Synthesis of 11C‐/13C‐Ketones by Suzuki Coupling

Abstract

AbstractAryl triflates, methyl‐ or arylboronic acids, and a low concentration of [11C]carbon monoxide were employed on small scale in the syntheses of fifteen 11C‐labelled ketones using palladium‐mediated Suzuki coupling reactions. The reagents were confined in a micro‐autoclave and heated at 150 °C for 5 min. The reaction required the presence of LiBr, but no additional base. The 11C‐labelled products were obtained with decay‐corrected radiochemical yields in the range 10−70% and with high specific radioactivity (150−640 GBq/μmol). The radiochemical purity of the final products exceeded 98%. One 13C‐substituted ketone ([13C]‐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 11C‐ as well as 13C‐labelled ketones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)