Au(III) complexes with tetradentate-cyclam-based ligands

Abstract

Chiral cyclam (1,4,8,11-tetraazacyclotetradecane) derivatives were synthesized stepwise from chiral mono-Boc-1,2-diamines and (dialkyl)malonyl dichloride via open diamide-bis(N-Boc-amino) intermediates (65–91%). Deprotection and ring closure with a second malonyl unit afforded the cyclam tetraamide precursors (80–95%). The new protocol allowed the preparation of the target cyclam derivatives (53–59%) by a final optimized hydride reduction. Both the open tetraamine intermediates and the cyclam derivatives successfully coordinated with AuCl3 to give moderate to excellent yields (50–96%) of the corresponding novel tetra-coordinated N,N,N,N-Au(III) complexes with alternating five- and six-membered chelate rings. The testing of the catalytic ability of the cyclam-based N,N,N,N-Au(III) complexes demonstrated high catalytic activity of some complexes in selected test reactions (full conversion in 1–24 h, 62–97% product yields).

Halogen Bond Activation in Gold Catalysis

“…The cationic iodolium complex 9 and the bidentate 10 and 11 are strong halogen bond donors. We chose to use one of the most well-studied gold-mediated synthetic procedures, the cyclopropanation of propargyl acetate 12 with the vinyl derivative styrene 13 to cyclopropane 14 (Scheme ) as a model reaction, which has previously been used for the evaluation of the catalytic ability of novel gold­(I) and gold­(III) catalysts. − …”