All 6 isomers of (bromo)(chloro)(iodo)benzo[b]thiophenes containing three different halogen atoms at the 2-, 4- and 7-positions were synthesized from the corresponding 2-(1-adamantylsulfanyl)-1,4-dihalo-3-(haloethynyl)benzene derivatives, through treatment with silica gel under thermal conditions. In contrast to our previous method using gold chloride catalyst, migration of adamantyl group did not occur in this method using silica gel. Moreover, by using this method, we synthesized 6 types of 4,7-dihalobenzo[b]thiophenes in 4 steps from 2-fluoro-3,6-dihalo-benzaldehydes in moderate to excellent overall yields, 42–82%.
|Number of pages||3|
|Journal||Phosphorus, Sulfur and Silicon and the Related Elements|
|Publication status||Published - 2019 Jul 3|
- facile cyclization
- fused thiophene
- quasi T-shape molecular scaffold