- Functionalization of α-C(sp3)?H Bonds in Amides Using Radical Translocating Arylating Groups
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α-C?H arylation of N-alkylamides using 2-iodoarylsulfonyl radical translocating arylating (RTA) groups is reported. The method allows the construction of α-quaternary carbon centers in amides. Various mono- and disubstituted RTA-groups are applied to the arylation of primary, secondary, and tertiary α-C(sp3)?H-bonds. These radical transformations proceed in good to excellent yields and the cascades comprise a 1,6-hydrogen atom transfer, followed by a 1,4-aryl migration with subsequent SO2 extrusion.
- Radhoff, Niklas,Studer, Armido
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p. 3561 - 3565
(2021/01/04)
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- Direct C-C Bond Formation from Alkanes Using Ni-Photoredox Catalysis
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A method for direct cross coupling between unactivated C(sp3)-H bonds and chloroformates has been accomplished via nickel and photoredox catalysis. A diverse range of feedstock chemicals, such as (a)cyclic alkanes and toluenes, along with late-stage intermediates, undergo intermolecular C-C bond formation to afford esters under mild conditions using only 3 equiv of the C-H partner. Site selectivity is predictable according to bond strength and polarity trends that are consistent with the intermediacy of a chlorine radical as the hydrogen atom-abstracting species.
- Ackerman, Laura K. G.,Martinez Alvarado, Jesus I.,Doyle, Abigail G.
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p. 14059 - 14063
(2018/10/24)
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- Unactivated C(sp3)-H hydroxylation through palladium catalysis with H2O as the oxygen source
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A novel palladium catalyzed hydroxylation of unactivated aliphatic C(sp3)-H bonds was successfully developed. Different from conventional methods, water serves as the hydroxyl group source in the reaction. This new reaction demonstrates good reactivity and broad functional group tolerance. The C-H hydroxylated products can be readily transformed into various highly valuable chemicals via known transformations. Based on experimental and theoretical studies, a mechanism involving the Pd(ii)/(iv) pathway is proposed for this hydroxylation reaction.
- Hu, Jiantao,Lan, Tianlong,Sun, Yihua,Chen, Hui,Yao, Jiannian,Rao, Yu
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p. 14929 - 14932
(2015/10/06)
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- Steric effects and mechanism in the formation of hemi-acetals from aliphatic aldehydes
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Some physical properties (pKa, log POW, boiling points) of hexanoic acid 1 (X = COOH) and its seven isomers 2, 3, 4, 5, 6, 7, 8 (X = COOH) are reported. Hexanal 1 (X = CHO) and its seven isomeric aldehydes 2, 3, 4, 5, 6, 7, 8 (X = CHO) are shown to equilibrate, in methanol solution, with their hemi-acetals. Logarithms of equilibrium constants correlate with values of Es for the isomeric C5H11 substituents, and with logs of relative rates for saponification of the corresponding methyl esters with ρ = 0.52, reflecting the reduced steric demand of hydrogen compared to oxygen in the quaternization of ester and aldehydic carbonyl groups. Rates of equilibration have also been measured in buffered methanol. For hexanal, with a 2:1 Et3N:AcOH buffer, the buffer-independent contribution is dominated by the methoxide catalysed pathway. Rates in this medium have been determined for isomers 1, 2, 3, 4, 5, 6, 7, 8 (X = CHO), and their logarithms do not correlate with logarithms of equilibrium constants for hemi-acetal formation or with substituent steric parameters derived from ester formation or saponification, indicating that the steric changes associated with full quaternization of the carbonyl group are not mirrored in the transition structures for hemi-acetal formation. It is suggested that transition states for hemi-acetal formation are relatively early so that steric interactions are effectively those between the nucleophile and ground state conformations of the aldehydes. A comparison of the entropies of hemi-acetal formation with entropies of activation has provided a basis for a suggested transition structure. Comparisons with acid chloride hydrolyses are made. Copyright 2013 John Wiley & Sons, Ltd. Logarithms of equilibrium constants for formation hemi-acetals of hexanal and its seven isomeric aldehydes correlate well with values of Es for the isomeric C5H11 substituents, and with logs of relative rates for saponification of the corresponding methyl esters. Logarithms of rate constants for hemi-acetal formation do not, indicating that the steric changes associated with full quaternization of the carbonyl group are not mirrored in the transition structures for hemi-acetal formation. The reasons for this are discussed. Copyright
- Daw, Graham,Regan, Andrew C.,Watt, C. Ian F.,Wood, Evan
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p. 1048 - 1057
(2014/01/06)
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- Synthesis and evaluation of antiallodynic and anticonvulsant activity of novel amide and urea derivatives of valproic acid analogues
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Valproic acid (VPA, 1) is a major broad spectrum antiepileptic and central nervous system drug widely used to treat epilepsy, bipolar disorder, and migraine. VPA's clinical use is limited by two severe and lifethreatening side effects, teratogenicity and hepatotoxicity. A number of VPA analogues and their amide, N-methylamide and urea derivatives, were synthesized and evaluated in animal models of neuropathic pain and epilepsy. Among these, two amide and two urea derivatives of 1 showed the highest potency as antineuropathic pain compounds, with ED50 values of 49 and 51 mg/kg for the amides (19 and 20) and 49 and 74 mg/kg for the urea derivatives (29 and 33), respectively. 19, 20, and 29 were equipotent to gabapentin, a leading drug for the treatment of neuropathic pain. These data indicate strong potential for the above-mentioned novel compounds as candidates for future drug development for the treatment of neuropathic pain. 2009 American Chemical Society.
