Phenyl Sulphonyl Acetaldehyde Diethyl Acetal: A New Robust 1,2-Diol Protective Group

Abstract

A simple preparation of a novel resilient protective group for 1,2-diols is described herein which is remarkably stable in the presence of extremely harsh basic conditions as well as acidic media. The title reagent's versatility is detailed with numerous examples.

     

Regioselective Substitutions of Unsymmetrical 1,2-Diols using Dioxaphospholanes: Applications to Carbohydrates

Abstract

For several years, the method employing 1,3,2λ⁵dioxaphospholanes to effect regioselective substitution of unsymmetrical 1,2-diols has been investigated.^[1] As carbohydrates are an abundant source of diols, this study has been extended to the use of 1,2-O-isopropylidene- D-ghCOfuranOSe 1. We have synthesized a single dioxaphospholane 2 and subsequently treated it with trimethylsilyltriflate to form oxyphosphonium ions 3 and 4.     

Reaction of Chlorosulfonyl Isocyanate With 1,2-Diols: Rearrangement and Formation of Carbonates

1,2-Diols, 1a-e, upon reaction with chloro-sulfonyl isocyanate (CSI) gave the ketones, 3a-e Under similar experimental conditions, 1,2-diols, 1f-k, gave carbonyl compounds, 3f-k, carbonates, 6f-k, carboxamides, 7h, i, and the epoxide, 5i.     

Search For A New Reagents From The Nitrosoamine Group For Spectrophotometric Determination Of Sulphur Dioxide

Abstract

p-Nitrosodiphenylamine as a representative of nitrosoamine group was tested as a new reagent for the spectrophotometric determination of SO₂. A mixture containing: p-nitrosodiphenylamine, formaldehyde, HCl, di-methylformamide and water was added to the aqueous test solutions of sulphites forming after 5 min, a blue complex with Λ_max=675 nm stable for one hour. The Lambert-Beer law was obeyed in the 0 to 50 /ug SO₂/cm³ range. Molar absorptivity was equal to 2000 and the specific absorption was 0.062. The investigations should lead to search for other reagents from the nitrosoamine group suitable for this purpose.     

Solvation and Enthalpy Coefficients of Interaction of Carboxylic Acid Amides with 1,2-Diols in Water

The enthalpies of solution of formamides, acetamides, and propionamides with various extents of N-substitution in aqueous solutions of propylene glycol and 1,2-butanediol (concentration 4 mol kg^{- 1}) at 298.15 K were measured. The enthalpies of transfer of the amides from water to mixed aqueous-organic solvents were determined and discussed in combination with data on the enthalpies of transfer of amides from water to aqueous ethylene glycol solutions. The enthalpy coefficients of pair interactions of amides with 1,2-diols in water were calculated and used for evaluating the group components on the basis of the principle of group additivity of contributions. As the hydrophobic properties of polyfunctional nonelectrolytes are enhanced, the coefficients increase, which is due to the growth of the hydrophobic component of the interaction.     

Two New Compounds in the Group of Zinc Phenoxides and Zinc Phenylamides

The synthesis and characterization of ethyl{2‐[(phenylamino)methyl]phenoxy}zinc ( 1 ) and ethyl{2‐[(propan‐2‐ylideneamino)methyl]phenylamido}zinc ( 2 ) are reported. The phenoxide 1 was prepared starting from 2‐(phenylaminomethyl)phenol and diethylzinc and the phenylamide 2 was obtained from 2,2‐dimethyl‐1,2,3,4‐tetrahydroquinazoline and diethylzinc. The compounds were characterized by NMR spectroscopy (¹H, ¹³C{¹H}), IR spectroscopy, elemental analysis, TGA measurements, and X‐ray structure analysis. In the solid state both compounds form dimers where ( 1 )₂ · 4thf shows a planar Zn₂O₂ and ( 2 )₂ a planar Zn₂N₂ unit. Noteworthy, the aminal ring of 2,2‐dimethyl‐1,2,3,4‐tetrahydroquinazoline was opened by its reaction with diethylzinc to give an ylidene moiety at the benzylic nitrogen atom.     

Cyclopentyl: A Novel Protective Group for Phenols

We have discovered cyclopentyl as a novel group for the protection of hydroxyl functionality of phenols. The key steps involved are cyclopentylation and decyclopentylation.     

Cyclopentyl: A Novel Protective Group for Phenols

We have discovered cyclopentyl as a novel group for the protection of hydroxyl functionality of phenols. The key steps involved are cyclopentylation and decyclopentylation.     

