2- -5-nitrothiazole

Aminothiazole and derivatives have been reported in reactivity studies starting from 2-p-nitrophenylsulfenylaminothiazole (4) (32), 2-tritylaminothiazole (5) (33), 2-nitrothiazole (34,35), and 5-methyI-2-phenylimino-4-thiazolidinone (36) (Scheme 4). 

Nitrothiazole and 5-nitrothiazole are known products, while 4-nitrothiazole does not appear to have been prepared. 2-Nitrothiazole (2,... 

The 2-nitrothiazole can be reduced to the corresponding aminothiazole by catalytic or chemical reduction (82, 85, 89). The 5-nitrothiazole can also be reduced with low yield to impure 5-aminothiazole (1, 85). All electrophilic substitution reactions are largely inhibited by the presence of the nitro substituent. Nevertheless, the nitration of 2-nitrothiazoIe to 2,4-dinitrothiazole can be accomplished (see Section IV). 

When 5-halogeno-2-nitrothiazole reacts with methoxide ion. the leaving group is the nitro group in position 2, following Scheme 17 (86). 

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 reacts with nucleophiles, such as MeO or F , yielding the normal ipso substitution product (Scheme 125). The 5-nitrothiazole, under similar conditions, decomposes. 

Nitrothiazoles are reduced to 2-aminothiazoles, either catalytically or chemically, whereas the reduction of 5-nitrothiazole gives poor yields of impure 5-aminothiazole. 2-Nitrobenzothiazole is reduced to the azo derivative by tin(II) chloride in basic medium (Scheme 126). 

Only one example of the nitration of thiazoles at position 2 has been described the action of the sulfuric-nitric acid mixture on 4,5-dimethylthiazole gave 4,5-dimethyl-2-nitrothiazole [199],... 

Nitrothiazole and also 4- and 5-substituted 2-nitrothiazoles were obtained from the corresponding 2-amino derivatives [415 420] (Scheme 56). 

NMR study of nitrothiazoles has been the subject of few number of works [525, 530-540], The proton chemical shifts of about 30 thiazole derivatives including 5-nitrothiazole and 2-nitrothiazole are presented in [536], The authors have found the coupling constants between H-2 and II-4 in most 5-substituted thiazoles to be negligible with the exception of 5-nitrothiazole and 5-thiazolecarboxylic acids [536], The change in the H-4 chemical shifts of the 2-substituted 5-nitrothiazole fragment enables the ratio of isomeric products of the reaction of 5-nitrothiazole 2-(T,3 -dicarbonyl) derivatives with hydrazine and hydroxylamine to be established (Scheme 3.8) [537],... 

The transition from 2-nitrobenzothiazole to 2-nitrothiazole is reported [780] to involve a 6 ppm upfield shift of the carbon atoms resonance (Scheme 3.14). 

An analysis of the mass spectra of 2-substituted 5-nitrothiazoles and 2-nitrothiazole has been carried out (Scheme 3.63) [1325] ... 

Only the 2.4-dinitrothiazole is known, being prepared by nitration of 2-nitrothiazole by N2O4-NO2/BF3. The yield is 80% (90). The reduction with Raney Ni/AcjO of 2,4-dinitrothiazole proceeded smoothly, yielding the corresponding 2,4-diacetamidothiazole. 

Nitro-5-halogenothiazoles, 57 8 preparation of, 578 reaction with MeO", 580 2-(4-Nitrophenylimino)-4-thiazolidone, from 4-nitrophenylthiourea and chloroacetic acid, 296 2-Nitrothiazole, 576 nitration of, 577 preparation of, 576 reaction with KF, 566 reaction with MeO", 577 reduction of, 577... 

Pedulli and co-workers have also studied anion-radicals in the thiazole system, including those from 2-nitrothiazole, 2,2 -bithiazolyl, 2-arylthiazoles, and bis(2-thiazolyl) ketone. Here the anion-radicals were generated by alkali-metal reduction in ethereal solvents and found to exist in contact ion-pairs. Whenever the organic component contained two adjacent binding sites, chelation of the counterion occurred and was revealed by examining the variation of its hyperfine splitting with temperature and solvent. The interaction of the ion-pairs with macrocyclic polyethers was also studied by ESR for certain of the chelating radicals. ... 

The replacement of a nitro group by fluorine in some triazoles has been achieved using anhydrous hydrogen fluoride (Eq. 13)58 and, in 2- and 4-nitropyridines and 2-nitrothiazole, by using potassium fluoride in aprotic solvents (Eq. 14).5 9... 

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