Under the optimal conditions (Table ), we investigated the generality of this concept (Table ). First, we examined substrates bearing various electron-withdrawing substituents on their benzene rings (1b and 1c). Both the bromocyclization and aromatization reactions required methanesulfonic acid (MsOH) and long reaction times (72 h) to achieve satisfactory yields. Iodothiophene 5c was also obtained in an acceptable yield with MsOH; otherwise, the conversion was very low. In contrast, the presence of only an electron-donating methoxy group allowed obtaining the corresponding iodothiophene 5d in a 60% yield, whereas the treatment of 1d with NBS led to the formation of a complex product mixture. We then synthesized iodothiophene 5e and its dihydro form 3e, a key intermediate of tubulin targeting agents, by this method in excellent yields on the 1.5 mmol scale. Notably, Flynn et al. synthesized 5e from alkynoic sulfides via iodocyclization and DDQ oxidation in two steps. 2,3'and 2,2'-iodobithiophene could be prepared by the same method (5f and 5g). Next, trisubstituted thiophenes were synthesized by introducing a phenyl group to the methylene linker in the alkynoic thioester. A simple treatment of 1h with NBS afforded 4h in a low yield due to the unavoidable formation of dibromothiophene 4h'. Although the iodocyclization of 1h with NIS proceeded well, the yield of iodothiophene 5h was unsatisfactory owing to the slow oxidative aromatization. On the other hand, 1i favored the synthesis of bromothiophene 4i. Since the oxidative aromatization of dihydrothiophene 3i with NIS was insufficient, 5i was obtained in a low yield. Next, we examined the applicability of non-aryl substituents on alkynes in this reaction. The treatment of alkyl-substituted 1j or 1k with NBS did not produce neither dihydrothiophenes nor thiophenes. This result will be discussed along with the proposed mechanism in Scheme 3. The iodocyclization of each of 1j and 1k with 2 equiv. of NIS provided the dihydrothiophenes 3j and 3k, respectively. An acceptable yield of the corresponding thiophene 5j could not be obtained even with 4 equiv. of NIS (29% NMR yield).