The thionium ions 10 generated by Pummerer reaction of N-aryl-N-methyl-3-(phenylsulfinyl) propionamides 4 caused not only an electrophilic cyclization reaction producing 2- quinolones 8, but also the formation of the vinyl sulfides 5 and 6 in favor of the latter reaction. On the other hand, the treatment of the vinyl sulfides 5 and 6 with p-toluenesulfonic acid induced cyclization to afford the 2-quinolones 8 in excellent to moderate yields, ...
