64436-59-5Relevant academic research and scientific papers
Palladium-NHC (NHC = N-heterocyclic Carbene)-Catalyzed Suzuki-Miyaura Cross-Coupling of Alkyl Amides
Wang, Chang-An,Rahman, Md. Mahbubur,Bisz, Elwira,Dziuk, B?az?ej,Szostak, Roman,Szostak, Michal
, p. 2426 - 2433 (2022/02/17)
We report the Pd-catalyzed Suzuki-Miyaura cross-coupling of aliphatic amides. Although tremendous advances have been made in the cross-coupling of aromatic amides, C-C bond formation from aliphatic amides by selective N-C(O) cleavage has remained a major challenge. This longstanding problem in Pd catalysis has been addressed herein by a combination of (1) the discovery of N,N-pym/Boc amides as a class of readily accessible amide-based reagents for cross-coupling and (2) steric tuning of well-defined Pd(II)-NHC catalysts for cross-coupling. The methodology is effective for the cross-coupling of an array of 3°, 2°, and 1° aliphatic amide derivatives. The catalyst system is user-friendly, since the catalysts are readily available and are air- and bench-stable. Mechanistic studies strongly support an amide bond twist and external nN → π*C═O/Ar delocalization as a unified enabling feature of N,N-pym/Boc amides in selective N-C(O) bond activation. The method provides a rare example of Pd-NHC-catalyzed cross-coupling of aliphatic acyl amide electrophiles.
Rhodium-Catalyzed and Chiral Zinc Carboxylate-Assisted Allenylation of Benzamides via Kinetic Resolution
Mao, Ruxia,Zhao, Yanliang,Zhu, Xiaohan,Wang, Fen,Deng, Wei-Qiao,Li, Xingwei
supporting information, p. 7038 - 7043 (2021/09/18)
Enantioenriched allenes are important building blocks. While they have been accessed by other coupling methodologies, enantioenriched allenes have been rarely obtained via C-H activation. In this work, kinetic resolution of tertiary propargyl alcohols as an allenylating reagent has been realized via rhodium(III)-catalyzed C-H allenylation of benzamides. The reaction proceeded efficiently under mild conditions, and both the allenylated products and the propargyl alcohols were obtained in high enantioselectivities with an s-factor of up to 139. The resolution results from bias of the two propargylic substituents and is assisted by a chiral zinc carboxylate additive.
N-Heterocyclic Carbene-Catalyzed Decarboxylative Alkylation of Aldehydes
Ishii, Takuya,Kakeno, Yuki,Nagao, Kazunori,Ohmiya, Hirohisa
supporting information, p. 3854 - 3858 (2019/04/25)
We found that N-heterocyclic carbene catalysis promoted the unprecedented decarboxylative coupling of aryl aldehydes and tertiary or secondary alkyl carboxylic acid-derived redox-active esters to produce aryl alkyl ketones. The mild and transition-metal-free reaction conditions are attractive features of this method. The power of this protocol was demonstrated by the functionalization of pharmaceutical drugs and natural product. A reaction pathway involving single electron transfer from an enolate form of Breslow intermediate to a redox ester followed by recombination of the resultant radical pair to form a carbon-carbon bond is proposed.
Synergistic interplay of a non-heme iron catalyst and amino acid coligands in H2O2 activation for asymmetric epoxidation of α-alkyl-substituted styrenes
Cuss, Olaf,Ribas, Xavi,Lloret-Fillol, Julio,Costas, Miquel
supporting information, p. 2729 - 2733 (2015/03/04)
Highly enantioselective epoxidation of α-substituted styrenes with aqueous H2O2 is described by using a chiral iron complex as the catalyst and N-protected amino acids (AAs) as coligands. The amino acids synergistically cooperate with the iron center in promoting an efficient activation of H2O2 to catalyze epoxidation of this challenging class of substrates with good yields and stereoselectivities (up to 97% ee) in short reaction times.
