Zirconocene-mediated intermolecular coupling of Si-tethered diynes with alkynes, ketones, aldehydes, and isocyanates by means of novel skeletal rearrangement of zirconacyclobutene-silacyclobutene and zirconacyclohexadiene-silacyclobutene fused-ring intermediates

Bis(alkynyl)silanes react with low valent zirconocene species to afford zirconacyclobutene intermediates. These in situ generated reactive organometallic intermediates can react with alkynes, ketones, aldehydes, and isocyanates by means of a novel skeletal rearrangement. When a zirconacyclobutene intermediate was treated with an alkyne, an alpha-alkynylsilyl zirconacyclopentadiene was formed. Addition of dimethyl acetylenedicarboxylate (DMAD) and CuCl resulted in one-pot formation of an alkynylsilyl-benzene derivative from three different alkynes. At a higher temperature, the alpha-alkynylsilylzirconacyclopentadiene was transformed by means of an intramolecular skeletal rearrangement to a zirconacyclohexadiene-silacyclobutene fused-ring compound, which reacted with DMAD in the presence of CuCl affording the same alkynylsilyl-benzene derivative. When treated with a ketone, an aldehdye, or an isocyanate, the zirconocyclobutene intermediate also underwent the above-mentioned skeletal rearrangement, generating zirconocene-mediated cross-coupling products.