“…Compounds 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h , 4i , 4j , 4k , 4l , 4m , 4n , 4o , 4p , 4q , 4r may react either with their sulfur atom, N 2 or N 4 as nucleophilic sites. On the other hand, it has been reported that the azomethine carbon and N 2 of 1 had taken part in the heterocyclization . The methine carbon of 4 had to act as a nucleophile in the sense of an “umpolung” .…”