Synthesis of 9,10-dihydrosilaanthracenes with substituents ortho to the silicon and methylene bridges

Article abstract of DOI:10.1016/0022-328X(91)86224-E

The generation of 9,10-dihydrosilaanthracenes with substituents on benzo ring carbons, specifically in the 4,5-positions adjacent to the methylene bridge, has been developed.Attempts to prepare the 1,8-isomer where the substituents are adjacent to the silicon bridge are also described.The diarylmethane precursors to the substituted 9,10-dihydrosilaanthracenes required the synthesis of 2,3-dihalotoluenes as well as isomeric 2,6-disubstituted benzaldehydes which were then condensed to diarylmethanols through the Grignard reagents.Ring closure to the 4,5-dimethyl-9,9-dialkyl-9,10-dihydro-9-silaanthracene, I, required the use of Rieke magnesium.The structure of I (alkyl = ⁱPr) was determined and demonstrates that the introduction of substituents adjacent to the methylene bridge causes the dihydrosilaanthracene framework to become nearly planar with a dihedral (or butterfly) angle of 170 deg C.