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

Abstract

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(μ-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.

Decarboxylative oxygenation of carboxylic acids with O2via a non-heme manganese catalyst

“…To date, only a few biomimetic metal complexes are known that can catalyze the aerobic oxidation in a controlled manner without using a co-reductant. [52][53][54][55][56][57] Following on from our recent study of aerobic cleavage of alkenes with a non-heme Mn(II) complex, 58 we investigated the decarboxylative oxygenation of carboxylic acids to aldehydes/ketones by O 2 with this and related complexes. Our findings are detailed below.…”

Transformation of triolein to biogasoline by photo-chemo-biocatalysis

“…53,54 Notwithstanding the process made, almost all the photocatalytic methods reported so far can only produce aldehydes or ketones, not acids, from the cleavage of CvC bonds. [55][56][57][58][59][60] Motivated by these investigations, we envisioned that suitable photocatalysts might directly transform oleic acid into shorter-chain fatty acids by harvesting direct solar energy under ambient conditions. However, to the best of our knowledge, no photocatalyst has been used to cleave oleic acid using atmospheric O 2 , while representing a challenge for our presumption.…”

Multidecagram Scale Synthesis of an Endoperoxide, Precursor of Anti-malarial and Anti-leishmanial Agents, via Free-Radical [2 + 2 + 2] Annulation with Molecular Oxygen

“…An example of aerobic process studied in our lab at the millimolar scale over the last 10 years is reported in Scheme as a general catalytic cycle . It is based on the use of manganese (Mn) salts, often employed in the field of peroxidation processes. − …”