Helquats (HQs) are structurally linked to helicenes and viologens, and they represent an attractive field of research in chemistry and medicinal chemistry. In the present work they were used as catalysts for the synthesis of 1,2,3,4-tetrahydroquinolines in good yields by the Povarov reaction. The substrate scope and the capability of different helquats to promote Povarov reactions are demonstrated. Studies to elucidate mechanistic details revealed that helquats act as single-electron transfer oxidants through a cation-radical mechanism. The screening of the catalytic activity of HQs confirmed that an active HQ must have a LUMO energy below -8.67 eV and the standard redox potential higher (less negative) than -1.2 V vs. the ferrocene/ferrocenium redox couple.

Department of Electrochemistry at Nanoscale J Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences Dolejškova 3 18223 Prague Czech Republic

Department of Inorganic Chemistry Faculty of Science Charles University Hlavova 2030 8 12843 Prague 2 Czech Republic

Department of Organic Synthesis Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo nám 2 16000 Prague 6 Czech Republic

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