Multigram-Scale Kinetic Resolution of 4-Acetyl[2.2]Paracyclophane via Ru-Catalyzed Enantioselective Hydrogenation: Accessing [2.2]Paracyclophanes with Planar and Central Chirality

Abstract

[2.2]Paracyclophane (PCP) derivatives have been promising platforms to study the element of planar chirality and through-space electronic communications in π-stacked molecular systems. To access enantiomerically pure derivatives thereof, a kinetic resolution of 4-acetyl[2.2]-PCP employing a ruthenium-catalyzed enantioselective hydrogenation process was developed. This method can be performed on a multigram-scale and gives access to enantiomerically pure derivatives with planar and central chirality of (Rp)-4-acetyl-PCP (≥97% ee, 43%) and (Sp,S)-PCP derivatives (≥97% ee, 46%), which are useful intermediates for the synthesis of sterically demanding PCP-based ligand/catalyst systems and chiral synthons for engineering cyclophane-based chiroptical materials. (Figure presented.).