16483-98-0

A visible-light-promoteded [3 + 2] cycloaddition reaction of 2H-azirines with quinones has been developed under mild reaction conditions. The reaction provides a general and efficient strategy for the synthesis of the benzo[f]isoindole-4,9-diones scaffold

The reported flow-batch approach enables the easy preparation of 2H-azirines and their stereoselective transformation into highly functionalized NH-aziridines, starting from vinyl azides and organolithium compounds. The protocol has been developed using c

Here we report a novel interrupted azirine-alkyne ring-expansion reaction with molecular oxygen for the direct synthesis of highly functionalized pyrrolones enabled by copper catalysis. Mechanistic investigations indicate that the present three-component reaction proceeds via two copper-catalyzed sequential reactions, an azirine-ring-opening alkynylation and an amine-directed radical oxygenation, leading to the formation of interesting pyrrolone structures under mild conditions.

A diastereoselective copper and NHC-ligand-catalyzed three-component difunctionalization of allenes with bis(pinacolato)diboron and 2H-azirines to afford borylated allylaziridines is described. The reaction exhibits complete diastereoselectivity and good yields, and the further chlorination of the corresponding borylated products was also performed. It is believed that the high ring-strain force of 2H-azirines facilitates the reaction. More chemical transformations of borylated allylaziridines are also reported.

A visible-light-driven photoredox reaction of tetrahydroisoquinoline with 2H-azirines is described. 4,7-Bis(4-methoxyphenyl)benzo[c][1,2,5]thiadiazole, a benzothiadiazole (BTD) derived fluorophore, is used as an organic photoredox catalyst, and the reacti

A diethylzinc-promoted unconventional annulation reaction of 2,2,2-trifluorodiazoethane with 2H-azirines is described. This transformation involves two [3 + 2] cycloaddition steps and one dinitrogen extrusion process in one pot, thus giving a broad array

A regio- and diastereoselective ring-expansion reaction of N-acylaziridines is described for the synthesis of 4-carboxamide oxazolines using InCl3. A domino Ugi-Joullié/ring-expansion reaction of arylphenylazirines, isocyanides, and carboxylic

A rapid and effective method has been established for the synthesis of N-acylated α-aminoketone derivatives by the reaction of 3-aryl-2H-azirines and highly substituted 2-Me/Ph-3-aryl-2H-azirines with various carboxylic acids under ambient air within 10 min at room temperature. N-Trifluoroacetylated α-aminoketones with different substituents have been reported in the presence of trifluoroacetic acid. This protocol is equally effective to synthesize N-formylated α-aminoketone and N-hydroxymethylated formamide derivatives.

A copper-catalyzed three-component reaction of O-acyl oximes, DABCO·(SO2)2, and 2H-azirines under mild conditions has been achieved. This protocol provides an efficient route for the construction of various tetrasubstituted β-sulfonyl N-unprotected enamines in moderate to good yields with excellent stereoselectivity and regioselectivity. Notably, this method represents a rare example of 2H-azirines as useful synthons for β-functionalized N-unprotected enamines. Preliminary mechanistic studies indicate that the reaction proceeds through coupling of a sulfonyl radical and α-carbon radical via copper-catalyzed ring-opening C-C bond cleavage of O-acyl oxime and C-N bond cleavage of 2H-azirine with the insertion of sulfur dioxide.

The general synthesis of fully substituted N2-aryl-1,2,3-triazoles is hitherto challenging compared with that of the N1-aryl counterparts. Herein, we describe a Cu-catalyzed annulation reaction of azirines and aryldiazonium salts. This regiospecific metho

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A formal [3 + 2]-cycloaddition reaction of 2H-azirines with nitrosoarenes has been achieved under irradiation by visible light with the assistance of organic dye photoredox catalyst. This method utilizes nitrosoarenes as efficient radical acceptors and pr

A new synthetic application of N-sulfonyl-1,2,3-triazoles acting as a 1-aza-[4C] synthon via the 1,2-shift reaction of an α-imine rhodium carbene was developed for the synthesis of fused pyrimidine derivatives. The high reactivity of the strained three-me

A modular 2H-azirine synthesis from ketoxime acetates via Cs2CO3-mediated cyclization has been developed. The reaction utilizes easily available starting materials and provides a general synthetic route to 2,3-diaryl-2H-azirines in good to excellent yields under mild conditions, which is complementary to the conventional approaches for the synthesis of 2H-azirines. A gram-scale reaction was performed to demonstrate the scale-up applicability of this synthetic method. Importantly, 2H-azirines can be efficiently converted to various azaheterocycles.

A regioselective synthetic method for the preparation of indolopyrazines was demonstrated through a sequential Rh-catalyzed formal [3+3] cycloaddition and aromatization reaction of a wide range of diazoindolinimines with azirines. Because the previously reported synthetic methods afforded mixtures of indolopyrazines, the present method using unsymmetrical azirines has a strong advantage from a regioselectivity viewpoint.

