Transition-metal-free synthesis of (Z)-3-ylidenephthalides from 2-acyl-benzoic acids

We report a highly efficient method for the synthesis of (Z)-3-ylidenephthalides via intramolecular cyclization of readily available 2-acyl-benzoic acids mediated by TSTU at room temperature. Using this method, diversely substituted (Z)-3-ylidenephthalides have been generated in good to excellent yields. The application of the method is highlighted by gram-scale preparation of the antiplatelet drug n-butylphthalide.     

Synthesis of 3-iodothiophenes via iodocyclization of (Z)-thiobutenynes

A simple synthesis of 3-iodothiophenes was demonstrated using a wide range of (Z)-thioenynes. The key step in the iodocyclofunctionalization was the selective reduction of the triple bond in (Z)-thioenynes by the addition of iodine as an electrophilic agent. The 3-iodothiophenes were obtained in good to excellent yields of 61–92%. The 3-iodothiophenes were used as substrates in Sonogashira cross-coupling reactions to obtain thiophene acetylenes.     

Suzuki–Miyaura cross-coupling reaction of 1,2-oxaborol-2(5H)-ols with carboxylic anhydrides: a new method to furans

An efficient one-step method has been developed to construct furans via a Suzuki–Miyaura cross-coupling reaction of 1,2-oxaborol-2(5H)-ols with carboxylic anhydrides. In the presence of Pd(OAc)₂/PCy₃, the multi-substituted alkenylboron compounds could couple with anhydrides to obtain furans in moderate-to-good yields. The addition of bases promoted the coupling reaction, and the plausible reaction mechanism was proposed.     

Synthesis of novel O-alkylbenzochromeno-1,5-benzodiazepinones. Study of the N–H····N and CO····HN hydrogen bonding interactions with 2-aminopyridines

A series of novel 6-(O-alky)lbenzochromeno-1,5-benzodiazepin-2-ones 4a–c was prepared through the condensation between the [1]benzopyrano[4,3-c][1,5]benzodiazepin-7(8H)one 1 and a series of alkylalcohols. Scaffold 4 exhibited interesting hydrogen-bonding interaction with 2-aminopyridine derivatives. The so obtained self-assembled systems 5 were fully characterized by 1D/2D-NMR techniques and mass spectrometry. The hydrogen-bonding interaction was supported by IR and Raman spectroscopy and by ¹H NMR titration experiments, and was confirmed by an X-ray crystal structure analysis.     

New SERS feature of β‐carotene: consequences for quantitative SERS analysis

While recording SERS spectra of pure β‐carotene at sub‐micromole concentrations for reference purpose, we discovered an unusual spectral response never reported before. In pre‐resonance conditions with the 532‐nm line, SERS of β‐carotene with AgNPs exhibits among the strong υ(CC) mode at 1512 cm⁻¹ unshifted from normal Raman spectrum, additional strong bands at 1649, 1575 and 1387 cm⁻¹ as well as other medium bands not observed in the Raman spectrum of the crystalline powder. Such behavior is explained in terms of selection rules relaxation upon cyclohexene terminal rings of the β‐carotene interaction with the NP surface. AFM images of the SERS system suggested dimers and trimers clustering of the nanoparticles with adsorbed β‐carotene. In light of the new SERS feature the consequences in correct interpretation of the SERS imaging from complex biosystems containing carotenoids are discussed. Relative intensity ratio of the β‐carotene band at 1512 cm⁻¹ and water against concentration allowed a reliable SERS calibration curve for 50 to 500 nmol l⁻¹ concentration range and provided quantitative SERS assessment of the carotenoid content in the sea urchin (Paracentrotus lividus) gonads extracts. Copyright © 2015 John Wiley & Sons, Ltd.     

Intramolecular enantiomerism as revealed from Raman optical activity spectrum

An algorithm is employed to retrieve the differential bond polarizabilities (DBP) of the C‐C bonds from the Raman optical activity spectrum of (‐)β‐pinene. (‐)β‐pinene possesses two stereo centers (chiral centers) and a local mirror reflection that interchanges the S type part and R type part in one molecular. It is demonstrated that this local mirror reflection could induce an approximate (or symmetry breaking) mirror reflection that reverses the signs of the DBP of the pair bond coordinates that are related to each other by the mirror reflection.This can be called intramolecular enantiomerism (IE). More cases of IE are discussed by the analysis of (‐)α‐pinene, (R)‐(+)‐4‐isopropyl‐1‐methylcyclohexene and (R)‐(+)‐3‐methylcyclohexanone together with previously studied limonene case. Copyright © 2015 John Wiley & Sons, Ltd.     

