Study the reactions of fluoroalkanesulfonyl azides with N-alkylindoles

The reactions of fluoroalkanesulfonyl azides R_fSO₂N₃1 with N-alkylindoles 2 have been studied in detail. It was found that both solvent and the amount of the azides seriously affected the product distribution. 1 reacted with equimolar of 2 in ether or 1,4-dioxane affording 2-(N-substituted-indolinylidene)fluoroalkane sulfonylimines 3 as major product; While, treatment of 2 with 2 equiv. of 1 in ethanol, an unexpected product N-substituted-2-fluoroalkanesulfonimino-3-diazo-indolines 4 were obtained in good yield. The reaction mechanism was discussed.     

Study on the reactions of fluoroalkanesulfonyl azides with indole derivatives

The reactions of fluoroalkanesulfonyl azides 1 with different indole derivatives have been studied in detail. Treatment of 1 with equimolar amount of 1,3-dimethylindole 3 in 1,4-dioxane at room temperature afforded 2-(1,3-dimethyl-1,3-dihydro-indolinylidene) fluoroalkanesulfonylimines 5 in moderate to good yields. However, under the same reaction conditions, in the case of 1 with 1,2-dimethylindole 4, the corresponding 2-fluoroalkanesulfonyl (1,2-dimethyl-1H-indol-3-yl)-amide 6 was obtained in moderate yields. In addition, the reactions of 1 and indole 7 gave different products under different conditions. Possible mechanisms of these reactions were proposed.     

Study on the reactions of fluoroalkanesulfonyl azides with cycloalkenyl ether and aryl ynamines

The reactions of fluoroalkanesulfonyl azides 1 with some electron-rich compounds have been studied in detail. Cycloalkenyl vinyl ethers reacted with 1 readily at 0 °C to give the corresponding ring-contraction N-fluoroalkanesulfonyl amidine analogues 3. In contrast, aryl ynamine generated in situ reacted with 1 affording fluorinated α-diazoamidines 9, which were decomposed slowly at room temperature to form [1-diethylamino-2-(4-nitro-phenyl)-2-oxo-eth-(Z)-ylidene]-fluoroalkanesulfinyl imine 10 with elimination of nitrogen gas. Possible mechanisms for these reactions were proposed.     

Unexpected sulfonylamino migration in the reactions of carbazole derivatives with fluoroalkanesulfonyl azides

The reactions of fluoroalkanesulfonyl azides 1 with carbazole derivatives have been studied in detail. At room temperature 1 reacted with 1,2,3,4-tetrahydrocarbazole 2 readily to afford ring-contraction spiroindole derivatives 3 together with an unexpected 4a-fluoroalkanesulfonylamino-1,2,3,4-tetra-hydrocarbazoles 4. However, in the case of 9-methyl-1,2,3,4-tetrahydrocarbazole 5, unexpected sulfonylamino migration occurred and a similar product 9-methyl-1-fluoroalkanesulfonylamino-2,3,4,9-tetrahydro-1H-carbazoles 6 were obtained as major products in moderate yields. These new products were fully characterized by spectral methods and single X-ray diffraction analyses. Possible mechanisms for these reactions were proposed.     

Reactions of fluoroalkanesulfonyl azides with cyclic vinyl ethers

The addition reactions of fluoroalkanesulfonyl azides to dihydropyran or dihydrofuran were studied. These reactions do not give the corresponding N-fluoroalkanesulfonyl azilidines but N-fluoroalkanesulfonyl-tetrahydropyranon-2-imines or N-fluoroalkanesulfonyl-tetrahydro-furano-2-imines. The reaction mechanism is discussed.     

Reactions of fluoroalkanesulfonyl azides with vinyl ether and tetrakis(dimethylamino)ethylene

The reactions of fluoroalkanesulfonyl azides 1 with some electron-rich olefins have been studied. Alkyl vinyl ethers reacted with 1 readily at 0 °C or room temperature (RT) and did not give the corresponding N-fluoroalkanesulfonyl azilidines but 1-fluoroalkanesulfonyl-1,2,3-triazolines 3, which decomposed slowly at room temperature to form 1,4-fluoroalkanesulfonyl-2,5-alkoxyl-piperazines 4 with elimination of nitrogen gas. In contrast, more electron-rich alkene, tetrakis(dimethylamino)ethylene (TDAE) reacted with 1 affording N-fluoroalkanesulfonyl bis(dimethylamino)amidines 6 accompanying the release of N₂. Reaction mechanisms are discussed.     

