- The Mechanisms of the Conversion of Thiophosphoryl Compounds into their Phosphoryl Analogues by Photochemically Excited 3-Methylpyridazine 2-Oxide and by 2-Methyl-3-p-nitrophenyloxaziridine; a Comparison
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Reactions of tri-p-substituted triarylphosphine sulphides with 3-methylpyridazine 2-oxide, under photolysis, and with 2-methyl-3-p-nitrophenyloxaziridine both give the corresponding phosphine oxides.A detailed study and comparison of the two reactions shows that they are mechanistically quite distinct and that it is unlikely that the active oxygenating species generated by photolysis of the N-oxide, which attacks the phosphine sulphides, is an oxaziridine.The evidence presented suggests that this species may in fact be 'oxene'.
- Rowley, Alan G.,Steedman, John R. F.
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p. 1113 - 1120
(2007/10/02)
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- Relative Conjugative Abilities of Three-Membered Ring Heterocycles with Benzene Based on 13C and 15N NMR
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The conjugative ability of various three-membered rings with benzene was investigated by observing the sensitivity of β-carbon 13C chemical shifts to para substituents.These Hammett ρ values were 2.0, 1.5, 1.0, and 0.9 ppm for arylcyclopropanes, N-methyl-2-arylaziridines, phenyloxiranes, and N,N-dimethyl-2-arylaziridinium fluorosulfonates, respectively.These values were intermediate to ones for para-substituted styrenes (6.5 ppm) and ethylbenzenes (-0.9 ppm), model compounds which were taken to represent extremes of conjugative ability.Similar results were found for 15N chemical shifts of trans-3-aryl-oxaziridines, which had a slope of 2.1 ppm, intermediate to those for benzylimines (20.2 ppm) and benzylamines (-1.3 ppm).The order of conjugative ability, which decreases with increasing electronegativity of the hetero group, could not be explained by hybridization changes based on comparing open chain analoques with the above compounds or by conformational factors.The trend can, however, be interpreted qualitatively by perturbation theory which shows that more electronegative hetero groups decrease the extent of interaction between aryl-? and cyclopropane orbitals as well as cross ring conjugation.
- Crist, DeLanson R.,Jordan, Guy J.,Moore, Donald W.,Hashmall, Joseph A.,Borsetti, Arnold P.,Turujman, Saleh A.
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p. 4136 - 4142
(2007/10/02)
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