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An efficient acid-mediated stereospecific skeletal rearrangement for the total synthesis of dl-hexahydroapoerysopine, an intriguing and historically important Apo rearrangement product of the aromatic Erythrina alkaloids, is described.

The development of high-efficiency bifunctional electrocatalysts toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline surroundings is essential and challenging for the large-scale generation of clean hydrogen. Herein, a novel self-assembled two-dimensional (2 D) NiO/CeO2 heterostructure (HS) consisting of NiO and CeO2 nanocrystals is prepared through a facile two-step approach, and utilized as an enhanced bifunctional electrocatalyst for the HER and OER under alkaline conditions. It is concluded that this 2 D NiO/CeO2 HS, rich in oxygen vacancies, demonstrates attractive electrocatalytic properties for both the HER and OER in 1 m KOH, including low onset overpotential (η1 ), η10 and Tafel slope, excellent durability, as well as large active surface area. Therefore, the self-assembled 2 D NiO/CeO2 HS is believed to be an efficient bifunctional electrocatalyst toward the HER and OER.

Tandem reactions of the yttrium(iii) catalyzed ring-opening reaction of 2,2′-diester aziridines with 3-(2-isocyanoethyl)indoles and the subsequent Friedel–Crafts/Mannich/desulfonylation were reported. A series of polycyclic spiroindolines containing tetrahydro-β-carbolines were obtained in moderate to excellent yields (56–92%) in one step under mild reaction conditions. A possible catalytic mechanism was also proposed.

Reductive coupling of sterically hindered neopentyl bromides with activated alkenes mediated by the in situ generated Ni(0) complexes along with some feedstock is achieved in good yield under the mild conditions. This practically useful method of C(sp3)−C(sp3) bond formation provides a complementary approach to the traditional conjugate addition of preformed organometallic reagents to electrophilic olefins, which often requires cryogenic temperature and rigorous exclusion of air and moisture. The robust application of this reductive coupling reaction was demonstrated in a formal synthesis of stereodivergent (−)-copacamphor and (−)-ylangocamphor, which are valuable intermediates for a class of tricyclo[5.3.0.03,8]decane sesquiterpenes. Moreover, this convenient protocol resulted in a facile access to the homolog of Corey aldehyde en route to prostaglandins, implying the possible involvement of radical-like species.

The development of high-efficiency bifunctional electrocatalysts toward the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline surroundings is essential and challenging for the large-scale generation of clean hydrogen. Herein, a novel self-assembled two-dimensional (2 D) NiO/CeO

Asymmetric synthesis of the pentacyclic alkaloid (-)-cephalotaxine was accomplished via palladium-catalyzed enantioselective Tsuji allylation for construction of the aza-containing tetrasubstituted stereogenic center (95% yield, 93% ee). The allyl enol carbonate precursor was prepared from Hanaoka's ketone intermediate, which was formed by a novel formic acid promoted ring-expansion reaction.

A concise synthetic approach to construct [6] , [6] , [6] -tricyclic core, bearing 14-membered carbocyclic skeleton and oxygen at C13 of lophotoxin, has been described. This approach features a diastereoselective intermolecular Diels−Alder furan reaction and intramolecular Michael reaction. N-methylmaleimide was found to be critical for achieving the stable intermolecular Diels−Alder furan outcome.

Structures and electrochemical performances of Na-rich layered cathode Na2RuO3 are studied by substitution of Zr for Ru. Na2Ru0.95Zr0.05O3 exhibits a combination of disordered and ordered stacking state with a weight fraction of ∼61.57% and 38.43%, respectively. The disordered and ordered Na2Ru0.95Zr0.05O3 exhibits reversible capacity of 137 mAh g−1 that is consistent with the theoretical capacity at a current density of 1 C. In addition, the material shows good cyclability with a capacity retention of 77% after 200 cycles at current density of 1 C, and the Coulombic efficiency remains at about 99% during cycling. The structural evolutions of the Na-rich layered Na2Ru0.95Zr0.05O3 during de(sodiation) have been investigated and found to proceed via a biphasic mechanism.

A hybrid PEO 20 -AlCl 3 -5% SiO 2 -70% Emim FSI is developed as solid electrolyte for aluminum-ion batteries. The electrical conductivity, variation of conductivity with time evolution and activation energy of the hybrid solid electrolyte is evaluated by AC impedance spectroscopy. The phase of the hybrid solid electrolyte is characterized by XRD. The electrochemical stability window of the hybrid solid electrolyte is determined by cyclic voltammetry. High ionic conductivity of 9.6 × 10 − 4 S cm − 1 at room temperature is achieved, moreover, the ionic conductivity is stabilized within 8 days at room temperature. An electrochemical stability window of 3 V is observed.

