Über eine Reaktion von o-Hydroxybenzylalkoholen mit Estern von Säuren des Phosphors mit der Koordinationszahl 3

Abstract

o-Hydroxybenzyl alcohol reacts with trimethyl phosphite under smooth conditions to o-hydroxyphenylmethane phosphonic acid dimethyl ester. This unusual reaction is of widest applicability. Derivatives of o-hydroxybenzyl alcohol independent of type, number or position of substituents in the ring, react with alkyl esters of phosphorous, phosphonous or phosphinous acids in an analogous process, forming the corresponding o-hydroxyphenylmethane phosphonic or phosphinic esters or phosphine oxides.     

Efficient Synthesis of a New Type of Baylis–Hillman Adducts and Their Stereoselective Bromination

A new type of Baylis–Hillman adducts derived from chlorovinyl aldehydes were prepared via Vilsmeier reaction of ketones with a bis(trichloromethyl) carbonate (BTC)/DMF system to construct chlorovinyl aldehydes, followed by sonochemical Baylis–Hillman reaction under solvent-free conditions. The stereoselective bromination of these new compounds with a Br₂-Ph₃P system has been achieved efficiently with good to excellent yields under mild conditions.     

Selective α-bromination of aryl carbonyl compounds: prospects and challenges

The α-bromination of carbonyl compounds is one of the most important transformations and also important precursors in synthetic organic chemistry. Particularly, the side chain monobromination of carbonyl compounds has been a challenging task, because during the reaction a small amount of disubstituted or ring brominated products as an impurity is always accompanied with monosubstituted product in the reaction mixture. In recent years substantial advances have been made for the synthesis of brominated aromatic carbonyl compounds with high selectivity. In this review, we have summarized various methods for the synthesis of α-bromo aromatic carbonyl compounds.     

Bromination of 4‐Dichloromethyl‐4‐methylcyclohexa‐2,5‐dien‐1‐ones

Bromination of 4‐dichloromethyl‐4‐methylcyclohexa‐2,5‐dien‐1‐one and 4‐dichloromethyl‐3,4‐dimethylcyclohexa‐2,5‐dien‐1‐one has been studied. The reaction conditions required for the formation of mono‐, di‐, and tribrominated products have been optimized.     

Convenient Electrochemical Method for the Synthesis of α-Bromo Alkyl Aryl Ketones

An electrochemical procedure for the effective α-bromination of alkyl aryl ketones in excellent yield has been reported. The simple experimental procedure, catalyst-free conversion, and excellent yield of monobrominated products are the advantages of this method.     

Preparation of highly hindered polyenes with tert-butyl groups in internal positions

The conjugated tetraenes 3 and 4 a – c have been prepared and shown to possess an orthogonal structure. This was not only demonstrated by their spectroscopic properties and X‐ray structural analysis of solid representatives (e.g., 4 a – c ) but also by the resolution of these chiral compounds by GC and HPLC chromatography using various chiral selector systems. The chemical behavior of the typical tetraene 4 a has been studied using bromination, hydrogenation, epoxidation, and photo equilibration reactions.     

五氟溴苯的合成工艺研究

五氟溴苯是一种非常重要的化工中间体.五氟苯甲酸通过脱羧、溴化两步反应可以得到五氟溴苯.本文通过采用加压脱羧的方法制备五氟苯,反应时间短,产品产率和纯度高,且操作简单方便,工艺绿色环保,适合工业化.同时分别研究了脱羧和溴化反应中反应条件对目的产物收率的影响.     

Preparing a functionalized thermoplastic elastomer—bromination and synthesis of poly(p-methylstyrene-co-styrene)-block-poly(ethylene-co-butene)-block-poly(p-methylstyrene-co-styrene)

A poly(p-methylstyrene-co-styrene)-block-poly(ethylene-co-butene)-block-poly(p-methylstyrene-co-styrene) thermoplastic elastomer was prepared via anionic synthesis of poly(p-methylstyrene-co-styrene)-block-polybutadiene-block-poly(p-methylstyrene-co-styrene) followed by a hydrogenation of the polybutadiene midblock. The sequential method used for the synthesis has resulted in a nearly monodispersed polymer with a polydispersity of 1.03. Bromination of such synthesized copolymer was next, conducted using two different methods. In the presence of a FeCl₃ catalyst in CCl₄ solvent, bromination occurred through forming a carbocationic complex to undergo an electrophilic substitution reaction on the aromatic rings of the end blocks. Nevertheless, the bromination occurred exclusively on the p-methyl groups of the end blocks when conducted in cyclohexane using photoinitiated free radicals. The microstructure of the brominated molecules were analyzed using ¹H-NMR and ¹³C-NMR, and bromination efficiencies of 48 and 44% have been attained from the two methods, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4108–4116, 1999     

Synthesis and characterization of novel aromatic polyimides from 4,4‐bis(p‐aminophenoxymethyl)‐ 1‐cyclohexene

A novel diamine, 4,4‐bis(p‐aminophenoxymethyl)‐1‐cyclohexene (CHEDA), was synthesized from 4,4‐bis(hydroxymethyl)‐1‐cyclohexene and p‐chloronitrobenzene by nucleophilic aromatic substitution and subsequent catalytic reduction of the intermediate dinitro compound. A series of aromatic polyimides were prepared from CHEDA and commercial dianhydrides with varying flexibility and electronic character in two‐step direct polycondensation reactions. High molecular weight polyimides with intrinsic viscosities between 0.57 and 10.2 dL/g were obtained. Most of these polyimides, excluding those from PMDA and BPDA, were soluble in polar aprotic solvents such as NMP and DMAc, and many were also soluble in CHCl₃ and THF. DSC analysis revealed glass transitions in the range of 190 to 250°C. No significant weight losses occurred below 450°C in nitrogen and 350°C in air. Bromination and epoxidation of cyclohexene double bond in CHDEA–6FDA (3e) were investigated as examples of possible polymer modifications. Qualitative epoxidation and selective bromination of the double bond were demonstated. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1189–1197, 1999