Amino substitution

Many methine cationic dyes, styrylic (141), pyrrolic. or amino-substituted (142) derivatives of thiazolium, possess interesting anthelmintic properties (143). This last class has been used as accelerators of the catabolism and activators of cellular exchanges (144). 

For uniformity with the stmctures given in the Colourindex the ammonium radical (9) is used for the amino-substituted xanthenes and the keto form for the hydroxy derivatives. The xanthene dyes may be classified into two main groups diphenylmethane derivatives, called pyronines, and triphenylmethane derivatives (eg, (4)), which are mainly phthaleins made from phthaUc anhydride condensations. A third much smaller group of rosamines (9-phenylxanthenes) is prepared from substituted ben2aldehydes. The phthaleins may be further subdivided into the following fluoresceins (hydroxy-substituted) rhodamines (amino-substituted), eg, (6) and mixed hydroxy/amino-substituted. 

The rhodamines are economically the most important amino-substituted xandiene dyes. The total sales of Rhodamine B in the United States in 1980 were over 10. The total domestic market for duorescein and uranine was estimated to be over 0.5 x 10 /yr. 

Dyestuff organic chemistry is concerned with designing molecules that can selectively absorb visible electromagnetic radiation and have affinity for the specified fiber, and balancing these requirements to achieve optimum performance. To be colored the dyestuff molecule must contain unsaturated chromophore groups, such as a2o, nitro, nitroso, carbonyl, etc. In addition, the molecule can contain auxochromes, groups that supplement the chromophore. Typical auxochromes are amino, substituted amino, hydroxyl, sulfonic, and carboxyl groups. 

The use of guanidine for cyclization gives amino substituted derivatives (e.g. 212) (52CB1012), and in this case o-aminonitriles may be used to furnish diamines (e.g. 8UOC1394). An unusual reaction involving nitriles occurred during the preparation of nicotinonitrile from the amide and ammonium sulfamate, when a 60% yield of the dimeric by-product (213) was formed via the nitrile (69BSB289). Similar products have been obtained from... 

In a series of reactions with potassium amide in liquid ammonia, 6-chloropyrido[2,3-f)]pyrazine gave reduction and ring contraction (Section 2.15.13.3), the 6-bromo analogue underwent only reduction, whilst the 6-fluoro derivative gave only the 6-amino substitution product (79JHC305). 

Several variations of this general procedure have been described. The functionalized dithiocarbamate (23) on heating with a mixture of phosphorus pentasulfide and tetrafluoroboric acid gave the 2-amino-substituted 1,3-dithiolylium tetrafluoroborate (24) in moderate to good yield (69CPB1924). 

A mechanism has been proposed to rationalize the results shown in Figure 23. The relative proportion of the A -pyrazolines obtained by the reduction of pyrazolium salts depends on steric and electronic effects. When all the substituents are alkyl groups, the hydride ion attacks the less hindered carbon atom for example when = Bu only C-5 is attacked. The smaller deuterohydride ion is less sensitive to steric effects and consequently the reaction is less selective (73BSF288). Phenyl substituents, both on the nitrogen atom and on the carbon atoms, direct the hydride attack selectively to one carbon atom and the isolated A -pyrazoline has the C—C double bond conjugated with the phenyl (328 R or R = Ph). Open-chain compounds are always formed during the reduction of pyrazolium salts, becoming predominant in the reduction of amino substituted pyrazoliums. 

Other amino substituted isoxazoles undergo ring-opening reactions on treatment with base. Thus the amidine derivative (249) gave the triazole (250) (64TL149), while the triazene (251) on reaction with ammonia gave the tetrazole (252) (64X461). 

Dimethoxybenzyl esters prepared from the acid chloride and the benzyl alcohol are readily cleaved oxidatively by DDQ (CH2CI2, H2O, rt, 18 h, 90-95% yield). A 4-methoxybenzyl ester was found not to be cleaved by DDQ. The authors have also explored the oxidative cleavage (ceric ammonium nitrate, CH3CN, H2O, 0°, 4 h, 65-97% yield) of a variety of 4-hydroxy- and 4-amino-substituted phenolic esters. ... 

