Oxidative Kupplung von Hückel-Anionen: Ein einfacher Zugang zu Fulvalenen

Abstract

Starting with a nearly quantitative coupling of cyclononatetraenide to 1,1’-dihydrofulvalene 3 by means of silver-tetrafluoroborate, a simple general synthetic concept for fulvalenes is outlined (Scheme 1). This plan consists in an oxidative coupling of Hueckel-anions 4 to 1,1’-dihydrofulvalenes 5 with silver(I)- or copper(II)-salts, followed by deprotonation 5 → 6 and final oxidation 6 → 7; it has been realised in the case of 1,2-3’,4’- dibenzo-pentafulvalene 1b as well as of pentafulvalene 1a. The ¹³C-NMR-spectra of pure 0,3-M-solutions of 1a have been recorded for the first time and are compared with those of some fulvenes. Dimerisation of the very instable 1a gives a formal [2 + 2]-cycloaddition product 12.