The development of solid electrolytes with superior electrical and electrochemical performances for the room-temperature operation of sodium (Na)-based batteries is at the infant stage and still remains a challenge. Herein, we, for the first time, report hybrid solid electrolytes consisting of PEO20–NaClO4–5% SiO2–x% Emim FSI (x = 50, 70) designed for solid-state Na-metal batteries. The hybrid design yields a solid electrolyte featuring a high room-temperature ionic conductivity of 1.3 × 10−3 S cm−1, suitable mechanical property, a wide voltage stability window of 4.2 V and a high Na+ transference number of 0.61. A prototypical Na-metal battery using this hybrid solid electrolyte demonstrates promising long-term cycling performances at room temperature and at an elevated temperature of 60 °C for 100 cycles. The finding implies that the hybrid solid electrolyte is promising for Na-metal batteries operating at room temperature.

Reduction of 2-methoxy-2, 4-hexadienoates with Dibal-H in toluene at −78 °C resulted in a facile formation of 5-hydroxyl cyclopentenone derivatives. This novel transformation was proposed as a variant of the oxy-Nazarov cyclization of the corresponding 2-methoxy aldehyde intermediate via the cationic Al-chelate as depicted in Fig. 2a.

The roles of alkaline earth ions in garnet-type superionic conductors Li7.1La3Zr1.95M0.05O12 (M=Mg, Sr, Ba) are further investigated. In contrast to previous reports, the alkaline earth ions are specifically allocated to the octahedral sites (Zr4+ sites) instead of dodecahedral sites (La3+ sites) in the present work. The alkaline-earth-ions-doping Li7.1La3Zr1.95M0.05O12 garnets exhibit enhanced room-temperature conductivities with the increasing ionic radii of alkaline earth ions. The Ba-doping Li7.1La3Zr1.95Ba0.05O12 provides the highest conductivity of 1.13×10-3 S cm-1 at room temperature, while the Mg- and Sr-doping garnets show conductivities of 4.32×10-4 and 8.91×10-4 S cm-1 at room temperature, respectively. The obtained ionic conductivities are comparable to other promising superionic conductors known so far. Moreover, the alkaline-earth-ions-doping garnets demonstrate wide electrochemical stability window of 9 V vs Li/Li+, and stability against metallic lithium by means of symmetrically galvanostatic cycling.

An unusual formal oxy transposition of vinylogous β-silyloxy-cyclobutanone 1 (a 1,5-difunctionalized substrate) under mild acidic conditions (aqueous HF in CH 3 CN at 0 °C) to the decalinic γ -lactone 2 was described. A plausible mechanistic pathway involving the Grob-type fragmentation and intramolecular γ -lactonization was proposed.

We report a protocol for efficient stereoselective installation of the chiral oxygen-containing tetrasubstituted tertiary carbon stereocenter of the side chain of cephalotaxus esters by means of highly diastereoselective Mukaiyama aldol reactions between α-keto esters (2) and a (Z)-α-chloro ketene silyl acetal. This protocol permitted synthesis of cephalotaxus esters including six natural products in good to excellent yields (up to 94%) with high diastereoselectivities (dr up to 97:3) and could be performed on a multigram scale.

The first total synthesis of (-)-andrographolide (1), an ent-Labdane diterpenoid lactone from Asian medicinal herb Andrographis paniculata, was achieved via the biomimetic cyclization of an epoxy homoiodo allylsilane precursor 7. Asymmetric total synthesis of (+)-rostratone (25), an antipodal Labdane diterpenoid, was also accomplished via similar biomimetic cyclization of a readily accessible epoxy homoiodo allylsilane precursor 18. (C) 2014 Elsevier Ltd. All rights reserved.

Azulenones with an angular acyl substituent were synthesized by the reactions of 2-aryl-2-chloroacylketenes with phenylthioacetylene or ethoxyethyne. Acyl-substituted azulenones with a methoxy group in the cycloheptatriene moiety could be rearranged to spiro[4.5] compounds. Spiro[4.5] and bicyclo[5.3.0]decane ring systems were constructed en route to a formal synthesis of (±)-acorenol and synthesis of the hydroazulene core of pseudolaric acid, respectively.

Transannular reductive rearrangement of bridged cyclic α-amino ketones led to the aza-tricyclic frameworks azepinoindole, hydrolulolidine, and hydrojulolidine of the typical alkaloids of Stemona, Aspidosperma, and Lycopodium, respectively. This facile approach demonstrates the potential applicability of the Clemmensen-Clemo-Prelog-Leonard reductive rearrangement of tricyclic α-amino ketones for the aza-heterocycle synthesis.

