Mechanistic elucidation of ketenimine-butynoate cycloaddition reaction: role of biradical intermediates in isotopomeric purity of benzyl (1,1a,6,6a-C4)-6-methyl anthranilic ester

Thermal Diels-Alder reaction of vinyl ketenimines with ¹³C-labeled 2-butynoate, efficiently prepared from ¹³C₄-acetoacetate via the enol triflate, rendered at 160 °C the corresponding methylanthranilic ester isotopomerically pure. However, when the reaction was run at 100 °C, 7% of isotope exchange between C^6a and C⁵ was observed. This result is explained through a base-like catalyzed isomerization of the alkyne to the corresponding allene. Combined DFT and coupled-cluster computations show the feasibility of this mechanistic proposal. Better agreement between DFT and coupled-cluster activation and reaction energies is observed for the meta-GGA MPWB1K functional as compared to previous B3LYP results.     

A tandem synthesis of N-(4-hydroxyquinolin-2-yl)sulfonamides from sulfonoketenimides and isatoic anhydride

The one-pot synthesis of a novel class of N-(4-hydroxyquinolin-2-yl)sulfonamide derivatives is achieved in moderate to good yields by the sequential copper-catalyzed reaction between sulfonyl azides, terminal alkynes, and isatoic anhydride in N,N-dimethylformamide.     

Structure and photochemical behaviour of 3-azido-acrylophenones: a matrix isolation infrared spectroscopy study

(Z)-3-Azido-3-methoxycarbonyl-2-chloro-acrylophenone (MACBP) has been synthesized, isolated in low temperature argon and xenon matrices and studied by FTIR spectroscopy, complemented by DFT(B3LYP)/6-311++G(d,p) calculations. The molecule was characterized both structurally and spectroscopically, and its photochemistry used to probe the mechanism of photo-induced conversion of 3-azido-acrylophenones into oxazoles. In situ UV irradiation (λ = 235 nm) of matrix-isolated MACBP yielded as primary photoproduct a 2H-azirine, which undergoes subsequent photoisomerization to methyl 4-chloro-5-phenyl-1,3-oxazole-2-carboxylate. In a competitive process, a ketenimine is also formed upon photolysis of MACBP. The reported results indicate that this ketenimine must be formed from the starting 3-azido-acrylophenone via a Curtius type concerted rearrangement.     

Copper‐Catalyzed One‐Pot Synthesis of N‐Sulfonylalkanimidoyl Thiocyanates from Sulfonyl Azides,Alkynes, and KSCN

Ketenimine intermediates generated by the addition of copper acetylides to sulfonyl azides are trapped by KSCN to afford N‐sulfonylalkanimidoyl thiocyanates in moderate‐to‐good yields.     

Copper‐Catalyzed Synthesis of 2H‐Thiopyran Derivatives from Alkynes,Sulfonyl Azides,Carbon Disulfide,and Malononitrile

A one‐pot synthesis of functionalized thiopyran derivatives via a Cu‐catalyzed multicomponent reaction of sulfonyl azides, arylacetylenes and dipotassium 2,2‐dicyanoethylene‐1,1‐dithiolate, generated from malononitrile and CS₂, has been developed. When alkylacetylenes were used as the terminal alkynes, N‐(alkanethioyl)‐N‐(2,2‐dicyanoethanethioyl)methanesulfonamides were obtained in good yields.     

One-pot synthesis of disulfide-linked N-sulfonylazetidin-2-imines via a copper-catalyzed multicomponent cascade reaction

A copper-catalyzed, three-component reaction between a sulfonyl azide, an alkyne, and a 2-aminothiophenol derived Schiff base is reported. This novel one-pot procedure involves a click reaction, a formal [2+2] cycloaddition, and S–S coupling, therefore, providing a unique method for the synthesis of novel disulfide-linked N-sulfonylazetidin-2-imines under mild conditions.     

N-Sulfonyl acetylketenimine as a highly reactive intermediate for synthesis of N-Aroylsulfonamides

A highly reactive intermediate N-sulfonyl acetylketenimine was generated from an ynone-participated CuAAC/ring-opening method. Its unique structure allowed it to react with aryl carboxylic acids to give N-aroylsulfonamides via a novel Mumm-type rearrangement.     

Reaction Between Isocyanides and Dialkyl Acetylenedicarboxylates in the Presence of Hydantoins – A One-pot Synthesis of Stable Ketenimines

Summary. The reactive 1:1 intermediate produced in the reaction between isocyanides and dialkyl acetylenedicarboxylates was trapped by hydantoins to yield highly functionalized stable ketenimines in fairly good yields.     

Facile synthesis of highly functionalized stable ketenimines by a three-component reaction of alkyl isocyanides, dialkyl acetylenedicarboxylates and ethyl carbazones

Abstract  The reactive intermediate generated by the reaction of alkyl isocyanides and dialkyl acetylenedicarboxylates was trapped by ethyl carbazones to produce stable ketenimine derivatives in good yield. The reaction is characterized by mild conditions, high selectivity, and tolerance to various functional groups. Graphical abstract        

Synthesis and Reactions of Ketenimines

Ketenimines R¹R²C?C?N? R³ were first reported in 1919, but the development of the chemistry of these compounds is of relatively recent origin. These heterocumulenes are becoming of increasing interest as a dehydrating agent for peptide syntheses, as a coreagent in dimethyl sulfoxide oxidations, and as a substrate in the synthesis of heterocycles by condensation with polar multiple bonds and dipolar systems. The cycloadditions are of special interest from the viewpoint of orbital symmetry considerations. Some unusual organometallic complexes of ketenimines have also been synthesized. Recently some triaryl ketenimines have been found to have insecticidal and miticidal activity. Polymeric ketenimines have been implicated as molecular precursors of life.