Thiazolyl thiourea rearrangement

An interesting rearrangement of the (4-methyl-2-thiazolyl)thioureas (263) has recently been reported (Scheme 160) (303). The reaction mechanism is currently under investigation. This reaction does not occur if the 4-methyl substituent in the thiazole ring of 263 is replaced by an hydrogen, which suggests an electrophilic attack on C-5 as the mechanism of this reaction. 

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. 

Dichloroethyl isothiocyanate reacts with thioureas R NHC(S)NR 2 at 100 °C to yield thiazolyl-2-thioureas (9), or at 20 °C to give the thiadiazines (10), which may be rearranged, on heating or with base, to the thiazoles (9). ... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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