Pt II ‐Catalyzed Hydroxylation of Terminal Aliphatic C(sp 3 )−H Bonds with Molecular Oxygen

The practical application of Shilov‐type Pt catalysis to the selective hydroxylation of terminal aliphatic C−H bonds remains a formidable challenge, due to difficulties in replacing Pt IV with a more economically viable oxidant, particularly O 2 . We report the potential of employing FeCl 2 as a suitable redox mediator to overcome the kinetic hurdles related to the direct use of O 2 in the Pt reoxidation. For the selective conversion of butyric acid to γ‐hydroxybutyric acid (GHB), a significantly enhanced catalyst activity and stability (turnover numbers (TON)>30) were achieved under 20 bar O 2 in comparison to current state‐of‐the‐art systems (TON<10). In this regard, essential reaction parameters affecting the overall activity were identified, along with specific additives to attain catalyst stability at longer reaction times. Notably, deactivation by reduction to Pt 0 was prevented by the addition of monodentate pyridine derivatives, such as 2‐fluoropyridine, but also by introducing varying partial pressures of N 2 in the gaseous atmosphere. Finally, stability tests revealed the involvement of Pt II and FeCl 2 in catalyzing the non‐selective overoxidation of GHB. Accordingly, in situ esterification with boric acid proved to be a suitable strategy to maintain enhanced selectivities at much higher conversions (TON>60). Altogether, a useful catalytic system for the selective hydroxylation of primary aliphatic C−H bonds with O 2 is presented.