High turnover frequency observed in catalytic enantioselective additions of enecarbamates and enamides to iminophosphonates

[Structure: see text] In addition reactions of enecarbamates and enamides, extremely high turnover frequency of the catalyst was observed in comparison with that of silicon enolate addition reactions. This is presumably due to fast transfer of the proton that locates on the nucleophiles.     

Development of a novel environmentally friendly electropolymerization of water-insoluble monomers in aqueous electrolytes using acoustic emulsification

Electropolymerization of water-insoluble monomers, such as 3,4-ethylenedioxythiophene (EDOT), 3,4-dimethylthiophene (3,4-DiMeTh), 3-methylthiophene (3-MeTh), and 3-ethylthiophene (3-EtTh), proceeded successfully in aqueous electrolytes using acoustic emulsification. Ultrasonication to the water-insoluble monomer/aqueous electrolyte mixtures allowed the formation of very stable emulsions having the characteristic of giving narrow monomer droplet size distributions in the submicrometer range in aqueous electrolytes without added surfactants, and the smooth electropolymerization in the emulsions took place via direct electron transfer between the electrode and the water-insoluble monomer droplets. In this kind of electron-transfer system, the supporting electrolyte should be dissolved not only in the aqueous phase but also in the monomer droplets and contribute to the formation of an electric bilayer inside the droplets. The properties of a polymer EDOT film obtained by the present method were also investigated.     

2D-grid layered Pd-based cationic infinite coordination polymer/polyoxometalate crystal with hydrophilic sorption

The inorganic-organic hybrid compound composed of the novel infinite-chain Pd(II) complex and the polyoxometalate ({[(en)Pd(p-bpy)]2[alpha-SiW12O40].8DMSO.4DMF}infinity (1a:1 with 8DMSO.4DMF; monoclinic P2(1)/c (No. 14), a = 15.0188(3) A, b = 15.6962(3) A, c = 26.9793(6) A, beta = 106.3580(10) degrees , V = 6102.6(2) A(3)) has been successfully synthesized by the reaction of [(en)Pd(OH2)2]2[alpha-SiW12O40] (2) with 4,4'-bipyridine (p-bpy). The treatment in dry N(2) at 50 degrees C or evacuation at room temperature forms {[(en)Pd(p-bpy)](2)[alpha-SiW(12)O(40)].6.0DMSO}(infinity) (1b:1 with 6DMSO) with a drastic reduction of the interlayer spacing, which is characterized by the powder diffraction analysis and the single-crystal analysis of 1c (1 with 4.5DMSO.3.5DMF; monoclinic P2(1)/a (No. 14), a = 14.200(9) A, b = 22.8865(8) A, c = 14.8558(5) A, beta = 114.7990(10) degrees , V = 4383.0(2) A(3)). Compound 1b reversibly sorbs the hydrophilic molecules with the maintenance of the intrinsic structure, which is much different from hydrophobic guest-inclusion properties reported in the other Pd-based supramolecular systems.     

Cellulose alkyl ester/poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone) blends: characterization of miscibility and crystallization behaviour

Cellulose valerate (CV)/poly(ε-caprolactone) (PCL) blends were investigated to clarify the effect of the degree of substitution (DS) of the cellulose ester component on the miscibility. CVs of DS > 2.15 were miscible with PCL in their amorphous states, as judged from the detection of a single T _g by differential scanning calorimetry (DSC). This result and other complementary data for cellulose acetate (CA), propionate (CP), and butyrate (CB) blends with PCL made up a miscibility map as a function of the number N of carbons in the normal acyl substituent as well as of DS. CB of N = 4 and CV of N = 5, the ester side-chains of which make a higher similarity in chemical structure with a repeating unit of PCL, were found to be miscible with the aliphatic polyester at a comparatively lower DS; the critical butyryl DS of ∼1.85 being still lower than 2.15. For PCL-rich compositions of CB(DS > 2.0)/PCL and CV(DS > 2.2)/PCL blends, isothermal melt-crystallization behaviour was characterized by calorimetry and polarized optical microscopy. The CB and CV components gave rise to a marked diminution of the crystallization rate of PCL, as a result of the diluent action of the cellulose esters in the respective miscible, molten mixtures. Through a quantitative analysis of the kinetics, it is suggested regarding the supramolecular morphology that the bulky cellulose esters would be trapped not only on the fold surfaces but also on the growth faces of PCL lamellar crystals, to form a non-crystalline mixed polymer phase in the crystal boundary regions.     

