Hydrogen auto-transfer

The alcohol-unsaturate couplings developed in our laboratory provide products of carbonyl addition. In contrast, related hydrogen auto-transfer processes provide products of alcohol substitution via pathways involving oxidation-condensation-reduction and the use of preactivated nucleophiles. For recent reviews, see [22-25]. 

Perhaps the most significant aspect of the superoxide-, hydroxide-, or electron-induced auto-oxidation of donor molecules (1,2-diphenylhydrazine, dihydrophenazine, dihydro-lumiflavin, and reduced flavoproteins) is the activation of dioxygen to hydrogen peroxide in biological matrices. Thus, within the normal cytochrome P-450 metabolic cycle, either hydroxide ion or an electron-transfer co-factor acts as an initiator (probably to produce Fl -) and reduced flavoproteins act as the H-atom donor. In contrast, the introduction of 02 - or hydrated electrons (from ionizing radiation or a disease state) into a biological matrix that contains donor molecules leads to the uncontrolled formation of hydrogen peroxide. If reduced metal ions are present, Fenton... 

N. Shindoh, H. Tokuyama, Y. Takemoto, K. Takasu, J. Org. Chem. 2008,73, 7451-7456. Auto-tandem catalysis in the synthesis of substituted quinolines from aldimines and electron-rich olefins cascade Povarov-hydrogen-transfer reaction. 

Electron transfer is considered to take place to the oxygen molecule to give the Oa radical with subsequent hydrogen-atom abstraction from the hydroxylamine yielding HOa and HNO. The mechanism of auto-oxid-ation of triethylborane in the presence of iodine has been described. Induction periods observed are dependent on the iodine oxygen concentration ratios, and a chain-reaction mechanism is proposed involving both ethyl and ethylperoxy-radicals. 

The synthesis started from 6-nitrocyclohex-2-enone 249 to provide the catechol 250 by two kinds of methodologies including the hydrogen transfer reaction followed by the auto-redox-catalytic reaction. Oxadecalin 247 was synthesized from glycosyl cyanide 246. The [3+3] cycloadduct was afforded in one pot by treatment of ketone 247 with AI2O3 in situ to form the enone 248, and then reacted with catechol 250 in the presence of boron trifluoride. The target product ep/-cochlioquinone A 252 was afforded after a series of regular reactions [110]. 

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