An Efficient Metal‐Free Method for the Denitrosation of Aryl N‐Nitrosamines at Room Temperature

Diboron Reagents in N-N Bond Cleavage of Hydrazines, N-Nitrosamines, and Azides: Reactivity and Mechanistic Insights

Diboron reagents are known for their ability to promote the deoxygenation of amine or pyridine oxides, nitroarenes, and nitrones through the formation of B-O-B bonds. In this study, we have investigated the potential of diboron reagents to induce N-N bond cleavage in hydrazines, N-nitrosamines and azides. Our findings show that the combination of B2nep2 as diboron source and KOMe as a Lewis base can effectively promote the N-N cleavage of a wide variety of substrates. For hydrazines and nitrosamines, the presence of an aryl group is essential for the reaction to proceed, probably due to a better stabilization of the negative charge developed during N-N bond cleavage. Both types of azides, aromatic and aliphatic, are easily reduced, and the resulting amines can be in situ converted into the corresponding amides by simple treatment with a carboxylic acid. Experimental and theoretical calculations suggest a non-radical mechanism, with concerted B-B and N-N bond cleavage in the case of hydrazines and azides, and a stepwise mechanism in the case of N-nitrosamines, where deoxygenation occurs as the first step, involving the formation of an N-nitrene intermediate.

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.

Oxidative coupling of N-nitrosoanilines with substituted allyl alcohols under rhodium (III) catalysis

Rhodium(III) catalysis has been used for C-H activation of N-nitrosoanilines with substituted allyl alcohols. This method provides an efficient synthesis of the functional N-nitroso ortho β-aryl aldehydes and ketones with low catalyst loading, high functional group tolerance, and superior reactivity of allyl alcohols toward N-nitrosoanilines. We demonstrated that reaction also proceeds through the one-pot synthesis of N-nitrosoaniline, followed by subsequent, C-H activation. The protocol was also feasible with acyrlaldehyde and methyl vinyl ketone which furnished the same oxidative N-nitroso coupling product.

Regioselective ortho C-H insertion of N-nitrosoanilines with naphthoquinone carbenes

A Rh(III)-catalyzed ortho C-H migratory insertion of N-nitrosoanilines with naphthoquinone carbenes has been developed. The products were obtained in good yields under mild reaction conditions. Diverse elaborations of the products were explored. This method is valuable for the synthesis of biarylamines and their derivatives.

Unraveling the Key Role of the Benzyl Group in the Synthesis of CL-20 Precursor HBIW

As one of the most important energetic material molecules, hexanitrohexaazaisowurtzitane (CL-20) can only be synthesized using an amine with a benzyl group. Moreover, the reaction mechanism remains unexplored and the special role of the benzyl group has not been revealed. To address these issues, we perform an extensive theoretical study to investigate the synthesis mechanism of CL-20 precursor HBIW by employing density functional theory. Our calculated results demonstrate that the benzyl group can reduce the energy of the intermediate and the energy barrier of the rate-determining step due to the π-π stack interaction between two benzene rings of the benzyl group. For the first time, we revealed that the reactions can produce 16 intermediates with different chiralities during the formation of the first two side five-membered rings and only two of which can further form the bottom six-membered ring and finally obtain the product HBIW. The steric hindrance effect of the benzyl group leads to the formation of a higher-energy intermediate first, thereby providing an opportunity to correct the wrong chirality. All of these factors make the diimine with the benzyl group the most suitable reactant for the synthesis of CL-20.

Diversification of α-ketoamides via transamidation reactions with alkyl and benzyl amines at room temperature

A wide range of N-tosyl α-ketoamides underwent transamidation with various alkyl amines in the absence of a catalyst, base, or additive. On the other hand, transamidation in N-Boc α-ketoamides was achieved in the presence of Cs₂CO₃. The reactions proceeded at room temperature and provided good to excellent yields of transamidation products under the optimized conditions. Broad substrate scope, functional group tolerance and quick conversions are the important features of the developed methodology.

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:

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One-Pot Tandem ortho-Naphthoquinone-Catalyzed Aerobic Nitrosation of N-Alkylanilines and Rh(III)-Catalyzed C-H Functionalization Sequence to Indole and Aniline Derivatives

The nitroso group served as a traceless directing group for the C-H functionalization of N-alkylanilines, ultimately removed after functioning either as an internal oxidant or under subsequent reducing conditions. The unique ability of o-NQ catalysts to aerobically oxidize the N-alkylanilines without using solvents and stoichiometric amounts of oxidants has rendered the new opportunity to develop the telescoped catalyst systems without a need for directly handling the hazardous N-nitroso compounds.

Rh(III)-Catalyzed N-Nitroso Directed C-H Arylation for Facile Construction of Diverse N-Hetero Biaryl Compounds

A Rh(III)-catalyzed C-H arylation reaction of N-nitrosoanilines has been developed in which arylboronic acids were used as arylation reagents. It provides an efficient strategy for the synthesis of N-nitroso-[1,1'-biphenyl]-2-amine, which is an important starting material for the synthesis of N-hetero biaryl compounds, such as 2-amine-1,1'-biphenyl, carbazole, phenanthridone. This protocol can be applied to various N-alkyl substituted N-nitrosoanilines and N-nitrosoanilines with substituents on the phenyl ring. Arylboronic acids with both electron-donating and electron-withdrawing groups are tolerated.

Synthesis of Mono-N-Methyl Aromatic Amines from Nitroso Compounds and Methylboronic Acid

The selective synthesis of mono-N-methyl aromatic amines was achieved by the reaction of aromatic nitroso compounds with methylboronic acid promoted by triethylphosphite under transition metal-free conditions. The target compounds are constructed efficiently without overmethylation, under environmentally benign reaction conditions that do not require bases or reductants and therefore are of interest in pharmaceutical, agricultural, and chemical industries.

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.

Potassium Persulfate‐Promoted N‐Nitrosation of Secondary and Tertiary Amines with Nitromethane under Mild Conditions

A simple and efficient route for the N‐nitrosation of various secondary amines with nitromethane is described in the presence of potassium persulfate and DBU. Under optimized condition, tertiary amines underwent a dealkylative N‐nitrosation with good yields. Inexpensive reagents, broad substrate scope and efficient conversion make the current protocol more attractive in organic synthesis.

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

A conversion of o-phenylenediamines into benzotriazoles was achieved at room temperature using tert-butyl nitrite. The optimized conditions are also well suited for the transformation of sulfonyl and acyl hydrazines into corresponding azides. This protocol does not require any catalyst or acidic medium. The desired products were obtained in excellent yields in a short span of time.

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.