3,3-Diazidoenones-new types of highly reactive bis-azides. Preparation and synthetic transformations

The interaction of geminal dichlorovinylketones with sodium azide was investigated by NMR and DFT calculations. It was found that the corresponding geminal 3,3-diazidoenones are the resultant species. These highly reactive compounds can be trapped with cyclooctyne to form bis-triazolyl substituted enones. In the absence of a trapping agent, 3,3-diazidoenones do cyclize into 3-azidoisoxazoles with the elimination of molecular nitrogen. The versatile reactivity of the resultant azidoisoxazoles was demonstrated in reactions with phosphorus(iii) derivatives, Huisgen 1,3-dipolar cycloaddition and Dimroth cyclization to provide efficient access to a variety of valuable compounds. © 2019 the Partner Organisations

Determination of the Absolute Configuration of CN-Palladacycles by 31P{1H} NMR Spectroscopy Using (1R,2S,5R)-Menthyloxydiphenylphosphine as the Chiral Derivatizing Agent: Efficient Chirality Transfer in Phosphinite Adducts

A series of (1R)-MenOPPh2 phosphinite derivatives of α-arylalkylaminate CN-palladacycles of known absolute configuration was prepared. Their structure and stereochemistry were determined using different experimental (NMR spectroscopy and X-ray diffraction) and theoretical (density functional theory calculation) methods. Despite the conformational mobility of the phosphinite reagent and the highly remote position of its stereocenters from those of the cyclopalladated amine, efficient chirality transfer in the phosphinite cyclopalladated complexes was established. On the basis of these results, a new method for the determination of the absolute configuration of chiral CN-palladacycles was elaborated using the (1R)-MenOPPh2 phosphinite as a highly sensitive referee ligand and in situ 31P{1H} NMR spectroscopy as a control method. The proposed approach is a remarkable addition to the classical NMR techniques, increasing their versatility and excluding the isolation of the phosphinite derivatives. © 2016 American Chemical Society

Reaction of 3-azidoisoxazoles with active methylene compounds

3-Azidoisoxazoles react with various active methylene compounds (malononitrile, ethyl cyanoacetate and ethyl acetoacetate) in the presence of base to give hybrid isoxazole–triazole molecules in good to nearly quantitative yields. © 201

Synthesis of a New Family of 1,1-Diazidoethenes: One-Pot Construction of 4-Azido-1,2,3-triazoles via Nitrene Cyclization

The reaction of 4,4-dichloro-1,2-diazabuta-1,3-dienes with sodium azide has been studied and found to provide straightforward access to extremely rare 1,1-bisazides. It was demonstrated that these highly unstable compounds are prone to eliminate the N2 molecule to cyclize into 4-azido-1,2,3-triazoles bearing two aryl (heteroaryl) groups at positions 2 and 5. The formation of bisazides was confirmed by their trapping with cyclooctyne and B3LYP calculations. Most likely, the elimination of nitrogen to form an intermediate nitrene is facilitated by the aza group via anchimeric-like participation. The reaction was found to be very general for the highly efficient synthesis of various 4-azidotriazoles. It was demonstrated that these heterocycles are highly attractive building blocks for subsequent preparation of 1,2,3-triazole-derived compounds. © 2018 American Chemical Society

When Applying the Mercury Poisoning Test to Palladacycle-Catalyzed Reactions, One Should Not Consider the Common Misconception of Mercury(0) Selectivity

The aim of this study was to demonstrate the absolute necessity of control experiments for a correct interpretation of mercury drop test results when applied to mechanistic studies of palladacycle-catalyzed reactions. It was shown that the interaction of diverse azapalladacycles with metallic mercury leads to the formation of organomercuric chlorides during the redox-transmetalation process. The structure of these organomercurials was confirmed by elemental analysis, 1H, 13C{1H}, and 199Hg{1H} NMR spectra, X-ray diffraction analysis, and DFT calculations. The behavior and properties of C,N-mercuracycles bearing the weak and labile N···Hg bond are discussed on the basis of the temperature dependence of the NMR spectra and calculated thermodynamic parameters of the dechelation process. © 2018 American Chemical Society

When Applying the Mercury Poisoning Test to Palladacycle-Catalyzed Reactions, One Should Not Consider the Common Misconception of Mercury(0) Selectivity

