Structure–Reactivity Relationship in the Frustrated Lewis Pair (FLP)‐Catalyzed Hydrogenation of Imines

The autoinduced, frustrated Lewis pair (FLP)‐catalyzed hydrogenation of 16‐benzene‐ring substituted N ‐benzylidene‐ tert ‐butylamines with B(2,6‐F 2 C 6 H 3 ) 3 and molecular hydrogen was investigated by kinetic analysis. The p K a values for imines and for the corresponding amines were determined by quantum‐mechanical methods and provided a direct proportional relationship. The correlation of the two rate constants k 1 (simple catalytic cycle) and k 2 (autoinduced catalytic cycle) with p K a difference between imine and amine pairs (Δp K a ) or Hammett's σ parameter served as useful parameters to establish a structure–reactivity relationship for the FLP‐catalyzed hydrogenation of imines.