Chemo- and regioselective hydroboration of Δ^(14,15) in certain cephalostatin analogue

The symmetrical diketone Ⅱ, which can be synthesized in gram scale using a well established method, was used as a starting material to prepare the 11α-methoxy ketomethylene Ⅵ. This is in continuation of our study aiming at the synthesis of multihydroxylated cephalostatin analogues, as for example cephalostatin 1Ⅰ, a potent anti-tumor natural product. Compound Ⅵ underwent chemo- and regioselective hydroboration reaction at only one of △14.15 double bonds furnishing compound Ⅸ as a major product in a fair yield.

Polyoxometalate-loaded Nanocellulose Sponge as a Novel Catalyst for the Regioselective Hydroboration of Phenylacetylene

In this work,an amino-modified cellulose nanofiber sponge was prepared and used as a support for polyoxometalate(POM)catalysts with a high loading efficiency.Fourier transform infrared spectroscopy,thermogravimetric analysis,and energy-dispersive X-ray spectroscopy revealed that an Anderson-type POM,(NH4)4[CuMo6O18(OH)6]·5H2O was successfully immobilized on the sponge based on electrostatic interactions.Morphological analysis indicated that the POM-loaded sponge retained its porous structure and that the POM was homogeneously distributed on the sponge walls.The POM-loaded sponge exhibited excellent mechanical properties by recovering 79.9%of its original thickness following a 60%compression strain.The POM-loaded sponge was found to effectively catalyze the hydroboration of phenylacetylenes,yielding excellent conversion and regioselectivity of up to 96%and 99%,respectively.Its catalytic activity remained unchanged after five reuse cycles.These findings represent a scalable strategy for immobilizing POMs on porous supports.

Nickel-catalyzed cooperative B-H bond activation for hydroboration of N–heteroarenes, ketones and imines

We report two air-stable nickel(II) half-sandwich complexes,Cp*Ni(1,2-Cy_(2)PC_(6)H_(4)O)(1) and Cp*Ni(1,2-Ph_(2)PC_(6)H4NH)(2),for cooperative B-H bond activation and their applications in catalytic hydroboration of unsaturated organic compounds.Both 1 and 2 react with HBpin by adding the B-H bond across the Ni-X bond (X=O or N),giving rise to the 18-electron Ni(II)-H active species,[H1(Bpin)]and[H_(2)(Bpin)].Subtle tuning of the Ni-X pair and the supporting ancillary phosphine have a significant effect on the reactivity and catalytic performance of Cp*Ni(1,2-R_(2)PC_(6)H_(4)X).Unlike[H_(2)(Bpin)],the activation of HBpin in[H1(Bpin)]is reversible,which enables the Ni-O complex to be an effective cooperative catalyst in the hydroboration of N-heteroarenes,and as well as ketones and imines.

Copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids under ligand-free or both ligand-and base-free conditions

An efficient copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids with bis（pinacolato）diboron was developed, affording b-vinylboronates as the only products in high yields. Extra hydrogen sources such as methanol are not needed in this catalytic system. This reaction could be performed successfully under ligand- and base-free conditions. It demonstrated that phenylpropiolic acids can be employed as alkyne synthons in the hydroboration reaction and exhibited good reactivity and higher selectivity than terminal alkynes.

Synthesis of difluoromethylated benzylborons via rhodium(Ⅰ)-catalyzed fluorine-retainable hydroboration of gem-difluoroalkenes

The synthesis of bo rylated orga nofluorines is of great interest due to their potential values as synthons in modular construction of fluorine-containing molecules.Reported herein is a rhodium-catalyzed hydrobo ration of arylgem-difluoroalkenes leading to a series of α-difluoromethylated benzylborons.The use of cationic rhodium catalyst and a biphosphine ligand with large bite angle was crucial for reactivity by offering good regioselectivity and diminishing the undesired β-F elimination.Preliminary derivatizations of the products were conducted to showcase the utility of this protocol.

Ligand controlled cobalt catalyzed regiodivergent 1,2-hydroboration of 1,3-dienes

Regiodivergent 1,2-hydroboration of 1,3-dienes with pinacolborane has been accomplished by well-defined cobalt complexes of different bidentate ligands. The iminopyridine-cobalt system is selective for Markovnikov 1,2-hydroboration to form allylboronates, while the FOXAP-cobalt(FOXAP=(S)-1-(diphenylphosphino)-2-[(S)-4-isopropyloxazolin-2-yl]ferrocene) catalyst effects the complementary anti-Markonikv 1,2-hydroboration to afford homoallyboronates with high regioselectivity.

