Coupling acid chlorides/aromatic amines

The yellow members of this pigment class are obtained by coupling a dia2oti2ed aminoben2oic acid with a bisacetoacetaryUde, followed by conversion to a diacid chloride and reaction with a substituted aromatic amine. An example is Pigment Yellow 93 [5580-57-4] (Fig. 2b). 

Diphenylcinnoline can be prepared from benzil monophenylhydrazone in the presence of about 80% sulfuric acid (49MI21200). Synthetically more important, however, is the cyclization of mesoxalyl chloride phenylhydrazones under Frledel-Crafts -conditions (61JCS2828). As outlined in Scheme 67, the starting mesoxalate phenylhydrazones are obtained by coupling dlazotized aromatic amines with diethyl malonate. After conversion... 

The dinitrophenyl derivatives are reduced by titanium(III) chloride in acidic medium in the first step of the reaction to the corresponding aromatic amines these are then diazotized and coupled with N-(l-naphthyl)-ethylenediamine to yield an azo dye (cf. Fig. 21). 

The technique of having the coupling step precede the condensation is similarly applied to the two types of yellow pigments. Type 1 (see p. 370) is synthesized by coupling two equivalents of diazotized aminobenzoic acid onto bisacetoacetylated aromatic diamine, especially diaminobenzene. Conversion to the disazo acid chloride, followed by condensation with two equivalents of usually carbonamide substituted amine, finally affords the desired pigment. 

HPLC methods can be ntilized for the pre-concentration of aromatic amines from polluted waters on silica gel or octadecyl silica (ODS) colnmns [55], The determination is then performed by RP HPLC using ODS packings as the stationary phases and a mixture of methanol, isopropanol, and water as the mobile phase [55], RP HPLC with diode array detector (DAD) methods coupled on-line with a continnons seqnential anaerobic/aerobic reactor system have been employed in wastewaters treatments [56], A continnons monitoring of the possible presence of aromatic amines in azo dyes wastes is based on indncing in the waste, the reaction of a reduction of the dye, followed by HPLC/ UV or HPLC/MS analysis [57-59], The redncing agent solutions are sodium dithionite or tin(II) chloride in an aqneons acidic medinm at 70°C, followed by SPE [58,59], LLE [60,61], or SEE [60-62],... 

Besides the mild conditions and excellent chemo- and regioselectivity the scope of this one-pot coupling-cycloaddition isoxazole synthesis is fairly broad. Due to acid chlorides as halide coupling partners, amines and hydroxy groups inevitably need to be protected prior to the reaction. Therefore, the use of acid chlorides 7 is principally limited to (hetero)aromatic compounds and derivatives without ot-hydrogen atoms. As an exception, the cyclopropyl group is tolerated as a... 

Fierz-David and Ziegler (301) first applied this method to azo compounds. Ethyl acetoacetate and various aromatic amines (aniline, o- and p-toluidines, m-xylidine, o-anisidine, and chloroanilines) were convereted to acetoacetanilides and then coupled with diazotized sulfanilic acid. The azo dyes (38) were reduced with stannous chloride in hydrochloric acid to the corresponding aminoaceto-acetanilides (39), which in alkali formed the dihydropyrazines (40). Catalytic reduction of o-hydroxyphenylglyoxal phenylhydrazone in acetic acid over palladium has been shown also to give 2,5-bis(o-hydroxyphenyl)pyrazine (302). Reduction of chemical means has been shown to give... 

Coupling in para or ortho positions is easily accomplished with phenols 912,1037,1095] and aromatic amines [915]. -Naphthol, on refluxing with anhydrous ferric chloride in ether, is converted in 60% yield into a,a -bi-p-naphthol [9i2], and 2,4-bis(rert-butyl)-5-methylphenol, on heating with chromic acid, yields the corresponding dimer [1095] (equation 44). 

Synthesis Efficient Coupling Chemistry Based on Acid Chlorides and Aromatic Amines... 

Nucleophilic displacement of chlorine, in a stepwise manner, from cyanuric chloride leads to triazines with heteroatom substituents (see Section 6.12.5.2.4) in symmetrical or unsymmetrical substitution patterns. New reactions for introduction of carbon nucleophiles are useful for the preparation of unsymmetrical 2,4,6-trisubstituted 1,3,5-triazines. The reaction of silyl enol ethers with cyanuric chloride replaces only one of the chlorine atoms and the remaining chlorines can be subjected to further nucleophilic substitution, but the ketone produced from the silyl enol ether reaction may need protection or transformation first. Palladium-catalyzed cross-coupling of 2-substituted 4,6-dichloro-l,3,5-triazine with phenylboronic acid gives 2,4-diaryl-6-substituted 1,3,5-triazines <93S33>. Cyanuric fluoride can be used in a similar manner to cyanuric chloride but has the added advantage of the reactions with aromatic amines, which react as carbon nucleophiles. New 2,4,6-trisubstituted 1,3,5-triazines are therefore available with aryl or heteroaryl and fluoro substituents (see Section 6.12.5.2.4). 

Aromatic nitro compounds can be reduced in several ways, either to nitroso compoimds only, or up to amines. The usual color tests can then be carried out with the products or the reduction. Electrolytic reduction or reduction with zinc in CaCl2 solution leads to nitroso compoimds which can be detected by the reaction with sodium pentacyanoammoferroate (25) reduction with zinc in glacial acetic acid or in NH4CI, as well as reduction with stannous chloride, give rise to primary aromatic amines which can be detected either with /7-dimethylaminobenzaldehyde, or, after diazotization, by coupling with a suitable passive component (p. 341). 

The specific detection of aromatic nitro compounds is a second example. These can be converted by reduction to primary amines, which are then diazotized and coupled to yield azo dyes (cf. reagent sequence Titanium(III) chloride — Bratton-Marshall reagent ). Sodium nitrite —naphthol reagent, diazotized sulfanilic acid and other reagents specific for amino groups (e.g. ninhydrin, fluorescamine, DOOB, NBD chloride [9]) can also be used in the second stage of the reaction (Fig. 21). 

Aromatic nitro compounds are reduced to the corresponding amines by tin(II) chloride in acidic medium. These are then diazotized via the gas phase with nitrous fumes and finally coupled with 1-naphthol to yield an azo dye. 

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