Efficient formation of σH-adducts as a key step in the synthesis of acridines via Lewis acid-promoted transformations of the nitro group

A step-by-step methodology was applied in the Lewis acid-promoted synthesis of fused heterocyclic systems from carbanions and nitroarenes. Efficient formation of σH-adducts of substituted nitrobenzenes and phenylacetonitrile derivatives followed by reductive transformation of the nitro group with silylating or acylating agents leads to 9-cyanoacridines. The method was found to be superior to the earlier one-pot approach, resulting in better yields and a broader scope of the reaction.