Reusable Nickel Nanoparticles‐Catalyzed Reductive Amination for Selective Synthesis of Primary Amines

The preparation of nickel nanoparticles as efficient reductive amination catalysts by pyrolysis of in situ generated Ni‐tartaric acid complex on silica is presented. The resulting stable and reusable Ni‐nanocatalyst enables the synthesis of functionalized and structurally diverse primary benzylic, heterocyclic and aliphatic amines starting from inexpensive and readily available carbonyl compounds and ammonia in presence of molecular hydrogen. Applying this Ni‐based amination protocol, ‐NH₂ moiety can be introduced in structurally complex compounds, for example, steroid derivatives and pharmaceuticals.     

First example of ring expansion of activated quinolines and isoquinolines: novel benzoazepines

Activated quinoline and isoquinoline undergo unexpected ring expansion by diazocarbonyl compounds via C-C insertion in the presence of 5 mol% of copper triflate to produce ethyl 1H-benzo[b]azepine-1-carboxylate and ethyl 3H-benzo[d]azepine-3-carboxylate, respectively, in excellent yields with a high degree of selectivity     

Magnetic properties of n-type CuInS2

The magnetic susceptibility, χ, of a polycrystalline n-type CuInS₂ sample has been measured in the temperature range 4.2–300 K. A shallow donor level at 0.017 eV has been identified and an antiferromagnetic exchange coupling between donors is observed. These results are inferred from the excellent fit of the data to the equation $\text{χ(10}{}^{\mathrm{?6}}\text{cm}{}^3\text{mole}{}^{\mathrm{?1}}\text{) = -83.7 + 185}\text{[1?exp (}\text{?100}\text{T}\text{)]}\text{(T + 3)}$ in the whole temperature range.     

Total synthesis and stereochemical revision of acortatarins A and B

A first total synthesis of acortatarins A, B, and an enantiomer of the proposed structure of acortatarin B is described by using readily available d-sugars. This convergent total synthesis revealed the revision of the absolute configuration of acortatarin A and structural revision of acortatarin B. The key steps involved are regioselective epoxide opening with deprotonated 2,5-disubstituted pyrrole and spiroketalization.     

Efficient and highly selective iron-catalyzed reduction of nitroarenes

Pyrolysis of iron-phenanthroline complexes supported on carbon leads to highly selective catalysts for the reduction of structurally diverse nitroarenes to anilines in 90-99% yields. Excellent chemoselectivity for the nitro group reduction is demonstrated.     

SYNTHESIS OF SOME NEW 1,2,4-TRIAZOLO[3,4-b]-THIADIAZOLE DERIVATIVES AS POSSIBLE ANTICANCER AGENTS

3-Substituted-4-amino-5-mercapto-1,2,4-triazoles are versatile synthons for constructing various biologically active heterocycles. Their cyclization with carboxylic acids gives fused five-membered derivatives, whereas with α-bromoketones gives a six-membered heterocycle. In this article we report the synthesis of a series of 1,2,4-triazolo[3,4-b]thiadiazoles 5 starting from 4-amino-3-substituted-5-mercapto-1,2,4-triazoles 3 and fluorobenzoic acids 4 using phosphorous oxychloride as cyclizing agent. Fourteen of the newly synthesized compounds were screened for anticancer properties. Four among them showed in vitro anticancer activity.     

