Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• academic research and industrial applications. As a result, significant efforts have been devoted to the development of various methods for the reduction of nitroarenes [39]. Recent advancements in the catalytic reduction of nitroarenes largely rely on transition-metal catalysis through direct

• nitroarenes 48 (Scheme 22). The protocol demonstrated excellent tolerance towards a wide range of reducible functional groups, including halogens (such as chlorine, bromine, and even iodine), aldehydes, ketones, carboxyl groups, and cyano groups. Iodination Alkyl iodide is considered to be the most reactive

• photocatalytic decarboxylative radical cascade alkylarylation. Proposed mechanism of the NaI/PPh3-driven photocatalytic decarboxylative radical cascade cyclization. Visible-light-promoted decarboxylative cyclization of vinylcycloalkanes. NaI/PPh3-mediated photochemical reduction and amination of nitroarenes

Clauson–Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

• Dileep Kumar Singh and
• Rajesh Kumar

Beilstein J. Org. Chem. 2023, 19, 928–955, doi:10.3762/bjoc.19.71

• aromatization steps led to product 43 upon catalyst regeneration. Recently, Ryabchuk et al. [74] used the 3d-metal cobalt catalyst Co/NGr-C@SiO2-L under solvent-free conditions to synthesize various N-aryl-substituted pyrroles 45 in 50–88% yields from the corresponding nitroarenes 44 via the Clauson–Kaas

• reaction involving benign reducing agents H2 or HCOOH or CO/H2O mixtures (Scheme 21). The main advantage of this heterogeneous Co catalyst is that it can be used up to 10 times without significant loss of activity and the active cobalt hydride species selectively reduces nitroarenes to their corresponding

Mild and selective reduction of aldehydes utilising sodium dithionite under flow conditions

• Nicole C. Neyt and
• Darren L. Riley

Beilstein J. Org. Chem. 2018, 14, 1529–1536, doi:10.3762/bjoc.14.129

• piperidines [17], benzil groups [19], nitroarenes and nitroalkanes in the presence of dialkyl viologen electron transfer catalysts [20][21] and immobilized nitroarene’s under phase transfer conditions [22][23]. In this publication we report the efficient reduction of aldehydes under flow conditions utilising

Transition-metal-free [3 + 3] annulation of indol-2-ylmethyl carbanions to nitroarenes. A novel synthesis of indolo[3,2-b]quinolines (quindolines)

• Michał Nowacki and
• Krzysztof Wojciechowski

Beilstein J. Org. Chem. 2018, 14, 194–202, doi:10.3762/bjoc.14.14

• Michal Nowacki Krzysztof Wojciechowski Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland 10.3762/bjoc.14.14 Abstract Indol-2-ylmethyl carbanions stabilized by alkoxycarbonyl, cyano or benzenesulfonyl groups react with nitroarenes to form σH-adducts

• , which in the presence of base (triethylamine or DBU) and trimethylchlorosilane transform into indolo[3,2-b]quinoline derivatives in moderate to good yields. Keywords: carbanions; cyclization; heterocycles; nitroarenes; nucleophilic substitution; silylation; Introduction The indolo[3,2-b]quinoline

• pharmaceutical applications [19]. During our studies on the reactions of nitroarenes with nucleophiles [20][21][22][23], particularly carbanions, we were interested in a direct transformation of the formed σH-adducts into heterocyclic systems – indoles [21][23] and quinolines [21][22]. Quinolines were formed

Nitration of 5,11-dihydroindolo[3,2-b]carbazoles and synthetic applications of their nitro-substituted derivatives

• Roman A. Irgashev,
• Nikita A. Kazin,
• Gennady L. Rusinov and
• Valery N. Charushin

Beilstein J. Org. Chem. 2017, 13, 1396–1406, doi:10.3762/bjoc.13.136

• anthraquinones. Anyway, the discussed transformation is the case of unusual reduction of nitroaromatic compounds. In general, the chemical reactions, leading to direct displacement of the nitro group in nitroarenes with a hydrogen atom, are rare phenomena. For instance, we can mention the reaction of

Continuous-flow synthesis of primary amines: Metal-free reduction of aliphatic and aromatic nitro derivatives with trichlorosilane

• Riccardo Porta,
• Alessandra Puglisi,
• Giacomo Colombo,
• Sergio Rossi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2016, 12, 2614–2619, doi:10.3762/bjoc.12.257

• conditions, but the presence of noble metal catalysts, packed into disposable cartridges, suffers from functional group compatibility and catalyst poisoning during time. In 2012 Kappe’s research group reported the microwave-assisted continuous-flow synthesis of anilines from nitroarenes using hydrazine as

