Ultrasonicwave-assisted tandem-reaction for synthesis of symmetrical vicinal diamines

A practical synthesis of symmetrical vicinal diamines with broad chemistry scope is described. The key step is the ultrasonicwave promoted tandem-reaction, two-step reaction sequence combining Mannich double condensations with benzo- triazole, glyoxal and primary or secondary amines and reduction of the bis（benzotriazole）-adducts with sodium borohydride proceeded smoothly in tetrahydrofuran in high yield at room temperature.

Vicinal hydroxyl group-inspired selective oxidation of glycerol to glyceric acid on hydroxyapatite supported Pd catalyst

Selective oxidation of glycerol provides a feasible route towards the sustainable synthesis of high value-added chemicals.Herein,the hydroxyapatite(HAP)supported palladium(Pd)species were fabricated by impregnation and subsequent calcination.The as-obtained heterogeneous Pd catalyst afforded not only excellent selectivity to glyceric acid(GLA)up to 90%with 59%conversion of glycerol but also good recyclability by using molecular oxygen as an oxidant under mild conditions.The characterization of catalysts indicated that both the surface basicity and Pd sites on the catalyst played a crucial role in promoting glycerol oxidation.Notably,it demonstrated that the presence of the vicinal hydroxyl group of glycerol molecule can assist the oxidation reaction via forming a coordination between the vicinal hydroxyl group and Ca^(2+) sites on HAP-derived catalysts.In this catalytic process,the secondary hydroxyl of glycerol kept untouched and the primary hydroxyl of glycerol was converted into carboxyl group,while the Pd species acted as active centers for cooperatively promoting the subsequent oxidation to generate GLA.Additionally,this catalytic system can be extended widely for the oxidative conversion of other vicinal diols into the corresponding a-hydroxycarboxylic acids selectively.Isotope labeling experiment using H_(2)^(18)O confirmed that H_(2)O not only acted as solvent but also was involved in the catalytic cycles.On the basis of the results,a possible reaction mechanism has been proposed.The HAP-supported Pd catalytic system has been shown to serve as an effective approach for the upgrading of bio-derived vicinal diols to high value-added chemicals.

STUDIES ON STEROIDAL PLANT GROWTH REGULATOR 24. STEREOCONTROLLED CONSTRUCTION OF THE SIDE CHAIN OF BRASSINOLIDE AND HOMOBRASSINOLIDE VIA A TANDEM VICINAL DIALKYLATION OF PYRANONE MOIETY

A stereocontrolled construction of the side chain of brassinclide and homobrassinolide has been achieved via the tandem vicinal dialkylation of the pyranone moiety as a key step.

Characterization of four diol dehydrogenases for enantioselective synthesis of chiral vicinal diols

Enantiopure vicinal diols are important building blocks used in the synthesis of fine chemicals and pharmaceutical compounds. Diol dehydrogenase(DDH) mediated stereoselective oxidation of racemic vicinal is an efficient way to prepare enantiopure vicinal diols. In this study, four new bacterial DDHs(AnDDH from Anoxybacillus sp. P3 H1 B, HcDDH from Hazenella coriacea, GzDDH from Geobacillus zalihae and LwDDH from Leptotrichia wadei) were mined from the GenBank database and expressed in E. coli T7.The four DDHs were purified and biochemically characterized for oxidation activity toward(R)-1-phenyl-1,2-ethanediol, with the optimal reaction condition of pH9.0(AnDDH), 10.0(HcDDH) and 11.0(GzDDH and LwDDH) and the temperatures at 40 ℃(AnDDH), 50 ℃(HcDDH) and 60 ℃(GzDDH and LwDDH), respectively. The four enzymes were stable at the pH from 7.0 to 9.0 and below 40 ℃.Kinetic parameters of four DDHs showed that the HcDDH from Hazenella coriacea had high activity toward a broad range of vicinal diols. A series of racemic vicinal diols were successfully resolved by recombinant E. coli(HcDDH-NOX) resting cells co-expression of an NADH oxidase(NOX), affording(S)-diols and(1 S, 2 S)-trans-diols in ≥99% ee. The synthetic potential of HcDDH was proved by E. coli(HcDDH-NOX) via kinetic resolution of racemic trans-1,2-indandiol on a 100 ml scale reaction,(S, S)-trans-1,2-indandiol was prepared in 46.7% yield and >99% ee. In addition, asymmetric reduction of four α-Hydroxy ketones(10–300 mmol·L^(-1)) by E. coli(HcDDH-GDH) resting cells resulted in >99% ee and69–98% yields of(R)-vicinal diols. The current research expands the toolbox of DDHs to synthesize chiral vicinal diols and demonstrated that the mined Hc DDH is a potential enzyme in the synthesis of a broad range of chiral vicinal diols.

