Synthesis of methylthiomaleimides for the preparation of pyridazines and related compounds

New functionalized maleimides (3-methylthio-2,5-dioxo-1H-pyrroles) were obtained by the reaction of ketene dithioacetals with nitromethane or the reaction of nitro ketene dithioacetal with active methylene compounds in the presence of the appropriate base in dimethyl sulfoxide followed by treatment with methanol. These maleimides reacted with various nucleophilic reagents such as electron-rich aromatic and heteroaromatic compounds like dialkylanilines, aminophenols, indoles, indolizines, and cyalazines to give the corresponding 3-aryl- or heteroaryl-1H-pyrole-2,5-diones. Styryl and merocyanine dyes, and polycyclic pyridazine-diones as chemiluminophors and succinimides were also obtained from these maleimides with good results.