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.