Aromatic Carbon-Nitrogen Bond Research Articles

Conversion of anilines to chiral benzylic amines via formal one-carbon insertion into aromatic C\u2013N bonds

Insertion of atoms into aromatic carbon-nitrogen bonds is an appealing method for the synthesis of nitrogen-containing molecules and it has the advantage of the availability and abundance of anilines. However, the direct cleavage of aromatic carbon-nitrogen bonds is challenging due to the particularly inert and stable nature of these bonds. Here we report a formal, enantioselective one-carbon insertion into an aromatic carbon-nitrogen bond via an aromaticity dissembly-reconstruction process to directly convert anilines to chiral α-branched benzylic amines. The process involves oxidative dearomatization of para-substituted anilines, chiral sulfur ylide-mediated asymmetric aziridination, and subsequent rearrangement. Chiral sulfur ylides serve as one-carbon insertion units.

Formal group insertion into aryl C\u2012N bonds through an aromaticity destruction-reconstruction process

Given the abundance and the ready availability of anilines, the selective insertion of atoms into the aryl carbon–nitrogen bonds will be an appealing route for the synthesis of nitrogen-containing aromatic molecules. However, because aryl carbon–nitrogen bonds are particularly inert, anilines are normally activated by conversion to more reactive intermediates such as aryldiazonium salts to achieve functionalization of the aryl carbon–nitrogen bonds, but the nitrogen atom is usually not incorporated into products, instead being discarded. The selective insertion of groups into aryl carbon–nitrogen bonds remains an elusive challenge and an unmet need in reaction design. Here we show an aromaticity destruction-reconstruction process that selectively inserts a trimethylenemethane (TMM) group into the aromatic carbon–nitrogen bond of anilines concomitant with a benzylic carbon–hydrogen bond functionalization. This process provides a transformative mode for anilines, and the insertion products are versatile precursor to various nitrogen-containing aromatic molecules through simple conversions.

Destruction and Construction: Application of Dearomatization Strategy in Aromatic Carbon–Nitrogen Bond Functionalization

AbstractThe formation of carbon–carbon bonds through the functionalization of aromatic carbon–nitrogen bonds is a highly attractive synthetic strategy in the synthesis of aromatic molecules. In this paper, we report a novel aromatic carbon–nitrogen bond functionalization reaction by using a simple dearomatization strategy. Through this process para‐substituted anilines serve as a potential aryl source in the construction of a range of functionalized aromatic molecules, such as quaternary carbon centers, α‐keto esters, and aldehydes.

Destruction and Construction: Application of Dearomatization Strategy in Aromatic Carbon-Nitrogen Bond Functionalization.

The formation of carbon-carbon bonds through the functionalization of aromatic carbon-nitrogen bonds is a highly attractive synthetic strategy in the synthesis of aromatic molecules. In this paper, we report a novel aromatic carbon-nitrogen bond functionalization reaction by using a simple dearomatization strategy. Through this process para-substituted anilines serve as a potential aryl source in the construction of a range of functionalized aromatic molecules, such as quaternary carbon centers, α-keto esters, and aldehydes.

ChemInform Abstract: Rational Development of Practical Catalysts for Aromatic Carbon-Nitrogen Bond Formation

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Cu(I)‐Catalyzed Intramolecular Cyclization of Ene‐Carbamates: Synthesis of Indoles and Pyrrolo[2,3‐c]pyridines.

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Cu(I)-catalyzed intramolecular cyclization of ene-carbamates: synthesis of indoles and pyrrolo[2,3- c]pyridines

Over the past few years, the use of palladium-catalyzed aromatic carbon–nitrogen bond forming reactions by the cross-coupling of aryl halides or triflates and amines has become a useful synthetic tool. Herein, we describe a copper(I) catalyst system that allows efficient synthesis of functionalized indoles and pyrrolo[2,3- c]pyridines. This method takes advantage of amino acid promoted copper coupling of amines with aryl halides, in particular, the use of the CuI/ l-proline catalyst system.

Palladium‐Catalyzed Aromatic Carbon—Nitrogen Bond Formation

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Direct Aromatic C–N Bond Cleavage Evidenced in the Hydrodenitrogenation of 2,6-Dimethylaniline over Cobalt-Promoted Mo/Al2O3 Sulfide Catalysts: A Reactivity and FT-IR Study

The hydrodenitrogenation of 2,6-dimethylaniline (DMA) was studied over a series of sulfided Co(0–4.7%)–Mo(8.7%)/Al2O3 catalysts at 573 K under 4 MPa total pressure and 0–56 kPa H2S partial pressure. Two NiMo samples were tested for comparison. The reaction network presents three parallel routes: dearomatization of DMA followed by either hydrogenation–elimination to dimethylcyclohexenes and dimethylcyclohexanes, or NH3 elimination to m-xylene, and disproportionation of DMA to 2-methylaniline and 2,4,6-trimethylaniline. We demonstrate that part of the xylene is formed by direct aromatic carbon–nitrogen bond cleavage through a nucleophilic substitution involving hydride species. On CoMo catalysts, in the presence of H2S, the amount of extra xylene is independent of Co content, while the dearomatization is promoted. Without H2S, this special substitution reaction is most important on the Mo catalyst, and strikingly Co acts as a poison. FT-IR spectroscopy of adsorbed carbon monoxide evidences a new type of sites on the sulfided catalysts after a mild hydrogen treatment. We propose that a site configuration located exclusively on unpromoted Mo atoms highly depleted in sulfur is responsible for the direct denitrogenation route. The NiMo couple behaves differently: xylene formation is independent of Ni content, which means that the specific Mo sites for direct C–N bond rupture are poisoned by nickel, even in the presence of H2S. The location of Co and Ni on the MoS2 slabs then appears different.

Ligand-Accelerated Catalysis of the Ullmann Condensation: Application to Hole Conducting Triarylamines

Ligand-Accelerated Catalysis of the Ullmann Condensation: Application to Hole Conducting Triarylamines

Hindered Rotation and Intramolecular Hydrogen Exchange in N-Phenyl-o-hydroxybenzylamines

Non-equivalence of the benzylic hydrogens was found in several N-phenyl-ortho-hydroxybenzyl-amines and, where possible, activation parameters were calculated for the processes causing non-equivalence. Hindered rotation about the aromatic carbon-nitrogen bond was the rate determining process with an ortho-t-butyl group on the aniline ring. Exchange of phenolic and amino hydrogens was studied over a range of temperature and concentration. Both intermolecular and intramolecular exchange were observed. The latter may be the first example of such a process to be studied by n.m.r.