Paper
2‐Amino‐2′‐[18F]fluorobenzhydrols, intermediates for the synthesis of [2′‐18F]‐1,4‐benzodiazepine‐2‐ones
Published Feb 1, 1994 · P. Johnström, S. Stone-Elander
Journal of Labelled Compounds and Radiopharmaceuticals
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Abstract
A method for synthesizing 18F-labelled 2-amino-2′-fluorobenzhydrols under nocarrier-added conditions for use as radiolabelled intermediates in the synthesis of[2′-18F]-1,4-benzodiazepine-2-ones is presented. Anilinodichloroborane reagents were formed by the reaction of boron trichloride with 4-chloro-N-methylaniline, 6a, 4-nitro-N-methylaniline, 6b, 4-nitro-N-ethylaniline, 6c, and 4-chloro-N-(2,2,2-trifluoroethyl)aniline, 6d. 2-[18F]Fluorobenzaldehyde, 5, synthesized in 55–70% yields by the nucleophilic aromatic substitution of 2-nitrobenzaldehyde with the Kryptofix/K+ complex of [18F]F−, was subsequently reacted with the anilinodichloroborane coupling reagents with aromatic substitution occurring ortho to the amino group. The resulting 2-amino-2′-[18F]fluorobenzhydrols, 7a - 7d, were produced in conversions of 60–95% with reaction time ⩽ 10 min at room temperature or 60°C, depending on the aniline used. The total synthesis time, including evaporation of the target water, was 60–65 min. The total radiochemical conversions were of the order of 50–65% for 7a - 7c and 35–45% for 7d, decay-corrected and based on [18F]F−.
This method efficiently synthesizes 18F-labelled 2-amino-2′-fluorobenzhydrols for use as radiolabelled intermediates in the synthesis of [2′-18F]-1,4-benzodiazepine-2-ones in 60-65 minutes at room temperature or 60°C.
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