Synthesis and structures of complexes ofN-(2-aminoethyl)diaziridines with transition metal salts

A series of complexes ofN-(2-aminoethyl)diaziridines with transition metal salts (Zn²⁺, Cd²⁺, Ni²⁺, Co²⁺, Mn²⁺, or Fe²⁺) were synthesized. Their structures were established by IR and NMR spectroscopy. The structure of bis[1,2-bis(2-aminoethyl)diaziridine]cadmium(II) diperehlorate was confirmed by X-ray diffraction analysis. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1910–1914, November, 2000.     

Structural and Spectral Study of Nickel(II) Complexes of Pyridyl bis{3‐piperidyl‐, bis{hexamethyleneiminyl‐, bis{N(4)‐diethyl‐, and bis{N(4)‐dipropylthiosemicarbazones}

Pyridyl bis(N(4)‐substituted thiosemicarbazones), in which the substituents replacing the NH₂ group on the thiosemicarbazone moieties are piperidyl, H₂Plpip; hexamethyleneiminyl, H₂Plhexim; diethylamino, H₂Pl4DE; and dipropylamino, H₂Pl4DP, have been synthesized. These bis(thiosemicarbazones) and their nickel(II) complexes have been characterized with IR, electronic, mass, and ¹H and ¹³C NMR spectra. Crystal structures have been solved for H₂Plpip and all four nickel(II) complexes. H₂Plpip does not possess hydrogen bonding between the thiosemicarbazone moieties, but is in the Z isomeric form with intramolecular hydrogen bonding from both thiosemicarbazone moieties to pyridine nitrogen atoms. The nickel(II) complexes possess square‐planar N₂S₂ (i. e., imine nitrogen and thiolato sulfur atoms) centers and the two pyridine ring nitrogen atoms are not coordinated.     

Magnesium perchlorate as efficient Lewis acid for the Knoevenagel condensation between β-diketones and aldehydes

A new protocol for the Knoevenagel condensation between β-diketones and aliphatic and aromatic aldehydes promoted by Mg(ClO₄)₂ under mild conditions is reported.     

CO2 Hydroboration: Impact of the Boryl Moieties on the Reactivity of Four Bis(boryl)acetal Compounds toward 2,6-Diisopropylaniline

The hydroboration of CO₂ into bis(boryl)acetal (BBA) compounds is an important transformation, since it enabled to selectively reduce CO₂ by 4e^- and to subsequently use the BBA compounds as C₁ and C_n sources. However, the influence of the nature of the boryl moieties on the reactivity of BBA compounds has not been evaluated so far. In the present study, four BBA compounds – including two new ones – were reacted with 2,6-diisopropylaniline to afford the expected imine. Significant differences in the rate of the reaction from minutes to weeks have been observed depending on the BBA used, showing the importance of the nature of the boryl moieties. Theoretical investigations enabled to propose a mechanism involving the addition of the aniline to the BBA as the rate-determining step and to determine that the steric hindrance of the BBA compounds is the main factor driving the rate of this condensation reaction.     

Preparation of β-cyclodextrin-polyaniline complex in supercritical CO2

A method is proposed to prepare β-cyclodextrin (β-CD)/polyaniline (PANI) inclusion complex. In this route, benzoyl peroxide (BPO, the oxidant) is first encapsulated into the cavity of β-CD. Aniline is then carried into the cavity of β-CD by supercritical (SC) CO₂, which polymerizes in situ to form inclusion complex. The product is characterized by FT-IR, UV-Vis, ¹H NMR and XRD techniques. The results suggest that the columnar inclusion complexes may be formed.     

A reliable synthesis of 2- and 6-amino-β-cyclodextrin and permethylated-β-cyclodextrin

A new, reliable method for the introduction of an amine group at positions 2 or 6 of β-cyclodextrin and permethyl-β-cyclodextrin is described. It involves selective tosylation followed by azide substitution and almost quantitative reduction with triphenylphosphine followed by hydrolysis of the phosphinimine intermediate.     

Asymmetric synthesis of α-fluoro-α-sulfenyl-β-ketoesters using DBFOX-Ph/Ni(II) complex

Enantioselective α-sulfenylation of α-fluoro-β-ketoesters 4 with phenylsulfenyl chloride catalyzed by DBFOX-Ph/Ni(II) complex afforded the corresponding α-fluoro-α-sulfenyl-β-ketoesters 2 in moderate to good yields with excellent enantiomeric excesses up to 93% ee. α-Fluoro-α-sulfenyl-β-ketoesters can be effectively converted to tri-fluorinated α-sulfenylcarboxylates by the use of DAST, which should be useful intermediates for the synthesis of non-racemized fluorinated isosteres of pharmaceutically attractive SM₃₂. The enantioselective α-phenylsulfenylation as well as α-pentafluoro-phenylsulfenylation of non-fluorinated β-ketoesters 5 were also carried out under the same catalyst conditions affording up to 95% ee of the products 6-8.     

Conduramine F-1 epoxides: synthesis and their glycosidase inhibitory activities

Starting from (±)-7-oxanorbornenone ((±)-14), (±)-(1RS,2RS,3SR,6SR)-6-azidocyclohex-4-en-1,2,3-triol ((±)-24) and (±)-(1RS,2RS,3SR,6RS)-6-azidocyclohex-4-en-1,2,3-triol ((±)-26) were obtained. Epoxidation of the latter cyclohexene derivative gave two epoxides (±)-30 and (±)-31 that were converted into (±)-conduramine F-1 epoxides (±)-10 and (±)-11 and N-substituted derivatives (±)-12 and (±)-13. Compound (±)-(1RS,2SR,3RS,4SR,5RS,6SR)-5-({[4-(trifluoromethyl)phenyl]methyl}amino)-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-12c) is a good, non-competitive inhibitor of β-xylosidase from Aspergillus niger (K_i=2.2 μM), and (±)-(1RS,2RS,3SR,4RS,5SR,6SR)-5-{[(biphenyl-4-yl)methyl]amino}-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-13d) is a good inhibitor of α-glucosidase from brewer's yeast (K_i=2.8 μM, non-competitive).     

Catalyst free,regioselective one-pot three-component synthesis of thiazol-2-imine derivatives in ionic liquid

A one-pot three-component approach for the synthesis of thiazol-2-imines has been described by the reaction of amine, phenyl isothiocyanate and β-nitroacrylate in [Hbim]BF₄ ionic liquid. The method is applicable for aromatic, benzylic, aliphatic and cyclic amines. Reusable reaction media, regioselectivity, mild reaction condition, catalyst free and high yield of products are the salient features of this protocol.     

Structure elucidation and stereoselective total synthesis of pavettamine, the causal agent of gousiekte

The structure elucidation of a novel natural product pavettamine (1), the causal agent of the plant toxicosis gousiekte, is reported. The structure was defined by analysis of NMR and MS data and the relative configuration followed from the ¹³C NMR data of the acetonide derivative. The absolute stereochemistry was established by total synthesis from (2S)-malic acid using chiral sulfoxide methodology as (2S,4R,8R,10S)-1,11-diamino-6-aza-undecane-2,4,8,10-tetraol.