Reactions of Arylamines

VVI lat product would you expect from 1 lofrudiin ellminaliun of a heterocyclic amine such as piperidine Write all the steps. 

Another drawback to the use of amino-substituted benzenes in electrophilic aromatic substitution reactions is that Friedel-Crafts reactions arc not successful (Section 16.3). The amino group forms an acid-base complex with Ihe AICI3 catalyst, which prevents further reaction from occurring, lioth drawbacks can be overcome, however, by carrying out electrophilic aromatic substitution reactions on the corresponding amide rather than on the free amine. 

Friedel-Crafts alkylations and acylations of A -aiylamides also proceed normalh For example, benzoyiation of acetan.lide (iV-acctyianiline) under Fricdel-Crafts conditions gives 4-aminobenzophenone in 80% yield after hydrolysis. 

Problem 24.16 Prt)pose a synthesis of the drug siilfathiazole from benzene and any nece.ssary amine 

Problem 24.17 Propose syntheses of the following compounds from benzene  

Thomson Click Organ/c Interactive to use a web-based palette to predict products from a variety of reactions involving arylamines. 

An amino group is strongly activating and ortho- and para-directing in electrophilic aromatic substitution reactions (Section 16.5). This high reactivity of amino-substituted benzenes can be a drawback at times because it s often difficult to prevent polysubstitution. Reaction of aniline with Bt2, for instance, takes 

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Modulating the reactivity of an amino-substituted benzene by forming an amide is a useful trick that allows many kinds of electrophilic aromatic substitutions to be carried out that would otherwise be impossible. An example is the preparation of the sulfa dmgs, such as sulfanilamide. 

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Yadav et al.110 employed montmorillonite KSF as a catalyst for the reaction of arylamines with 2-deoxy-D-eryf/tro-pentose. The reaction took place on the surface of the catalyst and proceeded with cyclization to afford sugar-derived chiral tetrahydro-quinolines in high yields and moderate diastereoselectivity. 

Anilines are converted into nitrosoarenes ArNO by the action of hydrogen peroxide in the presence of [Mo(0)(02)2(H20) (HMPA)]224, whereas catalysis of the reaction by titanium silicate and zeolites results in the formation of azoxybenzenes ArN (0)=NAr225. Azo compounds ArN=NAr are formed in 42-99% yields by the phase-transfer assisted potassium permanganate oxidation of primary aromatic amines in aqueous benzene containing a little tetrabutylammonium bromide226. The reaction of arylamines with chromyl chloride gives solid adducts which, on hydrolysis, yield mixtures of azo compounds, p-benzoquinone and p-benzoquinone anils 234227. 

Synthesis of 1,2,3-dithiazoles is the most extensively studied. The widely used and very long-known Herz reaction of arylamines with S2CI2 to give benzo-l,2,3-dithiazolium salts (Section 4.11.8.5) has been extended to hetarylamines (Scheme 17). More importantly, a new impetus for its investigation and development was provided when benzo-l,2,3-dithiazolyl radicals were shown by Mayer and co-workers to be intermediates. The reaction in a modified form was transformed by the above authors to an effective method for synthesis of this new class of stable radicals. When applied to acyclic enaminoketones the thiosulfinylamine precursor of the free radical could be isolated (Scheme 18). It was also extended to cyclic and acyclic oximes to afford fused and monocyclic... 

The most useful reaction of amines with nitrous acid is the reaction of arylamines to form arenediazonium salts. We consider next how these diazonium salts may be used as synthetic intermediates. 

Xiu-Juan, X. and Guang-Xu, C., Mannich reaction of arylamines. Acta Chim. Sinica, 40,... 

The most useful reaction of arylamines is conversion by diasiotization with nitrous acid into arenediazonium aatte. X. The diaxonio... 

A three-component reaction of arylamines 3 (e.g., 3-anisidine, 3,4- and 3,5-dimethoxyaniline, 3,4,5-trimethoxyaniline, 2-naphthylamine), guanidine-l-carbonitrile, and acetone in the presence of concentrated hydrochloric acid leads to moderate yields of 2-guanidino-4-methylquin-azolines 5. The reaction proceeds via the non-isolated intermediate 2,2,4-trimethyl-l,2-dihy-droquinoline 4 (for details see p 82). ... 

The most useful reaction of arylamines is conversion by diazotization with nitrous acid into arenediazonium salts, ArNg X . The diazonio group can then be replaced by many other substituents in the Sandmeyer reaction to give a wide variety of. substituted aromatic compounds. Aryl chlorides, bromides, iodides, and nitriles can be prepared from arenediazonium salts, as can arenes and phenols. In addition to their reactivity toward substitution reactions, diazonium salts undergo coupling with phenols and arylamines to give brightly colored azo dyes. 

J) Color Reactions of Arylamines. To 10 ml of water in a test tube add one drop of aniline, and shake. Add one or two drops of a suspension of bleaching powder or a drop of a solution of sodium hypochlorite. Note the color. Repeat with o-toluidine, and with dimethylaniline. The production of color is due first to oxidation, and second, to condensation to complex colored compounds. 

Aryl isothiocyanates The reaction of arylamines with the reagent affords 5-(A(-aryliinino)-4-chloro-l,2,3-dithiazoles which are decomposed to give ArN=C=S by a Grignard reagent. 

Diaryl ureas. Zeolite HSZ-360 promotes the reaction of arylamines with ethyl... 

Stolle synthesis. Formation of indole derivatives by the reaction of arylamines with a-haloacid chlorides or oxalyl chloride, followed by cyclization of the resulting amides with aluminum chloride. 

Table 16.3-10. Oxidation reactions of arylamines catalyzed by peroxidases.

The Mannich reactions of arylamines have not been studied in as much detail as those of phenols. Nevertheless, interesting features have been established and further developments can be envisaged. 

Isothiocanic esters are also readily accessible by acid fission of diaryl-ureas,1063 reaction of arylamines with iV,jV-diethylthiocarbamoyl chloride,812 and by treatment of iV-metalated amidophosphates with carbon disulfide.813... 

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