Direct catalytic aldol-type reactions using RCH2CN

[reaction: see text] A copper fluoride-catalyzed cyanomethylation that can be applied to a wide range of ketones and aldehydes was developed using TMSCH(2)CN as a nucleophile. The reaction was extended to a conceptually more advanced copper alkoxide-catalyzed direct addition of alkylnitriles to aldehydes, which can act as a surrogate direct catalytic aldol reaction of esters. These reactions can be applied to the first catalytic enantioselective cyanomethylation of ketones and direct catalytic enantioselective cyanomethylation of aldehydes.     

Small angle X-ray scattering from lamellar phase for β-3,7-dimethyloctylglucoside/water system: comparison with β-n-alkylglucosides

Small angle X-ray scattering (SAXS) is measured for the lamellar phase in aqueous systems of 1-o-β-3,7-dimethyoctyl-D-glucopyranoside (β-Glc(Ger)), which has recently been prepared by us, 1-o-β-decyl-D-glucopyranoside (β-GlcC₁₀), and 1-o-β-octyl-D-glucopyranoside (β-GlcC₈). The repeat distance d obtained from the position of the diffraction peak does not follow the swelling law d = 2δ_hc/_hc, where δ_hc and _hc are the thickness and the volume fraction of the hydrophobic layer, respectively. This may result from the fact that δ_hc increases and, equivalently, the surface area per surfactant molecule (a_s) decreases with increasing concentration. So we calculate δ_hc and a_s from the observed d value at each concentration using the above swelling law. The half-thickness δ_hc increases in the order β-GlcC₈ < β-Glc(Ger) < β-GlcC₁₀ at a fixed concentration. On the other hand, the data on a_s for β-GlcC₁₀ and β-GlcC₈ lie on the same line and the data for β-Glc(Ger) lies above this line. These results suggest that the cross-sectional area of the geranyl chain is larger than that of the glucose headgroup. Existence of water filled defects in bilayer sheets is also discussed based on the SAXS pattern and the concentration dependence of d.     

Catalytic asymmetric synthesis of both syn- and anti-3,5-dihydroxy esters: application to 1,3-polyol/alpha-pyrone natural product synthesis

[reaction: see text] We describe a catalytic asymmetric synthesis of both syn- and anti-3,5-dihydroxy esters. The method relies upon catalytic asymmetric epoxidation of alpha,beta-unsaturated imidazolides and amides, using lanthanide-BINOL complexes, and diastereoselective reduction of ketones. The method was applied to the enantioselective syntheses of 1,3-polyol/alpha-pyrone natural products 9a, 9b, and strictifolione (10). The absolute stereochemistry of 9a and 9b was also determined.     

Aqueous phase behavior of a 1-O-phytanyl-beta-D-xyloside/water system. Glycolipid-based bicontinuous cubic phases of crystallographic space groups Pn3m and Ia3d

Temperature- and concentration-dependent aqueous phase diagram of a novel alkylglycoside, 1-O-phytanyl-beta-D-xyloside (beta-Xyl(Phyt)), was studied using small-angle X-ray scattering, polarizing optical microscopy, and differential scanning calorimetry. The phases found in this system include an Lc phase, an Lalpha phase, an HII phase, two inverted cubic phases of crystallographic space groups Pn3m and Ia3d, and a fluid isotropic phase, FI. The phase diagram of the beta-Xyl(Phyt)/water system is similar to that for the 1-monooleylglycerol (MO)/water system, suggesting that the phase behavior is largely determined by the overall molecular shape rather than the details of surfactant molecular structure. Moreover, the structural parameters of the beta-Xyl(Phyt) liquid crystals are also similar to those of the MO/water, due primarily to the similar molecular dimensions of two molecules. As compared to the MO/water system, however, the beta-Xyl(Phyt)/water system displays a lower value of TK ( approximately 8.(5) degrees C) and a wider temperature window for the mesophases (8.(5)-120 degrees C). Moreover, beta-Xyl(Phyt) is chemically more robust than MO, as the ether linkage is more stable against hydrolysis than the ester linkage and the phytanyl chain is fully saturated.     

Asymmetric Catalysis with Bis(hydroxyphenyl)diamides/Rare‐Earth Metal Complexes

A series of asymmetric catalysts composed of conformationally flexible amide‐based chiral ligands and rare‐earth metals was developed for proton‐transfer catalysis. These ligands derived from amino acids provide an intriguing chiral platform for the formation of asymmetric catalysts upon complexation with rare‐earth metals. The scope of this arsenal of catalysts was further broadened by the development of heterobimetallic catalytic systems. The cooperative function of hydrogen bonding and metal coordination resulted in intriguing substrate specificity and stereocontrol, and the dynamic nature of the catalysts led to a switch of their function. Herein, we summarize our recent exploration of this class of catalysts.     

All Non-Carbon B3NO2 Exotic Heterocycles: Synthesis,Dynamics, and Catalysis

The B₃NO₂ six-membered heterocycle (1,3-dioxa-5-aza-2,4,6-triborinane=DATB), comprising three different non-carbon period 2 elements, has been recently demonstrated to be a powerful catalyst for dehydrative condensation of carboxylic acids and amines. The tedious synthesis of DATB, however, has significantly diminished its utility as a catalyst, and thus the inherent chemical properties of the ring system have remained virtually unexplored. Here, a general and facile synthetic strategy that harnesses a pyrimidine-containing scaffold for the reliable installation of boron atoms is disclosed, giving rise to a series of Pym-DATBs from inexpensive materials in a modular fashion. The identification of a soluble Pym-DATB derivative allowed for the investigation of the dynamic nature of the B₃NO₂ ring system, revealing differential ring-closing and -opening behaviors depending on the medium. Readily accessible Pym-DATBs proved their utility as efficient catalysts for dehydrative amidation with broad substrate scope and functional-group tolerance, offering a general and practical catalytic alternative to reagent-driven amidation.     

Amphoteric poly(vinyl alcohol) gel as a force generator: Observation of microporous gel formation with cryo-SEM

Amphoteric PVA hydrogels were made from mixed aqueous solutions of poly(acrylic acid), poly(allylamine) hydrochloride and poly(vinyl alcohol) by repetitive freezing and thawing. The hydrogen bond induced gelation produced an elastic and tough microporous hydrogel which generated tension as high as 0.3MPa corresponding to the solvent exchange from water to acetone. In this paper we show the microscopic structure of hydrogels determined by means of cryo-SEM technique and X-ray analysis.     

Direct catalytic asymmetric Mannich-type reactions of isomerizable aliphatic imines: chemoselective enolate formation from a hydroxyketone by a Zn-catalyst

A direct catalytic asymmetric Mannich-type reaction of isomerizable aliphatic imines is described. A Et₂Zn/(S,S)-linked-BINOL complex was suitable for chemoselective enolate formation from a hydroxyketone in the presence of isomerizable aliphatic N-diphenylphosphinoyl imines. The reaction proceeds smoothly and β-alkyl-β-amino-α-hydroxyketones were obtained in good yield and high enantioselectivity (up to 99% ee), albeit in modest to low diastereoselectivity.