All types of (bromo)(chloro)(iodo)benzo[b]thiophenes bearing halogen atoms at the 2-, 4-, and 7-positions were prepared from the corresponding 2-(1-alkylsulfanyl)-1,4-dihalo-3-(haloethynyl)benzene derivatives, through treatment with silica gel. 4,7-Dihalobenzo[b]thiophenes, bearing two different halogen atoms (chlorine, bromine, or iodine), were also prepared by a similar method.
S. Mikami, H. Tanaka, H. Kishi, S. Yoshida, K. Toyota
Heterocycles, 2018, 96(9) 1529.
DOI: 10.3987/COM-18-13937 https://www.heterocycles.jp/newlibrary/downloads/PDFwithLinks/25997/96/9