Replacement of aromatic amino groups

Reductive methylation of the tetrahydropyranyl ether of 17o -acetoxy-3/3-hy-droxypregn-5-en-20-one, 56 Replacement of aromatic amino groups by fluorine, 450... 

This reaction has general utility for replacement of aromatic amino groups by hydroxyl groups. In contrast to the behavior of alkylamines, no rearrangements occur. 

The replacement of aromatic amino groups by cyanide is easily accomplished by the action of cuprous cyanide on the diazonium compound (Sandmeyer). The procedure is illustrated by the preparation of o- and tolunitriles each is obtained in 64% to 70% yield. Several features are noteworthy. The diazonium solution is neutralized with sodium carbonate before treatment with cuprous cyanide solution so that the liberation of hydrogen cyanide is avoided. Also, vigorous stirring in the presence of an inert solvent is required during the addition of the cold neutralized diazonium solution to the cold cuprous cyanide solution so that the decomposition proceeds without violence. Methods for the preparation of cuprous cyanide have been described. ... 

The Bucherer reversible reaction of conversion of naphthols to anilines by aminolysis is of outstanding importance in naphthalene chemistry. The reaction is used for the replacement of aromatic amino groups by hydroxy groups, in the naphthalene series. The reaction is valuable in the synthesis of naphthalene dye intermediates and may be represented as follows ... 

Hydroxy-de-diazoniations are well-known standard reactions for the replacement of aromatic amino groups by hydroxy groups. An aqueous solution of the diazonium salt is added slowly to boiling 5-35% (v/v) aqueous sulfuric acid. The hydroxy-de-diazoniation may fail in the presence of reactive substituents in the o-position to the diazonio group (24 references mentioned by Cohen " in 1977 ). Cohen s method of adding large amounts of Cu(N03)2 (15-100-fold excess) and CU2O in equimolar amounts, relative to diazonium ions, is today hardly recommendable anymore due to environmental reasons. 

The two general reactions can be used to prepare a variety of compounds in which two aryl groups are linked. The unsymmetrical biaryls are of particular interest since they are not as accessible through other reactions as the symmetrical compounds. Some conception of the types of compounds available by replacement of the amino group of aromatic amines by aryl groups can be obtained from an examination of the following table, which shows the more important amines from which diazo... 

The chemical behavior of phenolic compounds 418 in the crosslinking is related to replacement of the amino group by the activated aromatic ring. Other nucleophilic compounds may give this reaction (see below). A significant example is afforded by the reaction of the oligomeric Mannich base 423 (Fig. 161), which, upon being heated to 210° C, releases dimethylamine with formation of the cros.slinked resin 424. ... 

As described in Chapter 8, the indirect replacement of an amino group by a halogen via diazotization of a primary aromatic amine is a valuable route to aryl halides. The chemistry of these processes covering the introduction of all the main halogens can be found in that chapter. 

The replacement of an amino group by a mercapto group on an aromatic nucleus is effected by treating the diazotized amine with potassium ethyl xanthate and hydrolyzing the resulting aryl ethyl xanthate (Leuckart). Yields of 40-80% are reported for thiophenols containing methyl, halo, and methoxyl groups. Potassium ethyl xanthate is readily prepared from alcoholic potassium hydroxide and carbon disulfide. ... 

Replacement, of aromatic chlorine atoms, by amino groups using ammonia, 40, 97... 

Replacement of Aromatic Primary Amino Groups by Hydrogen [594 ... 

Trifluoromethyl-3-amino-2-propanols are powerful (submicromolar) and reversible inhibitors of CEPT in human plasma. Reversibility of the inhibition seems to indicate that the inhibitor acts as a substrate analogue (Figure 7.64). Three important factors for the gain of affinity must be underlined (1) replacement of the propyl group by a trifluoromethyl (affinity 30x), (2) the R configuration at the hydroxyl (affinity 40x), and (3) the presence of a fluoroalkyl substituent on the third aromatic ring (affinity 40x)." ... 

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