Nitrogen atom insertion into arenols to access benzazepines

Advances in site-selective molecular editing have enabled structural modification on complex molecules. However, thus far, their applications have been restricted to C-H functionalization chemistry. The modification of the underlying molecular skeleton remains limited. Here, we describe a skeletal editing approach that provides access to benzazepine structures through direct nitrogen atom insertion into arenols. Using widely available arenols as benzazepine precursors, this alternative approach allowed the streamlined assembly of benzazepines with broad functional group tolerance. Experimental mechanistic studies support a reaction pathway involving dearomatizative azidation and then aryl migration. This study further highlights the potential for carbon-nitrogen transmutation sequences through combinations with oxidative carbon atom deletion, providing an alternative for the development of N-heteroarenes and demonstrating significant potential in materials chemistry.

Unanticipated switch of reactivity of isonitrile via N≡C bond scission: Cascade formation of symmetrical sulfonyl guanidine

Unanticipated formation of symmetrical sulfonyl guanidine was observed while treating isonitriles with N,N-dibromoarylsulfonamides in absence of an external amine source. Interesting feature of this work is that one molecule of isonitrile initially reacts with dibromoarylsulfonamide via the C-end to produce the intermediate carbodiimide while the other molecule undergoes C≡N triple bond cleavage to react as amine source with the intermediate. This switch of reactivity from C-center to N-center of the isonitrile generated symmetrical guanidine.

Rhodium-Catalyzed Intramolecular Nitrogen Atom Insertion into Arene Rings

In this study, we describe the direct insertion of an intramolecular nitrogen atom into an aromatic C-C bond. In this transformation, carbamoyl azides are activated by a Rh catalyst and subsequently directly inserted into the C-C bond of an arene ring to access fused azepine products. This transformation is challenging, owing to the existence of a competitive C-H amination pathway. The use of a paddlewheel dirhodium complex Rh2(esp)2 effectively inhibited the undesired C-H insertion. Density functional theory calculations were performed to reveal the reaction mechanism and origin of the chemoselectivity of the Rh-catalyzed reactions. The novel fused azepine products are highly robust and allow for downstream diversification.

A Unified Approach for the Synthesis of Isourea and Isothiourea from Isonitrile and N,N-Dibromoarylsulfonamides

A unified approach has been developed for the synthesis of both isourea and isothiourea in a three-component coupling reaction by treating alcohols or thiols respectively with N,N-dibromoarylsulfonamides and isonitrile and in the presence of K₂CO₃. This metal-free process proceeds via carbodiimide intermediate at room temperature within a very short reaction time. A library of sulfonylisoureas and isothioureas has been made using this synthetic protocol with wide substrate scope in good to high yields.

3-Arylaziridine-2-carboxylic Acid Derivatives and (3-Arylaziridin-2-yl)ketones: The Aziridination Approaches

Aziridination reactions represent a powerful tool in aziridine synthesis. Significant progress has been achieved in this field in the last decades, whereas highly functionalized aziridines including 3-arylated aziridine-2-carbonyl compounds play an important role in both medical and synthetic chemistry. For the reasons listed, in the current review we have focused on the ways to obtain 3-arylated aziridines and on the recent advances (mainly since the year 2000) in the methodology of the synthesis of these compounds via aziridination.

Palladium-Catalyzed Stereoselective Hydrodefluorination of Tetrasubstituted gem-Difluoroalkenes

A highly stereoselective palladium(0)-catalyzed hydrodefluorination (HDF) of tetrasubstituted gem-difluoroalkenes is developed. By using catalytic Pd(PPh₃)₄ (2.5-5 mol %) and hydrosilane Me₂PhSiH, various trisubstituted terminal (E)-monofluoroalkenes can be synthesized with excellent E/Z selectivity (>99:1) and good functional group tolerability. The key stereocontrol should be exerted by an ester-directed C-F bond oxidative addition step in the catalytic cycle.

Unprecedented 1,3-tert-butyl migration via the C–N single bond scission of isonitrile: an expedient metal-free route to N-sulfonyl amidines

Treatment of tert-butyl isonitrile with ArSO₂NBr₂ and nitrile led to simultaneous C–N single bond scission of isonitrile and migration of tert-alkyl group to nitrogen centre of the nitrile precursor, resulting in the formation of N-sufonyl amidine.

Facile, catalyst-free cascade synthesis of sulfonyl guanidinesviacarbodiimide coupling with amines

A facile, catalyst-free cascade synthesis of sulfonyl guanidinesviacarbodiimide intermediate coupling with amines at room temperature has been disclosed.

Mechanistic insights into intramolecular ortho-amination/hydroxylation by nonheme FeIV[double bond, length as m-dash]NTs/FeIV[double bond, length as m-dash]O species: the σ vs. the π channels

Comparative oxidative abilities of nonheme Fe^IV[double bond, length as m-dash]NTs and Fe^IV[double bond, length as m-dash]O species using DFT has been explored. Our calculations reveal that the Fe^IV[double bond, length as m-dash]NTs is found to be a stronger oxidant in two electron transfer reactions and react exclusively via π channels while the Fe^IV[double bond, length as m-dash]O species is found to be a stronger oxidant when the σ-pathway is activated such as in HAT reactions.

First graphene oxide promoted metal-free nitrene insertion into olefins in water: towards facile synthesis of activated aziridines

A facile metal-free graphene oxide (GO)-catalyzed synthesis of tosylaziridines using PhINTs as the nitrene source is reported.

A Metal-Free Protocol for Aminofunctionalization of Olefins Using TsNBr2

N,N-Dibromo-p-toluene sulfonamide (TsNBr2) has been found to be an effective reagent for various aminofunctionalization reactions. This reagent behaves both as an electrophilic bromine source as well as amine to react with olefins under different conditions to yield aminoether, imidazoline, diamine and amino bromine. The reaction proceeds rapidly under mild conditions with high regioselectivity. Olefins react with TsNBr2 in moist THF to form δ-amino ether at room temperature. Treatment of TsNBr2 with olefin in MeCN at room temperature produced imidazoline in high yield. Further modification of the reaction condition resulted in the development of a one-step procedure for the synthesis of N-acetyl,N'-tosyl diamine derivatives directly from olefin. When the olefin was treated with 2.4 mol equiv of TsNBr2 in the presence of K2CO3, N,N'-ditosyl diamine derivative was obtained in moderate yield. Instantaneous formation of aminobromine was observed when an olefin was treated with the reagent in dry CH2Cl2 at room temperature.

Use of Bromine and Bromo-Organic Compounds in Organic Synthesis

Bromination is one of the most important transformations in organic synthesis and can be carried out using bromine and many other bromo compounds. Use of molecular bromine in organic synthesis is well-known. However, due to the hazardous nature of bromine, enormous growth has been witnessed in the past several decades for the development of solid bromine carriers. This review outlines the use of bromine and different bromo-organic compounds in organic synthesis. The applications of bromine, a total of 107 bromo-organic compounds, 11 other brominating agents, and a few natural bromine sources were incorporated. The scope of these reagents for various organic transformations such as bromination, cohalogenation, oxidation, cyclization, ring-opening reactions, substitution, rearrangement, hydrolysis, catalysis, etc. has been described briefly to highlight important aspects of the bromo-organic compounds in organic synthesis.

Efficient pyrrolidine catalyzed cycloaddition of aziridines with isothiocyanates, isoselenocyanates and carbon disulfide “on water”

The cycloaddition of aziridines with isothiocyanates, isoselenocyanates and carbon disulfide is described using pyrrolidine on water. This protocol affords a potential route for the construction of the five membered heterocycles with high yields.