A simple method for the displacement of bromine by fluorine at tertiary, benzylic or non-classical secondary sites

Iodine fluoride or, being its operational equivalent, the mixture of N-iodosuccinimide and triethylamine tris(hydrogen fluoride) reacts with tertiary and benzylic bromoalkanes to afford the respective fluoroalkanes in moderate-to-excellent yields. In contrast, primary bromoalkanes are virtually inert under identical conditions. Secondary bromoalkanes do not react either unless the heterolytically generated cationic intermediates benefit from non-classical resonance stabilization.