Synthesis of [11C]Am80 via Novel Pd(0)-Mediated Rapid [11C]Carbonylation Using Arylboronate and [11C]Carbon Monoxide

11C-labeled methylbenzoates [11C]4a–d were synthesized using Pd(0)-mediated rapid cross-coupling reactions employing [11C]carbon monoxide and arylboronic acid neopentyl glycol esters 3a–d under atmospheric pressure in methanol–dimethylformamide (MeOH–DMF), in radiochemical yields of 12 ± 5–26 ± 13% (decay-corrected based on [11C]O). The reaction conditions were highly favorable for the synthesis of [11C]Am80 ([11C]2) and [11C]methyl 4-((5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-yl)carbamoyl)benzoate ([11C]2-Me) using 4-(5,5-dimethyl-1,3,2-dioxaborinan-2-yl)-N-(5,5,8,8-tetramethyl-5,6,7,8-tetrahydronaphthalen-2-yl)benzamide (5), both of which produced a decay-corrected radiochemical yield (RCY) of 26 ± 13%, with >99% radiochemical purity and an average specific radioactivity of 44 GBq/μmol. The yields of [11C]4a, [11C]2-Me, and [11C]2 were improved by the use of a 2-fold excess of the solvents and reagents under the same conditions to give respective yields of 66 ± 8, 65 ± 7, and 48 ± 2%.