Center for Magnetic Resonance

T.B. Anisimova, M.A. Kinzhalov, M.L. Kuznetsov, M.F.C. Guedes da Silva, A.A. Zolotarev, V.Yu. Kukushkin, A.J.L. Pombeiro, K.V. Luzyanin

“1,3-Dipolar cycloaddition of nitrones to gold(III)-bound isocyanides”

Organometallics, 2016, 35, 3569-3576
DOI:10.1021/acs.organomet.6b00635

Treatment of gold(III)-isocyanides [AuCl₃(CNR₁)] (R₁ = Xyl 1, Cy 2, But 3) with an equimolar amount of 5,5-dimethyl-1-pyrroline-N-oxide (4) in CH2Cl2 at −74 °C leads to the generation of the heterocyclic aminocarbene species [AuCl₃{C(ON^aCMe₂CH₂CH₂C^bH)═N^eR1}(N^a–C^b)(C^b–N^e)] 8 (for R₁ = But) or gold(III) complexes cis-[AuCl₂{N^a(CMe₂CH₂CH₂C^bN^eR₁)C^d═O}(N^a═C^b)(N^e–C^d)] 9 and 10 (for R₁ = Xyl and Cy) in good isolated yields (75–87%). DFT calculations show that deprotonation of the endocyclic CH group in the carbene ligand leads to spontaneous N–O bond cleavage, and acidity of this group is a factor controlling the different chemical behavior of 1–3 depending on the nature of substituent R1. The reaction of equimolar amounts of the aldonitrone p-TolCH═N⁺(Me)O^– (5) or the ketonitrones Ph₂C═N⁺(R₂)O^– (R₂ = Ph 6, CH₂Ph 7) with 1–3 in CD2Cl2 at −70 °C in air (or under N2) revealed the formation of the carbene complexes [AuCl₃{C(ONMeC^aH-p-Tol)═N^bR₁}(C^a–N^b)] (R₁ = Cy 11, Xyl 12, But 13), [AuCl₃{C(ONPhCaPh₂)═N^bR₁}(Ca–N^b)] (R₁ = Cy 14, But 15), or [AuCl₃{C(ON(CH₂Ph)C^aPh2)═N^bR₁}(C^a–N^b)] (R₁ = Cy 16, Xyl 17), as studied by ¹H NMR. The reaction of 6 with 1 and of 7 with 3 did not furnish carbene products. Compounds 8–10 were characterized by ESI-MS, IR, 1D (¹H, ¹³C{H}) and 2D (¹H,¹H–COSY, ¹H,¹³C-HSQC, ¹H,¹³C-HMBC) NMR spectroscopic techniques, and, only for 8, elemental analyses (C, H, N), while compounds 11–17 were characterized by 1D (¹H, ¹³C{H}) and 2D (¹H,¹³C-HSQC) NMR. Structures of compounds 8, 9, and 13 were additionally established by single-crystal X-ray diffraction.

D.S. Bolotin, A.S. Novikov, V.K. Burianova, M.Ya. Demakova, E.A. Daines, С. Pretorius, P. Mokolokolo, A. Roodt, N.A. Bokach, M.S. Avdontceva, A.P. Zhdanov, K.Yu. Zhizhin, N.T. Kuznetsov, V.Yu. Kukushkin

“Nucleophilicity of oximes based upon addition to а nitrilium closo-decaborate cluster”

Organometallics, 2016, 35, 3612-3623
DOI:10.1021/acs.organomet.6b00678

Three types of oxime species, i.e., 4-morpholylcarbamidoxime (hydroxyguanidine), phenylacetamidoxime and benzamidoxime (amidoximes), and cyclohexanone oxime and benzophenone oxime (ketoximes), react at room temperature with the 2-nitrilium closo-decaborate clusters, leading to 2-iminium closo-decaborates (14 examples; 57–94%). These species were characterized by ICPMS-based boron elemental analysis, HRESI–-MS, molar conductivity, IR, 1H{11B}, and 11B{1H} NMR spectroscopies, and additionally by single-crystal X-ray diffraction (for six compounds). On the basis of kinetic data, ΔH⧧, ΔS⧧, and ΔG⧧ of the additions were determined, showing a 4 order-of-magnitude decrease in reactivity from the hydroxyguanidine to the aromatic ketoxime as entering nucleophiles. The results of DFT calculations indicate that the mechanism for these reactions is stepwise and is realized through the formation of the orientation complex of the nitrone form, R2R3C═N+(H)O–, of oximes with [B10H9NCEt]−, giving further an acyclic intermediate (the rate-determining step), followed by proton migration, leading to the addition product. The calculated overall activation barrier for these transformations is consistent with the experimental kinetic observations. This work provides, for the first time, a broad nucleophilicity series of oximes, which is useful to control various nucleophilic additions of oxime species.

J.J. Medvedev, D.V. Semenok, X.V. Azarova, L.L. Rodina, V.A. Nikolaev

“A New Powerful Approach to Multi-Substituted 3(2H)-Furanones via Brønsted Acid-Catalyzed Reactions of 4-Diazodihydrofuran-3-ones”

Synthesis, 2016, 48, A-H
DOI:10.1055/s-0036-1588304

The interaction of 5,5-dialkyl(diaryl)-substituted 4-diazo-3(2H)furanones with Brønsted acids (TFA, TsOH, etc.) causes elimination of nitrogen accompanied by 1,2-nucleophilic rearrangement, giving rise to exclusive formation of 4,5-dialkyl(diaryl)-substituted 3(2Н)-furanones, ring-fused 3(2H)-furanones, and phenanthro[9,10-b]furan-3(2H)-ones in yields of up to 99%. The reaction is a new highly efficient way for the synthesis of multisubstituted 3(2Н)furanones.

D.V. Semenok, J.J. Medvedev, M.S. Avdontceva, S.I. Selivanov, J. Sieler, A.S. Mereshchenko, V.A. Nikolaev

“Experimental Evidence of Intramolecular CAr–H···O=C Hydrogen Bonds in the Structure of (Diaryl)tetrahydrofuranones Using Spectroscopic Tools”

Helvetica Chim. Acta, 2016, 99, 716-723
DOI:10.1002/hlca.201600149

The occurrence of bifurcate H-bonds CAr–H···O=C in the structure of (diaryl)-tetrahydrofuranones was experimentally demonstrated using different methods and techniques. The consistent increasing spin–spin coupling constants 1J(C,H) of the ortho-H-atoms and low-field shift of v (C=O) in IR spectra of 2,2-(diaryl)tetrahydrofuran-3(2H)-ones relative to their 5,5-diaryl counterparts, as well as pronounced dependence of the ortho-C–H H-atoms chemical shifts on the temperature and solvent polarity along with X-ray diffraction analysis data unambiguously point to the existence of weak CAr–H···O=C H-bonds in these molecules.