1,4‐Dihydropyrrolo[3,2‐b]pyrrole and Its π‐Expanded Analogues

Abstract

Various approaches to the synthesis of 1,4-dihydropyrrolo[3,2-b]pyrroles are summarized. Many two- and three-step reaction sequences have been developed, and have allowed access to a broad variety of structures, including not only the parent 1,4-dihydropyrrolo[3,2-b]pyrroles, but also their π-expanded analogues. The newest approaches are critically compared with older strategies. The reactivity of these compounds is also reviewed, with special emphasis on electrophilic aromatic substitution. The synthesis of indolo[3,2-b]indole derivatives has been the subject of intense investigation. Overall, a few interesting and ingenious approaches toward these ladder-type heteroacenes have been proposed, reaching total yields in the region of 30%. Finally, the optical, electrochemical, and other physicochemical properties are presented in the broader perspective of heteropentalenes. The parent 1,4-dihydro-pyrrolo[3,2-b]pyrroles constitute the most electron-rich, simple, aromatic heterocycles, and their simple derivatives and π-expanded analogues possess strong violet, blue, or green fluorescence both in solution and in the solid state.

Fused Pyrrole Core: A New Class of Quadrupolar Organic Moieties as Potential Resistive Memory Elements

“…The hypothesis that NH-π interaction ensures conjugation of electrons in either direction and increases the charge mobility is an interesting proposition to explore further. 8,10 Even so, the prospect remained largely unexploited until 2013, owing to the lack of an effi cient synthesis strategy. A simple one-pot-domino reaction to synthesize DHPP`s with relatively moderate yields developed by Gryko et al 11 (Figure 1) were synthesized following reported protocols.…”

Water‐Soluble Pyrrolo[3,2‐b]pyrroles: Synthesis, Luminescence and Two‐Photon Cellular Imaging Properties

“…These compounds have received increasing interest since Gryko and co‐workers developed a one‐pot synthetic process to access tetraaryl‐pyrrolo[3,2‐ b ]pyrroles in 2013 . PPs have high thermal and photo‐stability, high fluorescence quantum yields, good absorptivity and optical brightness . Along with thieno[3,2‐ b ]thiophenes, PPs are also attractive materials in current optoelectronics and in sensors…”

The Influence of Structural Variations on the Heteroacenes Containing Dihydropyrrolo[3,2‐b]pyrrole Core on Their OFET Performances

“…Our attention is focused on heteroacenes bearing a dihydropyrrolo[3,2‐ b ]pyrrole core. The pyrrolo[3,2‐ b ]pyrrole core is more electron‐rich than thieno[3,2‐ b ]thiophene, and the open valence on the N atom might be utilized to modify the solubility of the molecule for solution‐processable organic semiconductor . In the past several years, heteroacenes bearing a dihydropyrrolo[3,2‐ b ]pyrrole core have attracted an increasing attention as building blocks for organic light‐emitting diodes (OLEDs), organic solar cells (OSCs), and OFETs .…”

“…The pyrrolo [3,2-b] pyrrole core is more electron-rich than thieno [3,2-b]thiophene, and the open valence on the N atom might be utilized to modify the solubility of the molecule for solution-processable organic semiconductor. [5] In the past several years, heteroacenes bearing a dihydropyrrolo [3,2-b]pyrrole core have attracted an increasing attention as building blocks for organic light-emitting diodes (OLEDs), [6] organic solar cells (OSCs), [7] and OFETs. [8] For instance, Park et al [8b] synthesized a dihydropyrrolo [3,2-b]pyrrole based π-conjugated molecule with an exceptionally field-effect high hole mobility of 0.79 cm 2 V À 1 s À 1 .…”