From 3′-Keto-Isomaltulose to Polymers

Abstract

A new method was developed to prepare polymers with a saccharide in the main chain without blocking and deblocking procedures. The microbial oxidation product of isomaltulose, 3′-keto-isomaltulose, was converted to a diamine by reductive amination. The resulting diamine was employed as a difunctional monomer for direct polyaddition with diisocyanates. The polyureas formed were characterized by IR, ¹³C NMR, light scattering, and viscosity measurements.     

1,3-Dipolar cycloaddition of alkenes to 3’-azido-3’-deoxythymidine as a route to 3’-deoxythymidin-3’-yl derivatives

1. Download : Download full-size image

     

Photosensitization of trans-Vitamin D3 to cis-Vitamin D3 in Heterogeneous System

Two modes of heterogeneous photoisomerization of trans-vitamin D3 to cis-vitamin D3 are described. The occurrence of isomerization on the substrate bounded to the polymeric support gives us the possibility in succession synthesis of 1α-hydroxyvitamin D3. The polymer-bound anthracene can sensitize isomerization of trans-vitamin D3 to cis-vitamin D3 efficiently and ease the separation process.     

Access to β,γ-diamino acids. Application to the synthesis of 3-deoxyaminostatine

The synthesis of orthogonally protected diastereo- and enantiopure β,γ-diamino acids starting from natural α-amino acids is described, as well as its application to the synthesis of fully protected 3-deoxyaminostatine.     

Approaches to Epothilone Carboanalogs Starting from Δ3-Carene

Starting from (+)-³-carene, synthetic equivalents of the C¹⁰-C¹⁶ fragment of epothilone carbo- analogs were obtained.     

Facile Route to Control over the Morphological Evolution of β-Ga_2O_3 from Nanowires to Nanoflags and to Nanosheets

We report the fabrication of β-Ga_2O_3 nanostructures on Au-coated(0001) sapphire substrate by chemical vapor deposition. The morphologies and structural properties of β-Ga_2O_3 nanostructures were characterized by scanning electron microscopy, X-ray diffraction and transmission electron microscopy. Different morphologies including nanowire, nanoflag and nanosheet were controllably synthesized by adjusting the important growth parameters of ambient source contents. It is suggested that the relative ratio of oxygen and gallium contents plays a significant role in determining the morphologies of β-Ga_2O_3 nanostructure.     

Oxidative group transfer to a triiron complex to form a nucleophilic μ(3)-nitride, [Fe3(μ(3)-N)]-

Utilizing a hexadentate ligand platform, a high-spin trinuclear iron complex of the type ((tbs)L)Fe(3)(thf) was synthesized and characterized ([(tbs)L](6-) = [1,3,5-C(6)H(9)(NPh-o-NSi(t)BuMe(2))(3)](6-)). The silyl-amide groups only permit ligation of one solvent molecule to the tri-iron core, resulting in an asymmetric core wherein each iron ion exhibits a distinct local coordination environment. The triiron complex ((tbs)L)Fe(3)(thf) rapidly consumes inorganic azide ([N(3)]NBu(4)) to afford an anionic, trinuclear nitride complex [((tbs)L)Fe(3)(μ(3)-N)]NBu(4). The nearly C(3)-symmetric complex exhibits a highly pyramidalized nitride ligand that resides 1.205(3) ? above the mean triiron plane with short Fe-N (1.871(3) ?) distances and Fe-Fe separation (2.480(1) ?). The nucleophilic nitride can be readily alkylated via reaction with methyl iodide to afford the neutral, trinuclear methylimide complex ((tbs)L)Fe(3)(μ(3)-NCH(3)). Alkylation of the nitride maintains the approximate C(3)-symmetry in the imide complex, where the imide ligand resides 1.265(9) ? above the mean triiron plane featuring lengthened Fe-N(imide) bond distances (1.892(3) ?) with nearly equal Fe-Fe separation (2.483(1) ?).     

