The high utility of 2,4,6-trichlorophenyl formate, a highly reactive and easily accessible crystalline CO surrogate, is demonstrated. The decarbonylation with NEt(3) to generate CO proceeded rapidly at rt, thereby allowing external-CO-free Pd-catalyzed carbonylation of aryl/alkenyl halides and triflates. The high reactivity of the CO surrogate enabled carbonylation at rt and significantly reduced the quantities of formate to near-stoichiometric levels. The obtained trichlorophenyl esters can be readily converted to a variety of carboxylic acid derivatives in high yields.