A catalytic asymmetric nucleophilic addition of tertiary carbon nucleophiles to 2H-azirines was established in the presence of the chiral N,N′-dioxide/CuII complex. Various chiral aziridines with vicinal tetrasubstituted stereocenters were obta

A novel method for concisely synthesizing 1,2,4-triazolines via [3+2] cyclization under visible light is reported. These compounds can be easily converted into 1,2,4-triazoles under basic or photoredox conditions. The application of the 1,2,4-triazoles was also investigated via mild operations.

A rhodium-catalyzed reaction between 3-diazoindolin-2-imines and 2H-azirines, followed by treatment with a base, furnishes 5H-pyrazino[2,3-b]indoles in excellent yields. A number of functional groups tolerate the reaction conditions, and the resulting 5H-

Bromine azide (BrN3), a useful but extremely toxic and explosive reagent for the preparation of vicinal 1,2-bromine azide compounds, was safely generated and reacted in situ with alkenes in a continuous flow photoreactor. BrN3 was generated by a novel procedure from NaBr and NaN3 in water, and efficiently extracted into an organic phase containing the alkene thus avoiding decomposition. The resulting addition products have been used for the preparation of several useful building blocks.

2H-azirines can serve as three-atom synthons by C-C bond cleavage, however, it involves a high energy barrier under thermal conditions (>50.0 kcal mol-1). Reported is a ruthenium-catalyzed [3+2+2] cycloaddition reaction of 2H-azirines with diyn

Highly efficient kinetic resolution of 2H-azirines by an asymmetric imine amidation was achieved in the presence of a chiral N,N′-dioxide/ScIIIcomplex, thus providing a promising method to obtain the enantioenriched 2H-azirine derivatives and p

A ruthenium-catalyzed intermolecular [3 + 2] cycloaddition of 2H-azirines and activated alkynes is reported, which provides polysubstituted pyrroles in moderate to good yields. This approach features a C-N bond cleavage of 2H-azirines by a ruthenium catal

The Rh(ii)-catalyzed formal [3+2] and [3+3] cycloadditions of 1-tosyl 1,2,3-triazoles with 2H-azirines have been developed, which enable the efficient synthesis of polysubstituted 3-aminopyrroles and 1,2-dihydropyrazines, respectively. The reported [3+2] cycloaddition represents the first application of 1-sulfonyl 1,2,3-triazole as a [2C]-component in relevant cycloaddition reactions. This journal is

Synthesis of unsymmetrically substituted pyrazines has been a challenge. The reactivity of ?±-imino carbenoids derived from ?±-diazo oxime ethers has been exploited for pyrazine synthesis, in which the reaction of ?±-diazo oxime ethers with 2H-azirines provides highly substituted pyrazines in good to excellent yields.

An efficient rhodium(II)-catalyzed transannulation method of 1-sulfonyl-1,2,3-triazoles with 2H-azirines has been utilized for the synthesis of phenyl-substituted dihydropyrazines. The dihydropyrazine products can be further converted to pyrazines under b

(Chemical Equation Presented). An effective gold-catalyzed intermolecular nitrene transfer by the reaction of 2H-azirines and ynamides is reported, which provides highly substituted pyrroles in a straightforward manner. This transformation proceeds under mild conditions and gives the polysubstituted pyrroles in good-to-excellent yields. Preliminary results indicate that a nongold carbenoid pathway is preferred for current pyrrole synthesis.

A photocatalytic formal [3+2] cycloaddition of 2H-azirines with alkynes has been achieved under irradiation by visible light in the presence of organic dye photocatalysts. This transformation provides efficient access to highly functionalized pyrroles in good yields and has been applied to the synthesis of drug analogues. A primary trial of photocascade catalysis merging energy transfer and redox neutral reactions was shown to be successful. Photo(chemistry) op: A photocatalytic formal [3+2] cycloaddition of 2H-azirines with alkynes has been established under the irradiation of visible light in the presence of an organic dye. This transformation provides efficient access to highly functionalized pyrroles in good yields and has been applied to the formal synthesis of an inhibitor for HMG-CoA reductase.

Roaming the range: The title reaction tolerates a wide range of substituents on the resulting pyridine ring using mild reaction conditions (see scheme; esp=α,α,α′,α′-tetramethyl-1,3- benzenedipropionic acid). The formation of the key intermediate is catal

An unprecedented nickel-catalysed disproportional reaction of 2,3-diaryl-2H-azirines forming azabutadienes and aromatic nitriles was discovered. This reaction involves the cleavage of two bonds of the 2H-azirine framework, which provides a novel type of transformation of 2H-azirines.

An efficient and environmentally friendly method preparing 2H-azirines in good yield has been achieved by microwave irradiation of vinyl azides in solvent free conditions.

The pyrolysis of 1-aroylamino-4,5-diphenyl-1,2,3-triazoles 1 yields, pressumably via the 4,5-diphenyl-1,2,3-triazolyl radical (2a), 2,3-diphenyl-2H-azirine (11a) and 2-aryl-4,5-diphenylimidazoles 14 as the major products. Upon irradiation 1-benzoylamino-4,5-diphenyl-1,2,3-triazole (1a) gives 4,5-diphenyl-1(2)H-1,2,3-triazole (4a) via the 1,2,3-triazolyI radical 2a, together with benzamide (5a) and 1,2-bisbenzoylhydrazine (6a). Products 5a and 6a result from the benzoylamino radical 3a by hydrogen atom abstraction and dimerization respectively.

