Ueda, Kanichi published the artcilePyridine derivatives containing sulfur. L. Mechanism of cleavage of thiazole ring of 2-aminothiazolo[5,4-b]pyridines by means of aqueous alkali, Application In Synthesis of 31784-71-1, the publication is Pharmaceutical Bulletin (1956), 396-401, database is CAplus and MEDLINE.
cf. C.A. 51, 2741i. Determination of the structures of the previously reported (C.A. 48, 5187h) “Substances I (I), II (II), and III (III),” prepared from 6-Cl (IV) and 6-EtO (V) derivatives of 3-amino-2-mercaptopyridine should help clarify the mechanism of the cleavage of the thiazole ring of the title compounds Comparisons of the infrared and ultraviolet absorption spectra of I with those of the 3-amino (VI) and 3-acetamido (VII) derivatives of 6,2-Cl(MeS)C5H2N (VIII) led to the conclusion that I was 6,2,3-Cl(MeS)(H2NCONH)C5H2N. This conclusion was supported by heating 0.6 g. I 6 hrs. on a H2O bath with 40 cc. Ac2O and evaporating in vacuo to give 0.08 g. 3-AcNHCONH derivative of VIII, m. 209°, and 0.3 g. VII, m. 166° (from the mother liquor chromatographed in CHCl3 over Al2O3). Support also came from the synthesis of I:1.2 g. IV in 170 cc. AcOH treated slowly with 2.5 g. KNCO in 20 cc. H2O at 40°, stirred 3 hrs., diluted with much H2O, and kept overnight yielded 0.82 g. 6,2,3-Cl(HS)(H2NCONH)C5H2N (IX), m. 185-90° (effervescence); this gave I, m. 286-95°, methylated with MeI in alk. solution Also, 0.8 g. VI similarly treated with KNCO yielded 0.8 g. I. Likewise treated with KNCO, 2-MeS (X) and 2-EtS derivatives of 3,6-H2N(EtO)C5H3N gave II, m. 200-36°, and III, m. 160-1°, resp.; their ultraviolet spectra confirmed their structures as 6,2,3-EtO(MeS)(H2NCONH)C5H2N and 6,2,3-EtO(EtS)(H2NCONH)C5H2N, resp. The mechanism of cleavage of the thiazole ring in the 5-Cl (XI) and 5-EtO (XII) derivatives of the title compound was studied. XI (0.7 g.) was refluxed 1 hr. in an oil bath at 120-30° with 6 cc. 10% NaOH while NH3 evolved, the solution neutralized with AcOH, the resulting precipitate methylated with Me2SO4, the ether extract of the product evaporated, and the residue fractionally crystallized to give 0.21 g. VI, m. 56° (from petr. ether-ether), and 0.22 g. I, m. 290° (from MeOH). However, refluxing 7 hrs. instead of 1 hr. gave only VI. IX (0.7 g.) similarly hydrolyzed for 1 hr. and methylated yielded 0.15 g. VI and 0.12 g. I, but after 6 hrs. hydrolysis it gave only VI. XII (1 g.) refluxed 6.5 hrs. with 10 cc. 20% NaOH in the presence of 0.2 g. As2O3 while NH3 evolved, the mixture cooled, filtered, and the filtrate neutralized with AcOH yielded 0.7 g. V, m. 150-70° (characterized by methylation to X and acetylation to 3,6,2-AcNH(EtO)(MeS)C5H2N, m. 124°), and after standing overnight, 0.1 g. 6,2,3-EtO(HS)(H2NCONH)C5H2N, m. 195-8° (decomposition)(characterized by methylation with Me2SO4 to II). Longer hydrolysis (10 hrs.) of XII gave only V. Confirmation of the production of V from XII was obtained by condensing it (0.5 g.) in 1 cc. H2O and 5 cc. EtOH containing 0.2 g. NaOH with 0.6 g. BzCH2Br to yield, after standing overnight at room temperature, the expected 6-ethoxy-2-phenylpyrido[2,3-b]1,4-thiazine(0.42 g.), m. 125° (C.A. 50, 10101g). These results of hydrolysis of IX, XI, and XII led to the conclusion that amino-thiazolopyridines were converted to mercaptopyridines through mercaptopyridylureas as intermediates, which were somewhat resistant to the hydrolysis.
Pharmaceutical Bulletin published new progress about 31784-71-1. 31784-71-1 belongs to thiazole, auxiliary class Other Aromatic Heterocyclic,Chloride,Amine, name is 5-Chlorothiazolo[5,4-b]pyridin-2-amine, and the molecular formula is C11H10ClNO, Application In Synthesis of 31784-71-1.
Referemce:
https://pubchem.ncbi.nlm.nih.gov/compound/thiazole,
Thiazole | chemical compound | Britannica