- Catalytic Transfer Hydration of Cyanohydrins to α-Hydroxyamides
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We report the palladium(II)-catalyzed transfer hydration of cyanohydrins to α-hydroxyamides by using carboxamides as water donors. This method enables selective hydration of various aldehyde- and ketone-derived cyanohydrins to afford α-mono- and α,α-disubstituted-α-hydroxyamides, respectively, under mild conditions (50 °C, 10 min). The direct conversion of fenofibrate, a drug bearing a benzophenone moiety, into a functionalized α,α-diaryl-α-hydroxyamide was achieved by means of a hydrocyanation-transfer hydration sequence. Preliminary kinetic studies and the synthesis of a site-specifically 18O-labeled α-hydroxyamide demonstrated the carbonyl oxygen transfer from the carboxamide reagent into the α-hydroxyamide product.
- Kanda, Tomoya,Naraoka, Asuka,Naka, Hiroshi
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supporting information
p. 825 - 830
(2019/01/14)
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- A single-step, mild, neutral, catalyst-free method for cyanohydrin synthesis
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A wide variety of carbonyl compounds can be transformed to their corresponding cyanohydrins in a single step using a dimethyl sulfoxide (DMSO)-water system in excellent yields (75-94%). The major advantages of this system are that the reaction conditions are mild and neutral; the reaction proceeds without catalyst and gives the corresponding cyanohydrins in short time (15-120 min).
- Degani, Mariam S.,Kakwani, Manoj D.,Palsule Desai, Nutan H.,Bairwa, Ranjeet
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experimental part
p. 461 - 465
(2012/06/15)
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- Redox-neutral α-cyanation of amines
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α-Aminonitriles inaccessible by traditional Strecker chemistry are obtained in redox-neutral fashion by direct amine α-cyanation/N-alkylation or alternatively, α-aminonitrile isomerization. These unprecedented transformations are catalyzed by simple carboxylic acids.
- Ma, Longle,Chen, Weijie,Seidel, Daniel
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supporting information
p. 15305 - 15308
(2012/10/29)
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- OXYGEN TRANSFER FROM PERCARBOXYLIC ACIDS AND ALKYL HYDROPEROXIDES TO (MESO-TETRAPHENYLPORPHINATO)IRON(III) AND -CHROMIUM(III)
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The second order rate constants (kYOOH) for the reaction of (meso-tetraphenylporphinato)iron(III) chloride ((T-PP)FeIII(Cl)) with a series of percarboxylic acids and alkyl hydroperoxides (species YOOH) were determined in methanol by the trapping of the hypervalent iron-oxo porphyrin species with 2,4,6-tri-tert-butylphenol.The oxygen donors, TOOH, were chosen so that the leaving species, YOH, possessed pKa values spaced between 3.8 and 16.7.Values of kYOOH for oxidation of (TPP)CrIII(Cl) to (TPP)CrV(O) have been determined in dichloromethane by following the formation of ((TPP)CrIV)2O.The latter arises by non-rate-determining trapping of (TPP)CrV(O) by unreacted (TPP)CrIII(Cl).A plot of log kYOOH for (TPP)FeIII(Cl) versus the log of kYOOH for (TPP)CrIII(Cl) exhibits two linear portions.A slope of about unity is seen when YOOH represents percarboxylic acids.This reflects the similarity in mechanism for the reactions of percarboxylic acids with (TPP)FeIII(Cl) and (TPP)CrIII(Cl).Since phenylacetic acid is obtained as the product in the reaction of both (TPP)FeIII(Cl) and (TPP)CrIII(Cl) with phenylperacetic acid, the common mechanism is one of heterolytic scission of the percarboxylic acid O-O bond.With (TPP)CrIII(Cl), a linear free-energy plot of log kYOOH versus the pKa of the leaving YOH is shared by both percarboxylic acids and hydroperoxides.This finding is to be expected if oxygen transfer from hydroperoxides to (TPP)CrIII(Cl) shares with the percarboxylic acids the common mechanism of O-O bond heterolysis.A change in mechanism of oxygen transfer in the reactions of (TPP)FeIII(Cl) with percarboxylic acids and alkyl hydroperoxides is shown by the breaks in plots of the log kYOOH versus either the pKa of YOH or log kYOOH for (TPP)CrIII(Cl).The rate-limiting step on reaction of the less acidic alkyl hydroperoxides with (TPP)FeIII(Cl) is suggested to involve homolytic O-O bond scission to provide an intimate IV(OH)(X)-.O-alkyl> pair which may then dissociate as such or after H. transfer dissociate to (+.TPP)FeIV(O)(X) + HO-alkyl.Differentiation of mechanism on the basis of the products of YOH oxidation cannot be made.Details are discussed in the paper.The various linear free-energy plots exhibit a surprising independence of steric effects in the hydroperoxides.
- Lee, William A.,Yuan, Lung-Chi,Bruice, Thomas C.
