π‐Extended Polyaromatic Hydrocarbons by Sustainable Alkyne Annulations through Double C−H/N−H Activation

Abstract

The widespread applicationso fs ubstitutedd iketopyrrolopyrroles (DPPs) call for the development of efficient methods for their modular assembly.H erein,w e presentap-expansion strategy for polyaromatich ydrocarbons (PAHs) by CÀHa ctivationi nasustainable fashion. Thus, twofold CÀH/N-Ha ctivationsw ere accomplishedb y versatile ruthenium(II)carboxylatec atalysis,p roviding stepeconomical access to diversely decorated fluorogenic DPPs that was merged with late-stage palladium-catalyzed CÀHa rylation on the thus-assembled DPP motif.Since their first synthesis, [1] diketopyrrolopyrroles (DPPs) have attracted great attentionf rom researchers from various research arenas, including optoelectronic material sciences [2] and bioimaging. [3] These inconspicuous smallo rganic DPP molecules exhibit versatile propertiesr anging from low solubility, chemicalr esistance, outstanding stabilities and distinct colors, which render them excellent pigments. [4] N-Alkylationl eads to DPPs with improved solubilities,t he properties of which can be fine-tuned by the incorporationo fd ifferent aromatic motifs. [3] Due to their strong electron-withdrawing ability and opticalp roperties, DPPs are widely used as small molecules and conjugated semiconducting polymers in organic solarc ells (OSCs), [2a-e, g, 5] organic field-effect transistors (OFET), [2f, 6] organic photovoltaic cells (OPVs), [7] as well as fluorescentp robes, [3, 8] photocatalysts, [9] photosensitizers [10] or photothermal therapy agents, [11] promisinga nnihilatorm olecules, [12] self-assembled dyes, [13] and bioconjugated hybrids. [14] DPP derivatives with ah ighly decorated periphery as wella s DPP-based polymers are usually obtainedt hrough convention-

Multiple annulations of inert C(sp2)–H bonds with alkynes

“…Ackermann and co-workers demonstrated a Ru( ii )-catalyzed oxidative symmetrical double annulation of diketopyrrolopyrroles (DPPs; 76 ) that involves C–H/N–H bonds with alkynes builds π-conjugated fluorogenic DPPs 77 in moderate yields (Scheme 24D). 45 Furthermore, Pd-catalyzed oxidative di C–H arylation of thiophene motifs 77 could make new π-extended DPPs with improved photophysical properties.…”

Transition Metal‐Catalyzed Intermolecular Cascade C−H Activation/Annulation Processes for the Synthesis of Polycycles

“…In 2019, Ackermann's group reported a ruthenium(II)‐catalyzed double C−H activation/annulation from diketopyrrolopyrroles and alkynes for the synthesis of polyaromatic hydrocarbons in a sustainable and step‐economical fashion (Scheme 37). [67] …”

Rh(III)-Catalyzed Dual C–H Activation/Cascade Annulation of Benzimidates and CF3-Imidoyl Sulfoxonium Ylides for the Synthesis of Trifluoromethyl-Decorated Benzo[de][1,8]naphthyridines

“…The introduction of different heteroatoms into the aromatic moiety can modulate the physicochemical properties of PAHs . In recent years, the transition-metal-catalyzed C–H activation/annulation of arenes and heteroarenes with a transformable directing group has emerged as a powerful and straightforward approach for the construction of complex fused aromatic frameworks . In these transformations, the dual C–H activation reaction and annulation with the appropriate directing group usually occur sequentially.…”