Anthrones formation

Dr. Schowalter It appears that this is another mechanism that could account for the oxidation of dihydroanthracene without intermediate anthrone formation. 

Baughman, G. L., E. J. Weber and M. S. Brewer. 1992. Sediment reduction of anthraquinone dyes and related compounds anthrone formation. Presented at the American Chemical Symposium on the Oxidation-Reduction Transformations of Inorganic and Organic Species in the Environment, San Francisco, CA, April 5-10, 1992. 

Landucci, L. L. Formation of carbon-linked anthrone-lignin and anthrahydroquinone-lignin adducts. J. Wood Chem. Technol. 1981, 1, 61-74. 

In pulp and paper processing, anthraquinone (AQ) accelerates the delignification of wood and improves liquor selectivity. The kinetics of the liquid-phase oxidation of anthracene (AN) to AQ with NO2 in acetic acid as solvent has been studied by Rodriguez and Tijero (1989) in a semibatch reactor (batch with respect to the liquid phase), under conditions such that the kinetics of the overall gas-liquid process is controlled by the rate of the liquid-phase reaction. This reaction proceeds through the formation of the intermediate compound anthrone (ANT) ... 

Recently, Tan reported related bicyclic guanidine 20 as a chiral Br0nsted base to promote the highly enantioselective Diels-Alder reaction of various anthrones and maleimides (Scheme 5.41) [75]. Interestingly, use of dithranol led to the exclusive formation of the enantio-enriched Michael adducts. 

The direct reaction of oxygen with the carbanion from dihydroanthracene does not seem likely. Russell (5) has indicated a preference for a one-electron transfer process to convert the carbanion to a free radical, which then reacts with oxygen to form an oxygenated species. Therefore, we considered a mechanism involving one-electron transfer to form a free radical from the carbanion, which would lead to the formation of anthraquinone and anthracene without having either the hydroperoxide or anthrone as an intermediate. 

The hrst step in the preparation of the antidepressant maprotiline (33-5) takes advantage of the acidity of anthrone protons for incorporation of the side chain. Thus treatment of (30-1) with ethyl acrylate and a relatively mild base leads to the Michael adduct saponihcation of the ester group gives the corresponding acid (33-1). The ketone group is then reduced by means of zinc and ammonium hydroxide. Dehydration of the hrst-formed alcohol under acidic conditions leads to the formation of fully aromatic anthracene (33-2). Diels-Alder addition of ethylene under high pressure leads to the addition across the 9,10 positions and the formation of the central 2,2,2-bicyclooctyl moiety (33-3). The hnal steps involve the construction of the typical antidepressant side chain. The acid in (33-3) is thus converted to an acid chloride and that function reacted with methylamine to form the amide (33-4). Reduction to a secondary amine completes the synthesis of (33-5) [33]. 

Photochemical isomerizations by intramolecular 4n + An cycloaddition of carbon oxygen linked bichromophoric anthracenes to give oxetane derivatives have not been reported yet. Upon irradiation (X > 400 nm) in either toluene or ethyl acetate, the methoxycarbonyl substituted carbon oxygen linked bichromophoric anthracene 14 indeed isomerizes smoothly and efficiently (cp — 0.45). However, the two products, obtained in an approximate ratio of 5 1, are anthrone derivatives 15 and 16 whose formation can be rationalized by migration of the anthryloxy moiety [60], An analogous photolytic rearrangement has been found for 9-anthryloxy substituted dianthrylethylenes (see Section III.A). 

The 1,4-addition of heterocycles to aromatic systems has been reported. Photolysis of piperidine in benzene, for example, leads to the formation of the -substituted piperidine (222).204 Pyrrole, on photolysis in benzene, behaves differently and yields the 2-substituted pyrrole (223).208 In both instances, excitation of benzene, probably to the triplet, appears to be the initial step in the photolysis. The photolysis of iV-nitrosopiperidine in the presence of anthracene also results in 1,4-addition and the formation of an anthrone oxime,... 

The oxidation of 10 with chromic anhydride in aqueous acetic acid leads to anthrone 218 and to anthraquinone 219 with excess oxidant. According to the authors opinion (54JOC1533), the oxidation process was supposed to include the primary formation of diketone 9 it was this compound, but not the initial salt 10, which was oxidized to anthrone 218. 

Photostimulated, S r k 1 reactions of carbanion nucleophiles in DMSO have been used to advantage in C—C bond formation (Scheme 1).25-27 Thus, good yields of substitution products have been obtained from neopentyl iodide on reaction with enolates of acetophenone and anthrone, but not with the conjugate base of acetone or nitromethane (unless used in conjunction, whereby the former acts as an entrainment agent).25 1,3-Diiodoadamantane forms an intermediate 1-iodo mono substitution product on reaction with potassium enolates of acetophenone and pinacolone and with the anion of nitromethane subsequent fragmentation of the intermediate gives derivatives of 7-methylidenebicyclo[3.3.1]nonene. Reactions of 1,3-dibromo- and 1-bromo-3-chloro-adamantane are less effective.26... 

