Oxidative Cleavage of Alkenes by O2 with a Non-Heme Manganese Catalyst

The oxidative cleavage of C = C double bonds with molecular oxygen to produce carbonyl compounds is an important transformation in chemical and pharmaceutical synthesis. In nature, enzymes containing the first-row transition metals, particularly heme and non-heme iron-dependent enzymes, readily activate O-2 and oxidatively cleave C = C bonds with exquisite precision under ambient conditions. The reaction remains challenging for synthetic chemists, however. There are only a small number of known synthetic metal catalysts that allow for the oxidative cleavage of alkenes at an atmospheric pressure of O-2, with very few known to catalyze the cleavage of nonactivated alkenes. In this work, we describe a light-driven, Mn-catalyzed protocol for the selective oxidation of alkenes to carbonyls under 1 atm of O-2. For the first time, aromatic as well as various nonactivated aliphatic alkenes could be oxidized to afford ketones and aldehydes under clean, mild conditions with a first row, biorelevant metal catalyst. Moreover, the protocol shows a very good functional group tolerance. Mechanistic investigation suggests that Mn-oxo species, including an asymmetric, mixed-valent bis(mu-oxo)-Mn(III,IV) complex, are involved in the oxidation, and the solvent methanol participates in O-2 activation that leads to the formation of the oxo species.

Automated summary

The oxidative cleavage of C = C double bonds with molecular oxygen is a key transformation in chemical and pharmaceutical synthesis. While nature has efficient enzymes for this reaction, synthetic chemists face challenges in finding suitable metal catalysts. This work presents a light-driven, Mn-catalyzed method for selective oxidation of alkenes with good functional group tolerance, involving asymmetric Mn-oxo species and methanol as an activator for O-2.