(R)‐BINOL‐6,6’‐bistriflone: Shortened Synthesis, Characterization, and Enantioselective Catalytic Applications

Abstract

AbstractThe title compound, characterized by X‐ray crystallography, was accessed in 4 steps with 92 % ee. and 25 % yield from an O‐protected (R)‐BINOL precursor. This revised synthetic route relied on a chlorosulfonylation reaction, as a shortcut to a previously developed sequence requiring the use of toxic SO2 gas and bromine. The strongly electron‐impoverished (R)‐6,6′‐Tf2‐BINOL proved an effective ligand in metal‐catalyzed enantioselective transformations such as a Zr‐based Mannich‐type reaction. The catalytic species was characterized by X‐ray crystallography as a unique tetrameric metal cluster. The 6,6′‐bistriflone groups also allowed to exalt the H‐bond donor capacity of the BINOL moiety, as illustrated in an organocatalyzed Morita‐Baylis‐Hillman transformation. Theoretical study indicated that the 6,6′‐bistriflone groups induce a drop of the phenol acidity of 5 pKa units in DMSO. Overall, this work simplified the access, completed the characterization, and confirmed the potential of (R)‐6,6′‐Tf2‐BINOL as a promising platform to further elaborate activated chiral metal ligands or organocatalysts.