Synthesis and antifungal activities of novel 5,6-dihydro-indolo[1,2-a]quinoxaline derivatives

A series of new 5,6-dihydro-indolo[1,2-a]quinoxaline derivatives has been prepared in moderate to excellent yields from 2-(indol-1-yl)phenylamines with aromatic aldehydes by an efficient and economical iron-catalyzed Pictet–Spengler reaction. Meanwhile, as compared with hymexazol, a commercially available agricultural fungicide at the concentration of 50 μg/mL, some 5,6-dihydro-indolo[1,2-a]quinoxalines exhibited promising antifungal activities in vitro against the phytopathogenic fungi, and might be considered as novel promising lead candidates for further design and synthesis of agricultural fungicides.

Graphical abstract17 novel 5,6-dihydro-indolo[1,2-a]quinoxalines were efficiently prepared, and some derivatives exhibited promising antifungal activities in vitro against the phytopathogenic fungi.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► 5,6-Dihydro-indolo[1,2-a]quinoxalines were synthesized by a convenient, economic and efficient Pictet–Spengler cyclization reaction in the presence of FeCl3·6H2O. ► Their antifungal activities were evaluated against phytopathogenic fungi. ► Some compounds exhibited the promising and pronounced antifungal activities.