HYDROBORATION OF ALKENES,ALKADIENES AND OXYGEN-CONTAINING UNSATURATED COMPOUNDS WITH SODIUM BOROHY-DRIDES CATALYZED BY ZIRCONIUM COMPLEX

We have previously reported that the Ti complex generated from Cp2TiCl2 and LiBH4 serves as a catalyst for hydroboration of alkenes. Sodium borohydride can also be utilized as a reagent for hydroboration if reaction is carried out in the pre-

A Uranium(Ⅳ) Alkyl Complex: Synthesis and Catalytic Property in Carbonyl Hydroboration

The strong oxophilicity of actinide complexes prevents their applications in the transformation of oxygen-containing substrates.Herein,we report the use of a uranium(Ⅳ)alkyl complex as a catalyst for the hydroboration of carbonyl compounds.This reaction has good functional group tolerance and chemo-selectivity under mild conditions.This study represents the rare example of catalytic reaction promoted by a uranium alkyl complex and highlights the potential of uranium complexes in synthetic chemistry.

Et2Zn-promoted β-trans-selective hydroboration of ynamide

The trans-hydroboration of alkyne represents a challenging task in organic synthesis.Reported herein is an Et2 Zn promotedβ-trans hydroboration of ynamides by using N-heterocyclic carbene(NHC)-ligated borane as boryl source.The reaction leads to a stereoselective construction of enamides bearing a valuable boryl substituent.Both aromatic and aliphatic ynamides were applicable to the reaction.Synthetic transformation of the C-B bond in the product via Suzuki-Miyaura coupling provides a simple and stereospecific route to multi-substituted enamides.Mechanistic studies were conducted and the possible mechanism was discussed.

B(C_(6)F_(5))_(3)-Catalyzed Hydroboration of Alkenes with N-Heterocyclic Carbene Boranes via B-H Bond Activation

Main observation and conclusion In this work,a novel mode for the activation of N-heterocyclic carbene boranes(NHC-boranes)was developed by generating the highly reactive zwitterion species through hydride abstraction with Lewis acid B(C_(6)F_(5))_(3) in an frustrated Lewis pairs manner.A broad range of alkenes including stilbenes,β-methylstyrenes,styrenes,and alkyl-alkenes were suitable substrates for the B(C_(6)F_(5))_(3)-catalyzed hydroboration to furnish the desired products in good to high yields.Significantly,excellent regioselectivities were obtained in some cases.Mechanistic studies indicate that the B-H bond cleavage is likely involved in the rate-determining step.In addition,an electrophilic addition of NHC-borenium cation to alkenes and the subsequent formation of carbocation are also postulated.The current work provides a promising method for the activation of stable borane adducts,which might lead to some interesting transformations in the future.

Markovnikov-Selective Hydroboration of Aryl Alkenes Enabled by a Simple Nickel Salt

The sustainable development of synthetic reactions catalyzed by earth-abundant metals is one of the principal goals in homogeneous catalysis.However,so far most of the protocols are still plagued by sophisticated ligands,hazardous activators,high catalyst loading(1—10 mol%)and/or multistep synthesis of the metal complexes in the process development.Consequently,the development of earth-abundant metal catalysts with high activity from commercially available metal salts is highly desirable for practical utilization of base metal catalyzed synthetic methodology.Herein,we report the catalyst generated in situ from a mixture of catalytic amounts of Ni(acac)_(2)(as low as 0.005 mol%)and CsF,which is found highly active for Markovnikov-selective hydroboration of vinylarenes,including 1,1-disubstituted vinylarenes and internal olefins,affording a wide range of secondary and tertiary alkyl boronates in excellent yields.Mechanistic experiments indicate that the key to the success of this catalysis is the use of CsF,which in combination with pinacolborane acts as an effective activator for Ni(acac)_(2),probably generating metastable Ni nanoparticles in situ that demonstrate high activity in the catalytic hydroboration(TON up to 18800).

Stereoselective Access to Polypropionates Expedited by the Double Hydroboration of Allenes: Total Synthesis of Antitumor (−)-Pironetin

Polyketides,a large class of secondary metabolites,have been of long-standing interest to the synthetic community due to their intriguing biological activities and structural versatility and complexity.A typical structural unit of various natural products,polypropionate,has prompted enormous efforts in the development of novel synthetic methods and strategies in the past five decades.In this study,a non-aldol-type approach based on double hydroboration of allenes has been developed to provide a powerful method for the stereodivergent construction of various polyol stereotriads and stereotetrads that are amenable for synthesizing polypropionates.The stereochemical control is possibly attributable to the boronate complex that aligned itself as a rigid conformation for the second stereoselective hydroboration reaction by suppressing the barotropic rearrangement of allylborane intermediates.The feasibility of preparing the key polypropionate motif facilitates the efficient synthesis of(-)-pironetin,a potentα-tubulin inhibitor halting the cell cycle at M phase.

