10-Methylacridinium salts

In the presence of hydrogen peroxide and base, acridinium salts lead to chemiluminescence emission. Acridans, in their reduced forms, are able to react directly with oxygen in aprotic solvents with cl up to 10%246. Scheme 31 shows the proposed mechanism for chemiluminescence of 9-cyano-10-methylacridan and 9-cyano- 10-methylacridinium salt in the presence of oxidant and base, which postulates the cyclic peroxidic intermediate 44. 

Fission of the Sn-C bond in the stannanes (181) takes place on irradiation in the presence of 10-methylacridinium salts. The process is induced by a single electron transfer and this affords the cation that leads to (182). The other product obtained in the reaction is (183). ... 

Stable anhydro bases, e.g. (64), can be formed from 1-alkyl- or 1-benzyl-isoquinolinium salts on treatment with alkali the reaction is reversed in acid. 9-Methylacridinium salts similarly form stable anhydro bases, e.g. (65 Scheme 52). 

Treatment of tetramethylpiperidine and Y-methylacridinium salt [MA]" in the presence of a catalytic amount of the ruthenium complex [Cp RuH(dppm)] under gives monodeuterated products MAD and piperidinium salt in quantitative yields, respectively (Eq. 5). The stoichiometric reactions of [Cp RuH(dppm)] with Y-methylacridium salt [MA] in CHjCN or THF afford [Cp Ru(S)(dppm)] (S = CHjCN or THF) and MAH in high yields, respectively. This shows that the hydride at the Ru center is readily transferred to the acridium salt. A catalytic cycle proposed by Hembre and co-worker is shown in Scheme 6, where tetramethylpiperidine behaves as a base and the acridinium salt as a hydride... 

The aminoarylation of 9-methylacridinium salts with aromatic amines provides a well-established example of a SET from arylamines to the acridinium ion, as evidenced by the formation of diacridanyl and arylamine radical cation species (Scheme 62). Also, treatment of W-methylacridinium ion with W,W -tetramethyl-para-phenylenediamine, as the model compound, gave the characteristic color of the Wurster s Blue radical cation [11, 136, 137]. 

Redox disproportionation reactions of carbonylmetal species are a versatile preparative method for carbonylmetallates, and [Fe3(CO)ii(/t-H)] salts 2 are formed by the reaction of Fe2(CO)9 with THF a or A, A -diaryltetrahydropyrrolo-[2,l-f][l,4]-oxazine-3,4-diylidenediamine b. The anion 2 is also obtained by treatment of 1 with 1,3,5-trimethyl-1,3,5-triazacyclohexane via an apparent /3-hydride elimination c and by reaction of [Fe2(CO)8] with a methylacridinium salt (detected by IR). The cations of the obtained compounds are as shown below. 

Alkaline solutions of alkylpyridinium salts contain increasing amounts of pseudobases (106 equation 83) in equilibrium with the charged form as the series 1-methylquinolinium, 2-methylisoquinolinium, 10-methylphenanthridinium and 10-methylacridinium is traversed. Such species were first postulated as a result of the observation that alkaline solutions of quaternary salts do not obey the Beer-Lambert law. Pseudobase formation at... 

Amination of AT-alkylpyridinium salts with amide ions, which in principle should be easier than the reaction with the parent pyridine, has been little studied. The main reason for this is that solvent selection is difficult. Metal amides are only soluble in liquid ammonia (with which pyridinium salts react easily, vide infra), and pyridinium salts are soluble in solvents that are not suitable for use with metal amides. The A/ -methylacridinium cation undergoes direct imination to give (153) in 35% yield by treatment with potassium amide and iron (III) nitrate in liquid ammonia. Two other products (154) and (155) are also formed, probably by hydrolysis and subsequent disproportionation (Scheme 90). One might question whether sodamide is necessary to the above transformation in light of the fact that quin-olinium, isoquinolinium and certain pyridinium ions give cr-complexes (156), (157) and (158) in liquid ammonia alone at 0 °C (73JOC1949). 

Pyridine compounds in which phosphorus is directly attached to a ring carbon are relatively rare. Phosphorus nucleophiles are not able to replace ring hydrogen atoms in pyridines and pyridine 1-oxides. Some time ago it was found that pyridine yields a zwitterion (170) when it is heated under reflux in the presence of tetraphosphorus decasulfide (Scheme 105) (68MI20500). Recently, a product that contains a C—P bond was isolated after extended heating under the same conditions followed by treatment with hydrochloric acid (81 JCR(S)285). However, it is uncertain whether free pyridine undergoes reaction in this case. Attack by phosphorus nucleophiles on salts is well established. Af-Methylacridinium methosulfate affords a stable isolable 9,10-dihydro adduct (171) that readily forms a... 

A -Methylacridinium-4-olate (352 R = Me) has been obtained as a black solid which gives violet aqueous solutions. The method of preparation involves demethylation (AICI3) of a 4-methoxyacridinium salt followed by treatment of the resulting A-methyl-4-hydroxyacridinium salt with moist... 

The dioxetane (29) has been obtained quantitatively by photo-oxygenation of 9-(2-adamantylidene)-iV-methylacridan in CH2CI2 at -72 C using Methylene Blue as sensitizer. In toluene at 25 °C, (29) is catalytically decomposed by lanthanide chelates with energy transfer. Base-induced oxygenation and chemiluminescence of 10-methylacridinium and 1-methylquinolinium salts have been observed in DMSO. The chemiluminescence has its origin in... 