Study on the reactions of fluoroalkanesulfonyl azides with pyrazine and its derivatives

The thermal reactions of fluoroalkanesulfonyl azides R_fSO₂N₃ with pyrazine and its derivatives are studied in detail. All the reactions involved the fluoroalkanesulfonyl nitrene intermediates R_fSO₃N: which was captured by pyrazine to give the pyrazinium N-fluoroalkanesulfonyl ylides C₄NH₄N⁺-⁻NSO₂R_f and hydrogen abstraction product R_fSO₂NH₂, but no corresponding N-pyrazinyl fluoroalkanesulfonyl amide derivatives R_fSO₂NHC₄N₂H₃ were isolated. Excess azides did not afford the bisN-ylide product R_fSO₂N⁻-⁺NC₄H₄N⁺-⁻NSO₂R_f.     

Reactions of fluoroalkanesulfonyl azides with pyrrole and its derivatives

The reactions of fluoroalkanesulfonyl azides with pyrrole and its derivatives were studied. The reaction proceeded smoothly under mild conditions to give the 3-(fluoroalkanesulfonamido) pyrroles in good yield. The electron donating groups on the pyrrole core accelerated the reaction, while the electron withdrawing groups decelerated it. All the products were fully characterized by spectrum methods, and one of the products was further confirmed by X-ray diffraction analysis. A possible reaction mechanism for these reactions was proposed.     

Thermal ring-opening reaction of N-polynitromethyl tetrazoles: facile generation of nitrilimines and their reactivity

Thermal ring-opening reaction of N-(R-dinitromethyl)-5-nitrotetrazoles (R=NO₂, F, Cl) yielded highly reactive N-(R-dinitromethyl)-nitrilimine intermediates under mild conditions. These species underwent facile and regiospecific reaction with nitriles and acetylenes to afford the corresponding nitrotriazoles and nitropyrazoles in 50-90% yields. Treatment of N-(chlorodinitromethyl)-5-nitrotetrazole with the excess of azide led to a unique compound with the molecular formula C₂N₁₄. Based on the analytical data, it was assigned a structure of diazidomethylenecarbonohydrazonic diazide.     

Intramolecular cycloaddition of N-phthalimidoaziridines to double and triple carbon-carbon bonds

Thermolysis of 3-(2-allyloxyphenyl)- or 3-(2-propargyloxyphenyl)-1-phthalimidoaziridine-2-carboxylic acid derivatives results in stereospecific intramolecular cycloaddition of intermediate N-phthalimidoazomethine ylides to double or triple carbon-carbon bonds. This leads to condensed N-phthalimidopyrrolidines, N-phthalimidopyrrolines, or products of their subsequent transformations. On the other hand, thermolysis of similar dimethyl 3-aryl-1-phthalimidoaziridine-2,2-dicarboxylates gives exclusively 5-methoxyoxazoles, the products of a competitive 1,5-dipolar electrocyclization.     

Unexpected conversion of alkyl azides to alkyl iodides and of aryl azides to N-tert-butyl anilines

In the presence of tert-butyl iodide, alkyl azides are converted into the corresponding iodides at room temperature, whereas, N-t-Bu anilines are obtained from aryl azides under the same experimental conditions. A mechanism is proposed to explain this unusual reactivity.     

Synthesis of 5-aminoisoxazolines from N-allyl compounds and nitrile oxides via tandem isomerization-1,3-dipolar cycloaddition

A new strategy for the synthesis of derivatives of 5-aminoisoxazolines via tandem catalytic isomerization (of N-allyl systems to N-(1-propenyl) systems)—1,3-dipolar cycloaddition (of a stable nitrile oxide to N-(1-propenyl) systems) is presented. Rhodium and ruthenium complexes, Verkade’s superbase, and 18-crown-6/KOH system were used for the syntheses of the N-(1-propenyl) systems. 4-P-substituted isoxazoline was also synthesized via cycloaddition of diphenyl(1-propenyl)phosphine (prepared via isomerization of allyldiphenylphosphine) to 2,6-dichlorobenzonitrile oxide. All cycloadditions were regioselective but not stereoselective and not concerted. Cycloaddition to all N-(1-propenyl) systems yielded 5-N-substituted isoxazolines, but cycloaddition to P-(1-propenyl) system lead to the formation of a 4-P-regioisomer. This difference in regioselectivity is predicted by opposite FMO reactivity indices calculated for model compounds: N-(1-propenyl)amine and N-(1-propenyl)phosphine.     

