nitroarenes can be obtained by

Copyright © 2020 Elsevier B.V. or its licensors or contributors. (1995), and Nielsen (1995, 1996). Interestingly, here the addition of catalytic amounts of triethylamine (TEA) significantly improved the reaction rate: with just 5 mol % TEA, 95 % conversion was achieved (entry 2). Treatment of either 2-alkenylthioanilides <05H(66)241> or 2-(1-alkenyl) imidoyltellurides <05SL1893> provided 2,3-disubstituted indoles. [a] newly reported compound. The protocol is simple and safe because no high pressure equipment is needed for reduction and the product can be easily separated out from reaction mixture by simple centrifugation. Number of times cited according to CrossRef: Cobalt-Catalyzed Synthesis of Pyrroles from Nitroarenes, anie202007613-sup-0001-misc_information.pdf. The mild reaction conditions allowed for the late-stage C2 deuteration of sumatriptan, an indole-containing migraine drug (17ACSC7182). Upon further optimization of this reaction, ruthenium cyclic amine or bipyridine complexes were observed to possess significantly improved reactivity, and amination of adamantane, cyclohexene, ethylbenzene, cumene, indane, tetralin, and diphenylmethane afforded N-substituted sulfonamides in 80%–93% yields.60 Using an in situ formation of the iminoiodinane, high yields up to 89% could also be achieved. An asymmetric Heck cyclization reaction of triflate 108 led to dihydrocarbazole 109, which upon treatment with acid led to fused (iminoethano)carbazole 110 <05JA10186>. In an alternative strategy that has proven efficacious, Barbas and coworkers exploit the unique properties of a class of catalytic aldolase antibodies, often referred to in this context as “chemically programmed” (cpAb) antibodies. Deuterated pyrrole 113 was prepared with 94% deuterium incorporation from the corresponding pyrrole via an iridium-catalyzed hydrogen isotope exchange. Learn more. In this reaction, tertiary amines are the typical products and no secondary amine can be generated. Please check your email for instructions on resetting your password. The thiadiazine (31) also functions as a diene and undergoes further cycloaddition with the azadienophile (see Section 6.13.5.1). is available on our Permission Requests page. In addition, reductive aminations to prepare a wide variety of amines were realized.11 Apart from such basic C−N bond forming reactions, the synthesis of important N‐heterocycles has been explored to a lesser extent. Our robust catalyst can be used up to ten times without significant loss of activity. A variety of functional groups are tolerated on the phenylhydrazine including ethers, halides, and nitro groups (55%–91% yield, 19 examples; 17ACSO5000). An interesting feature of most of these catalysts is the presence of 3d‐metal/3d‐metal oxide core–shell nanoparticles embedded in N‐doped carbonaceous material.8, 9, 10 This specific architecture is believed to be crucial for the activation of hydrogen and related processes. (1994), Hayakawa et al. Distribution and (Yields) of Nitro-PAH Isomers (a) Formed from the Gas-Phase Reactions of Selected Volatile and Semivolatile PAHs with OH Radicals and NO3 Radicals (Each in the Presence of Oxides of Nitrogen), (b) Formed by Electrophilic Nitration, and (c) Present in Diesel Exhausta,b. Heck cyclization reactions of o-halo-N-(2-alkenyl)anilines have proven useful for the development of type Ic approaches to indoles. By continuing you agree to the use of cookies. Inspired by the recent success of M/N/C materials to promote selective hydrogenations of nitroarenes in the presence of sensitive functional groups, we became interested in the ability of these materials for pyrrole synthesis from nitroarenes. Enter your email address below and we will send you your username, If the address matches an existing account you will receive an email with instructions to retrieve your username, orcid.org/http://orcid.org/0000-0001-5709-0965, I have read and accept the Wiley Online Library Terms and Conditions of Use, ange202007613-sup-0001-misc_information.pdf, Take me to the International Edition version. In the presence of 1.8 mol % Co/NGr‐C@SiO2‐L under solvent‐free conditions, the starting nitroarenes were converted to their corresponding N‐phenylpyrroles. A) Co‐catalyzed synthesis of pyrroles from nitroarenes. More specifically, these nitroarenes were fully converted into the corresponding anilines, however, due to the basicity of the reaction media, condensation with dicarbonyl compounds and DMTHF was inefficient. Information about reproducing material from RSC articles with different licences Steric inhibition to the approach of the two reactants by the 2-hydroxy group is cited as a possible explanation for this failure 〈93SC107〉. Synthetic methodologies, such as tandem, domino, or cascade reactions, involve multiple reaction steps in a single pot. Fetching data from CrossRef. TABLE 10.33. Since its discovery in 1884,18, 19 the latter reaction (1,4‐diketones and primary amines) remains a reliable transformation that continues to be used, for example, in the total synthesis of natural products. F. Ragaini, in Reference Module in Chemistry, Molecular Sciences and Chemical Engineering, 2016. This alternative protocol uses formic acid, which is readily available from bio‐waste and does not require any special experimental setup, such as high‐pressure autoclaves. Reaction conditions: 0.5 mmol nitroarene, HCOOH/TEA 5:2 mixture (1.75 mmol HCOOH, 0.7 mmol TEA), 40 mg catalyst, 100 °C, 0.8 mL 2,5‐hexanedione, 24 hours. Obviously, the direct use of nitroarenes in Paal–Knorr type reactions has an attractive step‐economic advantage over anilines. While Chung demonstrated the principal feasibility of using CO/H2O as a hydrogen source in a single example using a Co2Rh2/C catalyst,23 Guerrero‐Ríos and co‐workers used formic acid as a reductant in the presence of stabilized rhodium nanoparticles in ionic liquids (two examples).24 In fact, only the Zhang group developed a general catalyst for the reaction of nitroarenes with formic acid to give pyrroles.25 To the best of our knowledge, only one report (one example) for such transformations using H2 is known, which is based on Pt and Pd as noble metals.26. A solution phase example involved the treatment of N-methylaniline 101 with iodine leading to 3-iodoindole 102 <05JOC9985>. N-Methylpyrrole was arylated with phenylhydrazine under transition metal-free conditions to give pyrrole 108 in 75% yield. The key transformation in these cobalt‐catalyzed pyrrole syntheses is the selective reduction of nitroarenes with active cobalt hydride species. The optimal catalytic system Co/NGr@SiO 2 ‐L is obtained … In addition to pyrroles, the amide bioisostere could be introduced to indoles, pyridines, and other heterocycles in good yield (17OL4090). As seen in Table 10.34, the isomeric distribution of the nitro-PAHs in diesel exhaust particles is consistent with electrophilic nitrations of their parent PAHs. was required to get decent yields as both the reactant and the solvent.

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