Amidinothioureas guanidines

The reaction of arylisothiocyanates with guanidines (233) affords amidinothioureas (234), which can be converted into 3,5-diarylimino-l,2,4-thiadiazolines (235) directly on treatment with bromine in ethanol. Alternatively, (234) can be alkylated with benzyl chloride to give the S-benzyl derivative (236) which on treatment with bromine in chloroform gives (235) (Scheme 51) <87JIC675>. 

Di(alkyl or aryl)amino-l,2,4-thiadiazoles (90 R,R = alkyl or aryl) are similarly obtainable in 60-85% yields from the appropriate disubstituted amidinothioureas (89 R,R = alkyl or aryl).56,57 The preparation of the latter from monosubstituted guanidines (87) and isothiocyanate esters (88) might conceivably yield the isomeric ami-... 

The scope of this mechanism for the reaction of a series of nucleophiles with hydroperoxides has been reviewed and a linear free-energy plot of ogkz against logArj derived for acid-catalysed oxidations. The reaction of l-aIkyl-3-aryl-thioureas with HgOa yields 1,2,4-thiadiazoles which rearrange in acidic solutions to thiazolyl-guanidines. The formation of amidinothioureas as precursors of the thiadiazoles has, however, been established. 

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