Efficient Debromination of Vicinal a, b-Dibromo Carboxylic Acid Derivatives with the Sm/HOAc System

The ? ?vicinal dibromo carboxylic acid and its derivatives were debrominated with Sm/HOAc system to afford the corresponding cinnamic acid and its derivatives in good yields under mild conditions.

The effects of vicinal sapphire substrates on the properties of AlGaN/GaN heterostructures

A1GaN/GaN heterostructures on vicinal sapphire substrates and just-oriented sapphire substrates （0001） are grown by the metalorganic chemical vapor deposition method. Samples are studied by high-resolution x-ray diffraction, atomic force microscopy, capacitance-voltage measurement and the Van der Panw Hall-effect technique. The investigation reveals that better crystal quality and surface morphology of the sample are obtained on the vicinal substrate. Fur- thermore, the electrical properties are also improved when the sample is grown on the vicinal substrate. This is due to the fact that the use of vicinal substrate can promote the step-flow mode of crystal growth, so many macro-steps are formed during crystal growth, which causes a reduction of threading dislocations in the crystal and an improvement in the electrical properties of the AlGaN/GaN heterostructure.

Asymmetric Synthesis of Fluorinated Vicinal Diamines from Fluoromethyl Sulfinyl Imines and Diphenylmethylene-Benzylamines

A novel strategy was developed for the asymmetric synthesis of fluorinated vicinal diamines.Deprotonation of N-(diphenylmethylene)-benzylamines under base,followed by asymmetric nucleophilic addition to N-tert-butanesulfinylfluoroacetaldimines,a pair of diastereomeric isomers were afforded.The diastereomeric isomers can be easily separated from each other by silica gel column chromatography.The absolute steric configuration of two isomers was confirmed by single crystal X-ray diffraction analyses.The proposed mechanism revealed that the configuration of the carbon next to tert-butanesulfinyl was well controlled to be R by the chiral auxiliary.

A FACILE METHOD FOR DEBROMINATION OF VICINAL DIBROMIDES

In the presence of equimolar triethylamine,vicinal dibromides were found to be easily debrominated by dibutyl telluride,forming the co- rresponding olefins.

New strategies for asymmetric photocatalysis: asymmetric organocatalytic/photoredox relay catalysis for efficient synthesis of polycyclic compounds containing vicinal amino alcohols

An asymmetric catalytic strategy in photocatalysis utilizing a chirality-induced approach through an organocatalytic/photoredox relay catalysis strategy is successfully achieved for the rapid construction of polycyclic compounds containing vicinal amino alcohols in a one-pot protocol. This methodology facilitates the efficient synthesis of diverse substituted polycyclic tetrahydroquinoline and benzofuran-derived vicinal amino alcohols, each containing five consecutive chiral centers, with high yields,excellent diastereoselectivities and enantioselectivities(up to 95% yield, >20:1 dr and 98% ee), under mild reaction conditions driven by sequential bifunctional squaramide organocatalyst-catalyzed [4+2] annulation and photocatalyst-catalyzed ketyl radical addition cyclization reaction process. Furthermore, investigations into the stereoselectivity mechanism and high-resolution mass spectrometry(HRMS) experiments on free radical trapping have provided evidence for elucidating the detailed mechanism of chirality-induced processes and chiral intermediate conversions in this procedure.

Asymmetric reduction of α-hydroxy aromatic ketones to chiral aryl vicinal diols using carrot enzymes system

Asymmetric reduction of ct-hydroxy aromatic ketones was carded out by using carrot enzymes system, yielding corresponding chiral vicinal diols with special functional groups. The optimum reaction conditions were obtained after investigation of various influencing factors. Chiral aryl vicinal diols were produced with good yields and excellent enantiomeric excesses under appropriate conditions. Meanwhile, the steric factors and electronic effects of the substituents on the aromatic ring were shown to have an interesting influence on both yield and enantioselectivity.