Theoretical Study on Photoisomerization of 2-Methylfuran to 3-Methylfuran

1 INTRODUCTION 2-Methylfuran belongs to the basic heteroaromatic compounds relevant to many fields of modern che- mistry, ranging from the study of natural products and biologically active substances to the develop- ment of building blocks for organic synthesis and conducting polymers[1]. Since the photochemistry ofR-furan was gradually recognized in 1960s[2～7], lots of interest has been aroused. Herein we only study one branch of photoche- mistry of R-furan: the isomerization of 2-methy…     

New route to 3-methacryloxypropyltrimethoxysilane-base organic–inorganic hybrid film

A series of poly(3-methacryloxypropyltrimethoxysilane)/waterborne polyurethane (PMPS/WPU) composite latexes and organic–inorganic hybrid films with PMPS contents of 0, 10, 20, 30, 40 and 50 wt.% were prepared via seeded emulsion polymerization initiated by AIBN and hydrolysis–condensation process of PMPS during the evaporation of water, respectively. WPU, that is anionic polyurethane emulsion, was synthesized using isophorone diisocyanate, polytetramethylene ether glycol, dimethylol propionic acid, 1,4-butanediol, and triethylamine. An investigation of transmission electron microscopy confirmed the core–shell morphology of the composite latex particle which was composed of a PMPS core and a polyurethane shell. A dynamic light scattering analysis showed that the average particle size distributed in the range of 42–134 nm. The proposed novel preparation method included the use of polyurethane as macromolecular emulsifier and steric stabilizer, control of (3-methacryloxypropyltrimethoxysilane) (MPS) content less than 50 wt.%, slow addition of MPS and application of AIBN ensured the preparation of a stable PMPS/WPU composite latex. Formed PMPS/WPU organic–inorganic hybrid film with high PMPS content via sol-gel process had uniform transparency at visible band because of less crystalline and phase separation between organic and inorganic phases.     

NMR: A good tool to ascertain σ-silane or σ-borane formulations?

NMR has played a major role in the characterization of dihydrogen complexes and a number of polyhydrides have been reformulated as dihydrogen complexes on the basis of NMR data. If dihydrogen complexes remain the most widely studied class of σ-complexes, silane compounds are also well recognized as an important family of σ-complexes and more recently a few σ-borane compounds have been isolated. One important problem is the discrimination between a σ-formulation and the corresponding hydrido(silyl) or hydrido(boryl) oxidative addition product. In this review we will discuss key literature data on silane and borane complexes to illustrate the benefit gained by using multinuclear NMR spectroscopy to better define the structures and bonding modes. Our goal is also to help the reader to appreciate the limits of the method and to provide valuable insights into the problem of secondary interactions.     

Secondary amine-catalyzed [3 + 3] benzannulation to access polysubstituted benzenes through iminium activation

An organocatalytic [3?+?3] benzannulation to access polysubstituted benzenes from readily available α,β-unsaturated aldehydes and 1,3-bis(phenylsulfonyl)propene or 4-sulfonylcrotonates is described. The key reaction step is considered to be the iminium activation of enals by a secondary aminocatalyst. This organocatalytic protocol avoids the traditional strategy which is always with the aid of a transition-metal or a stoichiometric amount of strong base, and allows the synthesis of trisubstituted benzenes in high to excellent yields (74–96%).     

New approach to nonracemic 1-alkylamino-3-aryloxypropan-2-ols belonging to β-blockers via cyclic sulfites

Nonracemic -blockers, viz., (S)-propranolol and (S)-timolol, were prepared from (S)-glycidol in three steps consisting in the reaction with SOCl₂ followed by the reaction of the resulting (4S)-4-chloromethyl-2-oxo-1,3,2-dioxathiolanes with the corresponding phenol and the final cleavage of (4R)-aryloxymethyl sulfites under the action of amines in DMF.     

What is required to stabilize Al3+? A gas-phase perspective

With a combination of experiment and theory (ab initio and DFT), we demonstrate that the Al(3+) cation can be stabilized in the gas phase using ligands, which have the ability to act as powerful sigma electron donors and electron acceptors. The latter property, which implies that electron density from the aluminum cation moves into ligand antibonding orbitals, has not previously been considered significant when accounting for the behavior of Al(3+). Of the three ligands identified as falling into the above category, acetonitrile appears to form the most stable complexes in the gas phase, which is in accord with the long established fact that solid-state complexes with Al(3+) are readily isolated. From the results, it is suggested that chain or ring compounds containing the -C triple bond N group might act as successful sequestering agents for Al(3+) from aqueous solutions.     