We present in this report the development of a convergent and highly stereocontrolled cycloaddition strategy toward the synthesis of C-1, C-6, and C-14 tris-oxygenated eudesmane sesquiterpenoids. This approach was demonstrated in the first total synthesis of (±)-6β,14-epoxyeudesm-4(15)-en-1β-ol (1), a structurally unique ethereal eudesmane sesquiterpenoid, via an effective Diels-Alder construction of a compact functionalized tricycle intermediate from readily available N-benzylfurfurylamine (2) and homoprenyl maleic anhydride (3) as the C(5) and C(10) building blocks, respectively.

A concise total synthesis of (±)-cephalotaxine (1) has been achieved from dioxolanone derivative 15 via a transannulation strategy. The key transformation is a facile reductive oxy-Nazarov cyclization as illustrated above, involving presumably a tethered 1,2-oxidopentadienyl cation species 7a or 7b, which represents a new variant of the oxy-Nazarov cyclization and constitutes an effective, regio- and stereospecific 5-hydroxy cyclopentenone annulation protocol under mild hydride reduction conditions.

cine Substitution arising from slow transmetallation occasionally occurs in classic Pd-catalyzed Stille cross-coupling reactions with sterically hindered vinyltin components. Mechanistic explanations of this "abnormal" cross-coupling mode and the intriguing co-catalytic effects of metallic Cu species in restoring the ipso selectivity are summarized. Typical synthetic applications of this unique Cu effect and the advent of Cu-catalyzed Stille-type cross-coupling are also demonstrated.

The first asymmetric total synthesis of (+)-iresin (4), an historically important ent-Drimane sesquiterpene lactone, was realized from aldehyde 3 via cyclic orthoester 6 in 5 steps. Notable transformations in this synthesis include a tandem trifluoroperacetic acid (TFPAA)-mediated Baeyer-Villiger oxidation-olefin epoxidation-epoxy ester cyclization, regioselective Burgess dehydration, and regioselective Fetizon oxidative lactonization.

Desilylation of O-tert-butyldimethylsilyl ethers was achieved by a reagent system consisting of chlorotrimethylsilane and potassium fluoride dihydrate in acetonitrile. This alternative desilylation procedure is chemoselective, generally effective and operationally simple, and should find practical applications in organic synthesis.

A facile one‐pot synthesis of nitriles via a ring‐opening reaction of cyclobutanone adducts with hydroxylamine hydrochloride was developed.

The classical Corey–Chaykovsky (CC) reaction of ketones in ethereal solvents (i.e., THF or Et2O) resulted in the production of a significant amount of β-hydroxy methylthioether 2 along with normal epoxide product 1 . Some interesting and synthetically useful transformations of the CC reaction product of cyclopropyl ketones were also described.

A novel short approach to the A-ring synthetic equivalents of Taxol was described. Oxabicyclic ketone 3 served as a versatile template for selective functionalization leading to oxabicyclic vinylic ether 6 in two steps, which was hydrolyzed under mild acidic conditions to afford the hydroxy aldehyde derivative 7 . Synthetic equivalents 2 of Taxol A-ring were thus, accessible from hydroxy aldehyde 7 .

An efficient and highly stereoselective synthesis of functionalized trisubstituted E-olefins from cyclopropyl carbinol derivatives via a Julia-type olefination mediated by an intriguing Lewis acidic system consisting of CeCl3·7H2O and NaI in refluxing acetonitrile is reported. This facile olefination allows for the iterative incorporation of methylcyclopropyl ketone as a C5 prenylation synthon in the synthesis of acyclic terpenoids, as demonstrated in the facile synthesis of plaunotol 6E-isomer 12, a biologically significant diterpene diol, and naturally occurring diterpene 17.

[reaction: see text] An unusual cyclopropanation of 9-bromocamphor derivatives 1 to a 7-spiro-cyclopropyl camphor derivative 3 was effected by the action of potassium tert-butoxide (or sodium hydride) in warm DMSO. The exo-hydroxy group and a non-hydrogen endo-substituent at C(2) have proven to be essential structural elements, and the solvent DMSO has proven to be the sole effective reaction medium. Tricyclic compound 3 undergoes a facile tandem Wagner-Meerwein rearrangement-cyclopropyl ring-opening under mild acidic conditions, leading to norbornenyl derivative 12 and subsequent Meinwald rearrangement of bicyclic epoxide 13 to a formal C(1)-C(7) bond cleavage product 14.

3,4-Dihydroisoquinoline carboxylate 1 undergoes a smooth annulation with ω-bromopropionate, butyrate or ortho -bromomethyl benzoate 2 to afford the isoquinoline heterocycle 3 upon treatment with potassium tert -butoxide in DMF at −60 °C. This novel annulation constitutes a formal direct synthesis of cyclic Reissert equivalent compounds, thus offers an expedient access towards certain medicinally important isoquinoline heterocycles and relevant natural alkaloids, that is, of berberine and erythrina types.

