Vertically π-Expanded Coumarins: The Synthesis and Optical Properties.

摘要: A regioselective synthesis of naphtho[2,1,8-def]coumarins has been realized through a concise route that involves the intramolecular Friedel–Crafts reaction benzo[f]coumarins. Tetracyclic, planar products were prepared starting from assembly suitably substituted coumarin via Pechmann 2-naphthols with acetone-1,3-dicarboxylates, followed by an reaction. In contrast to earlier report, main product condensation performed at 130 °C was corresponding sulfonic acid and not phenol itself. The one-pot process afforded desired in 39% yield. This extended some naphthalenediols. model 5-hydroxy-naphtho[2,1,8-def]coumarin transformed into dimer using various pathways including intermolecular oxidative aromatic coupling. Photophysical studies revealed most bathochromically shifted both absorption emission among all π-expanded cou...