Manganese-Catalyzed Acceptorless Dehydrogenative Coupling of Alcohols With Sulfones: A Tool To Access Highly Substituted Vinyl Sulfones.

The development of first-row-transition-metal catalysts that can match with the reactivities of the noble metals is considered to be challenging yet very much a desirable goal in homogeneous catalysis. It has become even more fascinating to develop processes where these metals show a unique reactivity and selectivity than their higher congeners. Herein, we report on the catalytic activity of a pincer complex of the abundant earth metal manganese for an unprecedented acceptorless dehydrogenative coupling of alkyl sulfones with alcohols. Thus, highly functionalized vinyl sulfones were obtained in moderate to good yields. Both benzylic and aliphatic alcohols could be utilized, and several functional groups including bromides and iodides are tolerated under the reaction conditions. The reaction is environmentally benign, producing dihydrogen and water as byproducts. Preliminary mechanistic experiments involving kinetic, deuterium-labeling, and NMR experiments were performed.