- Reactions of aryl phenylacetates with secondary amines in MeCN. Structure-reactivity relationship in the ketene-forming eliminations and concurrent E2 and E1cb mechanisms
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Elimination reactions of aryl esters of arylacetic acids 1 and 2 promoted by R2NH in MeCN have been investigated kinetically. The reactions are second-order and exhibit β = 0.44-0.84, β(lg) = 0.41-0.50, and ρ(H) = 2.0-3.6. Bronsted β and β(lg) decrease with the electron-withdrawing ability of the β-aryl substituent. Hammett ρ(H) values remain nearly the same, but the β(lg) value increases as the base strength becomes weaker. Both ρ(H) and β decrease with the change of the leaving group from 4-nitrophenoxide to 2,4-dinitrophenoxide. The results are consistent with an E2 mechanism and a reaction coordinate with a large horizontal component corresponding to proton transfer. When the base-solvent system is changed from R2NH-MeCN to R2NH/R2NH2+-70 mol% MeCN(aq), the Bronsted β, ρ(H), and β(lg) decrease. Finally, the ketene-forming elimination reactions from p-nitrophenyl p-nitrophenylacetate promoted by R2NH/R2NH2+ buffers in 70 mol% MeCN(aq) have been shown to proceed by concurrent E2 and E1cb mechanisms.
- Cho, Bong Rae,Kim, Yong Kwan,Yoon, Choon-Ock Maing
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p. 691 - 697
(2007/10/03)
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- SYNTHESIS OF ALKYL HALIDES UNDER NEUTRAL CONDITIONS
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Primary and secondary alcohols are efficiently converted to the corresponding alkyl halides under neutral conditions.
- Munyemana, Francois,Frisque-Hesbain, Anne-Marie,Devos, Alain,Ghosez, Leon
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p. 3077 - 3080
(2007/10/02)
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- PREPARATION OF GLYCOSYL HALIDES UNDER NEUTRAL CONDITIONS
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The anomeric hydroxyl group of various furanose and pyranose hemiacetals can be replaced by a fluorine, chlorine, bromine or iodine atom under neutral conditions using haloenamines.
- Ernst, Beat.,Winkler, Tammo.
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p. 3081 - 3084
(2007/10/02)
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