5131-95-3Relevant articles and documents
EPR studies of the formation and transformation of isomeric radicals [C3H5O].. Rearrangement of the allyloxyl radical in non-aqueous solution involving a formal 1,2-hydrogen-atom shift promoted by alcohols
Elford, Patrick E.,Roberts, Brian P.
, p. 2247 - 2256 (1996)
At 220 K in cyclopropane solvent, hydrogen-atom abstraction from allyl alcohol by Bu'O., EtO., PhMe2CO., (Me3Si)2N. or triplet-state acetone gives the 1-hydroxyallyl radical 3 as a ca. 3:1 mixture of the syn- and anti-isomers. In contrast, the allyloxyl radical does not react with allyl alcohol to bring about abstraction of hydrogen, but instead undergoes a more rapid alcohol-promoted rearrangement to give 3 as a ca. 1:1 mixture of the syn- and anti-forms. 2-Methylallyl alcohol, ethanol and propan-2-ol also induce this formal 1,2-H-atom shift in the allyloxyl radical. In the presence of ethan[2H]ol, both 3 and (3-OD) are formed and as [EtOD] is increased from 0.3 to 3.6 mol dm-3 [3-OD]/[3] first passes through a maximum value of ca. l and then decreases to 0.38. It is proposed that there is more than one mechanism for the alcohol-induced rearrangement of the allyloxyl radical, one that involves assisted migration of hydrogen from the α-carbon atom to the oxygen atom and another that results in incorporation of deuterium from the EtOD. The importance of the latter mechanism decreases at high alcohol concentrations and this behaviour is thought to be related to the extent of association of the alcohol by hydrogen-bonding. The allyloxyl radical was generated by UV photolysis of allyl tert-butyl peroxide and by ring opening of the oxiranylmethyl radical, derived from epibromohydrin or epichlorohydrin by halogen-atom abstraction. Ab initio molecular orbital calculations predict that an unassisted 1,2-H-atom shift in the allyloxyl radical will involve a very large activation energy. The alcohol is believed to serve a dual function in promoting the rearrangement: first, to increase the acidity of the α-CH2 group by hydrogen-bonding to the oxygen atom of the allyloxyl radical and, secondly, to provide a basic oxygen atom to facilitate the transfer/removal of a protic α-hydrogen atom.
The reactivity of ketyl and alkyl radicals in reactions with carbonyl compounds
Denisov
, p. 2110 - 2116 (2007/10/03)
A parabolic model of bimolecular radical reactions was used for analysis of the hydrogen transfer reactions of ketyl radicals: >C+OH + R1COR2 → >C=O + R1R2C+OH. The parameters describing the reactivity of the reagents were calculated from the experimental data. The parameters that characterize the reactions of ketyl and alkyl radicals as hydrogen donors with olefins and with carbonyl compounds were obtained: >C+OH + R1CH=CH2 → >C=O + R1C+ HCH3; >R1CH=CH2 + R2C+HCH2R3 → R2C+HCH3 + R2CH=CHR3. These parameters were used to calculate the activation energies of these transformations. The kinetic parameters of reactions of hydrogen abstraction by free radicals and molecules (aldehydes, ketones, and quinones) from the C-H and O-H bonds were compared.
Indolequinone antitumor agents: Reductive activation and elimination from (5-methoxy-1-methyl-4,7-dioxoindol-3-yl)methyl derivatives and hypoxia- selective cytotoxicity in vitro
Naylor, Matthew A.,Swann, Elizabeth,Everett, Steven A.,Jaffar, Mohammed,Nolan, John,Robertson, Naomi,Lockyer, Stacey D.,Patel, Kantilal B.,Dennis, Madeleine F.,Stratford, Michael R. L.,Wardman, Peter,Adams, Gerald E.,Moody, Christopher J.,Stratford, Ian J.
, p. 2720 - 2731 (2007/10/03)
A series of indolequinones bearing a variety of leaving groups at the (indol-3-yl)methyl position was synthesized by functionalization of the corresponding 3-(hydroxymethyl)indolequinone, and the resulting compounds were evaluated in vitro as bioreductively activated cytotoxins. The elimination of a range of functional groups-carboxylate, phenol, and thiol- was demonstrated upon reductive activation under both chemical and quantitative radiolytic conditions. Only those compounds which eliminated such groups under both sets of conditions exhibited significant hypoxia selectivity, with anoxic:oxic toxicity ratios in the range 10-200. With the exception of the 3-hydroxymethyl derivative, radiolytic generation of semiquinone radicals and HPLC analysis indicated that efficient elimination of the leaving group occurred following one-electron reduction of the parent compound. The active species in leaving group elimination was predominantly the hydroquinone rather than the semiquinone radical. The resulting iminium derivative acted as an alkylating agent and was efficiently trapped by added thiol following chemical reduction and by either water or 2-propanol following radiolytic reduction. A chain reaction in the radical-initiated reduction of these indolequinones (not seen in a simpler benzoquinone) in the presence of a hydrogen donor (2-propanol) was observed. Compounds that were unsubstituted at C-2 were found to be up to 300 times more potent as cytotoxins than their 2-alkyl-substituted analogues in V79-379A cells, but with lower hypoxic cytotoxicity ratios.
