Photocatalyzed Dehydration of 1-Aryl-1,2-Ethanediols to Methyl Ketones Driven by Eosin Y Fragmentation Products.

Herein, we report a mild photocatalytic redox-neutral dehydration of aryl-1,2-ethanediols forming the respective methyl ketones. In the proposed mechanistic cycle an initial hydrogen atom abstraction (HAT) is followed by a 1,2-spin center shift (SCS) as key steps. Interestingly, Eosin Y was found to act as a pre-catalyst dissociating into a catalytically active mixture under irradiation. To the best of our knowledge, this exemplifies the first synthetic utilization of Eosin Y degradation products. As a result, our reaction can be realized with a single organic photocatalyst and releases water as a sole by-product.