The Halogen-Samarium Exchange Reaction. Synthetic Applications and Kinetics.

Fast I/Sm and Br/Sm exchanges take place when various aromatic or heterocyclic iodides and bromides are treated with nBu(2)SmCl.4 LiCl and nBu(3)Sm.5 LiCl, respectively. The resulting organosamarium reagents were efficiently quenched with aldehydes, ketones, and imine& Also, they undergo acylations when treated with N,N-dimethylamides leading to ketones. The rate of the Br/Sm exchange for a typical aryl bromide was determined and found to be 8.5 x 10(5) faster than the Br/Mg exchange, indicating that the rate of a metal exchange is related to the ionic character of the carbon-metal bond and to the metal electronegativity.