Dichloro­(4,4′‐dialkyl‐2,2′‐bipyridine‐κ2N,N′)platinum(II), where alkyl is pentyl and heptyl

Dichloro­(4,4′‐dipentyl‐2,2′‐bipyridine‐κ²N,N′)platinum(II), [PtCl₂(C₂₀H₂₈N₂)], adopts a discrete π–π stacking structure, where the alkyl chains are located in a random manner. In contrast, dichloro­(4,4′‐diheptyl‐2,2′‐bipyridine‐κ²N,N′)platinum(II), [PtCl₂(C₂₄H₃₆N₂)], forms a layer structure comprised of alkyl chain layers and paired coordination sites, as observed for analogous complexes with longer alkyl chains.     

Selective Ortho‐Hydroxylation–Defluorination of 2‐Fluorophenolates with a Bis(μ‐oxo)dicopper(III) Species

The bis(μ‐oxo)dicopper(III) species [Cu^III₂(μ‐O)₂(m‐XYL^MeAN)]²⁺ ( 1 ) promotes the electrophilic ortho‐hydroxylation–defluorination of 2‐fluorophenolates to give the corresponding catechols, a reaction that is not accomplishable with a (η²:η²‐O₂)dicopper(II) complex. Isotopic labeling studies show that the incoming oxygen atom originates from the bis(μ‐oxo) unit. Ortho‐hydroxylation–defluorination occurs selectively in intramolecular competition with other ortho‐substituents such as chlorine or bromine.     

Topotactic Conversion of β‐Helix‐Layered Silicate into AST‐Type Zeolite through Successive Interlayer Modifications

AST‐type zeolite with a plate morphology can be synthesized by topotactic conversion of a layered silicate (β‐helix‐layered silicate; HLS) by using N,N‐dimethylpropionamide (DPA) to control the layer stacking of silicate layers and the subsequent interlayer condensation. Treatment of HLS twice with 1) hydrochloric acid/ethanol and 2) dimethylsulfoxide (DMSO) are needed to remove interlayer hydrated Na ions and tetramethylammonium (TMA) ions in intralayer cup‐like cavities (intracavity TMA ions), both of which are introduced during the preparation of HLS. The utilization of an amide molecule is effective for the control of the stacking sequence of silicate layers. This method could be applicable to various layered silicates that cannot be topotactically converted into three‐dimensional networks by simple interlayer condensation by judicious choice of amide molecules.     

Chemoselective and Direct Functionalization of Methyl Benzyl Ethers and Unsymmetrical Dibenzyl Ethers by Using Iron Trichloride

Methyl and benzyl ethers are widely utilized as protected alcohols due to their chemical stability, such as the low reactivity of the methoxy and benzyloxy groups as leaving groups under nucleophilic conditions. We have established the direct azidation of chemically stable methyl and benzyl ethers derived from secondary and tertiary benzyl alcohols. The present azidation chemoselectively proceeds at the secondary or tertiary benzylic positions of methyl benzyl ethers or unsymmetrical dibenzyl ethers and is also applicable to direct allylation, alkynylation, and cyanation reactions, as well as the azidation. The present methodologies provide not only a novel chemoselectivity but also the advantage of shortened synthetic steps, due to the direct process without the deprotection of the methyl and benzyl ethers.     

Catalytic asymmetric synthesis of alpha-amino phosphonates using enantioselective carbon-carbon bond-forming reactions

We have developed highly enantioselelctive reactions of silicon enolates with N-acyl-alpha-iminophosphonates leading to optically active alpha-amino phophonates. A copper (II)-diamine complex was shown to be effective in this reaction, and high levels of yield and selectivity were achieved. It is noteworthy that this reaction opens a way to various biologically important, optically active alpha-amino phosphonate derivatives.     

An efficient total synthesis of (+)-heliannuol D

An efficient total synthesis of (+)-heliannuol D was accomplished in 14 steps and in 12% overall yield by employing a diastereoselective conjugate addition reaction to create a tertiary benzylic stereogenic center and simple assembly of the functionalized oxepane framework by an efficient one-pot transformation procedure as the key steps.