Synthesis electrophilic substitution

However, the vast majority of research has been devoted to synthesis involving electrophilic substitution on the aromatic ring of hydroquinone. Hence, phenylhydroquinone can be obtained by the reaction of phenyl dia onium salts (18) with hydroquinone (82). 

The earliest reported reference describing the synthesis of phenylene sulfide stmctures is that of Friedel and Crafts in 1888 (6). The electrophilic reactions studied were based on reactions of benzene and various sulfur sources. These electrophilic substitution reactions were characterized by low yields (50—80%) of rather poorly characterized products by the standards of 1990s. Products contained many by-products, such as thianthrene. Results of self-condensation of thiophenol, catalyzed by aluminum chloride and sulfuric acid (7), were analogous to those of Friedel and Crafts. 

Anthraquinone dyes are derived from several key compounds called dye intermediates, and the methods for preparing these key intermediates can be divided into two types (/) introduction of substituent(s) onto the anthraquinone nucleus, and (2) synthesis of an anthraquinone nucleus having the desired substituents, starting from benzene or naphthalene derivatives (nucleus synthesis). The principal reactions ate nitration and sulfonation, which are very important ia preparing a-substituted anthraquiaones by electrophilic substitution. Nucleus synthesis is important for the production of P-substituted anthraquiaones such as 2-methylanthraquiQone and 2-chloroanthraquiaone. Friedel-Crafts acylation usiag aluminum chloride is appHed for this purpose. Synthesis of quinizatia (1,4-dihydroxyanthraquiQone) is also important. 

In those reactions where the fV-oxide group assists electrophilic or nucleophilic substitution reactions, and is not lost during the reaction, it is readily removed by a variety of reductive procedures and thus facilitates the synthesis of substituted derivatives of pyrazine, quinoxaline and phenazine. 

Acetanilides, benzoyl-colour couplers in colour photography, 1, 372 Acetanilides, pivaloyl-colour couplers in colour photography, 1, 372 Acetazolamide — see l,3,4-Thiadiazole-2-sulfonamide, 5-acetamido-Acetic acid, acetamidocyano-ethyl ester, 1, 307 Acetic acid, 2-acylphenyl-isochroman-3-one synthesis from, 3, 858 Acetic acid, 3-benzo[6]thiophenyl-biological activity, 4, 912 Acetic acid, l,2-benzoxazol-3-yl-electrophilic substitution, 6, 48... 

Benzo[c]furan, 1,3-dihydro-1,3-diphenyl-mass spectrometry, 4, 585 Benzo[c]furan, 1,3-dfmethyl-synthesis, 4, 699, 701 Benzo[c]furan, 1,3-diphenyl-cycloaddition reactions, 4, 67 electrophilic substitution, 4, 604 history, 4, 533... 

Benzopyrylium perchlorate, 3-ethyI-reduction, 3, 662 Benzopyrylium salts C NMR, 3, 590 chromene synthesis from, 3, 756 chromone synthesis from, 3, 829 electrophilic substitution, 2, 49 mass spectra, 3, 618 reactions... 

Benzo[6]thiophene, 2-(aryloxymethyl)-3-chloromethyl-synthesis, 4, 872 Benzo[6]thiophene, 2-arylthio-synthesis, 4, 931 Benzo[6]thiophene, 2-bromo-reaction with potassamide, 4, 829-830 synthesis, 4, 934 Benzo[6]thiophene, 3-bromo-Grignard reagents, 4, 831 reactions, 4, 830 synthesis, 4, 934 Benzo[6]thiophene, 4-bromo-synthesis, 4, 878, 934 Benzo[6]thiophene, 5-bromo-electrophilic substitution, 4, 797 Benzo[6]thiophene, 6-bromo-synthesis, 4, 878, 934 Benzo[6]thiophene, 5-t-buty 1-3-methyl-synthesis, 4, 880... 

Benzo[i]thiophene, 4,5,6,7-tetrafluoro-electrophilic substitution, 4, 797 synthesis, 4, 895, 932... 

Coumarin, 6-ethoxycarbonyl-4,5,7-trihydroxy-synthesis, 3, 805-806 Coumarin, 3-hydroxy-Mannich reaction, 3, 680 mass spectra, 3, 609 Coumarin, 4-hydroxy-alkylation, 3, 692 azo dyes from, I, 331 electrophilic substitution, 2, 30 IR spectra, 3, 596 Mannich reaction, 3, 680 mass spectra, 2, 23 3, 609 molecular structure, 3, 622 reactions... 

Imidazole, 2-amino-1 -methyl-4,5-diphenyl-tautomerism, 5, 368 Imidazole, 2-aroyl-mass spectra, 5, 360 synthesis, 5, 391, 402 UV spectra, 5, 356 Imidazole, 4-aroyl-synthesis, 5, 474 Imidazole, C-aroyl-UV spectra, 5, 356 Imidazole, aryl-nitration, 5, 396, 433 oxidation, 5, 433 Imidazole, 1-aryl-dipole moments, 5, 351 dearylation, 5, 449 ethylation, 5, 448 H NMR, 5, 353 hydroxymethylation, 5, 404 rearrangement, 5, 108 synthesis, 5, 390 thermal rearrangement, 5, 363 Imidazole, 2-aryl-chlorosulfonation, 5, 397 synthesis, 5, 475 Imidazole, 4-aryl-bromination, 5, 399 Imidazole, C-aryl-electrophilic substitution, 5, 432-433 nitration, 5, 433 Imidazole, N-aryl-reactions, 5, 448-449 structure, 5, 448-449 Imidazole, arylmercapto-... 

Imidazo[ 1,2-e]thiazoles biological activity, 6, 1024 reactions, 6, 1041 synthesis, 6, 1048 Imidazo[2, l-6]thiazoles electrophilic substitution, 6, 979 synthesis, 6, 992, 993, 1010, 1018 Imidazo[3,l-6]thiazoles synthesis, 6, 986 Imidazo[5,l-6]thi azoles biological activity, 6, 1024 synthesis, 6, 1017 Imidazo[2,l-6]thiazolium chloride synthesis, 6, 1013... 

Pyrazolo[3,4-c]pyrazole, tetrahydro-rearrangement, 5, 250 Pyrazolo[4,3-c]pyrazole, tetraaryl-electrophilic substitution, 6, 1035 oxidation, 6, 1034-1035 reduction, 6, 1035 vacuum pyrolysis, 6, 1035 Pyrazolo[ 1,2-n]pyrazole-1,5-diones synthesis, 6, 991 Pyrazolo[ 1,2-n]pyrazoles reactions, 6, 1038 ring opening, 6, 983... 

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