Small molecule fluorescent probes of protein vicinal dithiols

The vicinal dithiol motif is widely present in proteins, and is critical for proteins’ structures and functions.In recent years, a variety of fluorescent probes with high specificity and outstanding optical properties for sensing protein vicinal dithiols have been developed. In this review, we summarized the fluorescent probes of protein vicinal dithiols in literature. These probes are classified into four types based on their acceptor sites, i.e., biarsenical probes, monoarsenical probes, dimaleimide probes and diacrylate probes.Through analyzing the properties of different probes, we expect that this review would help readers further understand the structural factors of these probes and provide the design strategy for novel fluorescent probes with improved properties.

Synthetic studies towards daphniyunnine B: Construction of AC bicyclic skeleton with two vicinal all carbon quaternary stereocenters

The AC bicyclic skeleton of daphniyunnine B with the required 3 stereocenters(C4,C5 and C8)was accomplished in a concise route which featured two Claisen-type rearrangement reactions to construct the required vicinal all carbon quaternary stereocenters(C5 and C8)and an intramolecular iodocyclization reaction to assemble the cis-confused bicyclic lactam.

Constructing Tertiary Alcohols with Vicinal Stereocenters:Highly Diastereo-and Enantioselective Cyanosilylation of α-Branched Acyclic Ketones and Their Kinetic Resolution

We report the first highly diastereo-and enantioselective C-C bond-forming reaction of racemic α-branched ketones to construct tertiary alcohols with adjacent stereocenters.Accordingly,a highly stereoselective cyanosilylation of racemic ketones is developed using our bifunctional cyanating reagent,Me_(2)(CH_(2)Cl)SiCN,giving C^(α)-tetrasubstituted silyl cyanohydrins withtwovicinal stereocenters inupto>20:1 diastereomeric ratio(dr)and 90-98% enantiomeric excess(ee)values,which can undergo various diversification reactions bymanipulating the chloromethyl group.A highly selective kinetic resolution of acyclicα-branched ketones is also developed that allows facile access to acyclic α-alkyl,allyl,and propargyl ketones with good recovery and excellent ee values.The synthetic value of this protocol is further demonstrated by the formal synthesis of the anti-obesity agent,taranabant(MK-0364).The activation of Jacobsen’s privileged catalyst(salen)AlCl by a suitable phosphorane plays a crucial role in the reaction.X-ray crystallographic analysis of single crystals of phosphorane-(salen)AlCl complexes and theoretical calculations help provide a working model.The present transformation opens a new path for the catalytic stereoselective synthesis of stereochemically complex tertiary alcohols featuring two stereocenters(adjacent or not)from racemic ketones.

Catellani Reaction: An Enabling Technology for Vicinal Functionalization of Aryl Halides by Palladium(o)/Norbornene Cooperative Catalysis

The Catellani reaction,originally discovered by Catellani in 1997,and further developed by Catellani,Lautens and others,has emerged as a powerful strategy for the synthesis of polysubstituted arenes,which would be difficult to access via traditional methods.In this process,both ortho-and/pso-positions of aryl halides could be functionalized simultaneously with different electrophiles and terminating agents under the cooperative catalysis of palladium and norbornene(NBE).This review focuses on the significant progress of such transformations,and the section of typical Catellani reactions is divided into five parts according to the functionalization mode of ortho-C-H bond:alkylation,arylation,amination,acylation or thiolation.

Synthesis and Cytotoxic Evaluation of Novel Platinum(Ⅱ) Complexes with C2-Asymmetric and C2-Symmetric Chiral Vicinal Diamines

A series of new platinum（II） complexes with C2-asymmetric and C2-symmetric 1,2-diamines were designed and synthesized by convenient methods, involving samarium diiodide induced reductive coupling as the key step. The results of cytotoxicity showed that compounds （R,R）-lla and （S,S）-lla, two novel platinum（II） complexes with asymmetric 1,2-diamines, exhibited more potent cytotoxicity than that of oxaliplatin against all leukemia cell lines. Interestingly, （R,R）-lla and （S,S）-lla demonstrated less potent activity against three solid cancer cell lines than that of oxaliplatin, which indicated that these two compounds may only selectively inhibit the leukemia cell lines. In contrast, （R,R）-ISa and （S,S）-15a, two platinum（II） complexes with symmetric 1,2-diamines, showed similar cyto- toxicity to that of oxaliplatin against all leukemia cell lines and more potent activity against solid cancer cell lines. Further flow cytometry data indicated that （R,R）-lla could obviously arrest leukemia K562 cells in G2/M phases.

