Eine einfache Synthese chiraler Arylbenzochinone und Arylbenzohydrochinone; Versucheines NMR.‐Nachweises von Chiralität in isopropylsubstituierten Benzalanilinen

Atropisomeric diphenyls (V and VI) are easily prepared by the acid catalysed condensation of 2‐methoxycarbonyl‐1,4‐benzoquinone and 2‐acetyl‐1,4‐benzoquinone and trimethyl‐1,4‐benzoquinone respectively with 2‐isopropyl‐5‐methylanisole and 2‐isopropyl‐3,5dimethylanisole. The reaction is not affected by steric hindrance; the more highly substituted phenols gave better yields. One of the diphenylderivatives has been resolved with help of dehydroabietylamine. Thermodynamic data for the racemisation process have been determined by classical polarimetric techniques (Table 4). The chirality of most of the compounds prepared is easily detected by considering the signals of the diastereotopic isopropyl group in the NMR.‐spectrum. Probably because of solvent interaction NMR. kinetics have failed to give information about the racemisation process. Isopropyl‐substituted benzal‐anilines have been prepared. They did not show any ‘splitting’ of the isopropyl‐groups in the NMR.