Formation of Silicon Centered Spirocyclic Compounds: Reaction of N-Heterocyclic Stable Silylene with Benzoylpyridine, Diisopropyl Azodicarboxylate, and 1,2-Diphenylhydrazine

Three silicon centered spirocyclic compounds 1−3, possessing silicon fused six- and five-membered rings have been prepared by the reaction of NHSi (L) [L = CH{(C=CH2)(CMe)(2,6-iPr2C6H3N)2}Si] with benzoylpyridine, diisopropyl azodicarboxylate, and 1,2-diphenylhydrazine, respectively, in a 1:1 ratio. The three spirocyclic compounds (1− 3) were obtained by three different pathways. The reaction of L with benzoylpyridine leads to the activation of the pyridine ring, and dearomatization occurred. Treatment of diisopropyl azodicarboxylate with L favors a [1 + 4]- rather than a [1 + 2]-cycloaddition product, and the azo compound was converted to hydrazone derivative. Finally the reaction of 1,2-diphenylhydrazine and L results in the elimination of hydrogen by activating one of the C−H bonds present in the phenyl ring. All three complexes 1− 3 were characterized by single crystal X-ray structural analysis, NMR spectroscopy, EI-MS spectrometry, and elemental analysis. In addition the optimized structures of probable products and possible intermediates were investigated using density functional theory (DFT) calculations.