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.