Practical synthesis of 2-amino-5-fluorothiazole hydrochloride

Organic Process Research and Development

Volumn 10, Issue 2, 2006, Pages 346-348

  Briner, Paul H ^a   Fyfe, Matthew C T ^a   Martin, Pierre ^b   Murray, P John ^a   Naud, Frédéric ^b   Procter, Martin J ^b  

^a Prosidion Limited   (United Kingdom)

^b SOLVIAS AG   (Switzerland)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 33645550150     PISSN: 10836160     EISSN: None     Source Type: Journal    
DOI: 10.1021/op0502194     Document Type: Article

References (31)

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23. The fluorination of acetamidothiophenes with F-TEDA is also problematic, affording very low yields of the desired fluorinated products: Kobarfard, F.; Kauffman, J. M.; Boyko, W. J. J. Heterocycl. Chem. 1999, 36, 1247-1251.
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25. The only other electrophilic fluorinating agents commercially available in bulk at present are 1-fluoropyridinium pyridine heptafluorodiborate [AccuFluor NFPy] and 1-fluoro-4-hydroxy-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) [AccuFluor NFTh].
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27. The formation of sulfones by reaction of aryllithiums with NFSi has been observed previously: Snieckus, V.; Beaulieu, F1; Mohri, K.; Han, W.; Murphy, C. K.; Davis, F. A. Tetrahedron Lett. 1994, 35, 3465-3468.
28. It is believed that the proton source for the formation of 1c is NFSi itself, as quenching of the dianion with DMF gave a quantitative yield of the appropriate aldehyde.
29. The difluorinated compound 2-tert-butoxycarbonylamino-4,5- difluorothiazole (5) was produced in 5-10% yield (determined by HPLC at 275 nm) when a larger quantity of t-BuLi (2.4 equiv) was employed.
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31. This organometallic reagent was purchased on a multikilogram scale from Chemetall GmbH (Frankfurt a. M., Germany). CAUTION: t-BuLi is extremely pyrophoric and should be handled on a large scale only by experienced personnel. Solutions of t-BuLi react vigorously and often violently with oxygen, water, and other protic solvents. As a result, the reaction must be conducted with extreme care under a dry, oxygen free, inert atmosphere. Appropriate protective clothing should be worn, and a suitable safety shield should be employed. In case of fire, a dry-powder extinguisher should be used. For further information on the handling of t-BuLi solutions in large quantities, see: Bailey, W. F.; Longstaff, S. C. FMC Lithium Link, Fall 2000, tert-Butyllithium in Organic Synthesis (available via the Internet at http://www.fmclithium.com).