Carbon-14 labeling of hydrochlorothiazide via [14C]formaldehyde production from [14C]carbon dioxide at ambient temperature

[C-14]Formaldehyde was synthesized by reducing (CO2)-C-14 at ambient temperature with Schwartz's reagent. The [C-14]formaldehyde was then used in the radiosynthesis of high specific activity (2.1 GBq/mmol) [C-14]hydrochlorothiazide via cyclization of 4-amino-5-chloro-1,3-benzenedisulfonamide.