Selective Bromination of Perylene Diimides under Mild Conditions

  • 10.1021/jo070367n
  • The Journal of Organic Chemistry
  • p 5973-5979, Volume 72, Issue 16,
  • journal-article
A novel method for the bromination of perylene diimides, PDI (1), under mild conditions is reported. Variation of the reaction conditions allows mono- and dibromination of PDIs to afford 2 and 3 (these can be separated through standard procedures) or exclusive dibromination to afford 3. Pure 1,7 regioisomers are obtained through repetitive crystallization. The structure of 1,7-3b was elucidated by a single-crystal X-ray analysis. The facility of the bromination reaction, which decreases in the order 1a > 1b > 1c, depends on PDI aggregation propensities. Monobrominated PDIs were utilized for the syntheses of novel unsymmetrical piperidinyl (4a and 4b) and trimethylsilylethynyl derivatives (5a and 5b). Computational studies (DFT) on imide substituent rotation in PDIs reveal that in the case of bulky groups there is a restricted rotation leading to isomers, in agreement with our experimental results. An aromatic core twist in PDIs bearing one and two bromine substituents was also investigated by DFT.


Good experimental, some modification to work-up

In this paper, selective bromination of perylene diimides is described. I was able to reproduce the bromination of 1a. However, the workup involves evaporating large volumes of bromine. I was able to isolate similar yields of products by quenching the reaction with sodium...