Brønsted‐Acid‐Catalyzed para‐Selective Diazotization of Anilines with Aryl Diazonium Tetrafluoroborates

Abstract

An efficient brønsted acid‐catalyzed method for the para‐selective diazotization at the aromatic carbon‐hydrogen sites para to an amido substituent in nonpolar solvent is illustrated, using aryl diazonium tetrafluoroborates as diazotization reagents. The direct transformation occurs under mild reaction conditions with ample scope, avoids the use of metals, and is tolerated with valuable functional groups. It is a simple way to generate a broad spectrum of functionalized azo anilines from basic starting materials with good to excellent yields.

Direct Construction of Julolidines via Reductive Annulation of Quinolines and Conjugated Enones by a MOF-Derived Hierarchically Porous Iridium Catalyst

“…In consideration that hexahydrojulolidine constitutes the core structure of numerous bioactive Lycopodium alkaloids, we can synthesize a relevant product 7aa via full hydrogenation of the aryl ring of 3aa in the presence of 15 mol % Rh/C in i -propanol solution (Scheme d). Noteworthily, 1,2-diaryldiazenes are frequently utilized as laboratory indicators and dyes including biological stains . Here, by treating 3aa and 4-methoxyaryldiazonium tetrafluoroborate in DCE solution with diphenyl phosphonic acid catalyst, we efficiently prepared a yellow dye 8aa at room temperature (Scheme e).…”

Photoinduced, Direct C(sp2)−H Bond Azo Coupling of Imidazoheteroarenes and Imidazoanilines with Aryl Diazonium Salts Catalyzed by Eosin Y

“…Therefore, it is not surprising that the synthesis and functionalization of imidazoheteroarenes have received considerable attention in different areas of scientific research . Analogously, arylazo compounds are widely used in several areas, including the chemical industry, pharmaceuticals, chemosensors, electronics, and liquid crystals ( 1 a – d , Figure ) . In this way, very recently, Feringa described the photoisomerization and biological evaluation of a diazo‐based privileged series of novel photoswitchable quorum‐sensing agonists and antagonists …”

“…The development of new synthetic procedures to obtain multitargeted hybrids of these skeletons (arylazo imidazoheteroarenes) in a single structure would be useful, due to their diverse applications ( 1 e , f , Figure ) . Although, there are several reports on the preparation of arylazo compounds,– most of the protocols often suffer from acidic reaction conditions, long reaction times, low temperatures, inert atmospheres, low yields and reduced stability of the diazonium salts at room temperature . The majority of these methods proceed through strong acidic conditions, which limits their use in complex synthesis, especially when the substrates contain an acid‐labile group.…”

“…Furthermore, another main advantage of our method is that it is applicable to substituted anilines. The use of aryl diazonium tetrafluoroborate in such types of coupling is rare and only a limited number of reports are available in the literature . To our delight, when the optimized reaction conditions were tested for N , N ‐disubstituted anilines 7 , the diazo products 8 were obtained in good yields (Scheme ).…”

Conventional and microwave-irradiated synthesis of new bischalcone derivatives

“…It has been reported that they are effective as anti-proliferation agents in lung cancer and as antibacterials and carbonic anhydrase inhibitors. 3,9 Following our recent report of the synthesis of an azo-linked bischalcone with a sulfonamide 10 and a quinoline 11 and considering the pharmacological importance of both bischalcones and azo compounds, we set out to synthesize a new series of bischalcones possessing different…”