title: Synthesis of heterodinuclear hemisalen complexes on a hexaarylbenzene scaffold and their application for the cross-pinacol coupling reaction.
abstract: Intermolecular cross-pinacol coupling reaction between aliphatic and aromatic aldehydes by using heterodinuclear hemisalen complexes 1cis with vanadium(V) and titanium(IV) on a hexaarylbenzene scaffold is reported. Our ligand design is based on the individual activation of two aldehydes by vanadium and titanium, which are positioned with a suitable space on the rigid scaffold. Ligands such as 1cis were synthesized by Diels-Alder addition and decarbonylation reaction, followed by condensation of dialdehyde 3cis with various aminophenols. The influence of the substituents on the ligands on the pinacol coupling reaction was investigated. As a result, the reductive coupling reaction between aliphatic and aromatic aldehydes by using a catalytic amount of 1cis in the presence of Me3 SiCl and Zn provided the corresponding cross-coupled 1,2-diol in good yields with high cross-selectivity.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Yamada-oka, Suita, Osaka 565-0871 (Japan), Fax: (+81) 6-6879-7415.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Miyasaka
authors.forename: Toru
authors.initials: T
authors.lastname: Amaya
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Hirao
keywords: CC coupling; heterometallic complexes; ligand design; redox chemistry; titanium; vanadium