Some partially fluorinated cyclic and acyclic compounds of sulphur (II) and (IV) and partially fluorinated cyclic compounds of phosphorus (III) and (V)

Sulfinyl fluoride and N-(F-isoprophyl)iminosulfur difluoride form the compounds, O$\text{SN(CH}{}_3\text{)CH}{}_2\text{CH}{}_2\text{N}$(CH₃) and i-C₃F₇N$\text{SN(CH}{}_3\text{CH}{}_2\text{CH}{}_2\text{N}$(CH₃ with symdimethylethylenediamine (1). In contrast, CF₃C(O)NSF₂ and (R_f)₂SF₂ (R_f = CF₃, i-C₃F₇ form only acyclic compounds, CF₃C(O)N(CH₃)CH₂CH₂N(CH₃)C(O)CF₃ and R_fSN(CH₃)CH₂CH₂N(CH₃)SR_f with (1). With PF₃, PF₅ and OPF₃, cyclic compounds $\text{N(CH}{}_3\text{)CH}{}_2\text{CH}{}_2\text{N(CH}{}_3\text{)P}$F, $\text{N(CH}{}_3\text{)CH}{}_2\text{CH}{}_2\text{N(CH}{}_3\text{)P}$F₃, and $\text{N(CH}{}_3\text{)CH}{}_2\text{CH}{}_2\text{N(CH}{}_3\text{)P}$-(O)F result. When the latter two compounds are reacted further with LiNC(CF₃)₂, N(CH₃)CH₂CH₂N(CH₃)PF₂NC(CF₃)₂ and $\text{N(CH}{}_3\text{CH}{}_2\text{CH}{}_2\text{N(CH}{}_3\text{)P}$(O)NC(CF₃)₂) form.     

Stereoselective syntheses of 4-hydroxy 4-substituted glutamic acids

The 4-hydroxy 4-substituted glutamic acid moiety is a common substructure of biologically important natural products such as monatin [(2S,4S)-2], lycoperdic acid (3), and dysiherbaine (4). To develop methodology for syntheses of these natural products, cycloadditions of nitrone 5 with 2-substituted 2-propen-1-ols 6 and 2-substituted acrylates 8 were investigated. Reactions of nitrone 5 with alcohols 6 in the presence of MgBr2OEt2 gave cycloadducts 7 in a highly stereoselective manner, whereas noncatalyzed reactions of 5 with acrylates 8 afforded adducts 9. Using the former reaction, syntheses of monatin [(2S,4S)-2], monatin derivative 18, and lycoperdic acid (3) were accomplished. The C4-epimer of monatin [(2S,4R)-2)] was also synthesized by employing the latter cycloaddition.     

Synthesis and properties of rhenium tricarbonyl complex bearing N-fused tetraphenylporphyrin ligand

An N-fused porphyrin rhenium complex was synthesized by the thermal reaction of an N-confused porphyrin with Re2(CO)10 and its structure was determined by X-ray crystallographic analysis.     

Rhodium-catalyzed arylative cyclization of alkynones induced by addition of arylboronic acids

Alkynones react with arylboronic acids in the presence of a rhodium(I) catalyst to afford four- and five-membered-ring cyclic alcohols equipped with a tetrasubstituted exocyclic olefin. The cyclic allylic alcohol skeleton is constructed by the carbon-carbon bond formation between the carbonyl group and an alkenylrhodium(I) intermediate formed by the regioselective addition of an arylrhodium(I) species across the carbon-carbon triple bond.     

Scalar auxiliary variable approach for conservative/dissipative partial differential equations with unbounded energy functionals

BIT Numerical Mathematics - In this paper, we present a novel investigation of the so-called SAV approach, which is a framework to construct linearly implicit geometric numerical integrators for...     

