Benzene charge-transfer osmylation

Charge-transfer Osmylation cf Benzene, Naphthalene and Anthracene... 

The use of lower temperatures in the bromate-induced monobromopenta-hydroxylation of benzene by catalytic photoinduced charge transfer osmylation favours formation of the neo diastereoisomer of the deoxybromoinositol. Photolysis of N-(diphenylamino)-2,4,6-trimethylpyridinium tetrafluoroborate and N-[bis(4-methylphenyl)amino]-2,4,6-trimethylpyridinium salts induces nucleophilic addition of various 7i-nucleophiles such as electron rich alkenes to the o- and p-positions of one of the phenyl rings.These observations are thought to imply the presence of the diarylnitrenium ion (Ar2N ) as intermediate, but evidence is also presented for the involvement of radical species, as well as for the formation of indoles and indolinones. Some MO calculations are also reported. 

Photoinduced Charge Transfer Osmylation. The reaction of osmium tetroxide with benzenoid derivatives can only be accomplished by irradiation of the mixture. This reaction had previously been shown to work (with stoichiometric osmium tetroxide) by promotion of charge transfer between the two reactants to form an ion-pair this can then collapse to form an osmate ester of benzene diol. Subsequent dihydroxylation of this intermediate appears to follow a more conventional (and stereoselective) course. The use of catalytic osmium tetroxide (in conjunction with barium perchlorate as a reoxidant) for this reaction is noteworthy, as is the formation of both inositol and conduritol derivatives in one-pot (eq SS). The photoinduced osmylation of mono-substituted arenes was possible although the yields were lower and the amount of cyclitol-type products reduced. 

Benzene and toluene have also been transformed into cyclohexitols by way of a catalytic photoinduced charge-transfer osmylation in the presence of 0.22 M barium(II) chlorate. Higher concentrations of the chlorate cause a chlorine atom to be incorporated. Hydrogenation of tetrahydroxyquinone in the presence of a large amount of palladium on charcoal produces cu-inositol in modest yield. l,3,5-Trideoxy-l,3,5-tris(dimethylamino)-cw-inositol has been shown to be a powerful ligand for hard, highly charged metal ions. ... 

Photochemical osmylation. The irradiation of the charge-transfer bands (Fig. 13) of the EDA complex of 0s04 with various benzenes, naphthalenes, anthracenes, and phenanthrene yields the same osmylated adducts as obtained in the thermal reactions. For example, irradiation of the purple solution of anthracene and 0s04 in dichloromethane at k > 480 nm yields the same 2 1 adduct (B) together with its syn isomer as the sole products, i.e.,... 

Molecular complexes of OSO4 with various substituted benzenes, naphthalenes, and anthracenes have been identified by their charge-transfer absorption, which follows the Mulliken correlation in Eq. 8 [114, 161], The arene-0s04 complexes are quite stable when kept in the dark and only very slowly form osmium(VI) cycloadducts by thermal osmylation (Eq. 30). 

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