Relative reactivities of bromine-substituted substrates toward bromophilic attack by a carbanion

Halophilic attack on carbon-halogen bond by nucleophiles has recently become a sub-ject of interest and intensive study.A wide variety of substrates and nucleophiles has beenexamined.But no quantitative measurements on the reactivities of substrates have ever beenreported.The present work is a first attempt to evaluate the relative reactivities of perfluoro-bromoalkanes(R-Br)and some bromo organic compounds(R-Br)by intermolecular compe-tition kinetics.A large excess of Cl_3CCF_2CF_2Cl(1),a chlorine-containing substrate withconvenient reactivity toward halophilic attack,and R-Br is used to compete for a small amountof the enolate anion of mesityl isopropyl ketone(E-)in dimethyl formamide(DMF)at 20℃in their reactions to form α-chloroisopropyl mesityl ketone(A)and α-bromoisopropylmesityl ketone(B)as products(eq 1)

Relative reactivities of bromine-substituted substrates toward bromophilic attack by a carbanion