Molybdenum‐Catalyzed Sustainable Friedländer Synthesis of Quinolines

Abstract

Polysubstituted quinolines have been efficiently synthesized from nitroarenes and glycols, as reducing agents, under dioxomolybdenum(VI)catalysis. Interestingly, the waste reduction byproduct is incorporated into the final heterocycle. This method represents an efficient and sustainable variant of the Friedlä nder synthesis of quinolines.

Reductive Molybdenum‐Catalyzed Direct Amination of Boronic Acids with Nitro Compounds

“…[17] Based on these features,a chieving ad irect amination of boronic acids with nitro compounds is amajor milestone,which repurposes these two accessible and simple building blocks as coupling partners delivering an excellent platform to easily construct diverse libraries of valuable aromatic amines.O nly very recently,d uring the preparation of this manuscript, aprotocol for this reaction by using PhSiH 3 as reductant and phosphetane P III /O=P V catalysis was reported by Radosevich and co-workers. [18] Ideally, the design of am oisture and air tolerant procedure and the utilization of an affordable reducing agent would be crucial to provide ageneral, simple and scalable methodology.Based on our experience in molybdenum-catalyzed reactions, [19] we hypothesized that the Mo-catalyzed formation of apartiallyreduced intermediate from an itro compound may allow the direct electrophilic amination of boronic acids (Scheme 1d).…”

Dichlorodioxomolybdenum(VI) Complexes: Useful and Readily Available Catalysts in Organic Synthesis

“…Following this strategy, in 2018 we developed a sustainable variant of the Friedländer synthesis of quinolines (Scheme 22). 52 Starting from easily available 2-nitrophenyl aldehydes or ketones and di-tertiary glycols, a wide variety of polysubstituted quinolines were efficiently prepared under dioxomolybdenum catalysis. Again, a domino process in which the waste byproduct of the initial reduction is used as a reactant for the next step and embodied into the final product, accounts for the obtained result.…”

ZrO2/SO42−/Cu as a Multifunctional, Durable, Efficient, and Heterogeneous Recoverable Inorgano‐Nanocatalyst for the Green Preparation of Quinolines

“…[11] Various Brønsted acid-and Lewis acid-based catalysts as well as transition metalcatalyzed systems have been previously reported for the quinoline synthesis. [12][13][14] Among the recent advances can be pointed to: (1) [MoO 2 ] 2 + , [15] (2) [Mn(CO) 5 Br], [16] (3) microwave, [8] (4) malic acid, [9] (5) α-Chymotrypsin, [17] (6) sulfonyl imidazolium salt, [18] (7) Fe 3 O 4 @SiO 2 @ZnCl 2 , [19] (8) benzylamine, [20] (9) carbon aerogel, [21] (10) calcium silicate nanoparticles, [22] (11) nickel catalyst [Ni(MeTAA)] (MeTAA = tetramethyltetraaza [14] annulene), [23] ionoc liquid@Fe 3 O 4 , [24] CeO 2 -TiO 2 , [25] and Ru-catalyzed hydrogen transfer strategy. [26] However, some impediments are involved with them such as: long reaction times, unstable catalysts, high reaction temperatures, tedious work-up, low yields, high expensive catalyst, and toxic solvents, which limit their application for gram-scale synthesis, and also are not suitable from economicand environmentally friendly points of view.…”

“…Various Brønsted acid‐ and Lewis acid‐based catalysts as well as transition metal‐catalyzed systems have been previously reported for the quinoline synthesis . Among the recent advances can be pointed to: (1) [MoO 2 ] 2+ , (2) [Mn(CO) 5 Br], (3) microwave, (4) malic acid, (5) α‐Chymotrypsin, (6) sulfonyl imidazolium salt, (7) Fe 3 O 4 @SiO 2 @ZnCl 2 , (8) benzylamine, (9) carbon aerogel, (10) calcium silicate nanoparticles, (11) nickel catalyst [Ni(MeTAA)] (MeTAA= tetramethyltetraaza[14] annulene), ionoc liquid@Fe 3 O 4 , CeO 2 ‐TiO 2 , and Ru‐catalyzed hydrogen transfer strategy …”