Thiazolocyanines. XII. Polar substituents in thiazole rings of thiazolocyanines was written by Sych, E. D.;Umanskaya, L. P.. And the article was included in Zhurnal Obshchei Khimii in 1964.Electric Literature of C4H6N2S This article mentions the following:
Spectra of thiazolocyanines showed that the conjugation of electroneg. groups in the 5-position of the thiazole ring in thiazolocyanines with the rest of the mol. is developed more effectively than that of the electropos. groups in the 5-position or of electroneg. groups in the 4-position. Bromination of 2-methylthiazole in AcOH gave 2-methyl-5-bromothiazole (I); MeI adduct m. 243°; the Me tosylate (undescribed) was prepared from p-MeC6H4SO3Me at 90°. Refluxing 2-mercapto-5-acetamidothiazole with MeI in EtOH for 10 min. gave 2-(methylthio)-5-acetamidothiazole (II) m. 144°; the methiodide was prepared conventionally. NCCH2NH2.H2SO4 treated with aqueous KOH, followed by MeCS2K for 10 hrs., gave a low yield of 2-methyl-5-aminothiazole, m. 110°; Ac2O gave the 5-acetamido analog, m. 144°; the Et tosylate was prepared conventionally. I heated for 10 min. at 160° with PhN:CHOEt (III) followed by 0.5 hr. at 140° gave 2-(2-anilinovinyl)-5-bromothiazole Me tosylate, which with I Et tosylate in Ac2O-Et3N-EtOH for 5 min. gave after addition of NaClO4 bis[3-methyl-5-bromo-2-thiazole]trimethinecyanine perchlorate, m. 183-4°, λmaximum 566 mμ. 2,4-Dimethyl-5-acetylthiazole-EtI and EtOCH:C(CO2Et)2 in EtOH-Et3N for 0.5 hr. gave bis[3-ethyl-4-methyl-5-acetyl-2-thiazole]trimethinecyanine iodide, m. 240°, λmaximum 598 mμ. I Me tosylate and 2-(methylthio)benzothiazole Et tosylate similarly gave after addition of KI, yellow [3-methyl-5-bromo-2-thiazole] – [3 – ethyl – 2 – benzothiazole]methinecyanine iodide, m. >320°, λmaximum 423 mμ. II Et tosylate and 2-methylbenzothiazole Et tosylate similarly gave yellow [3-ethyl-5-acetamido-2-thiazole] – [3-ethyl- 2- benzothiazole]methinecyanine tosylate, m. 235°, λmaximum 434 mμ. Similarly, quinaldine Et tosylate gave red [3-methyl-5-acetamido-2-thiazole] – [3-ethyl-2-quinoline]methinecyanine iodide, m. 282°, λmaximum 489 mμ. 2-Methyl-5-aminothiazole-MeI and 2-(methylthio)benzothiazole Et tosylate rapidly gave orange [3-methyl-5-amino-2-thiazole]-[3-ethyl-2-benzothiazole]methinecyanine iodide, m. 245°, λmaximum 457 mμ. 2-Methyl-thiazole Me tosylate and III at 160° gave 81% 2-(2-anilinovinyl)-thiazole Me tosylate, which was directly treated with 3-ethyl-rhodanine in Ac2O-Et3N-EtOH and gave in 1 hr. 3-ethyl-5-[(3-methyl-2-thiazolinylidene)ethylidene]thiazolidine-2-thion-4-one, m. 220-1°, λmaximum 535 mμ. 2-(2-Anilinovinyl)-5-bromothiazole Me tosylate similarly gave blue 3-ethyl-5-[(3-methyl-5-bromo-2-thiazolinylidene)ethylidene] thiazolidine-2-thion-4-one, m. 168°, λmaximum 537 mμ. 2-Methyl-5-carbethoxythiazole and HC(OEt)3 refluxed in pyridine 40 min. and treated with KI gave violet bis-[3-ethyl-5-carbethoxy-2-thiazole]trimethinecyanine iodide, m. 134°, λmaximum 583 mμ. Similarly, 2-methyl-4-carbethoxythiazole Et tosylate gave bis[3-ethyl-4-carbethoxy-2-thiazole]trimethinecyanine iodide, m. 173° λmaximum 542 mμ. 2-Ethyl-5-carbethoxythiazole Et tosylate and 2-(methylthio)benzothiazole Et tosylate in EtOH-Et3N gave after addition of KI yellow [3-ethyl-5-carbethoxy-2-thiazole]-[3-ethyl-2-benzothiazole]methinecyanine iodide, m. 202°, λmaximum 428 mμ. Similarly, 2-methyl-5-carbomethoxythiazole Et tosylate gave [3-ethyl-5-carbomethoxy-2-thiazole]-[3-ethyl-2-benzothiazole]methinecyanine tosylate, m. 233°, λmaximum 430 mμ. II Et tosylate and 3-ethylrhodanine refluxed 10 min. in pyridine gave orange 3-ethyl-5-[3-ethyl-5-acetamido-2-thiazo-linylidene]thiazolidine-2-thion-4-one, m. 234-5°, λmaximum 443 mμ. I Et tosylate and p-Me2NC6H4CHO refluxed in Ac2O gave with KI gave violet 2-(p-dimethylaminostyryl)-5-bromothiazole-MeI, m. 238°, λmaximum 510 mμ; similarly prepared was 78% violet 2-(p-dimethylaminostyryl)-6-bromobenzothiazole Et tosylate, m. 272°, λmaximum 540 mμ. 2-Methyl-5-acetamidothiazole Et tosylate and HC(OEt)3 heated in PhNO2 and treated with NaClO4 gave bis[3-ethyl-5-acetamido-2-thiazole]trimethinecyanine perchlorate, λmaximum 576 mμ. Similarly was prepared rather unstable bis[3-methyl-5-amino-2-thiazole]trimethinecyanine tosylate, λmaximum 580 and 530 mμ, which lost the longer wavelength maximum on standing. In the experiment, the researchers used many compounds, for example, 2-Methylthiazol-5-amine (cas: 89281-44-7Electric Literature of C4H6N2S).
2-Methylthiazol-5-amine (cas: 89281-44-7) belongs to thiazole derivatives. Thiazoles frequently appear in peptide studies. Thiazoles can also be used as protected formyl groups, which can be released in later stages of complex natural product synthesis. The pyridine-type nitrogen in the thiazole ring deactivates the ring for electrophilic substitution reactions, which is further reduced in acid due to protonation of the thiazole ring.Electric Literature of C4H6N2S
Referemce:
Thiazole | C3H3NS – PubChem,
Thiazole | chemical compound | Britannica