Amidine‐Induced Ring Transformation of a Substituted 1,1‐Dioxo‐1,2‐thiazine‐4‐carbaldehyde into New Pyrimidine Derivatives

As a masked 1,3‐dicarbonyl compound, the 1,1‐dioxo‐2H‐1,2‐thiazine‐4‐carbaldehyde 1 undergoes ring transformation with amidines to produce 2‐substituted 4‐methyl‐5‐[1‐methyl‐2‐methylthio‐2‐(N‐phenylsulfamoyl)vinyl]pyrimidines 3a–f. For 3b, an X‐ray structure analysis is reported. From the 4‐methyl‐2‐methylthio‐5‐[1‐methyl‐2‐methylthio‐2‐(N‐phenylsulfamoyl)vinyl]pyrimidine (3e), the substituted pyrimidinone 4 is obtained by acidic hydrolysis.