An Extraordinarily Rapid Polymerization of Vinylpentafluorocyclopropane: Highly Stereo- and Regioselective Synthesis of Unsaturated Fluoropolymers^†

Vinylpentafluorocyclopropane 1 was prepared from the reaction of 1,1,2-trifluoro-4-bromobutene and hexafluoropropylene oxide at 190 °C, following by treatment with KOH. 1 is stable at low temperature (−40 °C) for 7 years, but it rearranged readily to 2,3,3,4,4-pentafluorocyclopentene-1, 2, at above 80 °C (Ea = 28.7 kcal/mol). Under radical conditions, 1 extraordinarily rapidly polymerizes to give highly crystalline Z-fluoropolyolefin (CF2CF2CFCHCH2)n, 3, which is very useful for cross-linking and grafting but difficult to obtain by other means. The stereochemistry of 3 was further confirmed by radical addition of iodine to 1 to form Z-ICF2CF2CFCHCH2I, 4, exclusively. The rapid polymerization with high stereoselectivity and regioselectivity could be rationalized by effects of a favorable polar transition state of a high ring strain and electron-deficient pentafluorocyclopropyl and a relative electron-rich double bond of 1

Nickel-Catalyzed Reaction of Highly Fluorinated Epoxides with Halogens^⊥

Nickel-Catalyzed Reaction of Highly Fluorinated Epoxides with Halogens⊥</sup

A Facile Perfluoroallylation of Olefins

The addition of F-allyl iodide to terminal alkenes is induced by a catalytic amount of copper powder in the absence of solvent at room temperature to 50 °C to give the corresponding 1:1 adducts in good yields. A variety of functional groups such as trimethylsilyl, alkyl, epoxy, ester, hydroxyl, bromo, ether, and phosphonate are tolerated in the addition reaction. This reaction also worked well with internal olefins such as cyclohexene, cyclopentene, and 4-octene. Reaction with dienes gives the corresponding linear adduct and cyclization adduct depending on the chain length of the dienes. With 1,7-octadiene, a bis(perfluoroallyl) product is formed, while a tetrahydrofuran derivative is obtained with diallyl ether. Reduction of the adducts with zinc in the presence of nickel dichloride in moist THF or zinc in moist DMF affords the perfluoroallyl derivatives. The adduct reacts with zinc in DMF to form a zinc reagent which couples with organic electrophiles in the presence of CuBr

A Simple Transformation of Polyethylenes to Environmentally Benign Acid Catalysts and Lithium Conductive Polymeric Electrolytes^†

A Simple Transformation of Polyethylenes to Environmentally Benign Acid Catalysts and Lithium Conductive Polymeric Electrolytes†</sup

Rate of Cyclization of Perfluoro-4-Oxa-5-hexenyl Radical. Use of Tributylgermanium Hydride as an Effective H-Transfer Agent for Perfluoro-<i>n</i>-alkenyl Radicals^†

Rate of Cyclization of Perfluoro-4-Oxa-5-hexenyl Radical. Use of Tributylgermanium Hydride as an Effective H-Transfer Agent for Perfluoro-n-alkenyl Radicals†</sup

Remarkable Cyclization Reactivities of Partially-Fluorinated 6-Heptenyl Radicals^†

Remarkable Cyclization Reactivities of Partially-Fluorinated 6-Heptenyl Radicals†</sup

Synthesis of Tricyclo[4,3,1,0^1,5]decane Core of Plumisclerin A Using Pauson–Khand Annulation and SmI₂‑Mediated Radical Cyclization

An efficient synthesis of the tricyclo­[4,3,1,0^1, 5]­decane core (B/C/D rings) of plumisclerin A, a unique cytotoxic marine diterpenoid, is described. A Pauson–Khand reaction and a SmI₂-mediated radical 1,4-conjugate addition successfully served as key reactions for construction of the fully functionalized 5,6-fused rings and the highly strained cyclobutanol moiety with correct relative stereochemistries, respectively

Facile Synthesis of a “Two-in-One” Sulfur Host Featuring Metallic-Cobalt-Embedded N‑Doped Carbon Nanotubes for Efficient Lithium-Sulfur Batteries

