4-Methylthiazole-3-oxide

Methylthiazole-3-oxide in the same conditions gave both 4-ace-toxymethylthiazole and 2-acetoxy-4-methylthiazole but in low yields. The reaction of 2,4-dimethylthiazole-3-oxide with p-tolyl chloride has also been studied (268), substitution occurring on the 2- and 4-methyl groups. 

Only one reaction of thiazole N-oxides has been studied in detail. The rearrangement in acetic anhydride of 2,4-dimethylthiazoIe-3-oxide gave 2-acetoxy-4-methylthiazole and 4-acetoxymethyl-2-methylthiazole in a ratio of about 4.5 to 1(264). 

Ozonolysis of 2-styryl-4-methylthiazole followed by oxidation of the intermediate carbonyl compound with peracetic acid yields 4-methyl-2-thiazolecarboxylic acid (30). 

Alkylthiazoles can be oxidized to nitriles in the presence of ammonia and a catalyst. For example, 4-cyanothiazole was prepared from 4-methylthiazole by a one-step vapor-phase process (94) involving reaction with a mixture of air, oxygen, and ammonia at 380 to 460°C. The catalyst was M0O3 and V Oj or M0O3, VjOj, and CoO on an alumina support. 

Chloro-5-methylthiazole, 2-chlorobenzothiazole, and 2-chlorobenzox-azole oxidatively add to [IrCl(CO)(PMe2Ph)2] to yield the neutral iridium(III) carbene species 47 and 48 (X = 0, S) (73JOM(50)C54,... 

Base catalysis is another area which has received a recent stimulus from developments in materials science and microporous solids in particular. The Merk company, for example, has developed a basic catalyst by supporting clusters of cesium oxide in a zeolite matrix [13]. This catalyst system has been developed to manufacture 4-methylthiazole from acetone and methylamine. 

The anodic oxidation of 2-amino-5-ethoxycarbonyl-4-methylthiazole (268) has been studied in CH3CN-LiC104.425 The mechanism of the formation of azo (273) and hydrazo (271) dimeric compounds as the main oxidation products is shown in Eq. (141). 

Volatile compounds generated by model systems of zeln, corn amylopectin and corn oil extruded at barrel temepratures of 120°C and 165°C were analyzed by GC and GC/MS. The largest quantities of lipid oxidation products were detected in systems containing all three components. In each system, the quantity of 2,4-deca-dienal was low relative to the quantities of hexanal, heptanal and benzaldehyde. Identification of the Maillard reaction products, 2-methyl-3(or 6)-pentyl-pyrazine, 2-methyl-3(or 6)-hexylpyrazine and 2,5-di-methyl-3-pentylpyrazine, suggested that lipid-derived aldehydes might be involved in the formation of substituted pyrazines. 4-Methylthiazole was identified as a major decomposition product of thiamin when corn meal containing 0.5% thiamin was extruded at a final temperature of 180°C. 

Phytopathogenic microorganisms, 136 Picrates, of amidines, 99 Pigments, 156-168 Piperidine, 46 Piscaine, 146 pKa. pKb, 18 of acylaminothiazoles, 91 and amino-imino equilibrium, 19 of azothiazoles, 107 correlation with sigma values, 19 of 2-methoxy-4-methylthiazole, 389 of 2-methylthiothiazole, in relation with nucleophilicity, 405 representative values, 20 and substituents effects. 19, 91 of A-2-thiazoline-4-one, from UV experiments, from potentiometry. 423 of A-4-thiazoline-one, 389 of 2-thiazolyl-oxides, 409 Plant growth regulator, 133, 134, 137 Plastics, 170... 

The l,2-diamino-4-methylthiazole 73 with phosgeniminium chloride gives the thiazolo[3,2-A [l,2,4]triazole derivative 74 (Scheme 45) <1973AGE806>. Reaction of the sulfimide 75 with nitrile oxides forms [l,2,4]triazolo[l,5- ] pyridine 3-oxides 76 in good yields (Scheme 46). This method is applicable to analogous pyrimidines and pyrazines <1976J(P1)2166, 1978BCJ563>. 

Thiazole-N oxides are prepared by the action at low temperature (—10°C) of hydrogen peroxide in acetic acid (474). 4-Methylthiazole and 2,4-dimethylthiazole afforded the corresponding N-oxides with yields of 27 and 58%, respectively (Scheme 88). Thiazole-N-oxides without a methyl group in the 2-position are so unstable that they have a tendency to form 2-hydroxythiazoles and are decomposed by oxidation, whereas a 2-methyl group would prevent such rearrangement (474). 

Thiazole A -oxides can easily be alkylated on the oxygen. For example, Ar-(alkoxy)-5-(p-methoxyphenyl)-4-methylthiazole-2(377)-thiones were prepared from Ar-(hydroxy)-5-( -methoxyphenyl)-4-methylthiazole-2(3//)-thione tetraethylammonium salt and an appropriate alkyl chloride or tosylate in moderate to good yields <20060BC2313>. A -Methoxythiazole-2(377)-thiones were synthesized from the A -hydroxythiazole-2(3//)-thiones by treatment first with a tetraalkylammonium hydroxide in methanol and then methyl ra-toluenesulfonate in DMF <2005EJ0869>. 

The ammoxidation of heteroeyelic compounds is not limited to methylpyridines. Other examples inelude the ammoxidation of 2,5-dimethylpyrazine, over molybdenum-cerium-titanium oxide [99], giving the corresponding mono-and dinitriles, and the ammoxidation of 4-methylthiazole to 4-eyanothiazole [100]. 

Miscellaneous. 2,4,5-Trichlorothiazole reacts with propargyl alcohol to form the 2-HC=CCH20-substituted M,5-dichlorothiazo le 4-Methylthiazole is transformed to 4-cyanothiazole by air/NH at 442°C over a Mn oxide-Cr oxide-Mo oxide catalytic mixture 2. 2-Mercapto-4,5-disubstituted thiazoles. are oxidised with NH4/heavy metal catalysts (or compounds thereof) to the corre-... 

Chlormethiazole is metabolized in the liver at a high rate and is excreted in the urine mainly in the form of inactive metabolites. The proportion of unchanged substance is usually less than 5% of the applied dose. The biological availability therefore increases in patients with impaired liver function. Metabolic deactivation proceeds by stepwise oxidation of the chloroethyl group to 4-methylthiazole-5-acetic acid. Other routes are shown in Fig. 8-36. The main metabolites in urine are the 1- and 2-hydroxyethyl derivatives. Some metabolites are excreted as conjugates [44],... 

Enzymatically cleaved to yield 4-methyl-5-thiazoleethanol (No. 1031) and 2-methyl-4-amino-5-hydroxymethylpyrimidine. The thiazole and pyrimidine fragments are further oxidized to yield 4-methylthiazole-4-acetic acid and the 5-pyrimidine carboxylic acid derivative, respectively, which, together with thiamine, are excreted in the urine. May also be converted to 2-methyl-4-amino-5-formylaminopyrimidine and thiamine acetic acid. 

The identification of fragment B of the vitamin molecule gave less trouble. It was recognized as a thiazole derivative by Clarke and Gurin . On oxidation with nitric acid it yielded 4-methylthiazole-5-carboxylic acid (VI), a compound that had already been synthesized in 1890. It appeared to contain an aliphatic hydroxyl group which could be replaced by chlorine without much change in the U.V. absorption spectrum, so it could be reconstructed as having structure VII. 

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