2-Bromo-5-nitrothiazole

The reaction of 2-bromo-5-nitrothiazole with weakly basic secondary aliphatic amines gave the expected 2-amino products. The isomeric 5-bromo-2-nitrothiazole with such amines gave mixtures of the expected 5-amino products along with 2-aminated 5-nitrothiazole rearrangement products. A mechanism was proposed which involves the slow thermal isomerisation of the 5-bromo-2-nitrothiazole to the much more reactive 2-bromo isomer which competes, in the case of relatively weak amine nucleophiles, with direct but slow displacement of the 5-bromo group to form the normal displacement product <96JHC1191>. 

Nitrothiazole is obtained by reductive dehaiogenation of 2-bromo-5-nitrothiazole (2, 14, 83). 

The 1 1 cocrystal of 2-amino-5-nitrothiazole with 4-aminobenzoic acid comprises two constituent molecules associated by a hydrogen-bonded graph set dimer through the carboxylic group across the N/N site of the thiazole [0-H...N, 2.614(3)A N-H...O, 2.991(3)A] [144], 2-Bromo-5-nitrothiazole [145], tetrakis (mefa-acetato)bis[2-(2-thionyl)-amino-5-nitrothiazole]-dirhodium-II-dihydrate [146], and /V-(4-melhoxyben/yl (-/WS-nilro-1,3-thia/ol-2-yl) urea [147] have been studied by X-ray analysis. 

The ESR and the ENDOR investigations of radicals formed by X-ray irradiation of a single crystal 2-bromo-5-nitrothiazole have been carried out [145], The experimental tensor HFS constants are compared with the theoretical constants, and calculated for azaallyl and allyl radicals. 

As in the case of oxazoles, the pyridine-like N-atom makes electrophilic substitution reactions more difficult. Thus thiazole does not react with halogens. Donor substituents enhance the reactivity, e.g. 2-methylthiazole reacts with bromine to give 5-bromo-2-methylthiazole. Thiazole cannot be nitrated. 4-Methylthiazole reacts slowly to yield the 5-nitro compound, 5-methylthiazole even more slowly to give the 4-nitro compound, but 2,4-dimethylthiazole reacts fastest producing 2,4-dimethyl-5-nitrothiazole. Sulfonation of thiazole demands the action of oleum at 250°C in the presence of mercury(II) acetate, and occurs at the 5-position. Acetoxymercuration of thiazole with mercury(II) acetate in acetic acid/water proceeds stepwise by way of the 5-acetoxymercury compound and the 4,5-disubstituted product to 2,4,5-tris(acetoxymercury)thiazole. 

Bromo-5-nitrothiazole in dimethyl sulfoxide added dropwise with stirring at 15-20° during 0.5 hr. to diisopropylamine in the same solvent, and stirred overnight at room temp. -> (l-nitro-2-diisopropylaminovinyl)thiocyanate. Y 79%. F. e., also mere replacement of the bromine by amino groups, s. A. O. Ilvespaa, Helv. 51, 1723 (1968). 

Red crystals formed from the reaction of 2-nitrothiophen with aliphatic secondary amines in the cold are tentatively assigned the structure R2NCH=CHCH=C(N02) 2Sj a very similar cleavage reaction with amines involving a stable five-membered heteroaromatic system, 2-bromo-5-nitrothiazole, was reported some time ago. "... 

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