In this study of 1,3-dipolar cycloadditions of nitrile ylids to olefin gem-substituted with withdrawing groups we have attempted to bring out the factors governing the diastereoselectivity of the reaction.Extensive studies have been made with allylic dipoles but few with propargyl dipoles.These reactions lead to stable pyrrol-1-ines in good yields. The adducts have been epimerized and, according to the method of generation of nitrile ylids, the isomerization of the dipoles or the dipolarophiles may occur. These facts have complicated the determination of the kinetic products.Owing to these difficulties, no interpretation of the results with perturbation theory has been attempted. - Keywords: stereochemistry / cycloaddition / 1,3-dipole / nitrile ylid / 1H-azirine / pyrrol-1-ine

A series of nucleophiles was allowed to react with 2,3-diphenylthiirene 1,1-dioxide (1) in dipolar aprotic solvents to produce a variety of derivatives.Fluoride ion gave diphenylacetylene and (E)-1,2-diphenylvinylsulfonyl fluoride (2);thiophenoxide gave (E)-1,2-diphenyl-2-(thiophenoxy)vinylsulfinate which gave the corresponding methyl sulfone 5 on treatment with methyl iodide.Azide ion gave a variety of products including diphenylvinyl azides 12 and 13, 2,3-diphenylazirine (14), 2,6-diphenyl-4-((E)-diphenylvinyl)-1,3,4,5-thiatriazine 1,1-dioxide (15),benzil (16), 4,5-diphenyltriazole (17), 2,4,5-triphenylimidazole (18),and (Z)-1,2-diphenyl-2-azidovinylsulfinate which gave the corresponding methyl sulfone 22 on treatment with methyl iodide.The diphenylvinyl group was removed from the new heterocycle 15 by ozonolysis followed by mild base hydrolysis to yield the thiatriazine 1,1-dioxide 20.Compound 20 undergoes thermolysis at 40 deg C to give stilbenes,and 20 also undergoes a facile base-catalyzed extrusion of sulfur dioxide to give imidazole 18.

2,2,3-Triphenyl-2H-azirine (4a) in a matrix of 2,2-dimethylbutane/pentane 8:3 (DMBP) at -185° gave rise on irradiation with light of 250-350 nm to a new UV.-maximum at 350 nm (Fig. 1). We assign the dipole benzonitrildiphenylmethylide (1a) to this new maximum. Irradiation with monochromatic light of 366 nm destroyed this maximum and the initial absorption curve reappeared (Fig. 2). When the azirine 4a was photolysed in DMBP at -185° in the presence of methyl trifluoracetate (TFEM), the maximum at 350 nm was obtained again. This maximum vanished upon increasing the temperature to -160°. Through gas chromatography we were able to show that 5-methoxy-5-trifluormethyl-2,2,4-triphenyl-3-oxazoline (6 a) was produced. 6 a was also obtained upon irradiation of 4 a at room temperature in the presence of TFEM (scheme 1 and table 1). Modification of the previously described experiment, in which the maximum at 350 nm was extinguished in the matrix due to irradiation at 366 nm gave, after warm up, almost no dipole adduct 6 a (table 1). From these experiments, an extinction coefficient of 17,000 for the 350 nm maximum of 1a, was calculated. These experiments have shown that irradiation of triphenylazirine 4a leads to the dipole 1a, which can be reversed photochemically but not thermally -into azirine 4a. 1a reacts at less than -160° with TFEM to give adduct 6a. The results which were obtained with triphenylazirine 4a could be correspondingly obtained with 2,3-diphenyl-2H- azirine 4b (Fig. 3, scheme 2 and table 2). The dipole 1b showed two UV.maxima at 330 nm (ε = 17,500) and 343 nm (ε = 21,000). Later experiments established, that the two maxima belonged to a single dipole species. The dipole 1c obtained upon irradiation of 2,2-dimethyl-3-phenyl-2H-azirine (4 c) in DMBP at -190°, appears to absorb in the same region as the azirine 4c. The presence of the dipole 1c was univocally established by low temperature trapping experiments with TFEM. The dipole 1a showed no ESR.-spectrum characteristic for a triplet state. We assume therefore, that 1a is in a singlet state. Photolysis of oxazolinone 7 at -190° in DMBP led to the dipole 1a with loss of CO 2. 1a recombines apparently in considerable amount with the CO 2 trapped in the matrix to give starting oxazolinone 7 because the 350 nm-maximum of 1a appeared with low extinction. Irradiation with light of 366 nm into this matrix produced triphenylazirine 4 a. Low temperature trapping experiments with TFEM led to small amounts of 5-methoxy-5-trifluormethyl-2,2, 4triphenyl-3-oxazoline (6a).