Acyl anthracenes

For the acylation of naphthalene, the ionic liquid gives the highest reported selectivity for the 1-position [95]. The acetylation of anthracene at 0 °C was found to be a reversible reaction. The initial product of the reaction between acetyl chloride (1.1 equivalents) and anthracene is 9-acetylanthracene, formed in 70 % yield in less than 5 minutes. The 9-acetylanthracene was then found to undergo diacetylation reactions, giving the 1,5- and 1,8-diacetylanthracenes and anthracene after 24 hours (Scheme 5.1-64). 

The important bluish mixing component 11.22 for whitening polyester is made by Friedel-Crafts acylation of pyrene (Scheme 11.17). This tetracyclic hydrocarbon is not unlike anthracene in its susceptibility to substitution reactions. The most stable bond arrangement in pyrene appears to be that shown as form 11.47a, which contains three benzenoid (b) rings. Canonical form 11.47b, containing only two such rings, contributes to a lesser extent (Scheme 11.18). In all monosubstitutions, pyrene is attacked initially at the 3-position, corresponding to the a-positions in anthracene or naphthalene. 

As described above, when CuCl is regenerated in the reaction, the process can be catalytic in copper. In other cases, a stoichiometric amount (2 equiv.) of CuCl is used. Although CuCN shows similar reactivity, CuBr and Cul are not so effective as compared to CuCl. Allylation benzene, naphthalene, and anthracene formation, as well as acylation are representative examples, which are described below. 

Anthraquinone itself is traditionally available from the anthracene of coal tar by oxidation, often with chromic acid or nitric acid a more modern alternative method is that of air oxidation using vanadium(V) oxide as catalyst. Anthraquinone is also produced in the reaction of benzene with benzene-1,2-dicarboxylic anhydride (6.4 phthalic anhydride) using a Lewis acid catalyst, typically aluminium chloride. This Friedel-Crafts acylation gives o-benzoylbenzoic acid (6.5) which undergoes cyclodehydration when heated in concentrated sulphuric acid (Scheme 6.2). Phthalic anhydride is readily available from naphthalene or from 1,2-dimethylbenzene (o-xylene) by catalytic air oxidation. 

Formally related reactions are observed when anthracene [210] or arylole-fines [211-213] are reduced in the presence of carboxylic acid derivatives such as anhydrides, esters, amides, or nitriles. Under these conditions, mono- or diacylated compounds are obtained. It is interesting to note that the yield of acylated products largely depends on the counterion of the reduced hydrocarbon species. It is especially high when lithium is used, which is supposed to prevent hydrodimerization of the carboxylic acid by ion-pair formation. In contrast to alkylation, acylation is assumed to prefer an Sn2 mechanism. However, it is not clear if the radical anion or the dianion are the reactive species. The addition of nitriles is usually followed by hydrolysis of the resulting ketimines [211-213]. 

Anthracenes from ort/io-acyl diarylmethanes via acid-catalyzed cyclodehydration. 

The 3-acyl-2(3F/)-oxazolones function as good dienophiles in cycloaddition reactions with cyclic 2,4-dienes such as cyclopentadienes and anthracenes. Thus, the thermal reaction of 3-acetyl-2(37/)-oxazolone with cyclopentadiene and the hexachloro and hexamethyl derivatives gives endo-cycloadducts exclusively. In particular, the chiral cycloadducts 221 and 223 derived from the diastereoselective Diels-Alder reactions of 3-(2-exo-alkoxy-l-apocamphanecarbonyl)-2(3/7)-oxazo-lones with hexamethylcyclopentadiene and 9,10-dimethylanthracene, respectively, are highly useful as chiral 2-oxazolidinone auxiliaries. The conformationally rigid roofed structures play a crucial role in affording excellent chiral induction (Fig. 5.54). 

The alkylation of enolates from some recently developed 2-oxazolidinone auxiliaries will be briefly discussed. The Diels-Alder reaction of the enantiomerically pure 3-(apocamphane-carbonyl)-2(3//)-oxazolone 13 with anthracene gives, diastereoselectively, a 97 3 ratio of diastereomeric adducts63. Recrystallization followed by removal of the apocamphanecarbonyl auxiliary and acylation gives the diastereomerically pure enantiomer 14 in good yield. Subsequent enolate formation and alkylation gives highly diastereoselective reactions and easily purified products due to the fact that the major product is readily crystallized. Thus alkylation... 

Friedel-Crafts reactions in the ionic liquid system l-methyl-3-ethylimidazolium chlo-ride-aluminium(ni) chloride can be performed with excellent yields and selectivities, and in the case of anthracene, have been found to be reversible. This ionic liquid has been shown to demonstrate catalytic activity in reactions such as Friedel-Crafts acylations (Surette et al., 1996 Boon et al., 1986) alkylation reactions (Koch et al., 1976),... 