Frovatriptan salts of aliphatic carboxylic acids

The interaction of the antimigraine pharmaceutical agent frovatriptan with acetic acid and succinic acid yields the salts (±)‐6‐carbamoyl‐N‐methyl‐2,3,4,9‐tetrahydro‐1H‐carbazol‐3‐aminium acetate, C₁₄H₁₈N₃O⁺·C₂H₃O₂⁻, (I), (R)‐(+)‐6‐carbamoyl‐N‐methyl‐2,3,4,9‐tetrahydro‐1H‐carbazol‐3‐aminium 3‐carboxypropanoate monohydrate, C₁₄H₁₈N₃O⁺·C₄H₅O₄⁻·H₂O, (II), and bis[(R)‐(+)‐6‐carbamoyl‐N‐methyl‐2,3,4,9‐tetrahydro‐1H‐carbazol‐3‐aminium] succinate trihydrate, 2C₁₄H₁₈N₃O⁺·C₄H₄O₄²⁻·3H₂O, (III). The methylazaniumyl substitutent is oriented differently in all three structures. Additionally, the amide group in (I) is in a different orientation. All the salts form three‐dimensional hydrogen‐bonded structures. In (I), the cations form head‐to‐head hydrogen‐bonded amide–amide catemers through N—H...O interactions, while in (II) and (III) the cations form head‐to‐head amide–amide dimers. The cation catemers in (I) are extended into a three‐dimensional network through further interactions with acetate anion acceptors. The presence of succinate anions and water molecules in (II) and (III) primarily governs the three‐dimensional network through water‐bridged cation–anion associations via O—H...O and N—H...O hydrogen bonds. The structures reported here shed some light on the possible mode of noncovalent interactions in the aggregation and interaction patterns of drug molecule adducts.     

Highly diastereoselective synthesis of spiro[cyclopropane-1,3′-indolin]-2′-ones via catalyst-free cyclopropanation using ethyl diazoacetate

Substituted 3-methyleneindolin-2-ones were efficiently cyclopropanated with ethyl diazoacetate to yield spiro[cyclopropane-1,3′-indolin]-2′-ones in a catalyst-free and highly diastereoselective reaction in a mixture of ethanol–acetonitrile (1:1 v/v) as solvent.     

Synthesis of New (Pyrazol‐3‐yl)‐1,3,4‐oxadiazole Derivatives by Unexpected Aromatization During Oxidative Cyclization of 4,5‐Dihydro‐1H‐pyrazole‐3‐carbohydrazones and Their Biological Activities

A series of novel 2‐(4‐(4‐chlorophenyl)‐1H‐pyrazol‐3‐yl)‐5‐(Aryl)‐1,3,4‐oxadiazoles were synthesized by unexpected aromatization during oxidative cyclization of 4‐(4‐chlorophenyl)‐4,5‐dihydro‐1H‐pyrazole‐3‐carbohydrazones using chloramine‐T as an oxidant. The hydrazones were derived from 4‐(4‐chlorophenyl)‐4,5‐dihydro‐1H‐pyrazole‐3‐carbohydrazide and various substituted aldehydes. The structure of the synthesized compounds was confirmed by FTIR, ¹H NMR, ¹³C NMR, and mass spectral data. The synthesized compounds were evaluated for their antitubercular and antioxidant activities. All the compounds 4a , 4b , 4c , 4d , 4e , 4f , 4g , 4h and 5a , 5b , 5c , 5d , 5e , 5f , 5g , 5h showed good antitubercular activity against Mycobacterium tuberculosis (minimum inhibitory concentration = 25 µg/mL for 4f and 4g , 50–100 µg/mL for the rest). However, all the compounds exhibited poor antioxidant activity against 1,1‐diphenyl‐2‐picryl‐hydrazil free radical.     

Convenient and Mild Epoxidation of Alkenes Using Heterogeneous Cobalt Oxide Catalysts

A general epoxidation of aromatic and aliphatic olefins has been developed under mild conditions using heterogeneous Co_xO_y–N/C (x=1,3; y=1,4) catalysts and tert‐butyl hydroperoxide as the terminal oxidant. Various stilbenes and aliphatic alkenes, including renewable olefins, and vitamin and cholesterol derivatives, were successfully transformed into the corresponding epoxides with high selectivity and often good yields. The cobalt oxide catalyst can be recycled up to five times without significant loss of activity or change in structure. Characterization of the catalyst by XRD, TEM, XPS, and EPR analysis revealed the formation of cobalt oxide nanoparticles with varying size (Co₃O₄ with some CoO) and very few large particles with a metallic Co core and an oxidic shell. During the pyrolysis process the nitrogen ligand forms graphene‐type layers, in which selected carbon atoms are substituted by nitrogen.