MAGNESIUM ANTHRACENE SYSTEMS .8. MAGNESIUM ADDUCTS OF SUBSTITUTED ANTHRACENES - PREPARATION AND PROPERTIES

2‐Methyl‐, 1,4‐dimethyl‐, 9‐methyl‐, 9‐ethyl‐, 9,10‐dimethyl‐, and 9‐phenylanthracene (1a–f) react with magnesium in THF at room temperature to afford the corresponding substituted magnesium anthracenes 2a‐i. 9,10‐Diphenylanthracene (1g), however, reacts with magnesium under the same conditions to produce the deep‐blue magnesium bis(9,10‐diphenylanthracenide) · 6 THF (4g). Upon heating to 60°C in THF, 4g reversibly dissociated to give magnesium 9,10‐diphenylanthracene · 3 THF (2g) and 1g, while prolonged heating at 60°C causes decomposition of 2g to active magnesium (Mg*) and 1g. In THF 2a–c, e, and f exhibit temperature‐dependent equilibria with 1a–c, e, and f and magnesium. Compared with magnesium anthracene · 3 THF (2), these equilibria are strongly shifted toward substituted anthracenes and magnesium, and only at 0°C high conversions are achieved. The magnesium exchange between 2 and the substituted anthracenes 1a,b, and f in THF has been experimentally verified. 2a,e, and f react with organic halides in the same way as 2, however, in the case of allyl, propargyl, and benzyl chloride the yields of Grignard compounds are lower than for 2; with bromobenzene, the tendency for the radical transfer reaction is stronger than for 2. Magnesium 9,10‐dimethylanthracene (2e) reacts with ethyl acetate to give the bicyclic tertiary alcohol 9 by an intramolecular C–C coupling reaction. Copyright © 1990 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim