Microwave-Assisted Synthesis of Mono- and Disubstituted 4-Hydroxyacetophenone Derivatives via Mannich Reaction: Synthesis, XRD and HS-Analysis.

An efficient microwave-assisted one-step synthetic route toward Mannich bases is developed from 4-hydroxyacetophenone and different secondary amines in quantitative yields, via a regioselective substitution reaction. The reaction takes a short time and is non-catalyzed and reproducible on a gram scale. The environmentally benign methodology provides a novel alternative, to the conventional methodologies, for the synthesis of mono- and disubstituted Mannich bases of 4-hydroxyacetophenone. All compounds were well-characterized by FT-IR, ¹H NMR, 13C NMR, and mass spectrometry. The structures of 1-{4-hydroxy-3-[(morpholin-4-yl)methyl]phenyl}ethan-1-one (2a) and 1-{4-hydroxy-3-[(pyrrolidin-1-yl)methyl]phenyl}ethan-1-one (3a) were determined by single crystal X-ray crystallography. Compound 2a and 3a crystallize in monoclinic, P21/n, and orthorhombic, Pbca, respectively. The most characteristic features of the molecular structure of 2a is that the morpholine fragment adopts a chair conformation with strong intramolecular hydrogen bonding. Compound 3a exhibits intermolecular hydrogen bonding, too. Furthermore, the computed Hirshfeld surface analysis confirms H-bonds and π⁻π stack interactions obtained by XRD packing analyses.

A new route for the synthesis of phosphate esters: 2,2'-[benzene-1,2-diylbis(oxy)]bis(5,5-dimethyl-1,3,2-dioxaphosphinane) 2,2'-dioxide.

Podand-type ligands are an interesting class of acyclic ligands which can form host-guest complexes with many transition metals and can undergo conformational changes. Organic phosphates are components of many biological molecules. A new route for the synthesis of phosphate esters with a retained six-membered ring has been used to prepare 2,2'-[benzene-1,2-diylbis(oxy)]bis(5,5-dimethyl-1,3,2-dioxaphosphinane) 2,2'-dioxide, C6H4{O[cyclo-P(O)OCH2CMe2CH2O]}2 or C16H24O8P2, (1), 2-[(2'-hydroxybiphenyl-2-yl)oxy]-5,5-dimethyl-1,3,2-dioxaphosphinane 2-oxide, [cyclo-P(O)OCH2CMe2CH2O](2,2'-OC6H4-C6H4OH), (2), and oxybis(5,5-dimethyl-1,3,2-dioxaphosphinane) 2,2'-dioxide, O[cyclo-P(O)OCH2CMe2CH2O]2, (3). Compound (1) is novel, whereas the results for compounds (2) and (3) have been reported previously, but we record here our results for compound (3), which we find are more precise and accurate than those currently reported in the literature. In (1), two cyclo-P(O)OCH2CMe2CH2O groups are linked through a catechol group. The conformations about the two catechol O atoms are quite different, viz. one C-C-O-P torsion angle is -169.11 (11)° and indicates a trans arrangement, whereas the other C-C-O-P torsion angle is 92.48 (16)°, showing a gauche conformation. Both six-membered POCCCO rings have good chair-shape conformations. In both the trans and gauche conformations, the catechol O atoms are in the axial sites and the short P=O bonds are equatorially bound.

Synthesis and characterization of some novel 1,2,4-triazoles, 1,3,4-thiadiazoles and Schiff bases incorporating imidazole moiety as potential antimicrobial agents.

