Sandmeyer method

The Sandmeyer method has been used with di- and trisubstituted anilines to prepare di-4,6,13,14,19,32,38-55 and tri-5,13,19,30,56 substituted isatins. Although -acetamidoaniline and 5-acetamido-2-aminotoluene gave 5-acetamido- and 5-acetamido-7-methylisatin, respectively,30 the use of 4-acetamido-2-aminotoluene and 5-acetamido-2,4-dimethyl-aniline gave the appropriate aminoisatins.30,52 Other examples of hydrolysis during this cyclization are in the conversion of diethyl 5-aminoisophthalate to isatin-4,6-dicarboxylic acid53 and 2-methyl-5-... 

The yields in the Gattermann reaction, however (e.g. o-bromotoluene, Expt 6.74), are usually not as high as those obtained by the Sandmeyer method. Copper powder is also employed in the preparation of sulphinic acids (e.g. benzenesul-phinic acid, Expt 6.75) which are obtained when a solution of a diazonium sulphate is saturated with sulphur dioxide and decomposed by the addition of copper powder. 

The yields by this method were superior to those obtained by the Sandmeyer method, probably because the copper powder was added to the diazonium solution in the cold, whereas Sandmeyer recommended adding the diazonium solution to a hot solution of the copper salt. 

These reactions do not by any means cover the whole field, but represent only the more important portions of it Later in this book, other less important reactions are mentioned, such as alkylation of amines, introduction of the aldehyde group by die Sandmeyer method, and phenylation. Although some of these reactions are carried out on a large scale, especially in die preparation of alkyl- and benzylanilines and toluidines, they are in terms of quantity of considerably less importance than the operations discussed above. 

The Sandmeyer method has been used with di- and trisubstituted anilines to prepare and substituted... 

Introduction. In the preceding experiment it was shown that an aqueous solution of a diazonium salt treated with a solution of an alkali iodide gives iodobenzene. The replacement of the diazo group, N2X, by chlorine or bromine atoms involves the catalytic action of copper salts. Thus, benzenediazonium chloride warmed with a solution of cuprous chloride and hydrochloric acid gives chlorobenzene with cuprous bromide, bromobenzene is formed. The use of the cuprous salt is known as the Sandmeyer method. Instead of cuprous salts, finely divided copper may be used according to Gatterman s method. 

The catalytic action of the cuprous salts is assumed to depend on the formation of addition compounds which aid in the elimination of nitrogen and direct the halogen to the nucleus. In the Sandmeyer method the diazonium salt solution is added to a freshly prepared solution of the cuprous halide at a temperature below 10°. The mixture is then warmed until the evolution of nitrogen ceases. In some cases better yields are obtained if the diazonium solution is added slowly to a boiling solution of the cuprous salt. In the Gatterman method the desired diazonium salt is prepared. In the case of bromide and iodide, the diazonium sulfate is prepared and is mixed with an excess of potassium bromide or iodide. Finely divided copper is added and the mixture is warmed until the evolution of nitrogen ceases. The finely divided copper may be prepared by adding zinc dust to copper sulfate solution. The object of this experiment is to illustrate both methods. For semimicro work either chlorobenzene or o-chlorotoluene may be used. 

Nitriles can be obtained from diazonium salts by the Sandmeyer method, which involves treatment with copper(i)in the hot.793 An example of this valuable reaction is the preparation of 0-nitrobenzonitrile from 0-nitroaniline 794... 

Aromatic nitriles (or aryl cyanides) can be obtained by methods (1) and (3). but not by method (2). In addition, aromatic nitriles can be prepared by two other methods, (a) from the corresponding diazo compound by Sandmeyer s Reaction (p. 189), (b) by fusing the corresponding sulphonic acid (or its salts)... 

Benzonitrile (Phenyl Cyanide). CeHaCN. (Sandmeyer s Method.)... 

The yields by the Gattermann reaction are usually not as high as those by Sandmeyer s method. Copper powder is also employed in the preparation of sulphinlc acids, for example ... 

The replacement of 2-amino group by a hydrogen can be achieved by diazotization, followed by reduction with hypophosphorous acid (1-8, 13). Another method starting from 2-aminothiazole is to prepare the 2-halo-thiazole by the Sandmeyer reaction (prepared also from the 2-hydroxy-thiazole), which is then dehalogenated chemically or catalytically (1, 9, 10). 

