Lewis Acid Mediated Addition of Indoles and Alcohols to Tetronic Acid and Tetramic Acids

The electrophilic substitution of indoles with tetronic acid and N-acetyltetramic acid mediated by BF3OEt2 was investigated. This strategy allowed for the preparation of nine indole-substituted furan-2-ones (indolyl--lactones) and 3-pyrrolin-2-ones (indolyl--lactams) and is more straightforward than previously reported synthetic methods. During the course of our investigation, we also discovered a facile synthesis of tetronates and a tetramate via a BF3-mediated addition of alcohols to tetronic acid and N-acetyltetramic acid, respectively.