4- , from 4-thiazole

A variation of the general method for the synthesis of 2-amino-selenazoles is to avoid the use of the free a-halogenocarbonyl compound and in its place react the corresponding ketone and iodine with selenourea.This procedure is also taken from thiazole chemistry. By contrast with thiourea, the reaction with selenourea needs a longer reaction time and the work up of the reaction mixture is somewhat more difficult. Usually an excess of the ketone is used. In the preparation of 2-amino-4-( n-nitrophenyl)selenazole, a very high yield, calculated on the amount of iodine used, was obtained. To explain this peculiar result, the oxidative action of the nitro group was invoked. This liberates free iodine from some of the hydrogen iodide eliminated in the condensation reaction, and the free iodine then re-enters into the reaction. 

Biosynthesis of Thiamine Diphosphate from Thiazole and Pyrimidine... 

Thiamine diphosphate, biosynthesis, from thiazole and pyrimidine precursors, 269-271... 

Addition of Heterocyclic Compounds Stereocontrolled nucleophilic addition of heterocyclic compounds to chiral nitrones is of great synthetic importance in the synthesis of natural and biologically active compounds. In these reactions, the nitrone group serves as an amino group precursor and the heterocycle furnishes the formyl group (from thiazole) (192, 195, 214, 215, 579) or the carboxyl group (fromfuran) (194-196, 580-584) (Scheme 2.149). 

A synthesis from thiazole precursors occurred when 2-imino-3,4-diarylthiazolines (234) were cyclized with formaldehyde to give 236 [79IJC(B)632]. 

The products from thiazole, and a number of derivatives, with DMAD were examined in 1964 by two research groups541,542 their conclusions... 

Bis-cationic dyes, which are usually used for spin dyeing polyacrylonitrile, are derived from thiazole [83], Compound 33 dyes acrylic fibers blue with good steamfastness [84],... 

Azole approach. Like phthalazinones, which can be formed from the reaction between phthalic acids and hydrazines, the thiazole analogues can be formed from thiazole-4,5-dicarboxylic acid derivatives. Other 4,5-substituted oxo groups react similarly to give a fused thiazole (451) (71BSF1491). 

Lappert developed the thermolysis of an electron-rich olefin in the presence of a transition metal complex as another way to synthesise these compounds [4], When, in 1975, Clarke and Taube published their findings on carbon coordinated purine transition metal complexes [5], transition metal NHC complexes with functionalised NHC made their debut in biochemistry. The chemistry of carbenes from natural products became firmly established following the discovery that the catalytic activity of thiamine (vitamin Bl) is based on the intermediate formation of a carbene derived from thiazole [6-9] (see Figure 1.2). 

Figure 6.2 Structures of asymmetric organocatalysts derived from thiazole.

Thiazol-2-ylidenes are less well studied than their imidazole and triazol analogues. Only one isolated and structurally characterised example is known in the literature, the 3-(2,6-diis opropylphenyl)thiazol-2-ylidene synthesised by Arduengo et al. in 1997 [2] (see Figure 6.8). The parent compound, 2,3-dihydrothiazol-2-ylidene, was generated in an argon matrix at 10 K from thiazol-2-carboxylic acid as the starting material [33] (see Figure 6.9). 

Cure system species, accelerators and their reaction products This class of additive can present problems as they are often thermally labile, reactive and, in some cases, have a degree of ionic character (e.g. zinc dithiocarbamate salts). In these cases LC-MS is a more appropriate technique than GC-MS. It is also easier to use LC-MS with a number of the approved food simulants as they can be injected directly into the instrument, being compatible with the mobile phase. In some cases the reaction products (e.g. aniline from diphenyl guanidine, and benzothiazole from thiazole and sulphonamide accelerators) are stable and so GC and GC-MS can be used. Peroxides are popular curatives for food use rubbers and the stable, breakdown products of these can be easily detected by GC-MS. 

PytidylUiiaZOles, table of products, 478 Pyrolysis, of aryl thiazole, 399 Pyrrolothiazine, from thiazole ylide, 95 Pyrrolyl thiazoles, table of products, 471... 

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