Effect of solvent exchange on the supramolecular structure, the molecular mobility and the dissolution behavior of cellulose in LiCl/DMAc.

We investigated the effect of solvent exchange on the supramolecular structure and the molecular mobility of the cellulose molecule to clarify the mechanism of the dissolution of cellulose in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc). Among the celluloses that were solvent exchanged in different ways, the DMAc-treated celluloses dissolved most rapidly. Dissolution of the acetone-treated celluloses was much slower than the DMAc-treated ones, but considerably faster than the untreated one.

Pd-catalyzed asymmetric allylic amination of Morita-Baylis-Hillman adduct derivatives using chiral diaminophosphine oxides: DIAPHOXs.

[reaction: see text] Asymmetric allylic amination of allylic carbonates prepared from racemic Morita-Baylis-Hillman adducts proceeded in the presence of Pd catalyst, chiral diaminophosphine oxide (DIAPHOX), and BSA, affording the corresponding chiral aza-Morita-Baylis-Hillman adduct derivatives in excellent yield with up to 99% ee. The cyclic reaction products could be converted into various synthetically useful compounds such as chiral cyclic beta-amino acids.

Characterization of aggregate structure in mercerized cellulose/LiCl.DMAc solution using light scattering and rheological measurements.

The structure of a semidilute solution of mercerized cellulose (CC1m) in 8% (w/w) LiCl.DMAc, which contained some aggregates, was investigated using static and dynamic light scattering measurements. The static scattering function of the polymer solution containing a small amount of aggregates can be separated into fast- and slow-mode components by combining static and dynamic light scattering measurements.

Investigation of the structure of cellulose in LiCl/DMAc solution and its gelation behavior by small-angle X-ray scattering measurements.

Cellulose gels were prepared from cellulose in lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) solution. When the cellulose concentration in the solution is above the one at which cellulose molecules overlap, cellulose gels were formed. While the gel prepared by the addition of water was turbid, the one prepared by the ion exchange was colorless, transparent, and optically anisotropic.

Development of a new class of chiral phosphorus ligands: P-chirogenic diaminophosphine oxides. A unique source of enantioselection in Pd-catalyzed asymmetric construction of quaternary carbons.

[reaction: see text] We have recently developed a new class of chiral phosphorus ligands: P-chirogenic diaminophosphine oxides. These pentavalent phosphorus compounds have been successfully applied to Pd-catalyzed asymmetric construction of tertiary and quaternary carbons. The actual ligand structure was the trivalent phosphorus species 17, which was generated in situ by BSA-induced P(V) to P(III) transformation of 6, the preligand.

P-Chirogenic diaminophosphine oxide: a new class of chiral phosphorus ligands for asymmetric catalysis.

We successfully synthesized a novel P-chirogenic diaminophosphine oxide 4, which was applied to catalytic enantioselective construction of quaternary carbon centers using Pd-catalyzed asymmetric allylic substitution with various beta-keto esters (up to 99% yield, 94% ee). Preliminary mechanistic studies indicated that two molecules of 8 coordinate to the Pd metal in a monodentate fashion, resulting in the formation of Pd complex 9 (Pd:8 = 1:2), which functions as the active species.

Rheological properties and molecular structure of tunicate cellulose in LiCl/1,3-dimethyl-2-imidazolidinone.

Solution properties and molecular structure of tunicate cellulose (TC), an animal cellulose from Halocynthia roretzi, were investigated in terms of rheological and dilute solution properties. The solvent used is 8 wt % LiCl/1,3-dimethyl-2-imidazolidinone (DMI). A solution of dissolving pulp (DP), derived from plant, was also used for comparison.

Effect of solvent exchange on the solid structure and dissolution behavior of cellulose.

Effects of solvent exchange and milling on the solid structure of cellulose were investigated, using small- and wide-angle X-ray scattering and solid-state NMR. The solvent exchange facilitated the dissolution of cellulose in LiCl/DMAc with no change of the crystalline structure of cellulose. In contrast, the milling never facilitated the dissolution of cellulose, though the crystalline structure was almost destroyed.

Structures of Fibrous Supramolecular Assemblies Constructed by Amino Acid Surfactants: Investigation by AFM, SANS, and SAXS.

Aqueous gel-like solutions of N-acyl-L-aspartic acids (C(n)Asp, n=14, 16, 18) and N-dodecanoyl-beta-alanine (C(12)Ala) were prepared at pH 5-6 at room temperature. Structures of supramolecular assemblies in the solutions were investigated by atomic force microscopy (AFM), small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS). The cross-sectional radii, 22-30 Å, of helical, fibrous assemblies were obtained from analysis of SANS for 1% gel-like C(n)Asp solutions.