tert-Butyl nitrite mediated nitrogen transfer reactions: synthesis of benzotriazoles and azides at room temperature

N-nitrosamine directed stereoselective O-glycosylation reactions of 2-amino thioglycosides with NIS-TfOH

We described here the stereoselective synthesis of O-glycosides from 2-amino thioglycosides using N-nitrosamine as the directing group. The reaction was activated by using the NIS/TfOH system in dichloromethane at -10 °C. Various sugar and non-sugar acceptors were successfully glycosylated with 2-amino 1-thioglucoside and 2-amino 1-thiogalactoside under mild reaction conditions. These reactions provided β-glycosides in good to excellent yields.

1,2-Bis-Triazenylarenes Enable Vicinal Sandmeyer-Type Reactions

The introduction of two nucleophiles in the vicinal position of arenes via Sandmeyer-type reactions is compromised by the problematic diazotization of ortho-diaminoarenes. Herein, it is shown that vicinal substitution reactions are facilitated by the use of 1,2-bis-triazenylarenes. Two distinct methodologies for the synthesis of these triazenes are presented. The first approach involves the sequential conversion of 1-amino-2-iodoarenes into first mono- and then bis-triazenylarenes. The second procedure is based on Ru-catalyzed [2 + 2 + 2] cycloaddition reactions between diynes and a 1,2-bis-triazenylalkyne. The two triazene groups in the products can be substituted sequentially by a range of nucleophiles including fluoride, chloride, bromide, iodide, azide, hydroxide, methoxide, and acetamide.

Visible Light-Induced Sequential Nitrogen Insertion and Benzotriazolation of Quinoxaline-2(1H)-ones

Herein, we report a visible light-mediated sequential reaction involving in situ generation of benzotriazole from benzene-1,2-diamine and tert-butyl nitrite via nitrogen insertion and concomitant cross-coupling with quinoxaline-2(1H)-ones via C-N bond formation in one pot. This protocol uses metal-free mild conditions and demonstrated 36 examples of ≤80% yield with wide functional group tolerance.

Synthesis of Triazolo[4',5':4,5]furo[2,3-c]pyridine via Post Modification of an Unusual Groebke-Blackburn-Bienaymé Multicomponent Reaction

The Groebke-Blackburn-Bienaymé (GBB) reaction is a well-established three-component reaction for synthesizing imidazofused scaffolds from heterocyclic amidines, aldehydes, and isonitriles. However, the replacement of pyridoxal as an aldehyde component in this reaction results in the formation of the furo[2,3-c]pyridine skeleton as an "unusual GBB product". Despite the interesting nature of this unusual reaction, not much work was further reported. The present research investigates the optimization strategy for the synthesis of novel tricyclic triazolo[4',5':4,5]furo[2,3-c]pyridines via diazotization of 2,3-diamino-furo[2,3-c]pyridines specifically synthesized utilizing the chemistry of tert-alkyl isocyanide.

Chemical Modification of Tiopronin for Dual Management of Cystinuria and Associated Bacterial Infections

Cystinuria is an inherited autosomal recessive disease of the kidneys of recurring nature that contributes to frequent urinary tract infections due to bacterial growth and biofilm formation surrounding the stone microenvironment. In the past, commonly used strategies for managing cystinuria involved the use of (a) cystine crystal growth inhibitors such as l-cystine dimethyl ester and lipoic acid, and (b) thiol-based small molecules such as N-(2-mercaptopropionyl) glycine, commonly known as tiopronin, that reduce the formation of cystine crystals by reacting with excess cystine and generating more soluble disulfide compounds. However, there is a dearth of simplistic chemical approaches that have focused on the dual treatment of cystinuria and the associated microbial infections. This work strategically exploited a single chemical approach to develop a nitric oxide (NO)-releasing therapeutic compound, S-nitroso-2-mercaptopropionyl glycine (tiopronin-NO), for the dual management of cystine stone formation and the related bacterial infections. The results successfully demonstrated that (a) the antibacterial activity of NO rendered tiopronin-NO effective against the stone microenvironment inhabitants, Escherichia coli and Pseudomonas aeruginosa, and (b) tiopronin-NO retained the ability to undergo disulfide exchange with cystine while being reported to be safe against canine kidney and mouse fibroblast cells. Thus, the synthesis of such a facile molecule aimed at the dual management of cystinuria and related infections is unprecedented in the literature.