Significant impact on the environment and generation of wastes (mainly associated with the less than 100% selectivity in the reduction and oxidation steps - formation ofhydroxyanthrones, anthrones, anthracenes, and epoxide, some solvent stripping by air used in the oxidation step, and in the crude H202 stream). 

Baughman (1992) measured the disappearance rate constants for a number of solvent and disperse azo, anthraquinone, and quinoline dyes in anaerobic sediments. The half-lives ranged from 0.1 to 140 days. Product studies of the azo dyes showed that reduction of the azo linkages and nitro groups resulted in the formation of substituted anilines. The 1,4-diaminoanthraquinone dyes underwent complex reactions thought to involve reduction and replacement of amino with hydroxy groups. Demethylation of methoxyanthraquinone dyes and reduction of anthraquinone dyes to anthrones also was observed. 

Anisic Alcohol, 456 Anisic Aldehyde, 524 Anisole, 456, 606 Anisyl Acetate, 456, 568, 606 Anisyl Acetone, 524 Anisyl Alcohol, 456, 606 Anisyl Formate, 456, 607 Annatto Extracts, 31 Anthrone TS, (Sl)114 Antimony Trichloride TS, 850, 851 APDC Extraction Method, 766 APM, 35, (S 1)4 APM-Ace, (S3)5 APO, 32 Apocarotenal, 32 p-Apo-8 -Carotenal, 32 Apparatus for Tests and Assays, 4, 727 D-Araboascorbic Acid, 134 L-Arginine, 32, (S3)5 l-Arginine Monohydrochloride, 33 Arsenic Specification, Requirements for Keeping, xv... 

The problem then is the route to hydrogen peroxide in the present case. Insertion of ozone into a carbon—hydrogen bond has been postulated by White and Bailey (14) to explain the ozonation of benzaldehydes, by Price and Tumolo (15) in the ozonation studies of ethers, and by Batter-bee and Bailey (16) in their studies on the ozonation of anthrone. We postulate a similar intermediate to explain the formation of hydrogen peroxide and subsequently the diaminoperoxide VII. 

A rare example of photochemical cycloaddition to a C=N group is provided by the formation of benzoxazole (19) from pentachloro-phenol in acetonitrile. The photoconversion of 2-methylbenzo-phenone into the anthrone (20) involves two sequential photoprocesses via the E-enol (21) which under the influence of high intensity laser light absorbs a second photon to give the cyclized intermediate (22) which undergoes air-oxidation to (20) (Wilson et al.). 

Unfortunately anthrahydroquinone is not very stable under acid conditions, which are needed for a reversible cyclization of the benzoquinone derivatives. There is an early preparative observation on the rapid formation of anthraquinone (AQ) 3 and anthrone (Ant) 4 from anthrahydroquinone (AQH2) 1 in cold concentrated sulfuric acid [83] according the overall reaction... 

Another silanization procedure for the derivatization of carbohydrates is the formation of trimethylsilyl oximes. The methyloxime is heated with hexarnethyl-disilazane trifluoroacetic anhydride (9 1 v/v) for 1 h at 100°C. Anthrone O-glucoside is an important ingredient in skin care cosmetics and can be fully silylated by reaction with A/,0-bistrimethylsilylacetamide acetonitrile mixture (1 1 v/v) for 1 h at 90°C, and subsequently separated by GC. 

Figure 34 PksA deconstruction, (a) Enzymatic domain architecture of PksA. (b) PksA utilizes a starter hexanoyl-CoA and seven malonyl-CoAs to produce the covalently linked intermediate (brackets). The PT domain acts as an aromatase/cyclase facilitating the closure of the first two rings on the intermediate. In the absence of the TE/CLC domain the intermediate undergoes C-O cyclization to spontaneously form the naphthopyrone. In the presence of the TE/CLC domain, the intermediate undergoes C-C cyclization to from the norsolorinic acid anthrone, which autooxidizes to form norsolorinic acid, (c) Observed PPant ejection ions confirming the structures of the proposed intermediates bound to the active site of the PksA T domain. The first intermediate (left) was detected on the T domain active site after incubation of SAT-KS-MAT with T domain alone. Incubation of SAT-KS-MAT with PT-T results in the formation of the intermediates containing first a single-cyclization product (middle) followed by a double-cyclization product (right).

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