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Issue 21, 2004
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Synthesis of 11C-labelled N,N′-diphenylurea and ethyl phenylcarbamate by a rhodium-promoted carbonylation via [11C]isocyanatobenzene using phenyl azide and [11C]carbon monoxide

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Abstract

The reaction with phenyl azide and [11C]carbon monoxide to give N,N′-diphenyl[11C]urea and ethyl phenyl[11C]carbamate has been studied with the aim of development of a new methodology for carbonylation using [11C]carbon monoxide with high specific radioactivity. The synthesis of 11C-labelled N,N′-diphenylurea from phenyl azide and [11C]carbon monoxide, with 1,2-bis(diphenylphosphino)ethane-bound Rh(I) complex at 120 °C at a pressure of 35 MPa in the presence of aniline was accomplished in 82% trapping efficiency and 82% conversion yield. This approach was also useful for the synthesis of ethyl phenyl[11C]carbamate with lithium ethoxide as a nucleophilic reagent giving 90% trapping efficiency and 76% conversion yield. These reactions can be considered to proceed via a [11C]isocyanate or a [11C]isocyanate-coordinated Rh complex to give the corresponding 11C-products. This protocol provides the chemical basis for the synthesis of [11C]urea and [11C]carbamate derived from [11C]isocyanates.

Graphical abstract: Synthesis of 11C-labelled N,N′-diphenylurea and ethyl phenylcarbamate by a rhodium-promoted carbonylation via [11C]isocyanatobenzene using phenyl azide and [11C]carbon monoxide

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Publication details

The article was received on 18 Jun 2004, accepted on 01 Sep 2004 and first published on 13 Sep 2004


Article type: Communication
DOI: 10.1039/B409294E
Citation: Org. Biomol. Chem., 2004,2, 3063-3066
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    Synthesis of 11C-labelled N,N′-diphenylurea and ethyl phenylcarbamate by a rhodium-promoted carbonylation via [11C]isocyanatobenzene using phenyl azide and [11C]carbon monoxide

    H. Doi, J. Barletta, M. Suzuki, R. Noyori, Y. Watanabe and B. Långström, Org. Biomol. Chem., 2004, 2, 3063
    DOI: 10.1039/B409294E

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