Field-free switching through bulk spin−orbit torque in L10-FePt films deposited on vicinal substrates

L1_(0)-FePt distinguishes itself for its ultrahigh perpendicular magnetic anisotropy(PMA),enabling thermally stabile memory cells to scale down to 3 nm.The recently discovered“bulk”spin−orbit torques in L1_(0)-FePt provide an efficient and scalable way to manipulate the L1_(0)-FePt magnetization.However,the existence of an external field during the switching limits its practical application,and therefore field-free switching of L1_(0)-FePt is highly demanded.In this manuscript,by growing the L1_(0)-FePt film on vicinal MgO(001)substrates,we realize the field-free switching of L1_(0)-FePt.This method is different from previously established strategies as it does not need to add other functional layers or create asymmetry in the film structure.The dependence on the vicinal angle,film thickness,and growth temperature demonstrates a wide operation window for the fieldfree switching of L1_(0)-FePt.We confirm the physical origin of the field-free switching is due to the tilted anisotropy of L1_(0)-FePt induced by the vicinal surface.We also quantitatively characterize the spin-orbit torques in the L1_(0)-FePt films.Our results extend beyond the established strategies to realize field-free switching,and potentially could be applied to mass production.

Infrared stimulated emission with an ultralow threshold from low-dislocation-density InN films grown on a vicinal GaN substrate

Near-infrared stimulated emission from a high-quality InN layer under optical pumping was observed with a threshold excitation power density of 0.3 and 4 kW cm^(−2) at T=8 and 77 K,respectively.To achieve such a low threshold power density,vicinal GaN substrates were used to reduce the edge-component threading dislocation(ETD)density of the InN film.Cross-sectional transmission electron microscopy images reveal that the annihilation of ETDs can be divided into two steps,and the ETD density can be reduced to approximately 5×10^(8) cm^(−2) near the surface of the 5-μm-thick film.The well-resolved phonon replica of the band-to-band emission in the photoluminescence spectra at 9 K confirm the high quality of the InN film.As a result,the feasibility of InN-based photonic structures and the underlying physics of their growth and emission properties are demonstrated.

Pinacol coupling going in a photocatalytic asymmetric manner:construction of chiral vicinal amino alcohols

Vicinal amino alcohols are a class of important motifs in pharmaceuticals,natural products as well as wide application in asymmetric catalysis（Scheme 1（a））.It is no doubt that development of efficient methods to access them has been a prominent research topic in the past decades.

Enantiomeric characterization and structure elucidation of Otamixaban

Otamixaban is a potent （Ki=0.5 nM） fXa inhibitor currently in late-stage clinical develop-ment at Sanofi for the management of acute coronary syndrome. Being unproductive in obtaining a suitable crystal of Otamixaban, the required enantiomeric characterization has been accomplished using vibrational circular dichroism （VCD） spectroscopy. Selected by a spectrum similarity index, the calculated spectra of several higher energy conformers were found to match well with the observed spectra. The characteristic IR bands of these conformers were also identified and attributed to the solvation effect. Combined with both the single crystal x-ray diffraction results for an intermediate and the proton NMR study, the absolute configuration of Otamixaban is unambiguously determined to be （R,R）.

Cenozoic Volcanism in South China Sea and Its Vicinity and South China Sea Spreading

The rock series, rock types and Sr-Nd isotopic dating of the Cenozoicvolcanic rocks in the South China Sea are similar to those in its vicinity. On the basis of thespreading age of the South China Sea, the Cenozoic volcanic rocks are divided into three stages: thepre-spreading stage, the spreading stage and the post-spreading stage. The deep processcharacteristics of the asthenosphere and lithosphere may be inferred from the study on primarybasaltic magma. The top layers of the asthenosphere both in the spreading stage and in thepre-spreading stage are closer to the earth surface than that in the post-spreading stage. From thepre-spreading stage to the spreading stage, the top layer of the asthenosphere decreased in depth,while the amount of interstitial partial melts increased. The evolution of the primary basalticmagma shows a progressive evolution sequence of the rifting volcanism and a faster lithosphericspreading velocity. From the spreading stage to the post-spreading stage, the top layer of theasthenosphere gradually increased in depth, but the amount of interstitial partial melts decreased.The evolution of primary basaltic magma shows a retrogressive evolution sequence of the riftingvolcanism and a gradual decrease in the lithospheric spreading velocity. The depth recognized by thestudy on the Cenozoic volcanism demonstrates the deep environment for the formation and evolutionof the South China Sea.