. Matthew Curtis for carrying out the mass spectrometry measurements.