Convenient synthesis of α-terthienyl and α-quinquethienyl via a Friedel-Crafts route

Article abstract of DOI:10.1055/s-1991-26494

Thiophene and bithiophene are converted into 1,4-bis(2-thienyl)-1,4-butanedione and the corresponding bis(bithienyl) substituted diketone, respectively, by acylation with succinyl chloride/aluminum chloride in dichloromethane or 1,2-dichloroethane. Reaction of the diketones with Lawesson's reagent gives 2,2': 5',2'-terthiophene or 2,2': 5',2'': 5'',2'': 5''',2''''-quinquethiophene (α-terthienyl or α-quinquethienyl) in high yields. Attempted acylation of α-terthienyl leads to 5,5-bis[5-(2,2'' : 5',2'-terthienyl)]tetrahydrofuran-2-one. As a side-product of the Friedel-Crafts acylation of thiophene a new indigo-like blue dye with α-quaterthienyl framework is isolated.