Frustrated Lewis pair-catalyzed hydrogenation of unactivated alkenes with sterically hindered 9-phosphatriptycenes

The frustrated Lewis pair-catalyzed hydrogenation of unactivated alkenes with H-2 is reported. The weak Lewis basicity and high steric hindrance of ortho-substituted 9-phosphatriptycene derivatives is taken as an advantage to catalyze this reaction in combination with tris(pentafluorophenyl)borane. A scope of unsaturated substrates is described. The thermodynamics and kinetics of hydrogenation investigated by density functional theory show that the protonation of the olefin by the strongly acidic phosphonium cation is the critical step of the reaction.

Automated summary

In this study, frustrated Lewis pairs were used as catalysts for the hydrogenation of unactivated alkenes with H-2. Ortho-substituted 9-phosphatriptycene derivatives, with weak Lewis basicity and high steric hindrance, were found to be advantageous in catalyzing this reaction in combination with tris(pentafluorophenyl)borane. The protonation of the olefin by the strongly acidic phosphonium cation was identified as the critical step in the reaction.