Phenyl (2-quinolyl) methanol: A Valuable Reagent for Metal-Free Reduction of Aromatic Nitro Compounds and Imines

Phenyl (2-quinolyl) methanol (PQM) behaves as a new efficient reagent for metal-free reduction of nitro aromatic and heteroaromatic compounds. The reduction proceeds in mild reaction conditions affording anilines in good yields. Phenyl (2-quinolyl) ketone (PQK), the oxidation product of PQM, can be quantitatively recovered and reused after reduction making sustainable the overall process. The reduction outcome changes with electron-deficient nitroarenes that afford the expected anilines and electron-rich nitro compounds that give reductive amination products via reduction of imines formed by condensation of nucleophilic anilines with PQK. These multicomponent reactions were observed also with activated aldehydes and in the presence of acrylates for the synthesis of beta-anilino esters. The synthetic value of the new metal-free reducing agent, unmatched by the well-known Hantzsch ester, has been exploited in metal-free Reissert indole and Friedlander quinoline syntheses.