- Kaufmann, Dan,Bialer, Meir,Shimshoni, Jakob Avi,Devor, Marshall,Yagen, Boris
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scheme or table
p. 7236 - 7248
(2010/07/04)
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- Structure-activity relationship observations for the bagworm moth pheromone
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Structure-activity relationship (SAR) observations were made for the bagworm moth pheromone. (R)-2-pentyl decanoate, and a series of analogs with modifications in the alcohol portion of the molecule. Observed attractiveness of these analogs was related to molecular structure and their physical attributes using computational chemistry. Electrostatic potential and Van der Waals (VdW) electrostatic coded surface three-dimensional (3D) maps of the molecular mechanics (MM) minimized lowest energy conformation of the pheromone show that size, shape, charge distribution, and chirality of the molecule are related to attractiveness.
- Warthen,Klun,DeVilbiss
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p. 1315 - 1324
(2007/10/03)
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- DECOMPOSITION DES ESTERS DE LA N-HYDROXYTHIOPYRIDONE-2. SYNTHESE DE QUELQUES NOUVEAUX HALOGENURES SECONDAIRES ET TERTIAIRES ENCOMBRES.
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Hindered α,α-disubstituted and α,α,α-trisubstituted acyl chlorides give with N-hydroxy-2-thiopyridone, the corresponding esters.The decomposition of this compound in tetrachloromethane or in bromotrichloromethane as solvent and halogen atom source results in the formation of new very hindered secondary R1R2CHX (R1 = iPr or tBu; R2 = iPr or tBu; X = Cl or Br) and tertiary R1R2R3CX (R1 = R2 = R3 = iPr; R1 = tBu, R2 = iPr, R3 = Et or Me, X = Cl) alkyl halides.
- Stofer, Edmond,Lion, Claude
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p. 623 - 628
(2007/10/02)
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- Synthesis of 4,4-Disubstituted 1,3-Thiazol-5(4H)-thiones
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An easy synthesis for the 1,3-thiazol-5(4H)-thiones 5, a class of heterocycles which have hitherto only been available with difficulty, is described.Reaction of 3-amino-2H-azirines 25 with thiocarboxylic acids at 0 deg yields monothiodiamides of type 20 (Scheme 6) which, on treatment with Lawesson reagent at 100 deg, undergo thiation and cyclization to give 5 in good yield.
- Jenny, Christjohannes,Heimgartner, Heinz
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p. 374 - 388
(2007/10/02)
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- Specificities of the α-Alkynone Cyclization
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Die Regio- und Stereospezifitaeten der α-Alkinon-Cyclisierung, einer thermischen Umwandlung von Alkinyl-alkyl-ketonen, welche in β'-Stellung mindestens ein H-Atom tragen, zu 2-Cyclopentenonen wurden untersucht.Cyclisierung zum hoeher substituierten C(β')-Atom ist dabei bevorzugt, vorausgesetzt, dass die zur Insertion zur Verfuegung stehende C(β'),H-Bindung zur Propioloylseitenkette eine moeglichst synplanare Anordnung einnehmen kann.In Cyclisierungen zu β'-Methylen-C-Atomen, welche diastereotope H-Atome tragen, wird daher eines der moeglichen epimeren Produkte bevorzugt oder ausschliesslich gebildet.Die mechanistischen Konsequenzen der gefundenen Specifitaeten werden diskutiert.
- Karpf, Martin,Huguet, Joan,Dreiding, Andre S.
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