The chemical reactivity of these two substituted ethylenes is in agreement with the ideas encompassed by both the MO and resonance descriptions. Enamines, as amino-substituted alkenes are called, are vety reactive toward electrophilic species, and it is the p carbon that is the site of attack. For example, enamines are protonated on the carbon. Acrolein is an electrophilic alkene, as predicted, and the nucleophile attacks the P carbon. 

The structure of guanine illustrates an important feature of substituted pyrimidines and purines. Oxygen substitution on the ring favors the keto form rather than the enol. Amino substitution does not. 

As previously described, the Gould-Jacobs reaction has been applied to heterocycles fused to anilines, and to some amino-substituted heterocycles. Selectivity of N- and C-cyclization of 2-aminopyridino-methylene malonates has been mentioned (51 and 56). The normal mode of cyclization of 2-aminopyridino-methylene malonates is on the nitrogen to form a pyridopyrimidine. If an electron-donating group (EDG) is in the 6-... 

Ri = N3, R.2 = H), and an equilibrium is observed in the case of the deuterated compound (59 Ri = R2 = N 02). Certain secondary amino-substituted compounds (59, 60 Rj =RNH, R2 = H) show solvent dependence of their equilibria solutions in dimethyl sulfoxide contain mainly form 59, whereas alcohols as solvents favor form 60. ... 

In the authors opinion (81UK1252), the evidence for such a scheme is the isolation of formamide transamination products, dialkylformamides (in case of l-dialkylaminoalk-l-en-3-ynes). Examples of formamide transamination, e.g., by /3-amino-substituted carbonyl compounds, are known [58CB2832 60CB1402 60HC( 14)272],... 

Tautomeric equilibrium in amino-substituted 1,2,6-thiadiazine 1,1-dioxides fused with five- or six-membered nitrogen heterocycles has been extensively studied by Goya and colleagues. No amino group participation in tautomeric equilibria in these systems has been observed. 

Another drawback to the use of amino-substituted benzenes in electrophilic aromatic substitution reactions is that Friedel-Crafts reactions are not successful (Section 16.3). The amino group forms an acid-base complex with the AICI3 catalyst, which prevents further reaction from occurring. Both drawbacks can be overcome, however, b3 carrying out electrophilic aromatic substitution reactions on the corresponding amide rather than on the free amine. 

Arylamine (Section 24.1) An amino-substituted aromatic compound, Ar—NH2. 

Reports on the synthesis of amino-substituted 1,2,4-triazocines3-4 were subsequently corrected the compounds were actually imidazotriazines, as proven by independent synthesis.5 6... 

An easy approach to obtain amino-substituted phthalocyanines is the reduction of nitro groups, which are easily introduced into the macrocycle by condensation of the respective phthalonitrile. 

Allyltrialkoxy- or -tris(dialkylamino)titanium reagents are not capable of chelation-controlled addition reactions with oxy- or amino-substituted carbonyl compounds due to their low Lewis acidity87. To attain chelation control, the application of allylsilanes (Section 1.3.3.3.5.2.2.) and allylstannanes (Section I.3.3.3.6.I.3.2.) in the presence of bidentate Lewis acids like titanium(IV) chloride, tin(lV) chloride or magnesium bromide are the better options. 

The oxidation of /(-amino-substituted iron acyl complexes which are prepared via condensation reactions of iron-acyl enolates and imines or iminium ions26,5 -47-54 generates /(-lactams 32,33,61. Brief treatment with bromine in dichloromethane at low temperature is the usual procedure. 

There is an analogous preparation of y-lactams from y-amino-substituted iron-acyl complexes46. 

The addition of a-amino-substituted lithium enolates to a,/ -unsaturated esters is a diastereoselective route to syn- or anti-glutamic acid derivatives and also to fratw-substituted 5-oxo-2-pyrrolidinecarboxylates. 

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