Determination of Enantiomeric Excess of Aromatic 1,2-Diols with HP-β-Cyclodextrin as Chiral Selector by CE

To determine optical purities of four aromatic 1,2-diol enantiomers synthesized by a Sharpless asymmetric dihydroxylation (AD) reaction of olefins, a simple and reliable separation method was achieved with high resolution (R _s > 2.2) by capillary zone electrophoresis (CZE) using hydroxypropyl-β-cyclodextrin (HP-β-CD) as chiral selector and borate combined with methanol additive as background buffer. Furthermore, the developed CZE method was successfully applied to the determination of enantiomeric excess of the tested enantiomers. RSD values of migration time and peak area fell within 1.0 and 3.8%, respectively. This method allowed for the determination of ee (%) values of targeted isomers as high as 99.6%. Impurities of undesired isomers could be detected at levels as low as 0.2% in the presence of the targeted isomers.     

新型玻璃刻蚀用光刻胶的研制

采用环氧树脂改性超支化聚酯制备了玻璃刻蚀用的光刻胶掩膜,研究了该感光树脂的感光活性、耐刻蚀性,以及加入HCI、HNO_3后刻蚀对玻璃刻蚀的影响。结果表明,所得感光树脂对玻璃有较好的附着力,厚度为40～50μm的胶膜在ω(HF)为40％的溶液中抗浮胶时间超过6 min,光刻胶初始曝光时间T_0为2．7 s,反差值γ_(gel)为2．8;混合刻蚀剂对载玻片玻璃的刻蚀速度≥35μm/min;以该光刻胶为单层掩膜,可得到线宽50μm的清晰刻蚀图样,玻璃的刻蚀深度超过38μm。     

Oxidation of Group II Metals with 3,5-Di-tert-butyl-1,2-benzoquinone

Kinetic regularities of zinc and cadmium oxidation in systems comprising 3,5-di-tert-butyl-1,2-benzoquinone and dimethylformamide or dimethyl sulfoxide are studied. Thermodynamic parameters of oxidant and ligand adsorption on metal surface are estimated. The oxidation of Group II metals (Be, Ca, Mg, Zn, Cd) with 3,5-di-tert-butyl-1,2-benzoquinone gives metal bis-o-semiquinolates. In the presence of excess metal in the medium of coordinating solvents, diradical products convert to the corresponding catecholate derivatives. It is shown that the dependence of the rates of metal reactions with 3,5-di-tert-butyl-1,2-benzoquinone on the donor number of solvent passes through a maximum. With less active metals, the maximum shifts to more basic ligands.     

New Thiol‐Responsive Mono‐Cleavable Block Copolymer Micelles Labeled with Single Disulfides

Thiol‐responsive symmetric triblock copolymers having single disulfide linkages in the middle blocks (called mono‐cleavable block copolymers, ss‐ABP₂) were synthesized by atom transfer radical polymerization in the presence of a disulfide‐labeled difunctional Br‐initiator. These brush‐like triblock copolymers consist of a hydrophobic polyacrylate block having pendent oligo(propylene oxide) and a hydrophilic polymethacrylate block having pendent oligo(ethylene oxide). Gel permeation chromatography and ¹H NMR results confirmed the synthesis of well‐defined mono‐cleavable block copolymers and revealed that polymerizations were well controlled. Because of amphiphilic nature, these copolymers self‐assembled to form colloidally stable micelles above critical micellar concentration of 0.032 mg · mL⁻¹. In response to reductive reactions, disulfides in thiol‐responsive micelles were cleaved. Atomic force microscopy and dynamic light scattering analysis suggested that the cleavage of disulfides caused dissociation of micelles to smaller‐sized assembled structures in water. Moreover, in a biomedical perspective, the mono‐cleavable block copolymer micelles are not cytotoxic and thus biocompatible.

     

Stannous Chloride Dihydrate : A New Catalyst For The Tetrahydropyranylation Of Alcohols

Catalytic Stannous chloride dihydrate in polar aprotic solvents like chloroform efficiently catalyse the tetrahydropyranylation of alcohols in a short time under mild conditions.     

A fascination with 1,2-diacetals

1,2-Diacetals are readily prepared, rigid structural motifs that provide a wide range of opportunities for applications in natural product assembly. These uses encompass selective 1,2-diol or alpha-hydroxy acid protection, enantiotopic recognition and desymmetrization methods, chiral memory applications, and reactivity control in oligosaccharide synthesis, as well as functioning as templating components, chiral auxiliaries, and building blocks. 1,2-Diacetals are often more stable and lead to products with enhanced crystallinity compared to their five-ring acetonide counterparts. Many 1,2-diacetals have favorable NMR parameters, which facilitate structural assignment, particularly during asymmetric reaction processes.     

A New Approach to 1-Substituted-1,2Alkadienephosphonates I

The possibility of the substitution of the H atom at the C1-position of the phosphorylated allenes with different kind of electrophiles has been discussed and evidence for the mechanism of the heterocyclization of allenephosphonates by the reaction with electrophilic reagents has been supplied. The new approach for the synthesis of 1-substituted-1,2-alkadiene phosphonates via the acetylene-allene rearrangement of acetylenecarboxylic acid has been discussed.