The exploration of efficient host materials of sulfur is significant for the practical lithium-sulfur (Li-S) batteries, and the hosts are expected to be highly conductive for high sulfur utilization and exhibit strong interaction toward polysulfides to suppress the shuttle effect for long-lasting cycle stability. Herein, we propose a simple synthesis of metallic cobalt-embedded N-doping carbon nanotubes (Co@NCNT) as a “two-in-one” host of sulfur for efficient Li-S batteries. In the binary host, the N-doped CNTs, cooperating with metallic Co nanoparticles, can serve as 3D conductive networks for fast electron transportation, while the synergetic effect of metallic Co and doping N heteroatoms helps to chemically confine polysulfides, acting as active sites to accelerate electrochemical kinetics. With these advantages, the S/Co@NCNT composite delivers an excellent cycling stability with a capacity decay of 0.08% per cycle averaged within 500 cycles at a current density of 1 A g–1 and a high rate performance of 530 mA h g–1 at 5 A g–1. Further, the superior electrochemical performance of the S/Co@NCNT electrode can be maintained under a high sulfur loading up to 4 mg cm–2. Our work demonstrates a feasible strategy to design promising host materials simultaneously featuring high conductivity and strong confinement toward polysulfides for high-performance Li-S batteries

Efficient Polysulfide Redox Enabled by Lattice-Distorted Ni₃Fe Intermetallic Electrocatalyst-Modified Separator for Lithium–Sulfur Batteries

Exploring efficient electrocatalysts for lithium–sulfur (Li–S) batteries is of great significance for the sulfur/polysulfide/sulfide multiphase conversion. Herein, we report nickel–iron intermetallic (Ni3Fe) as a novel electrocatalyst to trigger the highly efficient polysulfide-involving surface reactions. The incorporation of iron into the cubic nickel phase can induce strong electronic interaction and lattice distortion, thereby activating the inferior Ni phase to catalytically active Ni3Fe phase. Kinetics investigations reveal that the Ni3Fe phase promotes the redox kinetics of the multiphase conversion of Li–S electrochemistry. As a result, the Li–S cells assembled with a 70 wt % sulfur cathode and a Ni3Fe-modified separator deliver initial capacities of 1310.3 mA h g–1 at 0.1 C and 598 mA h g–1 at 4 C with excellent rate capability and a long cycle life of 1000 cycles at 1 C with a low capacity fading rate of ∼0.034 per cycle. More impressively, the Ni3Fe-catalyzed cells exhibit outstanding performance even at harsh working conditions, such as high sulfur loading (7.7 mg cm–2) or lean electrolyte/sulfur ratio (∼6 μL mg–1). This work provides a new concept on exploring advanced intermetallic catalysts for high-rate and long-life Li–S batteries

In Situ Constructing a Stable Solid Electrolyte Interface by Multifunctional Electrolyte Additive to Stabilize Lithium Metal Anodes for Li–S Batteries

Lithium (Li) metal is considered to be the most promising anode due to the ultrahigh capacity and extremely low electrochemical potential. The tricky thing is that the growth of dendritic Li brings huge safety hazards to Li metal batteries. Herein, we demonstrate cerium nitrate as a multifunctional electrolyte additive to form a stable solid electrolyte interface on the metallic Li anode surface for durable Li–S batteries. The presence of Ce3+ helps to modulate the electroplating/stripping of Li and inhibits the growth of dendritic Li. An excellent cycle life exceeding 1400 h at the current density of 1 mA cm–2 can be realized in symmetric Li||Li cells. In addition, the in situ formed robust solid–electrolyte interface (SEI) layer containing cerium sulfide on the Li anode surface conduces to weaken the reducibility of Li and regulate the electrochemical dissolution/deposition reaction on the Li anode. Surprisingly, by virtue of cerium nitrate additive with a low concentration of 0.03 M, the Li–S batteries can afford a capacity of 553 mA h g–1 at 5 C and a long cycle life at 1 C with a high capacity retention of 70.4%. Therefore, this study provides a novel idea to realize a uniform and dendrite-free Li anode for practical Li–S batteries