Modular Two‐Step Access to π‐Extended Naphthyridine Systems—Potent Building Blocks for Organic Electronics

Abstract

Efficient synthetic approaches for the incorporation of nitrogen into polyaromatic compounds (PACs) in different patterns as stabilising moiety for π‐extended systems and modification tool for optoelectronic properties remain a challenge until today. Herein, we developed a new versatile pathway to napthyridine‐based PACs as non‐symmetric and regioisomeric pendant to pyrazine‐based PACs. A combination of a gold‐catalysed synthesis of 2‐aminoquinolines and the development of an in situ desulfonation and condensation of these precursors are the key steps of the protocol. The shape and type of attached functional groups of the PACs can be designed in a late stage of the overall synthetic procedure by the chosen anthranile and backbone of the ynamide introduced in the gold‐catalysed step. Single‐crystal X‐ray diffraction and the investigation of electronic properties of the compounds show the influence of the attached substituents. All naphthyridine‐based PACs show halochromic behaviour implying their use as highly sensitive proton sensor in non‐protic solvents.

Ligand-Enabled Sustainable Gold Catalysis

“…17,18 As a matter of fact, gold catalysis now finds widespread applications in the synthesis of simple to complex molecular scaffolds such as natural products, biologically relevant molecules, 19−25 and compounds for materials science. 26,27 Despite these remarkable developments in gold catalysis, the requirements of high catalyst loading (usually 2−10 mol %), chlorinated organic solvents, and high temperature have greatly hampered its applicability at the industrial scale. Therefore, the identification and development of efficient gold catalysts that are capable of performing reactions at low loadings and under milder reactions conditions using greener solvents are deemed necessary.…”

“…Owing to the high biocompatibility and low toxicity profile, gold catalysts have become a viable alternative to many of the toxic and hazardous transition metals (for instance, mercury). , The high relativistic effects exhibited by gold complexes make them superior contenders as carbophilic activators. , As a result, gold catalysts have emerged as the privileged π-Lewis acid catalysts, allowing the development of complementary reactivity and selectivity. − Moreover, the significant progress in ligand design and development has further widened the scope of the reactivities and selectivities realized by gold catalysis. , As a matter of fact, gold catalysis now finds widespread applications in the synthesis of simple to complex molecular scaffolds such as natural products, biologically relevant molecules, − and compounds for materials science. , …”

Potential Building Blocks for 1,4‐Dihydro‐N‐heteroacenes

“…N ‐Heteroacenes are of interest for their electronic, [1–3] sensing [4] and fluorescent [5] properties and they have been considered as nanocarbon segments, [6] for two‐photon absorption [7] and for photovoltaics [8] . Progress has also been made in the synthesis of S,N‐heteroacenes which are novel types of sulfur‐nitrogen containing heteroacenes which have a high proportion of heteroatoms [9–11] .…”

Site Isolation in Metal–Organic Layers Enhances Photoredox Gold Catalysis

“…11,12 The (aryl)(phosphine)gold intermediate can also undergo aryl-phosphine reductive elimination to deactivate gold catalysts. 13 While Au catalysts have been used in total synthesis 14,15 and material design, 16,17 catalyst deactivation presents a hurdle to broader application of Au catalysis.…”

“…Homogeneous Au-catalyzed reactions typically require high catalyst loadings (1–10 mol %) due to the relatively low reactivity of Au complexes and rapid catalyst deactivation. , Hammond, Xu, and co-workers proposed the deactivation of Au catalysts via a ligand redistribution to form bis­(phosphine)-Au­(I) and noncoordinated Au­(I) compounds, followed by disproportionation of noncoordinated Au­(I) compounds into Au­(III) species and catalytically inactive Au(0) nanoparticles. , The (aryl)­(phosphine)gold intermediate can also undergo aryl-phosphine reductive elimination to deactivate gold catalysts . While Au catalysts have been used in total synthesis , and material design, , catalyst deactivation presents a hurdle to broader application of Au catalysis.…”