Why is BCl3 a stronger Lewis acid with respect to strong bases than BF3?

Geometries and bond dissociation energies of the complexes Cl(3)B[bond]NH(3) and F(3)B[bond]NH(3) have been calculated using DFT (PW91) and ab initio methods at the MP2 and CCSD(T) levels using large basis sets. The calculations give a larger bond dissociation energy for Cl(3)B[bond]NH(3) than for F(3)B[bond]NH(3). Calculations of the deformation energy of the bonded fragments reveal that the distortion of BCl(3) and BF(3) from the equilibrium geometry to the pyramidal form in the complexes requires nearly the same energy. The higher Lewis acid strength of BCl(3) in X(3)B[bond]H(3) compared with BF(3) is an intrinsic property of the molecule. The energy partitioning analysis of Cl(3)B[bond]NH(3) and F(3)B[bond]NH(3) shows that the stronger bond in the former complex comes from enhanced covalent interactions between the Lewis acid and the Lewis base which can be explained with the energetically lower lying LUMO of BCl(3).     

The Bond Nature in the AsCl3–POCl3 System According to ab initio Calculation Data

Russian Journal of General Chemistry - To study the nature of the coordination bond in the AsCl3–PОCl3 system, quantum-chemical calculations have been performed using the...     

Spectroscopic Studies on Charge Transfer from Ce^3＋ to Yb^3＋ in KMgF3 ： Ce, Yb Nanocrystals

Nanocrystals of KMgF3 single-doped and codoped with Ce^3＋ or/and Yb^3＋ were synthesized separately by the mi-croemulsion method. The X-ray diffraction（XRD） patterns were indexed to show that the KMgF3 crystal system was unchanged. The fluorescent spectra of KMgF3： Ce, Yb polycrystal powders were studied and compared with those of the Ce,Yb doped KMgF3 crystals produced using the high-temperature solid phase method. The diffuse reflection spectra and infrared emission of KMgF3： Ce, Yb were investigated. From the results, the authors could confirm that there were charge transfer processes from Ce^3＋ to Yb^3＋ in both KMgF3： Ce,Yb nanocrystals and polycrystal powders.     

A new access to β-methyl substituted secondary alcohols. Application to the synthesis of 4-methylheptan-3-ol

All four stereoisomers of 4-methylheptan-3-ol were synthesized by a five-step route starting from 4-thianones. Key steps in the synthesis include: (a) reduction of 3-propyl-4-thianone to yield an easily separable isomeric mixture of cis- and trans-3-propyl-4-thianols; and (b) a highly efficient resolution of the particular cis/trans-isomers through a chromatographic separation of their respective esters with (S)-chlorofluoroacetic acid. Subsequent hydrolysis and desulfurization gave the required compounds in 18% overall yield. All the stereoisomers are obtained with purities better than 90%.     

SmI3-Catalyzed Addition of Amines to α,β-Unsaturated N-Acylbenzotriazoles

The addition of amines to α,β-unsaturated N-acylbenzotriazoles could be catalyzed by samarium triiodide (SmI₃) at ambient temperature. α,β-Unsaturated aliphatic N-acylbenzotriazoles afforded bis-addition products (β-amino amides), whereas N-cinnamoylbenzotriazoles gave acylated products (cinnamoylamides) exclusively.     

Chiral sulfamide-catalyzed asymmetric Michael addition of protected 3-hydroxypropanal to β-nitrostyrenes

Organocatalytic asymmetric Michael addition of 3-(OTBS)-propanal to β-nitrostyrenes catalyzed by chiral sulfamides was investigated. Good d.r. (up to 80:20) and excellent enantioselectivities (up to >99% ee) were achieved. Both the N-[(1R,2R)-2-aminocyclohexyl]-N’-(phenylmethyl)sulfamide 7b and the novel chiral N-[(1R,2R)-2-aminocyclohexyl]-N’-[3,5-bis(trifluoromethyl)phenyl]sulfamide 7a were identified as efficient primary amine organocatalysts.     

Reductive Deoxygenation of Carbonyl to Methylene by LiAlH4／InBr3

The reductive deoxygenation of aldehydes and ketones into the corresponding alkanes is accomplished by LiAlH4 in the presence of Lewis acid InBr3. It provides a convenient method to complete the transformation from carbonyl compounds to alkanes.