N-CF3 Imidazolidin-2-one Derivatives via Photocatalytic and Silver-Catalyzed Cyclizations

While the N-trifluoromethylation of cyclic ureas is of interest for the potential to fundamentally change the properties of these biologically relevant moieties, the single synthetic procedure known to date describing their access only gives 4,4-disubstituted or fused aromatic cyclic N-CF₃ urea derivatives. We herein report an alternative approach to unleash access to the 4-monosubstituted imidazolidinone motif. The strategy relies on straightforward cyclization of readily accessible acyclic ureas, enabled by Ag-catalysis or light-assisted proton coupled electron transfer. The cyclic core is shown to be highly robust and amenable to various derivatizations, such as tandem Ni-catalysis, C−B, C−N, C−C cross couplings or C−H functionalizations, tolerating basic, nucleophilic and/or oxidizing conditions.     

The novel 4-hydroxyphenylpyruvate dioxygenase inhibitors in vivo and in silico approach: 3D-QSAR analysis,molecular docking,bioassay and molecular dynamics

4-Hydroxyphenylpyruvate dioxygenase (HPPD) is not only an important target enzyme for the treatment of type I tyrosinemia, but also a new target for design bleaching herbicides, and it plays key role in the biosynthesis of tocopherol and plastoquinone. Thirty-six known active pyridine derivatives were collected, and comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) models based on common skeleton were constructed to obtain novel HPPD herbicides with higher activity. Two new HPPD inhibitors were rationally designed and synthesized according to the CoMFA and CoMSIA models and verified by enzyme activity, biological assays, and molecular docking. The promising compound W1 ((E)-5-(3-(4-bromophenyl)acryloyl)-6-hydroxy-2,3-dihydropyridin-4(1H)-one) showed better AtHPPD inhibitory activity, and the bioassay results revealed that some weeds showed bleaching symptoms. The good binding stability of W1 and protein was confirmed by molecular dynamics simulation in 100 ns. These results would be highly useful in the progress of new HPPD inhibitors discovery.     

FeO(OH)@C-Catalyzed Selective Hydrazine Substitution of p-Nitro-Aryl Fluorides and their Application for the Synthesis of Phthalazinones

An efficient hydrazine substitution of p-nitro-aryl fluorides with hydrazine hydrates catalyzed by FeO(OH)@C nanoparticles is described. This hydrazine substitutions of p-nitro-aryl fluorides bearing electron-withdrawing groups proceeded efficiently with high yield and selectivity. Similarly, hydrogenations of p-nitro-aryl fluorides containing electron-donating groups also smoothly proceeded under mild conditions. Furthermore, with these prepared aryl hydrazines, some phthalazinones, interesting as potential structures for pharmaceuticals, have successfully been synthesized in high yields.     

SO2 Resisting Pd-doped Pr1-xCexMnO3 Perovskites for Efficient Denitration at Low Temperature

H₂-SCR is served as the promising technology for the controlling of NO_x emission, and the Pd-based derivative catalyst exhibited high NO_x reduction performance. Effectively regulating the electronic configuration of the active component is favorable to the rational optimization of noble Pd. In this work, a series of Pr_1-xCe_xMn_1-yPd_yO₃@Ni were successfully synthesized and exhibited superior NO conversion efficiency at low temperatures. 92.7 % conversion efficiency was achieved at 200 °C over Pr_0.9Ce_0.1Mn_0.9Pd_0.1O₃@Ni in the presence of 4 % O₂ with a GHSV of 32000 h⁻¹. Meanwhile, the outstanding performance was obtained in the resistance to SO₂ (200 ppm) and H₂O (8 %). Deduced from the results of XRD, Raman, XPS, and H₂-TPR, the modification of d orbit states in palladium was confirmed originating from the incorporation in the B site of Pr_0.9Ce_0.1Mn_0.9Pd_0.1O₃. The existence of higher valence (Pd³⁺ and Pd⁴⁺) than the bivalence in Pr_0.9Ce_0.1Mn_0.9Pd_0.1O₃ catalyst was evidenced by XPS analysis. Our research provides a new sight into the H₂-SCR through the higher utilization of Pd.