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p. 4277 - 4283
(2007/10/02)
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- Influence of Nitrogen Base Ligation and Hydrogen Bonding on the Rate Constants for Oxygen Transfer from Percarboxylic Acids and Alkyl Hydroperoxides to (meso-Tetraphenylporphinato>manganese(III) Chloride
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Equilibrium constants for axial ligation of imidazole (ImH), N-methylimidazole (N-MeIm), 4'-(imidazo-1-yl)-acetophenone (NAcPhIm), 2,6-lutidine (2,6-Py), and 3,4-lutidine (3,4-Py) with (meso-tetraphenylporphinato)manganese chloride ((TPP)MnIIICl) have been determined.The rates of oxygen atom transfer from percarboxylic acids and alkyl hydroperoxides (YOOH) to the manganese(III) porphyrin in the presence of varying concentrations of the nitrogen bases were determined.For this purpose, 2,2-diphenyl-1-picrylhydrazine (DPPH) was employed as a trap for the generated higher valent oxo-manganese porphyrin species.From the equilibrium and kinetic data, there was then calculated the second-order rate constants for oxygen atom transfer from YOOH compounds to the species (TPP)MnIIICl, TPP(Cl)MnIIIN, and TPP(Cl)MnIIIN2 (where N = ImH, N-MeIm, and 3,4-Py).Only the percarboxylic acids exhibit measurable rate constants for oxygen transfer to (TPP)MnIIICl, whereas alkyl hydroperoxides and percarboxylic acids transfer oxygen to the TPP(Cl)MnIIIN species.Of the species TPP(Cl)MnIIIN2, reaction with YOOH compounds is seen only when N is imidazole.This is attributed to an equilibrium of the unreactive bis axially ligated TPP(Cl)MnIII(ImH)2 with the reactive isomeric mono axial-ligated complex Cl(1-)...H-Im...H-Im...MnIIITPP.Nitrogen base ligation of (TPP)MnIIICl provides minimally a 1E3 increase in the rate constants for oxygen transfer in methylene chloride.Linear free-energy plots of the log of the second-order rate constants for oxygen transfer from YOOH vs. the pKa of YOH establish that β1g for oxygen transfer in which heterolytic O-O bond scission is rate-determining is large and negative.The value of β1g when oxygen transfer involves rate-determining homolytic O-O bond scission is small and negative.
- Yuan, Lung-Chi,Bruice, Thomas C.
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p. 1643 - 1650
(2007/10/02)
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- Monooxygen Donation Potential of 4a-Hydroperoxyflavins As Compared with Those of a Percarboxylic Acid and Other Hydroperoxides. Monooxygen Donation to Olefin, Tertiary Amine, Alkyl Sulfide, and Iodide Ion
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The reaction of the hydroxyperoxides diphenylhydroperoxyacetonitrile (4), methyl diphenylhydroperoxyacetate (5), and 5',6',7',8'-tetrahydro-4a'-hydroperoxy-3'-methylspiro-4'(3'H)-one (6) with I-, thioxane, and N,N-dimethylbenzylamine (DMBA) are first order in both hydroperoxide and substrate.For both 5 and 6, I3- is produced in 100percent yield.Product analysis for the reaction of 4, 5, and 6 with thioxane and DMBA established that the hydroxyperoxides are converted to the corresponding alcohols and that thioxane sulfoxide and N,N-dimethylbenzylamine N-oxide are formed.The reactions are quantitative.The reaction of 4 with I- proved to be complicated.The alcohol generated from 4 is the cyanohydrin of benzophenone.The dissociation of the benzophenone cyanohydrin product is competitive with I3- formation so that CN- produced in the dissociation reacts with I3- to yield ICN.Kinetic and thermodynamic analyses have provided the pertinent rate and equilibrium constants associated with the overall time course for reaction of 4 with I-.The second-order rate constant for the reaction of m-chloroperbenzoic acid (1) with I- has been determined and the second-order rate constant for reaction of 1 with thioxane was obtained from experiments in which thioxane and I- were employed as competitive substrates.The second-order rate constants for reaction of 1, 4, 5, and 6 with I-, thioxane, and DMBA were compared with like constants for the reactions of 4a-hydroperoxy-5-ethyl-3-methyllumiflavin (2), 1-carba-1-deaza-4a-hydroperoxy-5-ethyl-3-methyllumiflavin (3), t-BuOOH (7), and H2O2 (8).A log - log plot of the rate constants for monooxygen transfer from hydroperoxides to thioxane (kS) and to DMBA (kN) was found to be linear and of slope 1.0.The best line for the plot of log kS vs. the log of the rate constants for reactions with I- (kI) was of slope 1.1.The points for m-chloroperbenzoic acid were found to fit the log kS vs. log KI plot.These results show that the second-order rate constants for reactions of I-, thioxane, and DMBA are of like dependence on the electronic and steric characteristics of the hydroperoxides and percarboxylic acid 1.A linear free energy plot correlates the log of the second-order rate constants vs. pKa of YOH for oxygen transfer from YOOH = 1, 2, 4, 5, 7, and 8 (βlg = -0.6).In these reactions the 4a-hydroperoxyflavin 2 is the most efficient monooxygen donor of the hydroperoxides investigated, being 103 - 106 more reactive than t-BuOOH and ca. 103 less reactive than the peracid 1.The kinetics of epoxidation of 2,3-dimethyl-2-butene by the hydroperoxides 2 - 6 were invesigated by following both hydroperoxide disappearance and product formation.The results of these investigations, which include further reaction of epoxide with hydroperoxide to provide pinacol and 2,3-dimethyl-1-buten-3-ol, are discussed.Evidence for epoxidation of 2,3-dimethyl-2-butene ...
- Bruice, Thomas C.,Noar, J. Barry,Ball, Sheldon S.,Venkataram, U. V.
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p. 2452 - 2463
(2007/10/02)
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