Two-pot Procedure Research Articles

Gas Transport Properties of Asymmetric Block Copolyimide Membranes

We have synthesized fluorinated block copolyimides with different block chain lengths by chemical imidization in a two-pot procedure and prepared the asymmetric coployimide membranes using the dry-wet phase inversion process. The gas transport properties of the asymmetric membranes were measured using a high vacuum apparatus equipped with a Baratron absolute pressure gauge at 76 cmHg and 35 °C. We demonstrated that the skin layer thicknesses and the gas transport properties of the asymmetric membranes depended on the copolyimide structures. The phase separation in the block copolyimide solution instantaneously occurred so that the skin layer of the asymmetric block copolyimide membrane became thinner than that of the asymmetric random copolyimide membrane and the gas permeance of the asymmetric block copolyimide membrane had a high value. The apparent skin layer thickness of the asymmetric block coployimide membrane was 230 nm. The asymmetric copolyimide membrane indicated an O2 permeance of 2:7 × 10−4 [cm3(STP)/(cm2 sec cmHg)] (270 [GPU]) and an O2/N2 selectivity of 4.3.

Indium-Catalyzed syn-Addition of 1,3-Dicarbonyl Compounds

An indium-catalyzed syn-addition of 1,3-dicarbonyl compounds and 1-iodo-1-alkynes gives exclusively E-iodoalkenes in good yields for a variety of dicarbonyls and alkynes. The vinyl iodide that is formed can be further functionalized using a Sonogashira or a Suzuki coupling in a one-pot or two-pot procedure.

Stereoselective Synthesis of Trisubstituted E-Iodoalkenes by Indium-Catalyzed syn-Addition of 1,3-Dicarbonyl Compounds to 1-Iodoalkynes

Indium-catalyzed addition of 1,3-dicarbonyl compounds to 1-iodo-1-alkynes takes place exclusively in a syn-fashion to produce E-iodoalkenes. The iodine atom serves both as an activating group and as a group that controls the regioselectivity of the addition. The E-alkenyl iodide product can be further derivatized using either a one-pot or a two-pot procedure into trisubstituted olefins in high overall yield with retention of the stereochemistry.

Efficient Two‐Pot Procedure for the Preparation of Anilines from Readily Available Aldehydes

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Novel copolyimide membranes for gas separation

A series novel fluorinated copolyimides were synthesized with various diamine compositions by chemical imidization in a two-pot procedure. The gas permeation behavior of 2,2′-bis(3,4′-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA)–2,4,6-trimethyl-1,3-phenylenediamine (TMPDA)/2,6-diamino toluene (DAT) polyimides was investigated. The physical properties of the copolyimides were characterized by IR, DSC and TGA. All the copolyimides were soluble in most of the common solvents. The gas permeabilities and diffusion coefficients decreased with increasing DAT content; however, the permselectivity of gas pairs such as H 2/N 2, O 2/N 2, CO 2/CH 4 and CO 2/N 2 was enhanced with the incorporation of DAT moiety. The permeability coefficients of H 2, O 2, N 2, CO 2 and CH 4 were found to decrease with the increasing order of kinetic diameters of the penetrants gases. Moreover, all of the copolyimides studied in this work exhibited performance near, lying on or above the existing upper bound trade-off line between permselectivity and permeability.

スルホン酸基を有する長鎖ブロックコポリイミド膜のプロトン伝導性

We have synthesized a novel sulfonated block copolyimide with long block chains by chemical imidization using a two-pot procedure. The proton conductivity of a block copolyimide film, i.e., NTDA-BDSA-b-6FAP (140/60) was approximately 0.45 S cm-1, which is higher than that of Nafion 117®. Additionally, we demonstrated that the proton conductivity of the block copolyimide film strongly depends on the block chain lengths. The conductivities of the block copolyimide films increased with increasing block chain lengths. This may be due to the formation of ionic channels in the copolyimide films and its dependence on the block chain length. We are currently investigating the effects of the morphology and domain size of the block copolyimide film on the proton conductivity.

