Synthesis of [11C]cyanoalkyltriphenylphosphoranes via [11C]cyanide substitution on haloalkylphosphonium salts

✍ Scribed by Katarina Hörnfeldt; Bengt Långström

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: French
• Weight: 394 KB
• Volume: 34
• Category: Article
• ISSN: 0022-2135
• DOI: 10.1002/jlcr.2580340804

✦ Synopsis

Abstract

The synthesis of the ^11^C‐labelled bifunctional precursors 3‐[^11^C]cyanoethyltriphenylphosphonium bromide (1′), 4‐[^11^C]cyanopropyltriphenylphosphonium bromide (2′), 5‐[^11^C]cyanobutyltriphenylphosphonium bromide (3′), 4‐[^11^C]cyanobutyltriphenylphosphonium iodide (4′) and 5‐[^11^C]cyanobutyltriphenylphosphonium iodide (5′) is presented. The label was introduced using [^11^C]cyanide in a substitution reaction on the ω‐haloalkyltriphenylphosphonium salt (bromide or iodide salt). The phosphonium salts 1′ −5′ were formed in 33–99% radiochemical yield in 5–10 min reaction time. After addition of epichlorohydrin as generator of base, the precursors 1–3 were formed. The potential of the intermediates 1–3 in Witting reactions was shown in model reactions with aromatic and aliphatic aldehydes. The aromatic olefins obtained from 1′–5′ were formed in 85–96 % radiochemical yield, with Z/E ratios between 67/33–75/25. The aliphatic olefins were obtained in 60–78% radiochemical yield from 4′ and 5′. In the reaction with 1′ and an aliphatic aldehyde, the yield decreased to 5–10%. The Z/E ratios were 100/0 for the aliphatic olefins. In an experiment starting with 2,7 GBq (73 mCi) hydrogen [^11^C]cyanide, 451 MBq (12.2 mCi) olefin from 3′ and 4‐nitrobenzaldehyde was obtained in 44 min from hydrogen [^11^C]cyanide production, with a 55 % decay corrected radiochemical yield, the radiochemical purity was 96%.