11C-methylations using 11C-methyl iodide and tetrabutylammonium fluoride

Carbon-11 methylation reactions on functional groups such as phenols and amides require a base when using 11C-methyl iodide. This study demonstrates that tetrabutylammonium fluoride (TBAF) can be used as a base to prepare 11C-radiopharmaceuticals efficiently and in high yield. We have applied this method to raclopride, methylphenidate, PK11195, dihydrotetrabenazine and MDL100907 and have compared the results with the Alumina/KF and hydroxide methods. Our results indicate that TBAF gives equivalent or higher radiochemical yields compared to the other bases even when using as little as 200 μg of precursor. In the case of PK11195 the TBAF method was the only one that provided a reasonable yield of product.