As shown in Figure , an H-shaped reaction glass tube (COware) was employed as the two-chamber system. One side of the system (Chamber A, 5 mL) contained an aqueous ClO2 • solution prepared through the mixing of sodium chlorite with HCl. The other side of the system (Chamber B, 2 mL) contained a CHCl3 solution with the substrate. When visible-light irradiation from an LED light (λ = 405 nm) was applied to the whole vessel, gaseous ClO2 • was generated from Chamber A. The generated ClO2 • gas traveled through the glass-tube bridge connecting the two chambers, to dissolve in the CHCl3 solution in Chamber B. After 40 min of visible-light irradiation, when the deuterated CHCl3 was used without substrate, COCl2 was generated in the CHCl3 and confirmed through an observation of the characteristic signal of its carbonyl carbon at 143 ppm in its 13 C NMR spectrum. (Figure ). Encouraged by this result, we commenced the study by employing N-methylaniline 1a as the model amine substrate for reaction condition optimization (Table ). The target carbamoyl chloride 2a was obtained with an 84% NMR yield when 4 equivalents of ClO2 • and 5 equivalents of NEt3 as the base were applied under the visible-light irradiation of 90 mW cm -2 LED at room temperature (Entry 1). A decrease in the visible-light intensity of the reaction decreased the 2a yield to 78% (Entry 2), and the reaction did not occur under the dark condition (Entry 3). An increase in ClO2 • effectively afforded 2a with a 93% yield (Entry 4). On the other hand, the yield of 2a decreased slightly and a small amount of the urea 3a byproduct was obtained when the ClO2 • decreased (Entry 5). A brief base screening revealed that diisopropylethylamine (DIPEA) was optimal, and the applications of less than two equivalents of DIPEA resulted in poor yields (Entries 7-10). Furthermore, we investigated the optimal conditions to obtain urea 3a, and the best results were obtained when ClO2 • was decreased to one equivalent and pyridine was used as the base (Entry 13). It is considered that the pyridine activates the carbamoyl chloride and promotes the addition of a second amine. Because a change in the amount of ClO2 • or a decrease in the amount of pyridine led to a decrease in the 3a yield, Entry 13 was chosen as the optimal reaction condition for urea production. Using the optimized reaction conditions, we investigated the substrate scopes of the phosgenation reactions of N-nucleophiles (Figure ). First, the scopes of different aromatic amine (aniline) derivatives were examined. Both anilines with electron-donating and electron-withdrawing substituents afforded their corresponding carbamoyl chlorides (2b and 2c) in good yields. Interestingly, allyl-substituted aniline 1d and iminostilbene 1e underwent phosgenation reactions to afford their desired products in moderate yields and without side reactions such as chlorination of the double alkenyl C=C bond. However, trace amounts of the product were detected when the diphenylamine 1f was used as the substrate. This is partly owing to the lower nucleophilicity of the 1f compared with those of the N-methyl anilines 1a-c. In the case of the conformationally-restricted cyclic derivatives, an unknown byproduct was observed and was likely because of its higher reactivity. Hence, the desired products 2g and 2h were obtained in high yields through a decrease of ClO2 • to 4 equivalents. Aliphatic amines were compatible in the reactions and afforded the related products in moderate-to-good yields.