20333-68-0Relevant articles and documents
Concerted mechanisms of the reactions of phenyl and 4-nitrophenyl chlorothionoformates with substituted phenoxide ions
Castromaria Cubillos, Enrique A.,Santos, José G.
, p. 6820 - 6823 (1998)
The title reactions are subjected to a kinetic study in 3% (v/v) dioxane in water, 25.0 °C, ionic strength 0.2 M (KC1). By following the reactions spectrophotometrically, pseudo-first-order rate coefficients (￡0bsd) are found under an excess of the nucleophile. Plots of ￡0bsd vs phenoxide anion concentration at constant pH are linear, with the slope (￡N) independent of pH. The Bro?nstedtype plots (log AN vs pKa of the phenols) are linear with slopes β= 0.55 and 0.47 for the reactions of the phenyl and the 4-nitrophenyl derivatives, respectively. These Bro?nsted slopes are in agreement with the ones found in the concerted reactions of the same nucleophiles with reactive phenyl esters and acetic anhydride in water. In contrast to the concerted mechanism of the title reactions that of the same substrates with secondary alicyclic amines is stepwise, which means that substitution of an amino moiety in a tetrahedral intermediate with a phenoxy group by another phenoxy group destabilizes the intermediate to the point that it no longer exists.
Radical OfC transposition: A metal-free process for conversion of phenols into benzoates and benzamides
Baroudi, Abdulkader,Alicea, Jeremiah,Flack, Phillip,Kirincich, Jason,Alabugin, Igor V.
, p. 1521 - 1537 (2011/06/11)
We report a metal-free procedure for transformation of phenols into esters and amides of benzoic acids via a new radical cascade. Diaryl thiocarbonates and thiocarbamates, available in a single high-yielding step from phenols, selectively add silyl radicals at the sulfur atom of the CdS moiety. This addition step, analogous to the first step of the Barton-McCombie reaction, produces a carbon radical which undergoes 1,2 OfC transposition through an O-neophyl rearrangement. The usually unfavorable equilibrium in the reversible rearrangement step is shifted forward via a highly exothermic C-S bond scission in the O-centered radical, which furnishes the final benzoic ester or benzamide product. The metal-free preparation of benzoic acid derivatives from phenols provides a potentially useful alternative to metal-catalyzed carbonylation of aryl triflates.
Radical 1,2-o→c transposition for conversion of phenols into benzoates by o-neophyl rearrangement/fragmentation cascade
Baroudi, Abdulkader,Alicea, Jeremiah,Alabugin, Igor Y.
supporting information; experimental part, p. 7683 - 7687 (2010/08/22)
Figure Presented Radical merry-go-round! Diaryl thiocarbonates, available in a single step from phenols, can be directly transformed into benzoates by a new radical cascade that transposes O and C atoms at the aromatic core. The cascade bypasses the common Barton McCombie fragmentation in favor of the usually unfavorable O-neophyl rearrangement, which is rendered irreversible and efficient by a highly exothermic C-S bond scission in the O-centered radical (see scheme; FG = functional group).
