Thiazole mercuration

Anilino-4-arylthiazoles (211) are mercurated on the phenyl ring (Scheme 133) (453. 454). The phenyl ring is also the site of mercuration in 2-arylamino-4-(2-thienyl)thiazoles (213) (Scheme 134) (455). 

Thiazole Nitration Sulfonation Brominadon Mercuration Alkylation... 

All the early literature concerning thiazoles mentions numerous metallic complex-salts formed by addition to the thiazole of the aqueous solution of the metal salt and that could be used for identification purposes. The most usual complexes so obtained are platinum double salts, for example, (4-methylthiazole HC1)2 PtCU (m.p. deep 204°C) (25), or mercuric chloride derivatives, for example, 2,4-dimethyl-thiazole 2 HgCl (m.p. deep 176-177°C) (458). 

Mercurated thiazoles also yield 5-halothiazoles by the replacement of Hg by halogen. 

Mercuration has been also used as an extractive technique to separate thiazoles from complex mixtures such as crude petroleum (273. 861-863). 

The substrate was 2,4-diphenyl the 5-position on the thiazole nucleus is mercurated. 

Thiazole, 4-methyl-5-(2-hydroxyethyl)-in thiamine biosynthesis, 1, 97 Thiazole, 4-methyl-2-methylami nosynthesis, 6, 300 Thiazole, 4-methyl-2-phenyl-alkylation, 6, 256 mercuration, 6, 256 Thiazole, 2-(methylthio)-methylation, 6, 290 thermodynamic values, 6, 291 Thiazole, 2-methylthio-5-phenyl-synthesis, 5, 153 Thiazole, 4-methyl-5-vinyl-occurrence, 6, 327 Thiazole, 2-phenyl-acetylation, 6, 270-271 Conformation, 6, 237 synthesis, 5, 113, 6, 306 Thiazole, 4-phenyl-conformation, 6, 237 2,5-disubstituted synthesis, 6, 304 Thiazole, 5-phenyl-conformation, 6, 237 Thiazole, 2-phenyl-5-triphenylmethyl-synthesis, 6, 265 Thiazole, 2-(2-pyridyl)-metal complexes, 5, 51 6, 253 Thiazole, 4-(2-pyridyl)-metal complexes, S, 51 6, 253 Thiazole, tetrahydro-ring cleavage, 5, 80 Thiazole, 2,4,5-trimethyl-occurrence, 6, 327... 

Oxazoles are mercurated in acetic acid the ring positions react 5 > 4 > 2 (74AHC( 17)99). Thiazoles react under the same conditions and show the same order of ring position reactivities. Isoxazoles can be easily mercurated in the 4-position with mercury (II) acetate (63AHC(2)365). 3-Arylsydnones are mercurated at the 4-position. 

Mercuration, of alkylthiazoles, 380 as extractive technique, 380 Metallic complex, of thiazoles, 392 w Method, 27 ur" Method, 27... 

There is a differential reactivity to nitrogen heterocycles between Hg(II) and other types of electrophile, such as bromine, possibly due to a weaker coordination of the mercuric ion to a ring nitrogen for example mercuration is more successful in electrophilic substitutions for oxazoles. In both oxazoles and thiazoles, the preferred position for mercuration is C-5, but in the latter, trimercuration occurs quite readily. 

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