Six 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-adamantylsulfanyl)-1,4-dihalo-3-(haloethynyl)benzene derivatives, by treatment with silica gel under thermal conditions. 4,7-Dihalobenzo[b]thiophenes, bearing two different halogen atoms (chlorine, bromine, or iodine), were also prepared from 2-(1-adamantylsulfanyl)3-(ethynyl)-1,4-dihalobenzene derivatives.
Benzo[b]thiophene, 4,7-dibromobenzo[b]thiophene, thieno[3,2-b]thiophene, and 3-bromothieno[3,2-b]thiophene were prepared by AuCl-catalyzed cyclization of (t-butylsulfanyl)(ethynyl)benzenes or (t-butylsulfanyl)(ethynyl)thiophenes. Several reactions of 4,7-dibromobenzo[b]thiophene were investigated, including metallation and cross coupling reactions.
Synthesis of 4,7′-Bibenzo[b]thiophenes Bearing Several Different Substituents at 2-, 2′-, 4′-, and 7-Positions; Structurally Featured Molecular Scaffolds for Selective Substitution
halogen (Br, Cl) and triisopropylsilyl substituents have been synthesized from the two multihalobenzo[b]thiophenes via iodoselective Miyaura borylation reaction using potassium benzoate as a base. Further investigation into the reactivity of 4,7′-bibenzothiophenes in substitution reaction, Suzuki–Miyaura cross-coupling reaction, and C–H direct arylation reaction revealed that tetrasubstituted 4,7′-bibenzothiophenes