就地硼氢化法的改进——雌三醇合成工艺的研究

在前报中,我们应用外源性硼烷进行硼氢化反应,成功地改进了合成雌三醇(3)的工艺,收率高达85～95％;并以闪式柱层析分离出两个副产物:表雌三醇(4)和雌三醇-17-乙基醚(5):

Synthesis of Planar-Chiral[2.2]Paracyclophane-Based Oxazole-Pyrimidine Ligands and Application in Nickel-Catalyzed 1,2-Reduction ofα,β-Unsaturated Ketones

The planar-chiral ligands have been widely applied as a class of unique and significant ligands in asymmetric catalysis.Among them,chiral[2.2]paracycyclophane has emerged as a privileged type of planar-chiral framework and has been utilized as an important toolbox due to their structural stability.Herein,we design and synthesize[2.2]paracyclophane-derived oxazole-pyrimidine ligands(abberviated as PYMCOX).These N,N-ligands with stable properties,rigid structure and large steric hindrance performed successfully in nickel-catalyzed asymmetric 1,2-reduction ofα,β-unsaturated ketones,affording the chiral allylic alcohols with up to 99%yield and 99%ee.Meanwhile,this reduction reaction could be conducted on gram-scale without loss of activity and enantioselectivity,and the chiral ligand could be conveniently recovered with high yield.

Application of HSAB Theory in the Selective Reduction of Quinoline

It is very important to develop efficient synthetic strategies for site-specific functionalization of tetrahydroquinolines due to their indispensable roles in pharmaceutical and agrochemical industries.We apply hard/soft acid/base(HSAB)theory to selective reduction of quinoline and achieve a series of C3-functionalized tetrahydroquinoline in high to excellent yields(up to 99%)under mild conditions with the catalysis of B(C_(6)F_(5))_(3).A series of in situ NMR reactions are also performed to investigate this cascade reaction.Moreover,AB type monomer 6-(dimethylsilyl)quinoline and AA/BB type monomer 6,6'-biquinoline are synthesized for polymer synthesis,which represents the first example of silicon bridged polytetrahydroquinoline.

配位结构主导单原子Pt的烯烃反马氏硼氢化催化性能

单原子催化剂的高效合理设计具有十分重要的意义,但是目前对于结构和性能之间的关联关系认知不足,严重阻碍了催化剂的发展进程.因此,清晰阐释金属活性中心的配位结构对于其催化性能的影响将有利于单原子催化剂的高效设计.本文研究报道了单原子Pt催化剂的活性中心配位结构显著影响其在烯烃反马氏硼氢化反应中的性能表现.三个O原子配位的Pt单原子催化剂(Pt-O3)与另外两种配位结构(Pt-N4和Pt-O2)相比,表现出了更高的催化活性,在烯烃反马氏硼氢化反应中的转化数可达到3288.密度泛函理论计算表明,Pt-O3催化剂具有超高活性的主要原因是其在反应相图中具有最低的决速步能垒.

Iron(Ⅱ) hydrides bearing a tetradentate PSNP ligand

A new class of iron（II） hydrides based on a tetradentate PSNP ligand were synthesized and fully characterized. All the iron（II） complexes feature a folded PSNP ligand with cis reactive sites. The hydrido iron complex [2 H（NCMe[2_TD$IF]1）]（BF4） is capable of catalyzing aldehyde hydroboration by pinacolborane（HBpin） and with extremely high efficiency at room temperature. Aldehydes with various functional groups are compatible.

Low Na-β″-alumina electrolyte/cathode interfacial resistance enabled by a hydroborate electrolyte opening up new cell architecture designs for all-solid-state sodium batteries

Development of low-resistance electrode/electrolyte interfaces is key for enabling all-solid-state batteries with fast-charging capabilities.Low interfacial resistance and high current density were demonstrated for Na-β″-alumina/sodium metal interfaces,making Na-β″-alumina a promising solid electrolyte for high-energy all-solid-state batteries.However,integration of Na-β″-alumina with a high-energy sodium-ion intercalation cathode remains challenging.Here,we report a proof-of-concept study that targets the implementation of a Na-β″-alumina ceramic electrolyte with a slurry-casted porous NaCrO_(2) cathode with infiltrated sodium hydroborates as secondary electrolyte.The hydroborate Na4(B_(12)H_(12))(B_(10)H_(10))possesses similar sodium-ion conductivity of 1 mS cm^(-1) at room temperature as Na-β″-alumina and can be fully densified by cold pressing.Using the Na4(B_(12)H_(12))(B_(10)H_(10))secondary electrolyte as interlayer between Na-β″-alumina and NaCrO_(2),we obtain a cathode-electrolyte interfacial resistance of only 25Ωcm^(2) after cold pressing at 70 MPa.Proof-of-concept cells with a sodium metal anode and a NaCrO_(2) cathode feature an initial discharge capacity of 103 mAh g^(-1) at C/10 and 42 mAh g^(-1) at 1 C with an excellent capacity retention of 88%after 100 cycles at 1 C at room temperature.Ion-milled cross-sections of the cathode/electrolyte interface demonstrate that intimate contact is maintained during cycling,proving that the use of hydroborates as secondary electrolyte and as an interlayer is a promising approach for the development of all-solid-state batteries with ceramic electrolytes.