Benzanilide reactions

Benzanilide and similar compounds are very slowly hydrolysed by concentrated hydrochloric acid hydrolysis is quite rapid with 60-70 per cent, sulphuric acid (for experimental details, see Section IV,52). In the preliminary experiment boil 0 5-1 Og. of the compound with 10-20 ml. of dilute sulphuric acid (1 1 by volume) imder reflux for 20-30 minutes. Dilute with 10ml.of water and filteroflfanyacid which may be precipitated if the carboxyhc acid is hquid and volatile, distil it directly from the reaction mixture. Render the residue alkaline and isolate the base as above. 

Reaction of benzanilide (CgHjNHCCgHj) with chlorine in acetic acid yields a mixture of two monochloro derivatives formed by electrophilic aromatic substitution. Suggest reasonable structures for these two isomers. 

Benzoyl Chloride.—The formation of esters by ibe action of benzoyl chloride or othei acid chloride on an alcohol or ]ohcnol in presence of caustic soda is known as the Schotten- 13riumann reaction. The reaction may also be employed in the preparation of deri ati es of the aromatic amines containing i.n acid radical, like benzanilide, CjjH NH.CO... 

Addition of up to a tenfold molar excess of hydrogen chloride did not appreciably alter the reaction rate. Orton and Bradfield227 obtained the same kinetic form for the chlorination of formanilide, acetanilide, benzanilide, and benzene-sulphonanilide in 99 % aqueous acetic acid at 20 °C reaction rates were higher than previously obtained with the less aqueous medium, and this medium effect has been subsequently found to be general. 

Substituted amides suffer hydrolysis with greater difficulty. The choice of an acid or an alkaline medium vill depend upon (a) the solubility of the compound in the medium and (b) the effect of the reagent upon the products of hydrolysis. Substituted amides of comparatively low molecular weight (e.g., acetanilide) may be hydrolysed by boiling either with 10 per cent, sodium hydroxide solution or with 10 per cent, sulphuric acid for 2-3 hours. Other substituted amides are so insoluble in water that little reaction occurs when they are refluxed with dilute acid or dilute alkali for several hours. These include such substances as benzanilide (C(H(CONHC,Hg) and the benzoyl derivative of a naphthylamine (C.HjCONHCioH,) or a toluidine (C gCONHCjH,). For these substances satisfactory results may be obtained with 70 per cent, sulphuric acid this hydrolysis medium is a much better solvent for the substituted amide than is water or more dilute acid it also permits a higher reaction temperature (compare Section IV 192) ... 

The reaction of sodium azide with N-aryl chloroimines, obtained from benzanilides and thionyl chloride, to form 1,5-disubstituted tetrazoles is catalysed by tetra-n-butyl-ammonium bromide (Scheme 5.26, Table 5.40) [18] in variable yields, but generally <85%. 5-Butyl-2,3-diphenyltetrazolium salts have also been used as catalysts [18, 19]. 1,5-Disubstituted tetrazoles are also obtained from a one-pot sequential reaction of carbodimides with sodium azide and an aroyl chloride in the presence of tetra-n-butylammonium chloride [20]. 5-Chlorotetrazoles are obtained from the catalysed reaction of aryldichloroisocyanides with sodium azide (Scheme 5.26) [21],... 

Scheme 4.7. Reaction mechanism for the electrochemical reduction of 2-halo-N-methyl-benzanilides, illustrated for 2-chloro-N-methylbenzani1ide.

The oxadiazolylthio portion of 5-benzoate (74c) is a good leaving group and reaction with aniline to form benzanilide and thione (73a) is rapid at room temperature. The diester formed fipom thione (73a) and isophthaloyl chloride similarly reacts with diamines, under these mild conditions, to give polyamides <85JPS(A)2727>. 

For convenience of isolating the reaction product in a crystalline state, acid amides containing aromatic ring(s), i.e., acetanilide and benzanilide, were selected, and were allowed to react with AlMe3, AlEt3, or A1Bu 3. The reaction product could be obtained in a crystalline state by adding an aliphatic hydrocarbon such as iso-octane to the reaction mixture in toluene. The catalytic behavior of the isolated reaction products indicated that these products were the real active species of the catalyst system (36) (Table 2). 

This exothermic reaction usually begins at 90-1 io°, and the temperature rises in a few seconds to about 180°. In smaller runs, e.g., With 100 g. of benzanilide, it is not advisable to cool the flask before the temperature has reached about 180°, as some benzanilide may remain unchanged. The flask and the attached condenser should be readily detachable from the sup-... 

A number of related reactions are worthy of mention. Benzanilide (334) is converted into phenanthridone (335) by irradiation in benzene in the presence of iodine.362 Cyclodehydrogenation is also observed in the anilides of indole-2-carboxylic acid and indole-3-carboxylic acid on irradiation in acetone.363 Irradiation of diphenyl-amine304 and certain of its JV-substituted derivatives365 yields the corresponding carbazole. The mechanism of this reaction differs from... 

Potassium ferf-butoxide (1 mmol) was added to a premixed mixture of aniline (1 mmol) and metliylbenzoate (1 mmol) in a glass test tube which was placed in an alumina bath (neutral alumina 125 g, mesh 150, Aldrich bath 5.7 cm diameter) inside an unmodified household microwave oven and irradiated for the specified time at its full power of 900 W. On completion of the reaction, as determined by TLC (hexane-EtOAc, 4 1, v/v), the reaction mixture was extracted into ethyl acetate. The combined extracts were dried over anhydrous sodium sulfate and the solvent removed under reduced pressure to afford a residue that upon trituration with hexane gave pure product, benzanilide (83%). 

There is no analogous ring opening reaction if alkali alcoxides are used and thus they may be successfully used for the preparation of pure salts of caprolactam (8, 61, 66, 68, 92, 95, 97, 103) in analogy to the preparation of sodium benzamide (11, 74, 75). Although the alcohols formed do not affect directly the salt formed, it is necessary to remove them by distillation in order to avoid side reactions taking place in the polymerization process in the presence of alcohols and esters (see below). In the same way it is possible to prepare alkali salts of other N-alkylamides e. g. benzanilide which also may be used as basic catalysts. 

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