In situ kinetic studies of the trifluoromethylation of caffeine with Zn(SO2CF3)2

In situ monitoring of the trifluoromethylation of caffeine using Zn(SO2CF3)2 provides mechanistic insight into this important reaction. The concentration dependences of each of the reagents are probed, along with the effect of various additives. The kinetic profile is characterized by a rapid initial regime followed by a period of slower rate. Increasing the concentration of the Zn reagent extends the initial rapid period to higher conversions. Neither the caffeine concentration nor the concentration of the oxidant has a strong effect on the reaction rate. A multiple aliquot method is introduced to help deconvolute factors associated with each rate regime.