Ruthenium-catalyzed 1,3-dipolar cycloaddition of trifluoromethylated propargylic alcohols with azides

The 1,3-dipolar cycloaddition of trifluoromethylated propargylic alcohols 1 with azides in the presence of catalytic [Cp*RuCl₂]_n afforded exclusively 4-trifluoromethyl-1,4,5-trisubstituted-1,2,3-triazoles 2 in high yields.     

Electrochemical fluorination of N,N-dimethylperfluoroacylamides

The electrochemical fluorination (ECF) of N,N-dimethylperfluoroacylamides gives the corresponding perfluoro-N,N-dimethylacylamides in low yield. With increase of the number of carbon atoms in the perfluoroacyl radical the yield of the required perfluoro-N,N-dimethylacylamides is slightly increased.     

Simple pyridylmethylamines: efficient and robust N,N-ligands for Suzuki-Miyaura coupling reactions

A series of pyridylmethylamines have been synthesized in one step from commercially available starting material and identified as effective ligands for Pd-catalyzed carbon-carbon bond formation through Suzuki-Miyaura coupling reaction. The N,N-pyridylmethylamine-Pd catalytic systems appeared as an interesting and robust compromise between catalytic efficiency, substrate compatibility, and practical aspects.     

Enantioselective synthesis of homocarbocyclic-2′-oxo-3′-azanucleosides

The enantioselective synthesis of homocarbocyclic-2′oxo-3′-azanucleosides has been performed by cycloaddition reaction of the N-glycosyl nitrones with allyl nucleobases. The use of nitrones originated from two different carbohydrates, the N-ribosyl nitrone and the N-mannosyl nitrone, proceeded in a stereocontrolled and predictable manner with a good degree of enantioselectivity, so allowing an easy entry to both enantiomers.     

Reactions of fluoroalkanesulfonyl azides with diethyl phosphite,a new method for the synthesis of N‐fluoroalkane‐sulfonylphosphoramidates

N‐Fluoroalkanesulfonylphosphoramidates, R₁SO₂NHP(O)‐(OEt)₂, have been prepared by a one‐step reaction of fluoroalkanesulfonyl azides (R₁SO₂N₃) with diethyl phosphite at room temperature. The reaction mechanism was also discussed and a favored mechanism was suggested.     

Synthesis of N,N-dialkylaminobenzonitriles and halo-(N,N-dialkyl)benzamidines by reaction of halobenzonitriles with lithium amides

3- and 4-N,N-Dialkylaminobenzonitriles and 4-chloro-(N,N-dialkyl)benzamidines were isolated by reacting 4-chlorobenzonitrile with hindered lithium amides under thermodynamic (0 °C) and kinetic control conditions (−78 °C), respectively. As previously reported, a benzyne mechanism seems to be confirmed since N,N-dialkylaminobenzonitriles are formed. Only benzamidines were isolated in fair to high yields at both 0 °C and −78 °C with non-hindered lithium amides. Exploitation and mechanistic rationale of the reaction of different halobenzonitriles are also reported.     

Rational use of substituted N-allyl and N,N-diallylanilines in the stereoselective synthesis of novel 2-alkenyltetrahydro-1-benzazepines

Two new series of 1,4-epoxy-2-exo-vinyl(isopropenyl)tetrahydro-1-benzazepines and cis-2-vinyl(isopropenyl)-4-hydroxytetrahydro-1-benzazepines were prepared by an efficient three/four-step route from available substituted N,N-diallylanilines and mono N-allylanilines. The amino-Claisen rearrangement and the sequential oxidation/intramolecular 1,3-dipolar cycloaddition reactions were used as the key steps in this synthesis. All the synthesized compounds were fully characterized by IR, GC-MS and NMR techniques.     

Synthesis of monofluorinated indolizines and their derivatives by the 1,3-dipolar reaction of N-ylides with fluorinated vinyl tosylates

Monofluorinated indolizines 4, benzo[d]indolizines 7 and 4H-pyrrolo[1,2-a]benzimidazoles 8 were synthesized in moderate yields by 1,3-dipolar reaction between fluorinated vinyl tosylates 2a and N-ylides of pyridinium, isoquinolinium and benzimidazolinium, generated in situ from their halides salts. When the same N-ylides were allowed to react with 2,3,3-trifluoro-1-propenyl tosylate 2b, the unexpected product formylated indolizines and their derivatives 9 were obtained. The reaction mechanism is also proposed.