HIGH TURNOVER SELECTIVE OXIDATION OF ALKENES WITH H₂0₂ USING A DECEPTIVELY SIMPLE Mn(II) CATALYST SYSTEM - APPLICATION AND MECHANISTIC INSIGHTS

Recently, we reported a high yielding, simple method for selective dihydroxylation of electron deficient alkenes in acetone using near-stoichiometric H₂O₂ (2.0 equiv.) and a Mn(II) salt, pyridine-2-carboxylic acid (PCA) and a base.[1] In this contribution the expansion of this system to the epoxidation of electron rich alkenes and the highly selective oxidation of substrates with multiple functional groups and the expnasion of the solvent scope in an effort to reduce safety risks associated with the combination acetone/H₂O₂ will be summarized. The main part of the presentation will focus on the detailed mechanistic analysis of the system using a combination of kinetic analyses, and spectroscopy, especially Raman spectroscopy. Although apparently simple, the ability of this system to provide high yielding selective reactions on multigram scales with near-stoichiometric H₂O₂ under ambient conditions with remarkably high TON (10000) and TOF (40 s^-1) shows clearly that it is complex and that lessons can be potentially be drawn in our approach to designing new catalyst systems.

[1] P. Saisaha, D. Pijper, J.W. de Boer, R. Hoen, R. van Summeren, P. Alsters, R. Hage, B.L. Feringa, W.R. Browne, Org. Biomol. Chem. 2010, 8, 4444