Reactions that employ copper(I) salts as reagents for replacement of nitrogen m diazo mum salts are called Sandmeyer reactions The Sandmeyer reaction using copper(I) cyanide is a good method for the preparation of aromatic nitriles... 

Pure monochlorotoluene isomers are prepared by dia2oti2ation of the corresponding toluidine isomers followed by reaction with copper(I) chloride (Sandmeyer reaction). This is the preferred method of obtaining y -chlorotoluene. 

Dichlorotoluene (l,3-dichloro-2-methylben2ene) is prepared from the Sandmeyer reaction on 2-arnino-6-chlorotoluene. Other methods include ring chlorination of -toluenesulfonyl chloride followed by desulfonylation (81), and chlorination and dealkylation of 4-/ f2 -butyltoluene (82) or... 

Equally, all the attempts of Haginiwa to diazotize 2-amino-4-methylselenazole led to complete decomposition. Later these investigations were taken up by Metzger and Bailly. They tried to prepare selenazoles unsubstituted in the 2-position by means of diazo-tization and a special Sandmeyer reaction. In spite of variations in the reaction conditions, they were not able to deaminate 2-amino-4-phenylselenazole by this method. 

In aromatic compds, an amino group may be replaced by the nitro group by diazotization and reaction with nitric acid in the presence of cuprous salts (the Sandmeyer reaction). This method is used for lab work only and is described in standard textbooks on preparative organic chemistry... 

Cyano-de-diazoniations of the Sandmeyer type have been used for the synthesis of aromatic nitriles for many decades (example Clarke and Reed, 1964), as cyanide ions are comparable to bromide and iodide in many respects. A homolytic cyano-de-diazo-niation that does not use metal ions as reductant or ligand transfer reagent was described by Petrillo et al. (1987). They showed that substituted diazosulfides (XC6H4 — N2 — SC6H5), either isolated or generated in situ from arenediazonium tetrafluoroborates and sodium benzenethiolate, react with tetrabutylammonium cyanide in dimethylsulfoxide under photon stimulation, leading to nitriles (XC6H4CN). The method worked well with eleven benzenediazonium ions substituted in the 3- or 4-position, and was also used for the synthesis of phthalo-, isophthalo-, and tere-... 

With the ArH ArTlX2 Arl reaction sequence available as a rapid and reliable probe for aromatic thallation, a detailed study was undertaken of the various factors affecting orientation in this electrophilic metallation process (153). The results, which are summarized below, demonstrate that aromatic thallation is subject to an almost unprecedented degree of orientation control coupled with the ease with which thallium can then be displaced by other substitutent groups (this aspect of the synthetic exploitation of aromatic thallation is discussed in detail below), the sequential processes of thallation followed by displacement represent a new and versatile method for aromatic substitution which both rivals and complements the classic Sandmeyer reaction. 

This constitutes a useful method for generating ArC02, as in the thermolysis of (28) there is a danger of the further decomposition of (29) to Ar- + CO 2. Cu is also involved in the con version of diazonium salts, ArN2 Cle, to ArCl + N2 (Sandmeyer reaction), where Ar- is very probably formed transiently as an intermediate ... 

Meerwein-Gomberg reactions between pyridinediazonium salts and furans fail because the Sandmeyer reaction supervenes, and the isopentyl nitrite method also gives poor results.264 Fortunately, photolysis of 3-... 

For more than a century, stoichiometric methods were presumed in the preparation of benzonitriles in laboratory and industry. These particularly include the Rosenmund-von Braun reaction of aryl halides, the diazotization of anilines and subsequent Sandmeyer reaction, and the ammoxidation. Because of (over)stoichiometric amounts of metal waste, lack of functional group tolerance, and harsh reaction conditions, these methods do not meet the criteria of modern sustainable synthesis. 

Two of the most frequently used approaches for halothiazole synthesis are direct halogenation of thiazoles and the Sandmeyer reaction of aminothiazoles. The third method, an exchange between a stannylthiazole and a halogen, is not practical in the context of palladium chemistry simply because the stannylthiazole can be used directly in a Stille coupling. 

Sandmeyer s Reaction.—The ready formation of iodobenzene in the above method is due to the spontaneous decomposition of the diazonium iodide into iodobenzene and nitrogen... 

Sandmeyer s synthesis may be recommended also as a preparative method. 

Mercury Diphenyl Dimethylpyrone 1 5-Dibromopentane Diphenylnitrio Oxide Thioindigotin Thioindigo Scarlet Isatin (Sandmeyer s method)... 

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