Anils Schiffs Bases

Attempted chlorosulfonation of anils 439 containing different substituents by reaction with chlorosulfonic acid was unsuccessful. The chlorosulfonation was examined under various conditions, including the addition of thionyl chloride, but it always gave complex mixtures of products that could not be characterized as sulfonamides. The failure is probably due to partial hydrolytic decomposition of the crude sulfonyl chloride by attack on the CH=N bond during the aqueous work-up procedure, so that the sulfonyl chloride becomes contaminated with benzaldehydes, amines and other products.  

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U.S. production 1978 275000 tonnes, anils, A-phenylimides See Schiffs bases. 

Formation of the oxazole ring is not always the last step in synthesis of the brightener. Unsymmetrical compounds that contain both a benzoxazole group and an ethene linkage can be prepared by the anil synthesis [51], in which a compound possessing an activated methyl group reacts with a Schiff base. The preparation of brightener 11.31 is an illustration of this method (Scheme 11.12). 

Methylpyridine methiodide condenses with Ar,Ar-dimethyl-4-nitrosoaniline in the presence of piperidine to give the Schiff base (66 Scheme 53). The reaction fails with 2-methylpyridine itself but (V-oxide analogues condense similarly (63JCS4600). 9-Methyl-acridine condenses with C-nitroso compounds to yield anils or nitrones. 

This chapter is concerned with compounds containing the structure RR C=NR". These compounds are known as imines, azomethines, anils, or, more commonly, Schiff bases [la]. 

The reaction between MoX3 (X = Cl, Br), aniline and 2,6-diacetylpyridine in butanol yields [MoO py(anil)2 X2], where py(anil)2 is a tridentate Schiff base ligand formed in situ.im These complexes are isomorphous with [VO py(anil)2 X2] and, therefore, are considered to have octahedral coordination of the molybdenum. 

Besides benzalanilines, also anils derived from heterocyclic aldehydes may be employed (Table VI), as, for example, in the reactions of 4,5-diphenyl-2-(p-tolyl)oxazole (58) with SchifFs bases from p-chloro-aniline and 3-formylpyridine and 2-formylthiophene, leading, respectively, to the /3-(3-pyridyl)-4-(4,5-diphenyloxazol-2-yl)styrene (59) 33 and the /S-(2-thienyI) analog (60).11... 

The first attempt to add diazomethane to a Schiff base was made by Meerwein,326 and the first successful addition was observed by Mustafa.327 Anils bearing nitro groups on the phenyl rings gave a cyclic adduct to which a 1,2,4-triazoline structure was assigned.327 A later reexamination of the reaction established the correct orientation of addition, and the products of the reaction of diazomethane with Schiff bases were assigned a A2-l,2,3-... 

Primary aromatic amines generally condense directly with benzaldehyde to form benzylidene derivatives (Schiffs bases or anils). 

Finally, SchifFs bases of other heterocyclic aldehydes can also be reacted with p-tolyl-substituted benzo[6]- (see Table III) and naphtho-[2,1 -i]thiophenes.36,37,58 Thus, 2-(p-tolyl)naphtho [2,1 -i]thiophene (116) gives, on reaction with the anil derived from 3-formyldibenzofuran and p-chloroaniline, the styryl compound 117.38... 

Belousov-Zhabotinsky (B-Z) osciUations in a 1,2-dimethoxybenzene-BrOj-man-ganese(II)-H2S04 system have been studied.A system of fructose-BrOj-Ce" " -H2SO4 also gives rise to B-Z oscillations in the range 0.035-0.7 M fructose, which are promoted by tartaric acid. Potassium bromate has been used to oxidize the Schiff base 2-hydroxy-1-naphthalidene anil in aqueous acetic acid, and a kinetic study made. The kinetics of oxidation of formamide and dimethylformamide by HBrOa have been reported. ... 

In MeCN, most Schiff bases give a single two-electron wave the radical anions of imines are more basic than the corresponding ketyl anions and are able to abstract a proton from the medium [24]. Aliphatic ketimines behave similarly in dimethylformamide (DMF) [23], whereas some aldehyde anils give two peaks in cyclic voltammetry (CV), depending on the... 

Intensive investigations have been conducted to elucidate the nature of the mechanism of thermochromism of salicylidene Schiff bases. Different techniques or methods suitable for the study of the tautomeric equilibrium between the end form and the (Z)-keto form have been used, including X-ray diffraction, NMR, infrared (IR) and Raman spectroscopy, and theoretical calculations. In the anil-... 

Photolysis of aromatic Schiffs bases in strongly acidic media results in cyclisation to phenanthridines (A. Padwa. Chem. Rev.. 1977, 77, 37). Irradiation of anils of polyfluoroaromatic ketones in trifluoroacetic acid also yields phenanthridines by oxidative cyclisation examples are quoted which involve cleavage of a C-F bond (N. I. Danilehko et al., Izvestia, 1980, 1606). 

Anil formation can also be effected in alcoholic solution in the presence of catalytic amounts of sodium carbonate or piperidine the Schiff bases (usually deeply colored) are then precipitated and can be hydrolysed by acid in the usual way. 

Another unequivocal method of converting primary into secondary amines involves intermediate formation of Schiff bases and their quaternization. The quaternary salts are obtained almost quantitatively by heating the base with a lower alkyl halide in a sealed tube for several hours they are readily hydrolysed to the secondary amine. Benzaldehyde is usually taken to form the Schiff base. A number of A-alkyl-/ -methylphenethylamines have been prepared in excellent yield by this route.496 Also the allylmethylamine described above was obtained from allylamine in 71% yield by way of the anil.497... 

The iV-alkyl and iV-aryl derivatives (Schiff bases, azomethines, anils) that can be obtained from aldehydes and ketones by use of primary amines are considerably more important than the unsubstituted imines. 

In the aliphatic series no other useful route has yet been found for the synthesis of aldehydes which is the outcome usually desired from this reaction. Results are, however, more favorable with aromatic oxo carboxylic acids their thermal decomposition results in elimination of both carbon monoxide and carbon dioxide, but it can be directed towards formation of the aldehyde by decarboxylating the anils of the oxo acid 39 these yield Schiff bases in the first place ... 

The number of reagents that has been used for the identification of primary amines is possibly larger than for any other class of compounds [5], But most of these classical derivatives lie beyond the scope of this chapter. They are covered in other parts of the book acylation in Chapter 3, silylation in Chapter 4 and alkylation in Chapter 5. The different nitrophenyl derivatives are discussed in Chapter 8, and Chapter 9 presents the options for preparing fluorescent derivatives. The only derivatization fitting into the framework of this chapter is the condensation with carbonyls resulting in the formation of Schiff bases or, in the case of aromatic amines, anils. 

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