On Demand Flow Platform for the Generation of Anhydrous Dinitrogen Trioxide and Its Further Use in N-Nitrosative Reactions

Dinitrogen trioxide (N2 O3 ) is a powerful and efficient nitrosating agent that comes with an unprecedented atom economy. However, the synthetic application of N2 O3 is still underdeveloped mostly due to its inherent instability and the lack of reliable protocols for its preparation. This paper presents an open-source setup and procedure for the on-demand generation of anhydrous N2 O3 solution (up to 1 M), which can be further used for reactions under batch and flow conditions. The accuracy and stability of N2 O3 concentration are guaranteed with the absence of head-space in the setup and with the synchronization of the gas flows. The reliability of this protocol is demonstrated by >30 worked examples in the nitrosative synthesis of heterocycles-a library of structurally diverse benzotriazoles and sydnones. Kinetic and mechanistic aspects of the N-nitrosative steps are also explored.

TfNN15N: A γ-15N-Labeled Diazo-Transfer Reagent for the Synthesis of β-15N-Labeled Azides

Azides are infrared (IR) probes that are important for structure and dynamics studies of proteins. However, they often display complex IR spectra owing to Fermi resonances and multiple conformers. Isotopic substitution of azides weakens the Fermi resonance, allowing more accurate IR spectral analysis. Site-specifically ¹⁵N-labeled aromatic azides, but not aliphatic azides, are synthesized through nitrosation. Both ¹⁵N-labeled aromatic and aliphatic azides are synthesized through nucleophilic substitution or diazo-transfer reaction but as an isotopomeric mixture. We present the synthesis of TfNN¹⁵N, a γ-¹⁵N-labeled diazo-transfer reagent, and its use to prepare β-¹⁵N-labeled aliphatic as well as aromatic azides.

Cycloaddition of N-sulfonyl and N-sulfamoyl azides with alkynes in aqueous media for the selective synthesis of 1,2,3-triazoles

The cycloaddition of N-sulfonyl and N-sulfamoyl azides with terminal alkynes generally produces amide derivatives via ketenimine intermediates. We herein delineate a Cu(I) catalyzed method using a prolinamide ligand that selectively generate N-sulfonyl and sulfamoyltriazoles in aqueous media by inhibiting the cleavage of the N1-N2 bond of 5-cuprated triazole intermediates. The present method is mild and tolerant to air, moisture and a wide range of functional groups thereby providing an easy access to a variety of triazole products.

Highly Stable Univalent Copper of a Cu@Al/SBA-15 Nanocomposite Catalyzes the Synthesis of Fluorescent Aminobenzotriazoles Derivatives

With the development of green chemistry, it is still a challenge to maintain the unstable valence state of the metal in heterogeneous catalysts and realize new catalytic synthesis methods. In this paper, it is reported that an univalent copper nanocomposite (Cu@Al/SBA-15) can efficiently catalyze the formation of novel amino-containing benzotriazoles with great fluorescence properties in a new synthetic strategy. Subsequently, its application is further verified by an acylation reaction to produce a series of novel benzotriazoles derivatives with high yield. It is worth noting that the Cu@Al/SBA-15 nanocomposites not only enable the reaction completed with high yield in a short time, but can also be recycled many times without a significant reduction in activity, and the leaching of copper and aluminum species in reaction system is negligible. Finally, the detailed and feasible reaction mechanism is also provided.

