N-methylacridinium ion

The formal hydride transfer between NAD analogues has been interpreted as a multistep but nonchain process involving electron and proton transfers (Ohno et al., 1981) or alternatively as a one-step hydride transfer with an appreciable primary isotope effect (Ostovic et al., 1983). Although not as yet recognized, a free radical chain mechanism should be possible in certain cases where [8] transfers an electron to an easily reducible NAD analogue such as N-methylacridinium ion. The chain could continue by hydrogen atom abstraction from [8] by the N-methylacridinyl radical. 

Example 4. The Reaction of i-Benzyl-i,4-dihydronicotinimide (BNAH) with N-methylacridinium Ion (AdA ) in Acetonitrile. Detailed studies of the reactions of BNAH and analogs with substituted isoquinoHnium cations were pubhshed by Bunting and co-workers in the early 1980s and later reviewed. ... 

For instance, UV and nuclear magnetic resonance (NMR) studies of the reaction between A-methylacridinium ion and primary aromatic amines have revealed the formation of unstable N-adducts under kinetically controlled conditions (—50°C). Their formation is especially favored in case of anilines bearing in the /jara-position an electron-donating substituent R. At temperatures above 0°C, these N-adducts are gradually converted into thermodynamically more favored C-adducts. Also it has been shown that when no oxidant is added, the A-methylacridinium cation acts as oxidant of both N- and C-adducts, thus giving the corresponding products and 10-methyl-9,10-dihydroacridine (Scheme 36) [11, 136]. 

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]. 

Ohba, Y., Kubo, K., Igarashi, T, and Sakurai, T, Mechanism of the 10-methylacridinium ion-sensitized photooxidation of N,N-dibenzyLhydroxylamme and its derivatives in acetonitrile, /. Chem. Soc., Perkin Trans. 2, 491, 2001. 

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