A gemini amphiphilic phase transfer catalyst for dark singlet oxygenation

A new gemini surfactant phase transfer catalyst, namely diethyl‐ether‐α,ω‐bis‐(dimethyldodecylammonium molybdate) codified as 12‐EO‐12‐Mo, was prepared by anion exchange from the analogous gemini dichloride (12‐EO‐12‐Cl2). The physico‐chemical properties of these compounds such as Krafft temperature, critical micelle concentration, surface activity and binary water‐surfactant behavior were compared and the influence of the molybdate counterion was examined. Though both compounds are highly hydrophilic, the cmc of 12‐EO‐12‐Mo (0.4 mmol L−1) is about five times lower than of its dichloride analogue (2.2 mmol L−1). Moreover, 12‐EO‐12‐Mo exhibits an additional cubic liquid crystal phase between 53 and 64 wt%. The usefulness of 12‐EO‐12‐Mo as an amphiphilic phase transfer catalyst for the dark singlet oxygenation was demonstrated with the peroxidation of two typical organic substrates: α‐terpinene which reacts with 1O2 according to a [4 + 2] cycloaddition and the less reactive β‐citronellol, which provides two hydroperoxides according to the ene‐reaction. 12‐EO‐12‐Mo provides a simple reaction medium with only three components for the preparative peroxidation of hydrophobic substrates by chemically generated singlet oxygen.