A formal total synthesis of cephalotaxine (CET), the parent structure of antileukemia Cephalotaxus alkaloids, was achieved through a novel synthesis of the pentacyclic amino enone 4 by a rapid annulation of readily available beta-(3,4-methylenedioxy)phenethylamine (2), delta-valerolactone, and bromoacetone.

A novel facile synthesis of substituted and functionalized allylsilane has been developed. This essentially one-pot procedure involves (1) (dimethylphenylsilyl)methyl cerium chloride addition to cyclopropyl ketone and (2) MgI(2) etherate-mediated Julia homoallylic transposition of the corresponding cyclopropyl carbinol. The bifunctional homoiodo allylsilanes, readily accessible by this method, would be useful and versatile synthons in organic synthesis. [reaction: see text]

The first asymmetric total synthesis of two naturally occurring antitumor pseudoplexaurol and 14-deoxycrassin were achieved via two convergent synthetic sequences featured a chiral pool protocol to implement C-1 stereogenic center and Ti(0)-mediated cyclization leading to cembrane ring.

Mukaiyama-type aldol coupling of typical silyl enolates 2-4 with aryl or vinyl aldehydes and acetals was realized in the presence of 1-5 mol % of MgI(2) etherate (1) in a mild, efficient, and highly chemoselective manner. Iodide counterion, weakly coordinating peripheral ethereal ligands (Et(2)O) of Mg(II), and a noncoordinating reaction media (i.e. CH(2)Cl(2)) are among the critical factors for the unique reactivity of this catalytic system. [reaction: see text]

First convergent synthesis (±)-glyflavanone-A (1), a novel pyranoflavanone natural product, starting from phloroacetophenone and p-anisaldehyde is described.

A concise and efficient total synthesis of (+)-3,4-epoxycembrene-A 1 , an epoxy cembrane diterpenoid from tropical marine soft coral, is described. The synthesis features the use of an intramolecular McMurry coupling and Sharpless asymmetric epoxidation as key steps.

A facile and efficient approach for the syntheses of both C-8 and C-6 prenylated flavonoids has been developed that features a highly regioselective prenylation of 2,4,6-trihydroxyacetophenone and regioselective cyclization of prenylated polyhydroxy chalcones. Thus, the first efficient total syntheses of (+/-)-sophoraflavanone A (1) and (+/-)-bonannione A (2), two naturally occurring geranylated flavanones with antibacterial activities, have been achieved starting from the key intermediate 3 via regioselective cyclization of geranylated tetrahydroxychalcone 4.

A facile total synthesis of hainanensine (1), a structurally unique Cephalotaxus alkaloid, via an effective acid-mediated rearrangement/Friedel-Crafts annulation cascade (7a/7b --8a/8b), is described.

Two approaches for the enantioselective syntheses of naturally occurring kudtriol 2a and 5- epi -kudtriol 3a as well as their C-11 epimers are presented, both using the Sharpless asymmetric dihydroxylation as the key reaction. Through comparison of the spectral data of natural triols and synthetic samples, we could confirm the absolute configuration of the natural triols.

A concise and efficient total synthesis of (+)-11,12-epoxysarcophytol A (1), an epoxy cembrane diterpenoid from marine soft coral Lobophytum, is described, which allows the assignment of an absolute configuration (11S,12S) of the epoxide function unambiguously.

The first enantioselective total syntheses of (+)-11,12-epoxy-11,12-dihydrocembrene-C 1 and (−)-7,8-epoxy-7,8-dihydrocembrene-C 2, two naturally occurring cembranoxides isolated from tropical marine soft corals, are achieved via a general approach by employing an intramolecular McMurry coupling and Sharpless asymmetric epoxidation as key steps from readily available starting materials. The syntheses presented here verify the absolute stereochemistry assignment of 1 as (11S,12S) by Bowden et al. two decades ago, and the epoxy configuration of 2 was assumed as (7R,8R) accordingly.

Facile syntheses of two naturally occurring pyranoflavanoids, 3′,4′-methylenedioxy-2″,2″-dimethylpyrano-[5″,6″:7,8]-flavone (1) and (±)-ponganone III (2), have been achieved through the key intermediate chromene 6 by a DDQ-induced oxidative cyclization.

Efficient total syntheses of (±)-sarcophytol A and B, two antitumor cembrane diterpenoids isolated from marine soft corals, were presented by a low-valent titanium-mediated intramolecular McMurry olefination strategy starting from trans, trans-farnesol.