Recent Advances and Strategies for the Transition‐Metal‐Catalyzed C−H Functionalization of N‐Nitrosoanilines

The challenges faced in the activation and functionalization of C−H bonds while producing high‐value aromatic intermediates are significant for synthetic organic chemistry. This review summarizes the advancements made toward the C−H functionalization of N‐nitrosoanilines in the past decade, in which the nitroso group coordinates to a transition metal, such as rhodium, palladium, cobalt, iridium, and ruthenium, acting as a directing group to allow the activation of the ortho C−H bond. The versatility of this synthetic approach has led to the regio‐ and chemoselective introduction of various functional groups giving rise to aromatic congeners with diverse functional and structural properties. C−H functionalized nitroso compounds can be further transformed into valuable synthetic intermediates and unique heterocyclic compounds. A description of the mechanism underlying each reaction is also included. This review includes the following sections:

magnified image

A simple route towards the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles from primary amines and 1,3-dicarbonyl compounds under metal-free conditions

An acetic acid-promoted approach that enables the synthesis of 1,4,5-trisubstituted 1,2,3-triazole derivatives has been achieved. This transformation employs readily available primary amines, 1,3-dicarbonyls and tosyl azide as the starting materials via a cycloaddition reaction under metal-free conditions. The reaction provides a simple access to fully substituted 1,2,3-triazoles from commercial substrates in moderate to excellent yields.

Making endo-cyclizations favorable again: a conceptually new synthetic approach to benzotriazoles via azide group directed lithiation/cyclization of 2-azidoaryl bromides

Although benzotriazoles are important and ubiquitous, currently there is only one conceptual approach to their synthesis: bridging the two ortho-amino groups with an electrophilic nitrogen atom. Herein, we disclose a new practical alternative - the endo-cyclization of 2-azidoaryl lithiums obtained in situ from 2-azido-aryl bromides. The scope of the reaction is illustrated using twenty-four examples with a variety of alkyl, alkoxy, perfluoroalkyl, and halogen substituents. We found that the directing effect of the azide group allows selective metal-halogen exchange in aryl azides containing several bromine atoms. Furthermore, (2-bromophenyl)diazomethane undergoes similar cyclization to give an indazole. Thus, cyclizations of aryl lithiums containing an ortho-X = Y = Z group emerge as a new general approach for the synthesis of aromatic heterocycles. DFT computations suggested that the observed endo-selectivity applies to the anionic cyclizations of other functionalities that undergo "1,1-additions" (i.e., azides, diazo compounds, and isonitriles). In contrast, cyclizations with the heteroatomic functionalities that follow the "1,2-addition" pattern (cyanates, thiocyanates, isocyanates, isothiocyanates, and nitriles) prefer the exo-cyclization path. Hence, such reactions expand the current understanding of stereoelectronic factors in anionic cyclizations.

Copper-Catalyzed Redox Coupling of Nitroarenes with Sodium Sulfinates

A simple copper-catalyzed redox coupling of sodium sulfinates and nitroarenes is described. In this process, abundant and stable nitroarenes serve as both the nitrogen sources and oxidants, and sodium sulfinates act as both reactants and reductants. A variety of aromatic sulfonamides were obtained in moderate to good yields with broad substrate scope. No external additive is employed for this kind of transformation.

tert-Butyl nitrite promoted transamidation of secondary amides under metal and catalyst free conditions

A mild and efficient method is demonstrated for the transamidation of secondary amides with various amines including primary, secondary, cyclic and acyclic amines in the presence of tert-butyl nitrite. The reaction proceeds through the N-nitrosamide intermediate and provides the transamidation products in good to excellent yields at room temperature. Moreover, the developed methodology does not require any catalyst or additives.

Regioselective Nitration of N-Alkyl Anilines using tert-Butyl Nitrite under Mild Condition

Regioselective ring nitration of N-alkyl anilines is reported using tert-butyl nitrite. The reactions proceed efficiently with a wide range of substrates providing synthetically useful N-nitroso N-alkyl nitroanilines in excellent yields which can be easily converted into N-alkyl phenylenediamines and N-alkyl nitroanilines using Zn-AcOH and HCl/MeOH, respectively.

Solvent-controlled chemoselective N-dealkylation-N-nitrosation or C-nitration of N-alkyl anilines with tert-butyl nitrite

A metal-free, acid-free and chemoselective N-dealkylation-N-nitrosation or C-nitration of N-alkyl anilines has been developed.

Synthesis of 2-aminobenzophenones through acylation of anilines with α-oxocarboxylic acids assisted by tert-butyl nitrite

A highly facile all-in-one-pot synthesis of 2-aminobenzophenones directly from anilines, tert-butyl nitrite and α-oxocarboxylic acids under the catalysis of Pd(OAc)₂ is presented.