Purity and Yield

The (A/-alkylated) lactam of 8-aminonaphthalenecarboxylic acid (47) also is a valuable dye iatemiediate, eg, for cyclometbine-type dyes used for dyeiag polyacrylonitrile fibers and other synthetics. 1,8-Naphtholactams are prepared in high yield and purity by the reaction of naphtholactones with RNH2 (R = H, Cl—4 alkyl, cycloalkyl, or optionally substituted aryl) in aqueous medium, usually in the presence of bisulfite at 150°C over a period of 15 h (143). 

Use of mercuric catalysts has created a serious pollution problem thereby limiting the manufacture of such acids. Other catalysts such as palladium or mthenium have been proposed (17). Nitration of anthraquinone has been studied intensively in an effort to obtain 1-nitroanthraquinone [82-34-8] suitable for the manufacture of 1-aminoanthraquinone [82-45-1]. However, the nitration proceeds so rapidly that a mixture of mono- and dinitroanthraquinone is produced. It has not been possible, economically, to separate from this mixture 1-nitroanthraquinone in a yield and purity suitable for the manufacture of 1-aminoanthraquinone. Chlorination of anthraquinone cannot be used to manufacture 1-chloroanthraquinone [82-44-0] since polychlorinated products are formed readily. Consequentiy, 1-chloroanthraquinone is manufactured by reaction of anthraquinone-l-sulfonic acid [82-49-5] with sodium chlorate and hydrochloric acid (18). 

Friedel-Grafts Reaction. Until quite recently, the manufacture of anthraquiaone ia the United States was by the Friedel-Crafts reaction benzene [71-43-2] and phthaUc anhydride [85-44-9] condense ia the preseace of anhydrous aluminum chloride to give o-benzoylbenzoic acid [85-52-9] which, on treatment with concentrated sulfuric acid, is converted iato anthraquiaoae ia high yields and purity (33). 

In the case of l,4-ben2oquinone, the product is steam-distilled, chilled, and obtained in high yield and purity. Direct oxidation of the appropriate unoxygenated hydrocarbon has been described for a large number of ring systems, but is generally utilized only for the polynuclear quinones without side chains. A representative sample of quinone uses is given in Table 5. 

The reductions of chlorosilanes by lithium aluminum hydride, lithium hydride, and other metal hydrides, MH, offers the advantages of higher yield and purity as well as dexibiUty in producing a range of siUcon hydrides comparable to the range of siUcon haUdes (59). The general reaction is as follows ... 

The transalkylation reaction is essentiaHyisothermal and is reversible. A high ratio of benzene to polyethylbenzene favors the transalkylation reaction to the right and retards the disproportionation reaction to the left. Although alkylation and transalkylation can be carried out in the same reactor, as has been practiced in some processes, higher ethylbenzene yield and purity are achieved with a separate alkylator and transalkylator, operating under different conditions optimized for the respective reactions. 

A vapor-phase process primarily for ECC off-gas feeds was developed by Sinopec Technology Company based on a 2eoHte catalyst of the Pentasd type (24,25). It reHes on frequent regeneration of the catalyst to minimi2e pretreatment of the ECC off-gas and allows the impurities in the feed gas to react with ben2ene to form by-products. Consequently, the product yield and purity are low. Joint licensing by ABB Lummus Crest and Sinopec was announced in 1994. 

A novel route to azelaic acid is based on butadiene. Butadiene is dimerized to 1,5-cyclooctadiene, which is carbonylated to the monoester in the presence of an alcohol. Hydrolysis of this ester foUowed by a caustic cleavage step produces azelaic acid in both high yield and purity (56). 

The only satisfactory method of preparing /3-naphthoquinone is by the oxidation of 1,2-aminonaphthol in acid solution, and the chief problem involved is that of the preparation of this intermediate in suitable yield and purity. This problem and the literature pertaining to it are discussed elsewhere. Most reports of the preparation of the aminonaphthol include some description of its oxidation, but the only particularly helpful comment on the reaction is that ferric chloride is a better oxidizing agent than chromic acid because at a low temperature it docs not attack the quinone, even when present in excess. ... 

The merits of this method are as follows technological feasibility, no-waste technology, one-pot process, high yield, and purity of thiophene. Probably, for... 

The first step in this preparation, the epoxidation of 1,4,5,8-tetra-hydronaphthalene, exemplifies the well-known selectivity exerted by peracids in their reaction with alkenes possessing double bonds that differ in the degree of alkyl substitution.12 As regards the method of aromatization employed in the conversion of ll-oxatricyclo[4.4.1.01-6]-undeca-3,8-diene to l,6-oxido[10]annulene, the two-step bromination-dehydrobromination sequence is given preference to the one-step DDQ-dehydrogenation, which was advantageously applied in the synthesis of l,6-metliano[10]annulene,2,9 since it affords the product in higher yield and purity. 

The generality and functional group compatibility were also excellent with regard to the alkynes (Table 2). Free hydroxyl groups and even a remote double bond were compatible and give very good yields and purities. 

The reaction is performed either noncatalytically at temperatures of 600-800°C and at pressures of 30-100 bar, or catalytically on a CoO contact at 550-650°C and at the same pressure of 30-100 bar. A problem of the catalytic process is the poisoning of the catalyst by deposition of coke-like material, but the conversion, yield, and purity of the benzene are better (>99%) in the catalytic than in the noncatalytic process. In the noncatalytic process the benzene selectivity is about 95%, if the conversion of the toluene is kept at 60-80%. 

Microwave irradiation has been used to accelerate the Gewald reaction for the one-pot synthesis of N-acyl aminothiophenes on solid support [67]. A suspension of cyanoacetic acid Wang resin 35, elemental sulfur, DBU and an aldehyde or ketone 36 in toluene was irradiated for 20 min at 120 °C in a single-mode microwave synthesizer (Scheme 13). Acyl chloride 37 was added, followed by DIPEA, and the mixture was irradiated for 10 min at 100 °C. After cooling to room temperature, the washed resin was treated with a TEA solution to give M-acylated thiophenes 38 in 81-99% yield and purities ranging from 46-99%. 

The rapid synthesis of 1,2,4-triazines has also been developed under microwave-assisted conditions [80]. Irradiation of a 1,2-diketone with acyl hydrazides and ammonium acetate for 5-10 min at 180 °C in a single-mode microwave reactor gave 3,5,6-trisubstituted 1,2,4-triazines in excellent yield and purity and reaction times that were reduced 60-300 fold over conventional conductive heating methodology (Scheme 22). 

The use of microwaves to heat organic reactions has attracted considerable interest in the last 15 years. This technique allows to reduce the time of chemical transformations and, consequently, the formation of by-products is reduced, often with improved yields and purity of the products. Practically every kind of transformation has been tested imder microwave irradiation, in many instances giving better results than conventional heating [ 1 ]. 

The use of microwaves for the preparation of aromatic five-membered heterocycles has been intensely investigated with excellent results in terms of yields and purities of the products prepared. The Paal-Knorr reaction, namely the cyclocondensation of a 1,4-dicarbonyl compound to give furans, pyrroles and thiophenes has been successfully carried out with the aid of microwaves. 

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