Bis-enaminoketone, eine Gruppe neuer pH-Indikatoren

Abstract

Symm. bis-enaminoketones easily can be prepared by condensation of hydroxymethylene ketones in the presence of ammonium acetate. The properties of the new compounds are described. In alkaline medium a bathochromic shift of the absorption maximum of 80 to 160 nm can be observed, the products are pH-indicators. The conformations were established by means of¹H-NMR-spectroscopy and correspond to two types of symmetric bis-enaminoketones. In type I both enaminoketone groups are in thecis-s-cis arrangement, while type II shows a combination of thecis-s-cis andtrans-s-cis conformation.