A vast array of ketones can be prepared in high yields by reacting Grignard reagents with carboxylic acid chlorides in the presence of manganese chloride (MnCl2•2LiCl). The reaction is highly chemoselective.
We are also interested in manganese-catalyzed cross coupling reactions. The aryl-aryl coupling between aromatic Grignard reagents and activated aryl or heteroaryl halides is probably the most important reaction in this field.
It is also possible to couple aryl Grignard reagents with alkenyl halides under manganese catalysis.
Interesting results have been reported as well with ortho-halogeno aromatic ketones.
On the other hand, we have shown that aryl Grignard reagents are efficiently homocoupled in the presence of manganese salts by using atmospheric oxygen as an oxidant. The scope of this homocoupling oxidative reaction is very large since aryl, alkenyl and alkynyl Grignard reagents were successfully employed.
A careful mechanistic study of the influence of steric and electronic factors on the course of the reaction allowed us to achieve the first oxidative heterocoupling between two Grignard reagents.