• . Using both 0.5 mL and 5 mL reactors, under the best reaction conditions, the continuous-flow reduction of different nitroarenes was studied (Scheme 2). As already demonstrated for the batch procedure [8], the reaction in continuo tolerates a large variety of functional groups: aromatic nitro groups are

An efficient synthesis of N-substituted 3-nitrothiophen-2-amines

• Sundaravel Vivek Kumar,
• Shanmugam Muthusubramanian,
• J. Carlos Menéndez and
• Subbu Perumal

Beilstein J. Org. Chem. 2015, 11, 1707–1712, doi:10.3762/bjoc.11.185

• transformation generates two C–C bonds in a single operation and presumably proceeds through a reaction sequence comprising 2-mercaptoacetaldehyde generation, nucleophilic carbonyl addition, annelation and elimination steps. Keywords: C–C bond generation; nitroarenes; nitroketene acetals; sulfur heterocycles

Continuous flow nitration in miniaturized devices

• Amol A. Kulkarni

Beilstein J. Org. Chem. 2014, 10, 405–424, doi:10.3762/bjoc.10.38

• the dehydrating agent [17]. Theoretically, the application of undiluted nitric acid – usually used in excess – is expected to avoid the use of water. In practice, however, the separation of nitroarenes is facilitated in the diluted nitric acid. Nitration with diluted nitric acid generates the

• of different nitroarenes (e.g. nitroglycerin, ethylene glycol dinitrate, diethylene glycol dinitrate, cyclotrimethylenetrinitramine, pentaerythritol tetranitrate, nitrocellulose, etc.). Continuous processes were enforced as they allowed to retain the same scale of operation while keeping the plant

Synthesis of SF₅-containing benzisoxazoles, quinolines, and quinazolines by the Davis reaction of nitro-(pentafluorosulfanyl)benzenes

• Petr Beier and
• Tereza Pastýříková

Beilstein J. Org. Chem. 2013, 9, 411–416, doi:10.3762/bjoc.9.43

• of nitroarenes with nucleophiles have been the focus of many investigations and represent processes that provide a range of useful products. These reactions can proceed in several ways: (a) ipso substitution of the nitro group of nitroarenes; (b) substitution of a halogen in halogen-substituted

• nitroarenes; and (c) substitution of hydrogen in ortho- or para-positions to the nitro group through vicarious or oxidative nucleophilic substitutions. Mechanistic studies have revealed that in all of these reaction pathways, the primary process is the reversible addition of nucleophiles to the ring carbon

Synthesis of diverse indole libraries on polystyrene resin – Scope and limitations of an organometallic reaction on solid supports

• Kerstin Knepper,
• Sylvia Vanderheiden and
• Stefan Bräse

Beilstein J. Org. Chem. 2012, 8, 1191–1199, doi:10.3762/bjoc.8.132

• results in the liquid phase, ortho,ortho-unsubstituted nitroarenes also delivered indole moieties in good yields. Subsequent palladium-catalyzed reactions (Suzuki, Heck, Sonogashira, Stille) delivered, after cleavage, the desired molecules in moderate to good yields over four steps. The scope and

• reactions have been used to create the indole core. Among these, the Bartoli reaction is a straightforward route for the generation of the indole moiety starting from nitroarenes. Some limitations of this useful reaction have been reported, e.g., only ortho-substituted nitroarenes gave good yields of the

• ], palladium-catalyzed indole synthesis [34][35][36][37][38][39][40], cycloaddition strategies [41], C-arylation of substituted acetonitriles or 1,3-dicarbonyl compounds [42], halocyclization [43][44] and finally, reduction of ortho-fluoro-nitroarenes [42]. The significant biological properties and the

Chemoselective reduction of aldehydes by ruthenium trichloride and resin- bound formates

• Basudeb Basu,
• Bablee Mandal,
• Sajal Das,
• Pralay Das and
• Ashis K. Nanda

Beilstein J. Org. Chem. 2008, 4, No. 53, doi:10.3762/bjoc.4.53

• stable and potent hydride source in Pd-catalyzed transfer hydrogenation of functionalized alkenes, imines, nitroarenes and 1,2-diketones [23][24]. Danks et al. also carried out reduction of alkyl cinnamates using polymer supported formate and catalytic RhCl(PPh3)3 (2.5 mol%) under microwave irradiation

• [25]. Pd-catalyzed transfer hydrogenation of nitroarenes using recyclable polymer-supported formate has been investigated by Abiraj et al [26]. Neither of these conditions were, however, effective in reducing aryl ketones. Since aryl alcohols are important compounds, we became interested to look at