Arene Hydrides, 10 Michael Additions of Anthracene Hydride. Selective Reduction of the ArCC Moiety by Fragmentation of the Michael Adduct

Anthracene hydride ( AH − ) in THF undergoes Michael addition onto the acrylic acid derivatives 1 and 2 . Secondary reactions of the first formed anions 3 and 4 of the Michael adducts depend on the absence ( 3 ) or presence ( 4 ) of an aryl group in β position. The non‐benzylic 3 or its protonated or deprotonated form can cyclize via ester condensation to yield the “dibenzo‐bicyclo[3.2.2.]nonanones” 10b , c . Deprotonation of the anion 4 by excess AH − usually leads to fragmentation of the CCAr bond formed in the Michael addition. The overall result is a selective C = C reduction of cinnamonic acid derivatives and analogues: PhR′C = C → PhR′CH CH. This fragmentation is hampered in the Michael addition adduct 4h with dimethyl benzylidenemalonate 2h probably due to the necessity of a pronounced conformational reorganization during the fragmentation step.