Aryl bromides were successfully transformed into their corresponding N,N′-diacylhydrazines via a Pd-catalyzed carbonylative coupling with acylhydrazines. These reactions employed near-stoichiometric amounts of carbon monoxide generated ex situ from a non-gaseous precursor. A range of di(hetero)aryl diacylhydrazines was isolated in good to excellent yields. Furthermore, dehydration conditions were identified that could be used in a compatible one-pot synthesis of 1,3,4-oxadiazoles. The applicability of this method towards 13C-isotope labeling was also demonstrated, with the production of symmetrical and non-symmetrical doubly isotopically labeled 1,3,4-oxadiazoles. Finally, experimental conditions were identified for the carbonylative coupling of aryl bromides with amidoximes and CO producing 1,2,4-oxadiazoles after spontaneous dehydration.