Pd(0)-mediated [11C]carbonylation of aryl and heteroaryl boronic acid pinacol esters with [11C]carbon monoxide under ambient conditions and a facile process for the conversion of [carbonyl-11C]esters to [carbonyl-11C]amides

Abstract

A new method has been developed for the Pd(0)-mediated [11C]carbonylation of aryl/heteroaryl boronic acid pinacol esters with [11C]carbon monoxide in the presence of p-benzoquinone and triphenylphosphine in a mixture of N,N-dimethylformamide (DMF) and methanol (MeOH) or just MeOH under ambient pressure at 65 °C. This method was used to convert a variety of different aryl/heteroaryl boronates to the corresponding [carbonyl-11C]esters with decay-corrected radiochemical yields in the range of 6–80%. Furthermore, some of these [carbonyl-11C]esters were treated with sodium hydroxide or aqueous ammonium to give the corresponding [carbonyl-11C]carboxylic acids and amides, respectively. This new method was also used to achieve the direct syntheses of [11C]aspirin using water or tetramethylammonium hydroxide as the nucleophile instead of MeOH in DMF.