Sulfonamides prepared from 9-(chlorosulfonyl)anthracene and polystyrene-bound primary amines can be converted into amides by N-acylation of the sulfonamide (carboxylic acid anhydride, DMAP, pyridine, THF, 24 h) followed by nucleophilic desulfo-nylation with neat 1,3-propanedithiol/DIPEA [213] (Entry 4, Table 10.13). An example of the use of sulfonamides as linkers for amines is given in Table 3.23. 

The AuCl-catalysed 4 + 2-cycloaddition of benzyne with o-alkynyl(oxo)benzenes produced anthracene derivatives having a ketone in the 9-position, in good to high yields under mild conditions.118 Hypervalent iodine compounds, [5-acyl-2-(trimethyl-silyl)]iodonium triflates, readily yielded acylbenzynes which could be trapped with furan.119 Both DMAD and benzyne reacted with borabenzene to yield substituted borabarrelenes and borabenzobarrelenes, respectively.120... 

A Convenient method for obtaining pure 2-acylphenanthrene is the acylation of 9,10-dihydrophenanthrene followed by sulfur dehydrogenation. In this case, only the 2-position is attacked the over-all yield is about 48%. Anthracene is acylated in the 9-position (60%). The isomeric acetylacenaphthenes have been prepared from the hydrocarbon and acetic... 

Many organic compounds react with carboxylic acids, acyl halides, or anhydrides in the presence of certain metallic halides, metallic oxides, iodine, or inorganic acids to form carbonyl compounds. The reaction is generally applicable to aromatic hydrocarbons. Benzene, alkylbenzenes, biphenyl, fluorene, naphthalene, anthracene, acenaphthene, phenanthrene, higher aromatic ring systems, and many derivatives undergo the reaction. 

Nitrosyl cyanide (109) has been briefly examined as a dienophile by Kirby et This intermediate can be generated from nitrosyl chloride and silver cyanide (equation 42) and trapped with 9,10-diinethyl-anthracene to yield adduct (110). As with acyl nitroso compounds, this adduct can be used as a stable source of (109) via a retro Diels-Alder reaction. 

Microwave irradiation of a mixture of an acid anhydride, an amine adsorbed on silica gel, and TaCl5/Si02 is a solvent-free method for the synthesis of A-alkyl and A-aryl-imides [47]. Ni(II) promotes the conversion of an acrylamide to ethyl acrylate via a Diels-Alder adduct with (2-pyridyl)anthracene [48], Aromatic carboxylic acids [49] and mandelic acid [50] are efficiently esterified with Fc2(S04)3 XH2O as catalyst. Co(II) perchlorate in MeOH catalyzes the methanolysis of acetyl imidazole and acetyl pyrazole [51]. Hiyama et al. used FeCb as a catalyst for the acylation of a silylated cyanohydrin. The resulting ester was then cyclized to 4-amino-2(5H)-furanones (Sch. 5) [52]. 

Air, the cheapest oxidant, is used only rarely without irradiation and without catalysts. Examples of oxidations by air alone are the conversion of aldehydes into carboxylic acids (autoxidation) and the oxidation of acyl-oins to a-diketones. Usually, exposure to light, irradiation with ultraviolet light, or catalysts are needed. Under such circumstances, dehydrogenative coupling in benzylic positions takes place at very mild conditions [7]. In the presence of catalysts, terminal acetylenes are coupled to give diacetylenes [2], and anthracene is oxidized to anthraquinone [3]. Alcohols are converted into aldehydes or ketones with limited amounts of air [4, 5, 6, 7], Air oxidizes esters to keto esters [3], thiols to disulfides [9], and sulfoxides to sulfones [10. In the presence of mercuric bromide and under irradiation, methylene groups in allylic and benzylic positions are oxidized to carbonyls [11]. 

Derivatives of anthracene are seldom prepared from anthracene itself, but rather by ring-closure methods. As in the case of naphthalene, the most important method of ring closure involves adaptation of Friedel-Crafts acylation. The products initially obtained are anthraquinones, which can be converted into corresponding anthracenes by reduction with zinc and alkali. This last step is seldom carried out, since the quinones are by far the more important class of compounds. 

Anthracene, 9,10-dihydro-9,9-dimethyl-as antidepressant, 1, 169 Anthracene, 1,4,5,8,9-pentamethyl-synthesis, 2, 537 Anthracyclinones synthesis, 1, 414, 4, 700 Anthramycin synthesis, 7, 614 Anthranil, 3-acyl-rearrangement, 5, 93 Anthranil, 3-aiyl-acridones from, 2, 93 thermolysis, 5, 91 Anthranil, 3-(imidazol-2-yl)-rearrangement, 5, 433 Anthranil, 6-nitro-reactions... 

Iodine in trace amounts has been used as catalyst in Friedel-Crafts acylations of furane and thiophene and of more active members of the benzene series such as anisole and acetanilide. " Oddly enough, it is not effective for benzoylation of anthracene.""... 

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