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

Abstract

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.