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General procedure for the synthesis of 4-iododibenzofuran from dibenzofuran: 20 g (55 mmol) of dibenzofuran and 200 mL of tetrahydrofuran were added to a 500 mL three-necked flask, and a magnetic stirrer was turned on to mix the ingredients thoroughly. After the reaction system was cooled to -78 °C, 41 mL (66 mmol) of 1.6 M n-butyllithium hexane solution was slowly added dropwise, and the rate of dropwise acceleration was controlled to avoid violent exotherm. After the dropwise addition, the reaction mixture was gradually warmed up to room temperature with continuous stirring for 4 hours. The reaction system was again cooled to -78 °C and 16.7 g (66 mmol) of iodine monomer was added, followed by warming to room temperature and continued stirring for 2 hours. Upon completion of the reaction, the reaction was quenched by the addition of an appropriate amount of aqueous sodium thiosulfate and separated by extraction with ethyl acetate and deionized water. The organic phases were combined, dried over anhydrous sodium sulfate and concentrated under reduced pressure to remove the solvent. The crude product was purified by recrystallization to give 20.4 g of 4-iododibenzofuran in white crystalline form in 91% yield.

[1] Patent: KR2017/55704, 2017, A. Location in patent: Paragraph 0079-0085
[2] Synthesis (Germany), 2017, vol. 49, # 19, p. 4500 - 4516
[3] Patent: KR2015/124677, 2015, A. Location in patent: Paragraph 0321-0325
[4] Patent: EP2594573, 2013, A1. Location in patent: Paragraph 0105
[5] Patent: KR2015/114636, 2015, A. Location in patent: Paragraph 0393-0398