Iridium-catalyzed consecutive and enantio selective [2+2+2] cycloaddition of tetraynes and hexaynes for the construction of an axially chiral biaryl system

A chiral iridium complex catalyzed a consecutive and enantioselective [2+2+2] cycloaddition of polyynes to give axially chiral compounds. Intermolecular reaction of tetraynes, possessing aryl groups on their termini, with protected but-2-yne-1,4-diols gave C-2-symmetrical quateraryl compounds. Intramolecular reaction of hexaynes, possessing aryl or alkyl groups on their termini gave C-2-symmetrical biaryl compounds. The catalytic synthesis of a pentacene derivative with axial chiralities is also discussed. (c) 2007 Published by Elsevier Ltd.