(1,4,5-Triphenylimidazol-2-yl-thio)butyric acid hydrazide (3) was obtained via alkylation of 1,4,5-triphenylimidazol-2- thiol (1) with ethylbromobutyrate, followed by addition of hydrazine hydrate. Treatment of acid hydrazide 3 with carbon disulfide in an ethanolic potassium hydroxide solution gave the intermediate potassium dithiocarbazinate salt, which was cyclized to 4-amino-5-[(1,4,5-triphenylimidazol- -2-yl)thiopropyl]-2H-1,2,4-triazole-3-thione (4) in the presence of hydrazine hydrate. Condensation of compound 3 with alkyl/arylisothiocyanate afforded the corresponding 1-[4-(1,4,5-triphenylimidazol-2-ylthio)butanoyl]-4-alkyl/arylthiosemicarbazides (5-7), which upon refluxing with sodium hydroxide, yielded the corresponding 1,2,4-triazole - -3-thiols 8-10. Under acidic conditions, compounds 4-6 were converted to aminothiadiazoles 11-13. Moreover, the series of Schiff bases 14-18 were synthesized from the condensation of compound 3 with different aromatic aldehydes. The newly synthesized compounds were characterized by IR, 1H NMR, 13C NMR and mass spectral analyses. They were also preliminarily screened for their antimicrobial activity.

New eco-friendly 1-alkyl-3-(4-phenoxybutyl) imidazolium-based ionic liquids derivatives: a green ultrasound-assisted synthesis, characterization, antibacterial activity and POM analyses.

In view of the emerging importance of the ILs as "green" materials with wide applications and our general interests in green processes, a series of a twenty five new 1-alkyl-3-(4-phenoxybutyl) imidazolium-based ionic liquids (ILs) derivatives is synthesized using a facile and green ultrasound-assisted procedure. Their structures were characterized by FT-IR, 1H-NMR, 13C-NMR, 11B, 19F, 31P, and mass spectrometry. Antimicrobial screens of some selected ILs were conducted against a panel of Gram-positive and Gram-negative bacteria. The antimicrobial activity of each compound was measured by determination of the minimal inhibitory concentration (MIC) yielding very interesting and promising results. Their antibacterial activities are reported, and, on the basis of the experimental and virtual POM screening data available, attempt is also made to elucidate the structure activity relationship.

Synthesis and reactivity of a dipyrrinatolithium complex.

The synthesis and characterization of the first dipyrrinato-alkali-metal complex is reported herein. The novel reactivity of this lithium complex is demonstrated in the preparation, isolation, and characterization of a heteroleptic zinc(II) complex in high yield.

Asymmetric synthesis of mono- and dinuclear bis(dipyrrinato) complexes.

The diastereoselective syntheses of Zn(II) bis(dipyrrinato) helicates is reported, involving ligands templated by the incorporation of homochiral binol within the linker joining the two dipyrrinato units. The most diastereoselective formation of dinuclear bis(dipyrrinato) helicates to date is reported. The formation of either mononuclear or dinuclear helicates can be tuned by varying the length of the linker between the dipyrrinato units and by varying the complexation procedure. The neutral dipyrrinato helicates were readily analyzed by HPLC to ascertain diastereoselectivity, and circular dichroism studies revealed the helical nature of the complexes. The molar ellipticities of the helicates produced by diastereoselective complexation are very large in the visible region and typically correspond to binol moieties in the UV region. Extensive X-ray crystallographic investigations further confirmed the helicity of the mononuclear Zn(II) helicates and identified significant interlayer displacement and bending within crystals.

Synthesis and anti-cancer activity of C-ring-functionalized prodigiosin analogues.

Prodigiosin is the parent member of the 4-methoxypyrrolyldipyrromethene family of natural products and is known for its anti-cancer activity. A new series of analogues was synthesized, incorporating pendent functional esters and beta-carbonyl substituents on the C-ring. The beta-carbonyl group allowed for the facile isolation of the prodigiosenes, and the pendent esters allow for further derivatization. The novel prodigiosenes generally retain the anti-cancer activity of prodigiosin in 60 human cell lines derived from nine cancer cell types, with neither the conjugated beta-carbonyl group, as either ketone or ester, nor the pendent ester significantly reducing the anti-cancer activity of the core skeleton.