SYNTHESIS OF 9,10-DIHYDROSILAANTHRACENES WITH SUBSTITUENTS ORTHO TO THE SILICON AND METHYLENE BRIDGES

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 = (i)Pr) 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-degrees-C.