An evaluation of substituent effects on aromatic edge-to-face interactions and CF-π versus CH-π interactions using an imino torsion balance model
Jennings, W. Brian,O'Connell, Niamh,Malone, John F.,Boyd, Derek R.
, p. 5278 - 5291 (2013/08/23)
A selection of imines derived from phenyl t-butyl ketones and substituted 2-phenylethylamines or phenylalanine exhibit slow rotation around the aryl-imino bond at ambient temperature, resulting in a large non-equivalence of the ortho hydrogens in the 1H NMR spectra. This facilitates assessment of aryl substituent effects on the face tilted-T CH-π interaction between a phenyl ring (A) on the imino carbon proximate to the terminal phenyl ring (B). Analysis of the marked temperature dependence of the chemical shift of the interacting ortho hydrogen affords estimates of the opposing enthalpic and entropic factors involved in the rapid equilibrium between the closed edge-to-face conformation and alternative open conformations devoid of a CH-π interaction while in solution. Above ca. 80 °C the entropy term (TΔS) cancels out the enthalpy (ΔH) favouring the closed conformation and open conformations are preferred. Accordingly, commonly reported binding free energies may not be a good measure of the energetic strength of intramolecular aromatic interactions. Investigation of an ortho fluoro substituted compound indicates that a CF-π interaction is at least 1.0 kcal mol-1 weaker in enthalpy than the CH-π interaction. Several X-ray crystal structures depicting an intramolecular edge-to-face interaction are presented.
Synthesis of sterically hindered ketones from aldehydes via O-silyl oximes
Kim, Joong-Gon,Mishra, Mithilesh Kumar,Jang, Doo Ok
experimental part, p. 3527 - 3529 (2012/08/29)
A mild and efficient method to synthesize sterically hindered ketones from aldehydes via O-silyl oximes was developed. Treatment of O-triphenylsilylated oximes with alkyl iodides in the presence of triethyl borane afforded the corresponding ketones.
Catalyst-free alkanoylation of aromatic rings via arylstannanes. Scope and limitations
Lo Fiego, Marcos J.,Lockhart, María T.,Chopa, Alicia B.
supporting information; experimental part, p. 3674 - 3678 (2010/01/18)
The reaction of alkanoyl chlorides with arylstannanes in 1,2-dichlorobenzene (180 °C) is a simple and direct route for the catalyst-free and regioselective synthesis of tertiary alkyl aryl ketones in good to excellent isolated yields (55-77%). Nevertheles
The first regioselective metalation and functionalization of unprotected 4-halobenzoic acids
Gohier, Frederic,Castanet, Anne-Sophie,Mortier, Jacques
, p. 1501 - 1504 (2007/10/03)
(Chemical Equation Presented) By treatment with s-BuLi, s-BuLi/TMEDA, or t-BuLi at ～-78°C, 4-fluoro- and 4-chlorobenzoic acids (1a,b) are metalated preferentially in the position adjacent to the carboxylate. A complete reversal in regioselectivity is observed for 1a when treated with LTMP; a sequential process involving a rapid intraaggregate lithiation through a quasi dianion complex "QUADAC" is postulated to explain the unusual reactivity of Me2S2 and I2.
MECHANISM OF OXIDATION OF α,β-UNSATURATED THIONES BY SINGLET OXYGEN
Rac, V. Pushkara,Ramamurthy, V.
, p. 2169 - 2176 (2007/10/02)
Photo-oxidation of α,β-unsaturated thiones yields the corresponding ketones as the only product.Studies carried out three systems, namely thioketones, α,β-unsaturated thiones and thioketenes, have revealed that there exists a similarity in their mechanism of oxidation.It has been suggested that the thiocarbonyl chromophore is the site of attack by singlet oxygen in α,β-unsaturated thiones and that the adjacent C-C double bond is inert under these conditions.Absence of sulphine during the oxidation of α,β-unsaturated thiones is attributed to the electronic factors operating on the zwitterionic / diradical intermediate.While α,β-unsaturated ketones are poorly reactive, α,β-unsaturated thiones are highly reactive toward singlet oxygen.
