Reactions of 4‐chloro‐5 h ‐1,2,3‐dithiazole‐5‐thione with α,β‐unsaturated β‐amino esters: Formation of 2‐[2‐(1‐alkenylsulfanyl‐1‐alkoxycarbonyl‐2‐amino)‐1,2‐dicyano‐vinylsulfanyl]‐3‐amino‐2‐alkenoic alkyl esters

Treatment of 4‐chloro‐5 H ‐1,2,3‐dithiazole‐5‐thione with alkyl 3‐alkyl (or aryl)‐3‐amino‐2‐propenoates in the presence of pyridine (2 equivalents) in dichloromethane at reflux gave 2‐[2‐(1‐alkenylsulfanyl‐1‐alkoxy‐carbonyl‐2‐amino)‐1,2‐dicyanovinylsulfanyl]‐ 4 and‐1,2‐dicyanovinyldisulfanyl]‐3‐amino‐2‐alkenoic alkyl esters 7 in 16 to 60% and 8 to 48% yields, respectively.