Facile Synthesis of Regioisomeric N-Alkyl Substituted 3-Methylene-3,4-dihydroquinoxalin-2(1H)-ones

Facile and convenient synthetic approaches towards pharmaceutically important regioisomeric N‐alkyl substituted 3‐methylene‐3,4‐dihydroquinoxalin‐2(1H)‐ones have been developed. Various approaches to the target compounds were tested and compared. Products having bulky N⁴‐propyl substituent were found to exist in two forms in solutions due to solvent‐dependent rotational processes in 2‐oxoethylidene moiety, which is of interest for construction of optical, electronic, and other functional materials. The proposed procedures proceed in a highly regioselective manner under mild conditions, and the products are isolated without usage of column chromatography.