Preparation of novel sulfonated block copolyimides for proton conductivity membranes

In this article novel sulfonated block copolyimides with various diamine compositions and block chain lengths were synthesized by chemical imidization using a two-pot procedure. The proton conductivities of the block copolyimide membranes were measured as functions of the relative humidity and temperature using four-point-probe electrochemical impedance spectroscopy. The proton conductivity of the membranes strongly depended on the block chain lengths and increased with an increase in the block chain lengths. The proton conductivity of NTDA-BDSA-b-6FAP (112/48) as the block copolyimide membrane was approximately 0.35 S cm−1 which indicated a higher value when compared to that determined for Nafion®. Copyright © 2005 John Wiley & Sons, Ltd.

A Practical Synthesis of Optically Active Aromatic Epoxides via Asymmetric Transfer Hydrogenation of α‐Chlorinated Ketones with Chiral Rhodium‐Diamine Catalyst.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Chiral benzyl centers through asymmetric catalysis. a three-step synthesis of (R)-(-)-alpha-curcumene via asymmetric hydrovinylation.

[reaction: see text] A three-step, two-pot procedure involving asymmetric hydrovinylation followed by Suzuki-Miyaura reaction represents by far the shortest synthesis of this popular bisabolane. Other applications for the synthesis of similar compounds with chiral benzyl centers can be easily envisioned.

A practical synthesis of optically active aromatic epoxides via asymmetric transfer hydrogenation of α-chlorinated ketones with chiral rhodium–diamine catalyst

A practical method for the synthesis of optically active aromatic epoxides has been developed via the formation of optically active α-chlorinated alcohols and intramolecular etherification. Optically active alcohols with up to 99% ee can be obtained from the asymmetric reduction of aromatic ketones with a substrate/catalyst ratio of 1000–5000 using a formic acid/triethylamine mixture containing a well-defined chiral Rh complex, Cp*RhCl[( R, R)-Tsdpen]. The asymmetric reduction of α-chlorinated aromatic ketones with a chiral Rh catalyst is characterized by a rapid and carbonyl group-selective transformation because of the coordinatively saturated nature of diamine-based Cp*Rh(III) hydride complexes. The outcome of the reduction is significantly influenced by the structures of the ketonic substrates as well as the hydrogen source such as formic acid or 2-propanol. Commercially available reagents and solvents can be used in this reaction without special purification. This epoxide synthetic process in either a one- or two-pot procedure is practical and particularly useful for the large-scale production of optically active styrene oxides from α-chlorinated ketones.

Rapid Improvement of a Reductive Sulfonylation Using Design of Experiment Methods

Sulfone 2 was initially prepared using a zinc-mediated one-pot coupling procedure. A traditional sodium sulfite-mediated two-pot procedure was found to eliminate a major impurity, yet modest yields prevailed. Design of experiment methods with the aid of a basic parallel synthesizer rapidly led to a high-yielding one-pot process.

ChemInform Abstract: A Very Short Synthesis of 3‐Methoxyestra‐1,3,5,8,14‐pentaen‐17‐one.

3-Methoxyestra-1,3,5,8,14-pentaen-17-one (4) was prepared from 6-methoxy-1-tetralone (8) by an efficient two-pot procedure in which the D ring was generated by the Lewis acid catalysed reaction of 1,2-bis(trimethylsiloxy)cyclobutene (5) with an appropriate ketal (10). Keywords: steroid, estrone, annellation.

A very short synthesis of 3-methoxyestra-1,3,5,8,14-pentaen-17-one

3-Methoxyestra-1,3,5,8,14-pentaen-17-one (4) was prepared from 6-methoxy-1-tetralone (8) by an efficient two-pot procedure in which the D ring was generated by the Lewis acid catalysed reaction of 1,2-bis(trimethylsiloxy)cyclobutene (5) with an appropriate ketal (10). Keywords: steroid, estrone, annellation.