title: 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.
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 degrees 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.
authors.affiliation: Division of Regeneration and Advanced Medical Science, Gifu University Graduate School of Medicine, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Doi
authors.forename: Julien
authors.initials: J
authors.lastname: Barletta
authors.forename: Masaaki
authors.initials: M
authors.lastname: Suzuki
authors.forename: Ryoji
authors.initials: R
authors.lastname: Noyori
authors.forename: Yasuyushi
authors.initials: Y
authors.lastname: Watanabe
authors.forename: Bengt
authors.initials: B
authors.lastname: Langstrom