Preparation of substituted 9,10-dihydro-9-sila-3-azaanthracenes and their derivatives

3-Methyl-4-dimethylphenylsilylpyridine and 3-methyl-4-methyldiphenylsilylpyridine, which were obtained from β-picoline and dimethylphenylchlorosilane and methyldiphenylchlorosilane, respectively, were converted by catalytic dehydrocyclization to 9,9-dimethyl-9,10-dihydro-9-sila-3-azaanthracene and 9-methyl-9-phenyl-9,10-dihydro-9-sila-3-azaanthracene. The corresponding silaazaanthrones were obtained from them and were converted to tertiary silaazaanthrols with a methyl or phenyl group attached to the C10 atom. On the basis of an analysis of data from the PMR spectra of the silaazaanthracenes it was assumed that they exist in the form of an equilibrium mixture of "boat" conformations. 9-Methyl-9-phenyl-10-methylene-9,10-dihydro-9-sila-3-azaanthracene was obtained in the form of a stable crystalline substance by dehydration of the corresponding silaazaanthrol. Potassium tert-butoxide cleaves the Si-C bond in the silaazaanthrone system; this was confirmed by isolation of 1,2-dimethyl-1,2-diphenyl-1,2-bis (2-nicotinoylphenyl)disiloxane. © 1981 Plenum Publishing Corporation.