Baeyer-Villiger oxidation tuned to chemoselective conversion of non-activated [18 F]fluorobenzaldehydes to [18 F]fluorophenols.
J Labelled Comp Radiopharm
; 62(8): 380-392, 2019 06 30.
Article
en En
| MEDLINE
| ID: mdl-31026351
ABSTRACT
A reaction pathway via oxidation of [18 F]fluorobenzaldehydes offers a very useful tool for the no-carrier-added radiosynthesis of [18 F]fluorophenols, a structural motive of several potential radiopharmaceuticals. A considerably improved chemoselectivity of the Baeyer-Villiger oxidation (BVO) towards phenols was achieved, employing 2,2,2-trifluoroethanol as reaction solvent in combination with Oxone or m-CPBA as oxidation agent. The studies showed the necessity of H2 SO4 addition, which appears to have a dual effect, acting as catalyst and desiccant. For example, 2-[18 F]fluorophenol was obtained with a RCY of 97% under optimised conditions of 80°C and 30-minute reaction time. The changed performance of the BVO, which is in agreement with known reaction mechanisms via Criegee intermediates, provided the best results with regard to radiochemical yield (RCY) and chemoselectivity, i.e. formation of [18 F]fluorophenols rather than [18 F]fluorobenzoic acids. Thus, after a long history of the BVO, the new modification now allows an almost specific formation of phenols, even from electron-deficient benzaldehydes. Further, the applicability of the tuned, chemoselective BVO to the n.c.a. level and to more complex compounds was demonstrated for the products n.c.a. 4-[18 F]fluorophenol (RCY 95%; relating to 4-[18 F]fluorobenzaldehyde) and 4-[18 F]fluoro-m-tyramine (RCY 32%; relating to [18 F]fluoride), respectively.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Fenoles
/
Benzaldehídos
/
Radioisótopos de Flúor
Idioma:
En
Revista:
J Labelled Comp Radiopharm
Año:
2019
Tipo del documento:
Article
País de afiliación:
Alemania
Pais de publicación:
ENGLAND
/
ESCOCIA
/
GB
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GREAT BRITAIN
/
INGLATERRA
/
REINO UNIDO
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SCOTLAND
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UK
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UNITED KINGDOM