Zirconocene-Mediated Intramolecular Cyclization of Bis Alkynyl Silanes

Zirconocene-Mediated Intramolecular Cyclization of Bis(Alkynyl)Silanes... 

Scheme 1.13 Zirconocene-mediated intramolecular cyclization of bis(alkynyl)silanes to give zirconacyclobutene-silaeyelobutene 1-21...

The author explored the reaction chemistry of intermediates 2-6 with isocyanides. Isocyanides bearing less-bulky and bulky substituents led to mono- and bis (iminoacyl)-Zr intermediates, respectively. Upon hydrolysis, the isolated mono (iminoacyl)-Zr intermediates underwent intramolecular cyclization to afford tetra-substituted 5-azaindoles, while intramolecular cyclization of bis(iminoacyl)-Zr intermediates led to the formation of dihydropyrrolo[3,2-c]azepines. Based on the above results, the author developed zirconocene-mediated multi-component coupling of bis(alkynyl)silanes, nitriles, and isocyanides. The structure of a bis(imi-noacyl)-Zr intermediate, formed via insertion of two molecules of CyNC into the Zr-C bond, and structures of two dihydropyrrolo[3,2-c]azepines were characterized by single-crystal X-ray structural analysis (Scheme 2.9). 

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