The condensation of 2-aminoindole-3-carbonitriles and their 3-aminoindole-2-carbonitrile isomers with various DMF-dialkoxyacetals was investigated under microwaves. The appearance of reactive and versatile alkoxyiminium species allowed convenient access to indole precursors of building blocks with potential biological activity. The experimental results have been rationalised using DFT calculations of theoretical descriptors based on the electrostatic potential.