Utilization of n-Alkyl Methyl Ketones in the Pfitzinger Reaction¹

Titania‐Supported Iridium Subnanoclusters as an Efficient Heterogeneous Catalyst for Direct Synthesis of Quinolines from Nitroarenes and Aliphatic Alcohols

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Dedicated to the Fritz Haber Institute, Berlin, on the occasion of its 100th anniversary

The use of metal nanoparticles (NPs) or nanoclusters (NCs) as versatile catalysts for green and sustainable organic synthesis has attracted tremendous interest in recent years owing to their unique properties, such as a large surface-tovolume ratio and tunable shapes. [8] The most frequent routes to prepare functionalized quinolines include several named reactions, such as Skraup, [9] Doebner-Von Miller, [10] Conrad-Limpach, [11] Friedländer, [12] and Pfitzinger [13] syntheses based on the reaction of substituted anilines with carbonyl compounds. [2] Although in many classical transformations, reusable supported metal NPs/NCs have exhibited far superior performance than those of conventional metal complex catalysts, [3] the possibilities offered by metal NPs/NCs for sustainable tandem catalysis that allows a rapid increase in molecular complexity through one-pot multistep reactions have scarcely been explored.

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“…[6] Quinolines and their derivatives are an important class of bioactive compounds that are prescribed as antimalarial, antibacterial, antihypertensive, and antiinflammatory drugs. [8] The most frequent routes to prepare functionalized quinolines include several named reactions, such as Skraup, [9] Doebner-Von Miller, [10] Conrad-Limpach, [11] Friedländer, [12] and Pfitzinger [13] syntheses based on the reaction of substituted anilines with carbonyl compounds. [8] The most frequent routes to prepare functionalized quinolines include several named reactions, such as Skraup, [9] Doebner-Von Miller, [10] Conrad-Limpach, [11] Friedländer, [12] and Pfitzinger [13] syntheses based on the reaction of substituted anilines with carbonyl compounds.…”

“…[7] In addition, quinolines are valuable synthons used for the preparation of nanostructures and polymers that combine enhanced electronic, optoelectronic, or nonlinear optical properties with excellent mechanical properties. [8] The most frequent routes to prepare functionalized quinolines include several named reactions, such as Skraup, [9] Doebner-Von Miller, [10] Conrad-Limpach, [11] Friedländer, [12] and Pfitzinger [13] syntheses based on the reaction of substituted anilines with carbonyl compounds. Despite their utility, these methods often suffer from the requirement of costly aromatic amines and unstable carbonyl compounds, harsh conditions, and the use of large amounts of hazardous acids or bases.…”

“…[19] Summarizing these experiments, we observed that small Ir NPs (average size ca. 1.5 nm) supported on titanium oxide (denoted as Ir/TiO 2 -NPs, Ir content: 1 wt %; see the Supporting Information for preparation details) gave an impressive conversion of nitrobenzene to afford 3 a in 63 % yield at 120 8C within 8 h ( [10][11][12][13].…”

Cobalt and Nickel Catalyzed Reactions Involving CH and CN Activation Reactions

“…Catalytic processes employing palladium [4 -6] , rhodium [7 -9] , ruthenium [10 -14] , and iron [15] have been studied and developed to synthesize quinoline skeletons. There are fi ve common methods used to prepare substituted quinolines: the Skraup reaction [16] , the Doebner -Von Miller reaction [17] , the Conrad -Limpach reaction [18] , the Friedlaender reaction [19,20] , and the Pfi tzinger reaction [21,22] . All fi ve of the reactions require environmentally unfriendly acids or bases, high temperatures, or harsh conditions.…”