Halides from phenols

Aryl halides from phenols and triphen-ylphosphine-halogen adducts, 49, 6... 

VIII. CARBENE FORMATION A. Elimination of Hydrogen Halides from Phenols... 

Phosphorus pentahalide Aryl halides from phenols s. 77,616... 

Write out a complete synthesis of tyrosine using this approach with the appropriate alkyl halide and also show a synthesis of the requisite halide from phenol. 

II. Halides from Alcohols and Phenols by Triphenylphosphine Dihalide... 

In a corresponding manner, the mono-esters of P(III) systems can be produced by controlled reaction of the P(III) halides with the appropriate hydroxyl compound. Significantly better yields are obtained for the aryl esters (from phenols — Equation 4.3) than for alkyl esters (from alcohol), and primary alcohols provide better yields than do secondary alcohols.5 6... 

Aryldiazonium salts, usually obtained from arylamines, undergo replacement of the diazonium group with a variety of nucleophiles to provide advantageous methods for producing aryl halides, cyanides, phenols and arenes by reductive removal of the diazo group. Coupling reaction of aryldiazonium salts with phenols or arylamines give rise to the formation of azo dyes. 

Xu, W. Mohan, R. Morrissey, M. M. Polymer-Supported Bases in Combinatorial Chemistry Synthesis of Aryl Ethers from Phenols and Alkyl Halides and Aryl Halides, Tetrahedron Lett. 1997, 38, 7337. 

General methods for the preparation of acid halides from aliphatic carboxylic acids are described in Section 5.12.1, p. 692. Phosphorus pentachloride is the preferred chlorinating agent for aromatic acids which contain electron-withdrawing substituents, and which do not react readily with thionyl chloride. The preparation of both p-nitrobenzoyl chloride and 3,5-dinitrobenzoyl chloride is described in Expt 6.161. These particular acid chlorides are valuable reagents for the characterisation of aliphatic alcohols and simple phenols, with which they form crystalline esters (see Section 9.6.4, p. 1241 and Section 9.6.6, p. 1248). 

In addition to halides, some pseudohalides undergo facile oxidative addition to Pd and Ni complexes. Trifluoromethanesulfonates (triflates), namely aiyl triflates 3 derived from phenols and enol triflates of carbonyl compounds, are most useful. 

As another alternative to triflates, aryl nonaflates (ONf) are easily prepared from phenol and commerically available perfluorobutane sulfonyl fluoride 243, and used for Pd-catalysed coupling with halides [111]. Aryl nonaflates are more reactive than aryl triflates. / -Iodophcnyl nonaflate (244) gives 245 by chemoselective reaction of the... 

The Grignard reagent 7 is made from the halide that comes eventually from phenol by chlorination and methylation.2 We shall discuss the synthesis of ketones like 6 in chapter 19. 

Xu W, Mohan R, Morrissey MM, Polymer supported bases in combinatorial chemistry synthesis of aryl ethers from phenols and alkyl halides and aryl halides, Tetrahedron Lett., 38 7337-7340, 1997. 

The reaction will also occur if the vinyl or aryl halide is used in place of the triflate. However, t triflates have been more widely used as they are readily prepared from phenols or enolizable aldeh des or ketones. In these reactions, the presence of a source of halide (typically LiCl) is genera required. This maybe because the triflate is a counterion and is not bound to the metal as a ligand, transmetallation is to occur some other ligand must be added to give the necessary square coplan geometry. 

The reactions between i-dinitrobenzene or 1,3,5-trinitrobenzene, aryl halides, and copper(I) oxide in quinoline 17-19, 21) provide a simple synthesis of nitrobiphenyls uncontaminated by symmetrical biphenyls. These couplings may be related to the Ullmann reaction, the decarboxylative coupling of benzoic acids with aryl halides, and the preparation of ethers from phenols 165). Although no intermediates... 

In the reaction of butyllithium or lithium di-isopropylaminc with the Mannich bases derived from hydrogen cyanide, phosphine oxides, and phosphorous esters, as well as from phenols, jhc metal atom is prevalently bound to the CH2—N moiety (313 in big. 119, route b). This intermediate is then allowed to react with halides, epoxides, and other alkylating reagents in order to link an alkyl group to methylene. Under proper conditions, aldehydes, ketones and enamines can be prepared by this method. 

This reaction has wide application for the preparation of esters. The difficulties encountered in method 285 because of a reversible reaction are avoided. Esters of tertiary alcohols and phenols are best prepared in this way. The formation of tertiary halides from tertiary alcohols is prevented by carrying out the reaction in the presence of powdered magnesium or dimethylaniline which react with the hydrogen chloride as it is formed. The esterification of phenols is effected in the same manner. Magnesium or pyridine is added to combine with the hydrogen halide. Pyridine has replaced aqueous alkali formerly used for this purpose... 

Utilization of this principle for the synthesis of the target tree-like (dendritic) macromolecule is shown in Scheme 4.31. The basic reaction chosen was again very simple, namely the formation of benzyl ethers from phenols and benzylic halides. It was found that the coupling of benzylic bromide 91 with 2 equivalents of 3,5-dihydroxybenzyl alcohol 92 could be carried out without affecting the... 

Polymerization reactions involve the union of a number of similar molecules to form a single complex molecule. A polymer is any compound, each molecule of which is formed out of a number of molecules which are all alike, and which are called monomers. In many cases polsonerization can be reversed and the poisoner be resolved to the monomer. Many polymerization reactions which are of industrial importance involve in the initial stages condensations, that is, reactions in which elimination of water or other simple molecules takes place. Compounds which polymerize have some type of unsaturation in the molecule. Olefins, unsaturated halides, esters, aldehydes, dicarboxylic acids, anhydrides, amino acids and amides are among the important groups of compounds which are used in industrial polymerization reactions. The commercial products produced by polymerization reactions may be conveniently classified into (a) resinotds, or synthetic resins (b) elastomers, which possess rubber-like properties and (c) fibroids, used as textile fibers. Two types of resinoids are illustrated in this experiment Bakelite, formed from phenol and formaldehyde, and methacrylate resin formed from an unsaturated ester. 

Reaction with alcohols and phenols. Horner and co-workers introduced use of the reagents for the preparation of alkyl and aryl halides from alcohols or phenols, and Wiley and co-workers established that the reagents have considerable advantage over phosphorus pentahalides in the C—OH—C—X conversion and discussed the mechanism. For the preparation of n-butyl bromide the Wiley group added bromine under nitrogen to a solution of n-butanol and triphenylphosphine in dimethyl-formamide until 2 drops persisted in giving the solution an orange tint. Volatile... 

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