Letters in Organic Chemistry - Volume 11, Issue 1, 2014

Using benzo-15-crown-5 derivatives as starting materials, two novel benzo-15-crown-5/C60 dyads with different linking chains were designed and synthesized in good yields by 1,3-dipolar cycloaddition of azomethine ylide generated in situ from aldehyde and sarcosine tied to C60. It was found that their UV-Vis absorption spectra could be regulated hypsochromically by metal ions complexation. The long and soft linking chain was favorable for cooperate interaction of crown ether unit and C60 unit.

Racemic solketal (2,2-Dimethyl-1,3-dioxolan-4-yl)methanol 1, was treated with carboxylic acids of varying chain length or their vinyl esters in the presence of different lipases. The esterification reaction was carried out in n-hexane or diisopropyl ether as a solvent. The yield of the solketal esters and their enantiopurity were satisfactory, as indicated by gas chromatography using chiral column. Lipases from Rhizopus oryzae and Pseudomonas fluorescence gave the best enantiomeric excess (ee) when the solketal was treated with vinyl butyrate in a solution of diisopropyl ether at room temperature.

Novel optically active spiro-sultam-oxindole compounds with middle yields and excellent stereoselectivites were prepared through consecutive N-mesylation/cyclization reactions. The enantioselectivities of the reactants could transfer to the desired products completely.

Sym- collidinium chlorochromate (S-COCC), is a new, rapid and useful reagent for the oxidative deprotection of oximes to the corresponding carbonyl compounds. The interesting feature of this catalytic system is that oximes which have conjugated C=C bonds, the C=N bond will selectively convert to the relevant C=O bond. The reactions proceed under room temperature, ethylacetate as solvent and in the presence of catalytic amount of aluminum chloride to offer the products in excellent yields. Furthermore, in this study, it is indicated that both oximes with electron-withdrawing groups and oximes with electron-donating groups produced carbonyl compounds in good yields. In this protocol, the deprotection of oximes is less dependent on the electronic property of substrates. A theoretical study of NMR shielding tensors and thermochemical parameters of substrates has also been carried out.

The first synthesis of azo bearing coumarins from azo aldehydes and malononitrile in the presence of efficient recyclable catalyst, nano particle Fe3O4 under ultrasound irradiation and under grinding reaction in high yield and short reaction time is reported. In the other study, the first electrophilic substitution under ultrasound irradiation for the synthesis of azo bearing coumarins was developed. All of synthesized compounds were characterized by IR, NMR and elemental analysis.

During this study the application of Natrolite zeolite was investigated as a solid acid catalyst for efficient preparation of 5-substituted 1H-tetrazole derivatives. Excellent yields of products were obtained with a wide range of substrates. After completion of the reaction, the catalyst was recovered by filtration and reused several times with only a slight decrease of activity observed under the same reaction conditions.

The structure and tautomerism of N-(1-naphthyl)-3-amino-5-oxo-4-phenyl-1H-pyrazole-1-carboxamide with antibacterial activity have been investigated with experimental approaches (X-ray studies, IR, 1H and 13C NMR spectra, including NOESY and N-HSQC spectra) and quantum chemical calculations. It is found that the tautomer with the keto group in position 5 is energetically privileged in the crystalline state while in DMSO and water solution the equilibrium is shifted towards the form with the hydroxyl group at this position. These findings are related to antibacterial activity of the studied compound and are crucial for future molecular docking and structure-activity relationship studies.

A new method for the synthesis of formamides has been developed by the N-formylation of amines with formic acid in the presence of nano cerium oxide as an efficient and recyclable catalyst under ultrasound irradiation. The reaction system is remarkably simple and environmentally benign.

An efficient and direct protocol is described for the preparation of 1-substituted 1H-1,2,3,4-tetrazoles by the reaction of primary amines, triethyl orthoformate and sodium azide in the presence of catalytic amount of silica-supported perchloric acid under solvent-free and heterogeneous conditions. The thermal solvent-free green procedure offers advantages such as simple methodology, easy work-up, high yield, recovery and reusability of catalyst.

We herein describe the synthesis and antibacterial activity of cyclic sulfamide linked to tetrathiafulvalene (TTF). This approach exploits the inherent chemistry of biomolecules and π-donors compounds to generate symmetric bis-trimethyltetrathiafulvalenyl-2-thiophenyl cyclic sulfamides. Two strategies are revealed, one centres on the Ringclosing olefin metathesis using the Grubbs catalyst a second strategy based on the direct alkylation of dibromoalkane derivatives with symmetric sulfamide under basic conditions. All the newly synthesized compounds were screened for their antimicrobial activities and some of them were found to possess good or moderate antimicrobial activity.

During the research on the Pd-catalyzed intramolecular cyclization reaction via C-H activation, the dehalogenation of 3-halo-2(5H)-furanones is unexpectedly discovered. Under the optimized conditions without any special anaerobic and anhydrous treatments, using N,N-diisopropylethylamine (DIPEA) simultaneously as hydrogen source and base, the reactions of 27 substrates with less Pd catalyst (5 mol% Pd(PPh3)4) usually give higher yields (70-99%, mostly over 82%). Especially for 3-halo-2(5H)-furanone substrates simultaneously containing aryl halide structure, this kind of Pd-catalyzed dehalogenation has good selectivity. After the selectivity is explained via the substrate theoretical calculation, a possible reaction mechanism of the Pd-catalyzed dehalogenation is proposed. These novel investigations provide an efficient, simple, practical and selective Pd-catalyzed dehalogenation method for the non-aromatic halide substrates with many different functional groups.