Additive‐free oxidation of isochromans with molecular oxygen synergistically catalyzed by mixed‐addendum polyoxometalate‐based coordination polymers

Abstract Attaining the selective oxidation of isochroman into isochromanone in a molecular oxygen (O 2 ) environment without any additives, via a heterogeneous oxidation process, is highly desirable and challenging work. Herein, we prepare two mixed‐addendum polyoxometalate‐based coordination polymers of the general formula [H x M 1‐ x ( i ‐Pr‐Im) 4 ][H 2 N(CH 3 ) 2 ] 4 [HPMo 8 V 6 O 42 ] (M = Co 1, Ni, 2; i ‐Pr‐Im = 1‐isopropyl‐1H‐imidazole). Needing no additives, they can catalyze the selective oxidation of isochroman to isochromanone with O 2 as an oxidant, with yields of 91.5% (1) and 46.8% (2), respectively. Mechanistic studies indicate that the excellent performance of catalyst 1 is attributed to the synergistic operation of [Co( i ‐Pr‐Im) 4 )] complex and PMo 8 V 6 unit, and that the catalytic reaction is a radical pathway involving superoxide radicals. Additionally, the catalyst 1 can be recycled and reused at least four times with uncompromised performance. These results provide fundamental guidelines for designing efficient and multi‐site heterogeneous catalysts for the selective oxidation of benzyl C(sp 3 )‐H bonds by activating O 2 .