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.

Broadly Applicable Synthesis of Arylated Dithieno[3,2‐b:2′,3′‐d]pyrroles as Building Blocks for Organic Electronic Materials

“…We have recently disclosed a straightforward and safe method for the large‐scale synthesis of basic 4 H −dithieno[3,2‐ b :2′,3′‐ d ]pyrrole 1 ( H −DTP). [11] This progress now allowed us to test and optimize the synthesis of a variety of arylated DTPs comprising larger aryls and acenes by Pd‐ or Cu‐catalyzed coupling of H −DTP 1 and well available aryl and acene halides 2 a – k (Scheme 1 ). The resulting N‐arylated and N‐acene‐substituted DTPs represent interesting building blocks for functional materials applicable in organic electronics.…”

Dithieno[3,2‐b:2′,3′‐d]pyrrol‐Cored Hole Transport Material Enabling Over 21% Efficiency Dopant‐Free Perovskite Solar Cells

“…The synthesis for DTP‐C6Th is outlined in Scheme , and detailed procedures are available in the Supporting Information. DTP‐tin regent was prepared via a three‐step procedure, i.e., cyclization, Buchwald–Hartwig cross‐coupling and preparing tin reagent following earlier procedures . TPA derivative was prepared according to literature .…”

“…DTP-tin regent was prepared via a three-step procedure, i.e., cyclization, Buchwald-Hartwig cross-coupling and preparing tin reagent following earlier procedures. [43,52] TPA derivative was prepared according to literature. [27,53] The target compound DTP-C6Th was then synthesized by a Pd-catalyzed Stille coupling reaction.…”

Synthesis and characterization of S,N-heterotetracenes

“…Well-known examples are the reductive cyclization of 2-nitro-1,1’-biphenyls with triethyl phosphite or phosphanes as reducing agent to provide carbazoles covering a wide substrate and functional group spectrum [ 41 ]. Moreover, penta- and heptafused heteroacenes were prepared by the Cadogan reaction by annulation of nitrophenyl or nitrobenzothienyl precursors [ 42 – 45 ]. In this respect, we recently reported a Cadogan cyclization of 3-nitro-2,2’-bithiophene with triethyl phosphite under microwave irradiation and surprisingly obtained targeted heterotriacene H -DTP (vide supra ) with only 11% yield [ 45 ].…”

“…Moreover, penta- and heptafused heteroacenes were prepared by the Cadogan reaction by annulation of nitrophenyl or nitrobenzothienyl precursors [ 42 – 45 ]. In this respect, we recently reported a Cadogan cyclization of 3-nitro-2,2’-bithiophene with triethyl phosphite under microwave irradiation and surprisingly obtained targeted heterotriacene H -DTP (vide supra ) with only 11% yield [ 45 ]. This result prompted us to have a closer look on the applicability of the Cadogan reaction/cyclization in order to provide S,N -heterotetracenes and related derivatives from nitro-substituted thiophene-based precursors.…”