Dynamic covalent approach to [2]- and [3]roxtanes by utilizing a reversible thiol-disulfide interchange reaction

A dynamic covalent approach to disulfide-containing [2]- and [3]rotaxanes is described. Symmetrical dumbbell-shaped compounds with two secondary ammonium centers and a central located disulfide bond were synthesized as components of rotaxanes. The rotaxanes were synthesized from the dumbbell-shaped compounds and dibenzo-[24]crown-8 (DB24C8) with catalysis by benzenethiol. The yields of isolated rotaxanes reached about 90 % under optimized conditions. A kinetic study on the reaction forming [2]rotaxane 2 a and [3]rotaxane 3 a suggested a plausible reaction mechanism comprising several steps, including 1) initiation, 2) [2]rotaxane formation, and 3) [3]rotaxane formation. The whole reaction was found to be reversible in the presence of thiols, and thermodynamic control over product distribution was thus possible by varying the temperature, solvent, initial ratio of substrates, and concentration. The steric bulk of the end-capping groups had almost no influence on rotaxane yields, but the structure of the thiol was crucial for reaction rates. Amines and phosphines were also effective as catalysts. The structural characterization of the rotaxanes included an X-ray crystallographic study on [3]rotaxane 3 a.     

W(CO)5(L)-catalyzed formal cope rearrangement of allenyl silyl enol ethers

[reaction: see text] On treatment of 5-siloxyhexa-1,2,5-trienes with a catalytic amount of W(CO)(6) under photoirradiation, formal Cope rearrangement proceeded to give 2-siloxyhex-1-en-5-ynes in good yield. The electrophilic activation of the allenyl moiety by W(CO)(5) triggers the intramolecular attack of the silyl enol ether in a 6-endo manner to produce a cyclohexenyl tungsten species. Carbon-carbon bond cleavage occurs by electron donation from the anionic W(CO)(5) into the silyloxonium moiety to afford the products with regeneration of the W(CO)(5)(L).     

Enantioselective carbanion cyclization of 5-alkenyl carbamates induced by asymmetric lithiation with s-butyllithium/(−)-sparteine system

Treatment of (E)-6-phenyl-5-hexenyl carbamates with s-BuLi/(−)-sparteine is shown to afford the trans-1,2-disubstituted cyclopentane derivatives in high % ee, along with the bicyclo[3.1.0]hexanes (bicyclization products).     

Synthesis of fluorinated materials catalyzed by proline or antibody 38C2 in ionic liquid

The utility of reusable ionic liquid-proline (or aldolase antibody 38C2) reaction system, proceeding the aldol reactions, is described. Further, obtained α-chloro-β-hydroxy compounds were transformed to the optically active α,β-epoxy carbonyl compounds. The aldolase antibody 38C2-ionic liquid system was able to reuse in Michael additions and the reaction of fluoromethylated imines.     

Synthesis of directly linked zinc(II) porphyrin-imide dyads and energy gap dependence of intramolecular electron transfer reactions

A series of zinc(II) porphyrin-imide dyads (ZP-Im), in which an electron donating ZP moiety is directly connected to an electron accepting imide moiety in the meso position, have been prepared for the examination of energy gap dependence of intramolecular electron transfer reactions with large electronic coupling. The nearly perpendicular conformation of the imide moiety towards the porphyrin plane has been revealed by Xray crystal structures. The energy gap for charge separation, 1ZP* - Im --> ZP+ - Im-, is varied by changing the electron accepting imide moiety to cover a range of about 0.8 eV in DMF. Definitive evidence for electron transfer has been obtained in three solvents (toluene, THF, and DMF) through picosecond-femtosecond transient absorption studies, which have allowed us to determine the rates of photoinduced charge separation, 1ZP* - Im --> ZP+ - Im-, and subsequent thermal charge recombination ZP+ - Im- --> ZP - Im. The free-energy gap dependence (energy gap law) has been probed from the normal to the nearly top region for the charge separation rate alone, and only the inverted region for the charge recombination rate. Although both of the energy gap dependencies can be approximately reproduced by means of the simplified semiclassical equation, when we take into consideration the effect of the high frequency vibrations replaced by one mode of averaged frequency, many features, including the effects of solvent polarity and the electron tunneling matrix element on the energy gap law, differ considerably from those of the previously studied porphyrin-quinone systems, which have weaker interchromophore electronic interactions.