116849-48-0Relevant articles and documents
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.
DIRECT CONVERSION OF PHENOLS INTO AMIDES AND ESTERS OF BENZOIC ACID
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Page/Page column 14-15; 17, (2011/10/12)
A method is provided for the preparation of an aromatic carboxylic acid aryl ester or an N-aryl aromatic carboxamide. The method comprises contacting an O,O-diaryl thiocarbonate or an O-aryl-N-aryl thiocarbamate with a reactant that regioselectively reacts with sulfur, which contact causes an O-neophyl rearrangement, thereby forming either the aromatic carboxylic acid aryl ester or the N-aryl aromatic carboxamide, respectively.
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).
Kinetic study of the phenolysis of O-methyl and O-phenyl O-2,4-dinitrophenyl thiocarbonates and O-ethyl 2,4-dinitrophenyl dithiocarbonate
Castro, Enrique A.,Arellano, David,Pavez, Paulina,Santos, Jose G.
, p. 6192 - 6196 (2007/10/03)
The reactions of a series of phenols with O-methyl O-2,4-dinitrophenyl thiocarbonate (MDNPTOC), O-phenyl O-2,4-dinitrophenyl thiocarbonate (PDNPTOC), and O-ethyl 2,4-dinitrophenyl dithiocarbonate (EDNPDTC) are studied kinetically in water, at 25.0 °C and an ionic strength of 0.2 M (KCl). All reactions show pseudo-first-order kinetics under an excess of phenol over the substrate, and are first order in phenoxide anion. The reactions of EDNPDTC show a linear Bronsted-type plot of slope β = 0.67, suggesting a concerted mechanism. On the other hand, the phenolyses of MDNPTOC and PDNPTOC exhibit linear Bronsted-type plots of slopes β = 0.27 and 0.28, respectively, consistent with stepwise mechanisms where the formation of an anionic tetrahedral intermediate (T-) is rate determining. By comparison of the kinetics and mechanisms of the reactions under investigation with similar reactions, the following conclusions arise: (i) Substitution of S- by O- in the intermediate T- destabilizes this species. (ii) The change of DNPO in T- to DNPS also destabilizes this intermediate. (iii) Substitution of MeO by PhO as the nonleaving group of the substrate does not affect the kinetics, probably by a compensation of electronic and steric effects. (iv) The change of an amino group in a tetrahedral intermediate to a phenoxy group destabilizes the intermediate.
Kinetics and mechanism of the aminolysis of phenyl and 4-nitrophenyl ethyl thionocarbonates
Castro, Enrique A.,Cubillos, Maria,Santos, Jose G.
, p. 3501 - 3505 (2007/10/03)
The reactions of the title substrates (PTOC and NPTOC, respectively) with secondary alicyclic amines are subjected to a kinetic study in aqueous solution at 25.0°C, ionic strength 0.2 M (KCl). Under amine excess, pseudo-first-order rate coefficients (kobsd) are found throughout. The order in amine is one for the reactions of piperidine but is of intermediate order between 1 and 2 for the reactions of the other amines. The kinetic results can be accommodated by a reaction scheme with two hypothetical tetrahedral intermediates: a zwitterionic (T±) and an anionic (T-) one, whereby amine catalysis (deprotonation of T± to give T-) is kinetically important. Both the pKa of T± and the rate coefficient for proton transfer (k3 ca. 1010 s-1 M-1) are estimated. The values of the other rate microcoefficients of the scheme are found by a nonlinear least-squares fitting, and these values are compared with those exhibited in the aminolysis of phenyl thionoacetate (PTOA), and S-phenyl and S-(4-nitrophenyl) O-ethyl dithiocarbonates (PDTC and NPDTC, respectively). The Broensted type plots for amine basicity have slopes βN ca. 0.2 for rate-determining amine attack (k1) and βN ca. 0.8 for amine expulsion from T± (k-1), in accord with the βN values found in similar aminolyses. The general base catalysis by amine found in the aminolysis of NPTOC, in contrast with the lack of such catalysis in the aminolysis of 4-nitrophenyl methyl carbonate, is explained by a smaller rate coefficient for expulsion of 4-nitrophenoxide (k2) from T±(which competes with amine deprotonation of T±) relative to the same expulsion from the analogous oxy intermediate.
The Mechanism of Thermal Eliminations. Part 24. Elimination from Mono-, Di-, and Trithiocarbonates. The Dependence of the Transition State Polarity, Thione to Thiol Rearrangement, and Ether Formation via Nucleophilic Substitution, on Compound Type.
Al-Awadi, Nouria,Taylor, Roger
, p. 177 - 182 (2007/10/02)
We have measured rates of thermal decomposition and Arrhenius parameters for S-alkyl O-phenyl thiocarbonates, O-alkyl O'-phenyl thiocarbonates, S-alkyl O-phenyl and O-alkyl S-phenyl dithiocarbonates (xanthates), and alkyl phenyl trithiocarbonates between 671.4 and 819.2 deg K.The reactivity order is: PhOCSOR>PhOCO2R>PhSCSOR>PhSCO2R>PhOCSSR>PhSCSSR>PhOCOSR>(PhSCOSR).Compared with the pyrolysis of acetates the rate decrease accompanying change of carbonyl to thiocarbonyl is smaller, whilst that accompanying change of OR to SR is greater, because the transition state for carbonate pyrolysis is more E1-like within the overall semi-concerted process.The accelerating effect of thion sulphur is greatest for ethyl derivatives which have the least E1-like transition state.The iPr/Et rate ratios at 700 deg K are: 30.7 (PhOCO2R), α-X bond breaking may be the most important rate determining step.Compounds containing thione sulphur and O-alkyl groups (but not O-phenyl groups) undergo sulphur-oxygen exchange.A mechanism for this exchange is given which accounts both for these structural aspects and the much slower exchange in thionacetates.For carbonates, exchange is more severe for compounds which have the slowest competing elimination.Compounds PSCSSiPr, PhSCSSEt, PhOCSSEt, and PhOCOSEt each gave abnormally low activation energies (and low stoicheiometry) due to competing nucleophilic substitution which gives ethers.This reaction is predicted to be important also for compounds PhSCOSR.
