- Relative Reactivities of Three Isomeric Aromatic Biradicals with a 1,4-Biradical Topology Are Controlled by Polar Effects
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Unexpectedly, the 5-dehydroquinoline radical cation was formed in the gas phase from the 5-iodo-8-nitroquinolinium cation upon ion-trap collision-activated dissociation. This reaction involves the cleavage of a nitro group to generate an intermediate monoradical, namely, the 8-dehydro-5-iodoquinolinium cation, followed by rearrangement through abstraction of a hydrogen atom from the protonated nitrogen atom by the radical site. Dissociation of the rearranged radical cation through elimination of an iodine atom generates the 5-dehydroquinoline radical cation. The mechanism was probed by studying isomeric biradicals and performing quantum chemical calculations. The 5-dehydroquinoline radical cation showed greater gas-phase reactivity toward dimethyl disulfide, cyclohexane, and allyl iodide than the isomeric 5,8-didehydroquinolinium cation, which is more reactive than the isomeric 5,8-didehydroisoquinolinium cation studied previously. All three isomers have a 1,4-biradical topology. The order of reactivity is rationalized by the vertical electron affinities of the radical sites of these biradicals instead of their widely differing singlet–triplet splittings.
- Ma, Xin,Jin, Chunfen,Wang, Duanda,Nash, John J.,Kentt?maa, Hilkka I.
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supporting information
p. 6355 - 6361
(2019/04/17)
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- Structure-activity relationships for pyrido-, imidazo-, pyrazolo-, pyrazino-, and pyrrolophenazinecarboxamides as topoisomerase-targeted anticancer agents
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Heterocyclic phenazinecarboxamides were prepared by condensation of aminoheterocycles and 2-halo-3-nitrobenzoic acids, followed by reductive ring closure and amidation. They showed similar inhibition of paired cell lines that underexpressed topo II or overexpressed P-glycoprotein, indicating a non topo II mechanism of cytotoxicity and indifference to P-glycoprotein mediated multidrug resistance. Compounds with a fused five-membered heterocyclic ring were generally less potent than the pyrido[4,3-a]phenazines. A 4-methoxypyrido[4,3-a]phenazine (IC50s 2.5-26 nM) gave modest (ca. 5 day) growth delays in H69/P xenografts with oral dosing.
- Gamage, Swarna A.,Spicer, Julie A.,Rewcastle, Gordon W.,Milton, John,Sohal, Sukhjit,Dangerfield, Wendy,Mistry, Prakash,Vicker, Nigel,Charlton, Peter A.,Denny, William A.
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p. 740 - 743
(2007/10/03)
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