The aim of this study was to demonstrate the absolute necessity of control experiments for a correct interpretation of mercury drop test results when applied to mechanistic studies of palladacycle-catalyzed reactions. It was shown that the interaction of diverse azapalladacycles with metallic mercury leads to the formation of organomercuric chlorides during the redox-transmetalation process. The structure of these organomercurials was confirmed by elemental analysis, 1H, 13C{1H}, and 199Hg{1H} NMR spectra, X-ray diffraction analysis, and DFT calculations. The behavior and properties of C,N-mercuracycles bearing the weak and labile N···Hg bond are discussed on the basis of the temperature dependence of the NMR spectra and calculated thermodynamic parameters of the dechelation process. © 2018 American Chemical Society

Determination of the Absolute Configuration of CN-Palladacycles by 31P{1H} NMR Spectroscopy Using (1R,2S,5R)-Menthyloxydiphenylphosphine as the Chiral Derivatizing Agent: Efficient Chirality Transfer in Phosphinite Adducts

A series of (1R)-MenOPPh2 phosphinite derivatives of α-arylalkylaminate CN-palladacycles of known absolute configuration was prepared. Their structure and stereochemistry were determined using different experimental (NMR spectroscopy and X-ray diffraction) and theoretical (density functional theory calculation) methods. Despite the conformational mobility of the phosphinite reagent and the highly remote position of its stereocenters from those of the cyclopalladated amine, efficient chirality transfer in the phosphinite cyclopalladated complexes was established. On the basis of these results, a new method for the determination of the absolute configuration of chiral CN-palladacycles was elaborated using the (1R)-MenOPPh2 phosphinite as a highly sensitive referee ligand and in situ 31P{1H} NMR spectroscopy as a control method. The proposed approach is a remarkable addition to the classical NMR techniques, increasing their versatility and excluding the isolation of the phosphinite derivatives. © 2016 American Chemical Society

The use of control experiments as the sole route to correct the mechanistic interpretation of mercury poisoning test results: The case of P,C-palladacycle-catalysed reactions

In the study of the metallic mercury interaction with cyclopalladated derivatives of tris-ortho-tolylphosphine [{(κ2P,C-L)Pd(μ-X)}2], the redox-transmetallation of palladacycles by metallic mercury with the formation of P,C-chelated benzylmercurials [(κ2P,C-L)HgX] was revealed at moderate temperature in the presence of excess Hg(0). In contrast, the mercury(0) testing of the Suzuki reaction with the same chloride P,C-precatalyst gave a negative result, even at a higher temperature and with a greater excess of Hg(0). The structures of these mercurials have been convincingly confirmed spectrally (1Н, 13С, 31Р and 199Hg NMR), and via X-ray diffraction study and DFT calculations for the chloride mercurial. Our results and the analysis of known data on the mercury diagnostics of catalytic systems with classical and anomalous P,C-precatalysts enable us to assume that the intact state of palladacycle is present in the key anionic intermediate [(κ2P,C-L)Pd0]– of catalytic cycles of the Suzuki and Heck reactions and a lower reactivity of Hg(0) with palladium(0) complexes in comparison with that of palladium(II) analogues. © 202

The impact of alicyclic substituents on the extraction ability of new family of 1,10-phenanthroline-2,9-diamides

Development of efficient extractants for the separation of actinides and lanthanides in the technologies of nuclear fuel cycle is one of the most urgent and complex tasks in modern nuclear energetics. New family of 4,7-dichloro-1,10-phenanthroline-2,9-dicarboxylic acid diamides based on cyclic amines was synthesized and shown to exhibit high selectivity in the La/Am pair separation (SF (Am/La ≈ 10)) and in the Am/Eu pair separation (SF (Am/Eu ≈ 12)). It was shown that pyrrolidine derived diamide is more efficient extractant for americium, curium and lanthanides from highly acidic HNO3 solution than its non-cyclic N,N,N′,N′-tetraalkyl analogues. The structures of synthesized compounds were studied in details by IR, NMR spectroscopy, and single crystal X-ray diffraction. According to spectroscopy data, incorporation of aromatic rings to the amide fragment of ligand leads to complex dynamic behavior in solutions what is believed to strongly affect the extraction ability of synthesized ligands. © 2020 The Royal Society of Chemistry