Synthesis of 11C-/13C-ketones by Suzuki coupling

Aryl triflates, methyl- or arylboronic acids, and a low concentration of [C-11]carbon monoxide were employed on small scale in the syntheses of fifteen C-11-labelled ketones using palladium-mediated Suzuki coupling reactions. The reagents were confined in a micro-autoclave and heated at 150 degreesC for 5 min. The reaction required the presence of LiBr, but no additional base. The C-11-labelled products were obtained with decay-corrected radiochemical yields in the range 10-70% and with high specific radioactivity (150-640 GBq/mumol). The radiochemical purity of the final products exceeded 98%. One C-13-substituted ketone ([C-13]-2'-benzonaphthone) was prepared and analysed by NMR spectroscopy for confirmation of the labelling position. The reference compound 2'-benzonaphthone was prepared by a palladium-catalysed reaction between sodium tetraphenylborate and 2-naphthoyl chloride. 2-Thienyl p-tolyl ketone, 4-nitrophenyl 2-thienyl ketone and 2-naphthyl 2-thienyl ketone were prepared by reactions between thiophene-2-boronic acid and the corresponding acid chlorides. The presented approach is novel and seems to be an efficient method for the synthesis of a wide range of C-11- as well as C-13-labelled ketones. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).