Microwave activation in Fe-catalyzed reaction of Binor-S with nitriles

The classical method for the synthesis of N-substituted amides is the Ritter reaction of alcohols, haloalkanes, or olefins with nitriles and water catalyzed by H2SO4. The Ritter reaction can also be catalyzed by various Lewis acids based on salts of such transition metals as iridium, cobalt, copper, iron and niobium. Of particular interest is the Ritter reaction with cyclopropane derivatives. Only a few examples of such interaction are known. Thus, iron compounds, and in particular FeCl3*6H2O, catalyze the amidation of binor-S with a number of organic nitriles at a temperature of 140-150 oC during the reaction in an autoclave for 6 hours. We found that the catalytic system, consisting of 20 mol. % FeCl3*6H2O and 10 mol. % trifluoromethanesulfonic acid, with the simultaneous use of microwave irradiation allows to reduce the reaction time of binor-S amidation to 30 minutes with a simultaneous decrease in the reaction temperature to 80 ÷ 100 oC. In addition, it was possible to reduce the amount of excess organic nitrile used by a factor of four. Thus, for the first time, we have discovered the activating effect of catalytic amounts of trifluoromethanesulfonic acid and microwave irradiation on the reaction under study.