In Situ Coupled Oxidation Cycle Catalyzed by Reusable Platinum Catalysts

Significance

An organic-inorganic hybrid platinum nanocluster catalyst (HB Pt) and the polymer-incarcerated platinum catalyst (RPI Pt) were synthesized and applied to the oxidation of dihydropyridine with a catalytic amount of o-chloranil under oxygen atmosphere. Thus, HB Pt and RPI Pt were prepared from copolymer 1 and 2, sodium borohydride, and sodium hexachloroplatinate(IV) according to the reported procedures with a slight modification (S. Kobayashi and co-workers ­Angew. Chem. Int. Ed. 2008, 47, 8093). The oxidation of dihydropyridine 5 was performed with HB Pt 3 and o-chloranil (7) under aerobic conditions to give pyridine 6 in 99% yield. This ­catalyst was recovered and reused seven times without any loss of catalytic activity.