- Oxyfunctionalization of non-natural targets by dioxiranes. 5. Selective oxidation of hydrocarbons bearing cyclopropyl moieties
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The powerful methyl(trifluoromethyl)dioxirane (lb) was employed to achieve the direct oxyfunctionalization of 2,4-didehydroadamantane (5), spiro[cyclopropane-1,2′-adamantane] (9), spiro[2.5]-octane (17), and bicyclo[6.1.0]nonane (19). The results are compared with those attained in the analogous oxidation of two alkylcyclopropanes, i.e., n-butylcyclopropane (11) and (3-methyl-butyl)-cyclopropane (14). The product distributions observed for 11 and 14 show that cyclopropyl activation of α-C-H bonds largely prevails when no tertiary C-H are present in the open chain in the tether; however, in the oxyfunctionalixation of 14 cyclopropyl activation competes only mildly with hydroxylation at the tertiary C-H. The application of dioxirane 1b to polycyclic alkanes possessing a sufficiently rigid framework (such as 5 and 9) demonstrates the relevance of relative orientation of the cyclopropane moiety with respect to the proximal C-H undergoing oxidation. At one extreme, as observed in the oxidation of rigid spiro compound 9, even bridgehead tertiary C-H's become deactivated by the proximal cyclopropyl moiety laying in the unfavorable eclipsed (perpendicular) orientation; at the other end, a cyclopropane moiety constrained in a favorable bisected orientation (as for didehydroadamantane 5) can activate an α methylene CH2 to compete effectively with dioxirane O-insertion into tertiary C-H bonds. Comparison with literature reports describing similar oxidations by dimethyldioxirane (1a) demonstrate that methyl(trifluoromethyl)dioxirane (1b) presents similar selectivity and remarkably superior reactivity.
- D'Accolti, Lucia,Dinoi, Anna,Fusco, Caterina,Russo, Antonella,Curci, Ruggero
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p. 7806 - 7810
(2007/10/03)
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- Regioselective Route to Sterically Hindered Cyclopropylcarbinyl Halides
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Reaction of cyclopropylcarbinyl alcohols 1 with hexachloroacetone and triphenylphosphine resulted in 80 - 90 percent yields of the corresponding cyclopropylcarbinyl chlorides 4 regioselectively, with no trace of the homoallylic chloride 2 or the chlorocyclobutane derivative 6a.Similar reaction of 1 with bromine and triphenylphosphine, in dimethylformamide, gave 65 - 80 percent yields of the cyclopropylcarbinyl bromide 5 with trace amounts of the homoallylic bromide 3 but no detectable bromocyclobutane derivative 6b.These reactions are amenable to the preparation of very sterically hindered cyclopropylcarbonyl halides, heretofore inaccessible, regioselectively and in a facile manner.
- Hrubiec, Robert T.,Smith, Michael B.
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p. 431 - 435
(2007/10/02)
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- Synthesis and Antimalarial Activity of 8--6-methoxy-4-methylquinolines
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Three analogues of the causal prophylactic antimalarial primaquine were prepared and their antimalarial activity was evaluated. 8--6-methoxy-4-methylquinoline (2a) demonstrated activity against Plasmodium berghei in mice at 20 mg/kg, with all animals cured at 320 mg/kg, and is without toxicity at 640 mg/kg.It also possessed outstanding causal prophylactic activity against Plasmodium cynomolgi in rhesus monkeys at very low dosages.
- Yan, Shou-Jen,Chien, Ping-Lu,Cheng, C. C.
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p. 215 - 217
(2007/10/02)
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