Bart reaction modifications

The success of the Bart reaction when applied to nuclear- substituted anilines is often much affected by the pH of the reaction-mixture. Furthermore, the yields obtained from some m-substituted anilines, which under the normal conditions are usually low, arc considerably increased by the modifications introduced by Scheller, and by Doak, in which the diazotisation is carried out in ethanolic solution followed by reaction with arsenic trichloride in the presence of a cuprous chloride or bromide catalyst. 

The conversion of an aromatic diazonium compound into the corresponding arsonic acid by treatment with sodium arsenite in the presence of a catalyst, such as copper or a copper salt, is called the Bart reaction. A modification of the reaction employs the more stable diazonium fluoborate in place of the diazonium chlorid.i. This is illustrated by the preparation of />-nitrophenylarsonic acid ... 

Three methods for the preparation of aromatic arsonic adds are de- scribed in this review. By far the most widely applicable of these is the Bart reaction, which involves the interaction of a diazonium salt with an inorganic arsenic compound. In the original Bart process 1 and most of its modifications an alkali arsenite is used, as shown in the following equation. 

In general, primary aromatic amines can be converted into the corresponding arsonic acids by the Bart reaction or by one of its modifications. This method has been used to prepare arsonic acids of the benzene, naphthalene, fluorene, and anthraquinone series as well as of a number... 

Arsonic acids have been prepared from readily available compounds such as arsenic(III) oxide and arsenic trichloride. Reaction of sodium arsenite with alkyl halides has been named the Meyer reaction, and reaction with arenediazonium salts the Bart reaction. In addition, some modifications have been made for the preparation of arsonic acids. Some examples are shown in equations 326 and 327. ... 

Bart reaction. (Scheller modification Star-key modification). Formation of aromatic arsonic acids by treating aromatic diazonium compounds with alkali arsenites in the presence of cupric salts or powdered silver or copper in the Scheller modification, primary aromatic amines are diazotized in the presence of arsenious chloride and a trace of cuprous chloride. 

It is pertinent to mention here that the success of the Bart Reaction when applied to nuclear-substituted anilines e.g., m-substitued anilines) is invariably effected by the prevailing pH of the reaction medium. Scheller (1992) and Doak et al. (1946) suggested certain modifications whereby the yields obtained from certain m-substituted anilines, which under the usual conditions of reactions are very low, could be enhanced considerably by carrying out... 

This reaction was first reported by Bart in 1910. It is the synthesis of arylarsenic acids from aromatic diazonium compounds with alkali arsenites in the presence of cupric salts, powdered silver, or copper. Therefore, this reaction is generally known as the Bart reaction. In addition, the reaction between aromatic diazonium and arsenious chloride in the presence of trace amounts of cuprous chloride is referred to as the Scheller modification. Besides the Scheller modification, the Sakellarios modification is the reaction between sulfanilamide and phenyldisodium arenite. ... 

A few modifications have been developed for the Bart reaction, including the Scheller modification and the Sakellarios modification. The most useful and famous one is the Scheller modification. 

This reaction was discovered by Bart in 1911 (see also Bart, 1922 a, 1922 b). The yields are highly dependent on the alkalinity of the system. Bart s claim (1922b) that arylarsonic acid anions are formed directly from (Z)-diazoates is, however, doubtful (see below). Various modifications with increased yields are described in the review by Hamilton and Morgan (1944). The reaction can also be carried out with heteroaromatic diazonium salts (Capps and Hamilton, 1938). 

The most recent modification of Bart s reaction involves the use of aryldiazonium borofluorides in place of the customary diazonium chlorides. Because of their increased stability the diazonium borofluorides were observed to have less tendency to decompose or to form byproducts when allowed to react with sodium arsenite furthermore, the reactions could be carried out at room temperature. The modification appears to be particularly useful in the preparation of p-nitrophenylar-sonic acid, the yield being 79% as compared with 45% by the original method of Bart. When other diazonium borofluorides were used as starting materials the yields were sometimes lower than those reported by the usual Bart procedure, but more often they were as good or slightly... 

The preparation of phenylarsonic acid, which proceeds in an average yield of 45-55%, must of necessity serve as the basis for comparison of yields from substituted amines. The following discussion deals primarily with reactions taking place in neutral or alkaline solution practically all the yields reported in this discussion are by either the original Bart process or by Schmidt s modification, the few exceptions being noted. 

An important modification of the original Bart procedure was made by Scheller who diazotized primary amines, dissolved in alcohol or glacial acetic acid, in the presence of arsenic trichloride and found that better yields of arsonic acids could sometimes be obtained, particularly if the amine carried negative substituents in the meta position. The method has been slightly modified 140). The Scheller reaction has recently been used to prepare arsonic acids of 3-nitro-4-fluorobenzene and 2,5-dimethylpyridine 141, 142), and to prepare a number of arsinic acids such as (CeHs)[4,3-CH3(N02)C6H3]As02H by the reaction 143)... 

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