New methods for the synthesis of 4H-dithieno[3,2-b:2′,3′-d]pyrrole

Abstract

Various alternative methods for the synthesis of 4H-dithieno[3,2-b:2′,3′-d]pyrrole (DTP) starting from commercially available bromothiophene precursors are presented. Crucial steps involve the Cadogan reaction, Ullmann-type C─N couplings, or Buchwald-Hartwig–type aminations to build up the central pyrrole ring of DTP, respectively. The use of ammonia surrogates afforded the fused target heteroacene in overall yields of 33% to 63%, and the corresponding methods are applicable on large scale.