TheKnoevenagel reaction of malononitrile with some cyclic ?-ketocarbothionic acid anilides synthesis of cycloalkeno-pyridines and cycloalkeno-thiopyrans
Tricyclic cyclopenta[b]pyrrolo[3,4-c]pyridine-3,5-dione and pyrrolo[3,4-d]quinoline-3,5-diones with stable hemiaminal function or bicyclic azaspiro[4.4]nonanes and azaspiro[4.5]decanes were obtained in a domino reaction of cycloalkenecarbothioamides with maleimides. The proposed mechanism involves Michael addition, ring transformation, aqueous hydrolysis of the imine, and additional ring closure which is observed exclusively for one diastereoisomer.