2-Chloro-1,4-quinones

Diels-Alder reactions. This diene reacts with 2-chloro-1,4-quinones to give adducts that undergo aromatiz tion when heated. Yields tend to be low in reactions with benzo-quinones, but are usuajlly satisfactory with naphthoquinones. The reagent was developed to provide a synthesis pf the trimethyl ether (2) of erythrolaccin. 

The present method is the result of a study by Cason, Harman, Goodwin, and Allen.6 7 The sequence of electrolytic reduction followed by oxidation has been used for the preparation of 5-bromotoluquinone,8 5-chlorotoluquinone,9 and 3-chlorotolu-quinone.10 The preparation of an intermediate />-aminophenol from the corresponding aromatic nitro compound by electrolytic reduction is a useful general method.11-18 Chloro-/>-quinone has been prepared by acid dichromate oxidation of chlorohydro-quinone 19-22 or 2-chloro-4-aminophenol.23 24 It has been shown that pure chloro-/>-quinone is obtained only with some difficulty when chlorohydroquinone is used.7... 

There is obtained by filtration 5.0-5.5 g. (48-54%) of yellow chloro-/>-quinone of m.p. 53-55° ether extraction of the filtrate yields a further 1.0 g., which brings the total yield to 58-63% (Notes 12 and 13). Crystallization from a small volume of aqueous ethanol (85-90%) raises the melting point to 55-56°. 

Fluorinations with Silver Fluoride. Reaction of AgF with alkyl and aryl halides often results in the formation of the corresponding fluorides usually under mild conditions. With gemi-nal dihalides, this conversion has been shown to involve a carbo-nium ion intermediate (eq 1). Chloro quinones react with AgF under high pressure and temperature conditions to give partial conversion to the fluoro quinone (eq 2). Cis- and trans-2,3-difluoro-2,3-dihydrobenzofuran can be similarly obtained by the reaction of AgF with trans-2,3-dibromo-2,3-dihydrobenzofuran (eq 3). Bromoadamantanes and l-bromobicyclo[3.3.1]nonan-3-one undergo fluorination with AgF to yield bridgehead fluorine derivatives (eq 4). 

When 5-HT is oxidized at potentials equal to or more positive than Ep for peak Ila only a single product, tryptamine-4,5-dione (B), is initially formed. This indicates that at such potentials the primary oxidation product, radical 1, is oxidized to quinone imine 6 more rapidly than it can dimerize. At peak Ila potentials 4-chloro-5-hydroxytryptamine (C) is oxidized to dione B. It is probable that this process involves oxidation of C (2e", 2H ) to the 4-chloro quinone imine 7 which is attacked by water with loss of HCl to yield dione B (Figure 8). 

Electrophilic addition to quinones, eg, the reaction of 2-chloro-l,4-ben2oquinones with dia2onium salts, represents a marked contrast with acetoxylation in product distribution (58). Phenyldia2onium chloride (Ar = C H ) yields 8% 2,3-substitution [80632-59-3] 75% 2,5-substitution [39171-11-4] and 17% 2,6-substitution [80632-60-6]. Fory)-chlorophenyldia2onium chloride, the pattern is 28% 2,3-substitution [80632-61-7], 35%... 

Benzo[b]thiophene-2,3-quinone, 5-chloro-oxidation, 4, 824 Benzothiophenes, 4, 863-934 biological activity, 4, 911-913 intramolecular acylation, 4, 761 mass spectrometry, 4, 739 metabolism, 1, 242 phosphorescence, 4, 16 reactivity, 4, 741-861 spectroscopy, 4, 713-740 structure, 4, 713-740 substituents reactivity, 4, 796-839... 

The more interesting situation arises in quinones which possess two dissimilar substituents. The site of initial carbon-to-carbon condensation is explicable in terms of the relative electronic effects. Thus condensation of 2-chloro-5-methylbenzoquinone (19) with t-butyl 3-aminocrotonate (20) in hot acetic acid furnished the 4-chloro-7-methylindole (21) in 51% yield. ... 

A 2-1. three-necked flask fitted with a stirrer (Notes 1 and 2), condenser, and dropping funnel (Note 3) is mounted in the hood, and in it are placed 20 g. (0.061 mole) of potassium anthra-quinone-a-sulfonate (p. 72), 500 cc. of water, and 85 cc. (1 mole) of concentrated hydrochloric acid. The solution is heated to boiling and stirred, while a solution of 20 g. (0.19 mole) of sodium chlorate (Note 4) in 100 cc. of water is added dropwise over a period of three hours (Note 5). The mixture is refluxed very slowly for an additional hour before the precipitated a-chloro-anthraquinone is collected by suction filtration and washed free from acid with hot water (about 350 cc.). After drying in vacuo at ioo°, the bright yellow product melts at 158-160° (corr.) and weighs 14.6-14.7 g. (97-98 per cent of the theoretical amount) (Notes 6 and 7). 