Heteroaromatic cations undergo reduction when treated with 1,4-dihydronicotinamide. An early study showed that the 10-methylacridinium ion (87) was rapidly reduced in a redox reaction to the 9,10-dihydro adduct by 1,4-dihydronicotinamides (M Scheme 18). A variety of systems including py-ridines, isoquinolines, quinolines and phenanthridines have been studied using this and related procedures. The selective reduction of pyridinium and quinolinium salts with 1-benzyl-1,2-dihydro-isonicotinamide (89) has been achieved. The selective conversion to the thermodynamically more stable 1,4-dihydro species (90 Scheme 18) is rationalized by the reversibility in the formation of the kinetic products (i.e. the 1,2-adducts) in the presence of pyridinium ions. In the pyridinium case 1,6-di-hydro adducts were also observed in some cases. Reactivity in such systems is sometimes hindered due to hydration of the dihydropyridine system. This is particularly so in aqueous systems designed to replicate biological activity. Dihydroazines derived from isoquinolines and 3,5-disubstituted pyridines have been reported to overcome some of these difficulties. ... 

The isostructural pentacarbonyl metallates Mn(CO)5 and Re(CO)5" form a series of thermally or photochemically unstable charge-transfer salts with N-methylpyridinium cations. For example, A-methylacridinium reacts with penta-carbonylrhenate immediately upon mixing in acetonitrile to form the (A-methyl-9-acridanyl)pentacarbonylrhenium(I) adduct in 90 % yield [126] (Eq. 46). 

Mukaiyama aldol reactions using a catalytic amount of a Lewis acidic metal salt afford silylated aldols (silyl ethers) as major products, but not free aldols (alcohols). Three mechanistic pathways which account for the formation of the silylated aldols are illustrated in Scheme 10.14. In a metal-catalyzed process the Lewis acidic metal catalyst is regenerated on silylation of the metal aldolate by intramolecular or intermolecular silicon transfer (paths a and b, respectively). If aldolate silylation is slow, a silicon-catalyzed process (path c) might effectively compete with the metal-catalyzed process. Carreira and Bosnich have concluded that some metal triflates serve as precursors of silyl triflates, which promote the aldol reaction as the actual catalysts, as shown in path c [46, 47]. Three similar pathways are possible in the triarylcarbenium ion-catalyzed reaction. According to Denmark et al. triarylcarbenium ions are the actual catalysts (path b) [48], whereas Bosnich has insisted that hydrolysis of the salts by a trace amount of water generates the silicon-based Lewis acids working as the actual catalysts (path c) [47]. Otera et al. have reported that 10-methylacridinium perchlorate is an efficient catalyst of the aldol reaction of ketene triethylsilyl acetals [49]. In this reaction, the perchlorate reacts smoothly with the acetals to produce the actual catalyst, triethylsilyl perchlorate. 

Two mechanistic studies relevant to photocuring processes have appeared. One deals with the efficient photoinduced generation of radical cations in solvents of medium and low polarity ". These cations act as sensitizers of the polymerization of N-methylacridinium hexafluorophosphate. The other is a study of the photochemistry of triarylsulphonium salts . 

Reductive alkylation of N-methylacridinium (87) occurs when it is irradiated with carboxylic acid salts. The reaction is thought to proceed by electron transfer from the carboxylate to the excited acrldinium ring followed by decarboxylation of RCOO coupling of the alkyl radical produced with the acridinyl radical then gives (88). A very similar sequence probably occurs in a reaction proposed as a synthetic procedure for decarboxylation of carboxylic acids.In this case an aza-aromatic compound such as acridine is irradiated with a carboxylic acid in benzene in the presence of tert-butyl thiol. The authors propose that a hydrogen bonded acridine-acid complex is excited and that adiabatic proton transfer is followed by electron transfer. This produces RCOO which decarboxylates, and reduction of the alkyl radical then ensues. The major fate of the acridine is coupling to (89) if the reaction is perfonned in the absence of oxygen. 

Unequivocal evidence for the formation of o -adducts has been obtained by X-ray diffraction analysis of those adducts which are stable enough to obtain their single crystals [11]. Indeed, the X-ray crystallography data are available for the anionic trinitrobenzene-methoxide and the Janovsky trinitrobenzene-acetone complexes [11, 201, 202] and for the o -adducts of isoquinoline [203], phthalazine [160], and 4,7-phenanthroline [161, 162] with dialkyl phosphonates. Also the X-ray data have been obtained for the neutral o -adducts resulting from the reactions of iV-methylacridinium ion with N-nucleophiles [204, 205] and for the o -adducts of iV-alkyl-substituted 2,3-dicyanopyrazinium and quinoxalinium salts with 0-, C-and P-nucleophiles [163, 194]. 

New catalysts have heen recently developed for promoting the aldol-type addition of acetate-derived silyl ketene acetals with high efficiency 10-methylacridinium perchlorate (5 mol %), cationic mono- and dinuclear iron complexes (5 mol %), t-hutyldimethylsilyl chloride-indium(III) chloride (10 mol %), [l,2-henzenediolato(2—)-0,0 ]oxotitanium(20 mol%), phos-phonium salts (7 mol%), and trityl salts (5-20 mol%). ... 

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