Lipase-Catalyzed Dynamic Kinetic Resolution of C1 - and C2 -Symmetric Racemic Axially Chiral 2,2'-Dihydroxy-1,1'-biaryls.

We have discovered that the racemization of configurationally stable, axially chiral 2,2'-dihydroxy-1,1'-biaryls proceeds with a catalytic amount of a cyclopentadienylruthenium(II) complex at 35-50 °C. Combining this racemization procedure with lipase-catalyzed kinetic resolution led to the first lipase/metal-integrated dynamic kinetic resolution of racemic axially chiral biaryl compounds. The method was applied to the synthesis of various enantio-enriched C1 - and C2 -symmetric biaryl diols in yields of up to 98 % and enantiomeric excesses of up to 98 %, which paves the way for new developments in the field of asymmetric synthesis.