B. 2-Chloro-3,6-di-tert-butyl-l,4-benzoquirwne. A 2-1. Erlenmeyer flask is charged with a solution of 112 g. (0.385 mole) of 2,3-dichloro-2,5-di-fer<-butylcyclohex-5-ene-l,4-dione in 800 ml. of ether. A solution of 28.4 g. (0.383 mole) of diethylamine (N-ethylethanamine) in 50 ml. of ether is added in one portion to the vigorously swirled flask (Note 5). The reaction is instantaneous, resulting in a voluminous precipitate. The mixture is washed with two 1-1. portions of water and then with 500 ml. of aqueous saturated sodium chloride. The yellow ether solution is dried over anhydrous magnesium sulfate, the drying agent removed by filtration, and the solvent removed on a rotary evaporator to yield 96-97 g. (98-99%) of 2-chloro-3,6-di-ferf-butyl-l,4-benzo-quinone as a yellow oil which is used without further purification (Note 6). 

It is of interest to note that attachment of a basic side chain on carbon of an isomeric dibenzazepine affords a compound in which anticholinergic activity predominates, elantrine (50). Reaction of anthra-quinone (45) with the Grignard reagent from 3-chloro-N,N-dimethylaminopropane in THF in the cold results in addition to but one of the carbonyl groups to yield hydroxyketone 46. This is then converted to oxime 47 in a straightforward manner. Treatment of that intermediate with a mixture of phosphoric and polyphosphoric acids results in net dehydration of... 

The synthetic route involves treating l-chloro-2-aminoanthraquinone with phthalic anhydride (PA), which initially affords l-chloro-2-phthalimidoanthra-quinone 95. Subsequent Ullmann reaction with copper powder in refluxing trichlorobenzene yields 2,2 -diphthalimido-l,l -dianthraquinonyl 96 through dimerization. This product is cyclized with 5% aqueous sodium hydroxide solution at 100°C, cleaving phthalic acid units, to yield 94 ... 

Dichlorobenzo quinone -4-chloroimide Diethyl acetylenedicarboxylate Dimethyl 2-chloro-4-nitrophenyl thionophosphate Dimethyl 3-chloro-4-nitrophenyl thionophosphate Dimethyl 4-nitrophenyl thionophosphate A,A-Dimethyl-4-nitrosoaniline, Acetic anhydride. Acetic acid t Dimethyl sulfoxide... 

Various nitrosoarenes have been utilized as benzofurazan precursors including o-azido derivatives generated from the o-chloro analogues <66JCS(B)1004>, and 1-amino-2-nitrosoarenes which can be oxidized with ferricyanide or hypochlorite. Treatment of o-nitrosophenols with hydroxylamine also affords the furazan, presumably via an oximation-dehydration pathway involving the tautomeric o-quinone monooxime. Other related approaches involve the reduction of o-dinitroarenes with borohydride, and the thermolysis of o-nitroanilines and o-nitroacetanilides. 

Another redox switchable system is based on dyad 21 in which 2-chloro-1,4-naphthoquinone is covalently attached to 5-dimethyl-aminonaphthalene via a non-conjugated spacer. The intrinsic fluorescence of the dansyl excited state in dyad 21 is strongly quenched, due to the intramolecular electron transfer from the excited dansyl to the adjacent quinone acceptor. However, the fluorescence can be switched on by addition of a reducing agent. Apart from chemical switching, the fluorescence of dyad 21 can also be switched electrochemically. This can be realized using a photoelec -trochemical cell, and the solution starts to fluoresce upon application of a reductive potential.31... 

Acetylanthracene, 30,1 Acetylation, of 2- -acetylphenylhydro-quinone, 34, 1 of hydrogen sulfide, 31, 105 a-Acetyl-7-butyrolactone, 31, 74 Acetyl chloride, 30, 1 (X-ACETYL-5-CHLORO-7-VALEROLACTONE, 31, 1... 

Phenoxazin-3-ones and phenothiazin-3-ones can be prepared by condensation of 2-aminophenols or -thiols with quinones. Alizarin Green G (61), for example, is obtained from (59) and (60). Similarly, 2-aminothiophenols and 6-chloro-2-methoxy-l,4-benzoquinone (62) afford phenothiazin-3-ones (63). 

Benzo[6]thiophene-2,3-quinones are reported to undergo several interesting transformations. Oxidation of 5-chIorobenzo[6]thiophene-2,3-quinone with H202 in the presence of ammonia gives 5-chloro-l,2-benzisothiazole-3-carboxamide (Scheme 157) (70AHC(11)177). 

Nitroso-2-chlorophend or 2-Chloro- p -benzo quinone-4-oxime, HC =C(OH)—C.C1... 

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