6721-67-1Relevant articles and documents
Asymmetric Enamide–Imine Tautomerism in the Kinetic Resolution of Tertiary Alcohols
Gu, Huanchao,He, Shunlong,Rajkumar, Subramani,Tang, Mengyao,Yang, Xiaoyu
supporting information, p. 21334 - 21339 (2021/08/23)
An efficient protocol for kinetic resolution of tertiary alcohols has been developed through an unprecedented asymmetric enamide-imine tautomerism process enabled by chiral phosphoric acid catalysis. A broad range of racemic 2-arylsulfonamido tertiary allyl alcohols could be kinetically resolved with excellent kinetic resolution performances (with s-factor up to >200). This method is particularly effective for a series of 1,1-dialkyl substituted allyl alcohols, which produced chiral tertiary alcohols that would be difficult to access via other asymmetric methods. Facile and versatile transformations of the chiral α-hydroxy imine and enamide products, especially the efficient stereodivergent synthesis of all four stereoisomers of β-amino tertiary alcohols using one enantiomer of the catalyst, demonstrated the value of this kinetic resolution method.
Ring size and nothing else matters: unusual regioselectivity of alkyne hydration by NHC gold(i) complexes
Ageshina, Alexandra A.,Asachenko, Andrey F.,Chesnokov, Gleb A.,Minaeva, Lidiya I.,Nechaev, Mikhail S.,Philippova, Anna N.,Rzhevskiy, Sergey A.,Topchiy, Maxim A.
supporting information, p. 5686 - 5689 (2021/06/16)
We have investigated the role of ring sizes and substituents in NHC ligands in some (NHC)Au(i) complexes in the hydration of internal alkynes. Despite the fact that using (NHC)Au(i) complexes in the hydration of diarylacetylenes leads to Markovnikov-type products, the precise tuning of ligands allows changing the regioselectivity in arylalkylacetylene hydration to the anti-Markovnikov-type.
Ketone Synthesis from Benzyldiboronates and Esters: Leveraging α-Boryl Carbanions for Carbon-Carbon Bond Formation
Lee, Boran,Chirik, Paul J.
supporting information, p. 2429 - 2437 (2020/03/03)
An alkoxide-promoted method for the synthesis of ketones from readily available esters and benzyldiboronates is described. The synthetic method is compatible with a host of sterically differentiated alkyl groups, alkenes, acidic protons α to carbonyl groups, tertiary amides, and aryl rings having common organic functional groups. With esters bearing α-stereocenters, high enantiomeric excess was maintained during ketone formation, establishing minimal competing racemization by deprotonation. Monitoring the reaction between benzyldiboronate and LiOtBu in THF at 23 °C allowed for the identification of products arising from deborylation to form an α-boryl carbanion, deprotonation, and alkoxide addition to form an "-ate" complex. Addition of 4-trifluoromethylbenzoate to this mixture established the α-boryl carbanion as the intermediate responsible for C-C bond formation and ultimately ketone synthesis. Elucidation of the role of this intermediate leveraged additional bond-forming chemistry and enabled the one-pot synthesis of ketones with α-halogen atoms and quaternary centers with four-different carbon substituents.
Synthesis of unsymmetrical ketones by applying visible-light benzophenone/nickel dual catalysis for direct benzylic acylation
Krach, Patricia E.,Dewanji, Abhishek,Yuan, Tingting,Rueping, Magnus
supporting information, p. 6082 - 6085 (2020/06/18)
Herein, we report a dual catalytic system for the direct benzylic C-H acylation reaction furnishing a variety of unsymmetrical ketones. A benzophenone-derived photosensitizer combined with a nickel catalyst has been established as the catalytic system. Both acid chlorides and anhydrides are able to acylate the benzylic position of toluene and other methylbenzenes. The method offers a valuable alternative to late transition metal catalyzed C-H acylation reactions.
Super electron donor-mediated reductive desulfurization reactions
Nozawa-Kumada, Kanako,Ito, Shungo,Noguchi, Koto,Shigeno, Masanori,Kondo, Yoshinori
supporting information, p. 12968 - 12971 (2019/11/05)
The desulfurization of thioacetals and thioethers by a pyridine-derived electron donor is described. This methodology provides efficient access to the reduced products in high yields and does not require the use of transition-metals, elemental alkali-metals, or hydrogen atom donors.
Coupling of Sulfoxonium Ylides with Arynes: A Direct Synthesis of Pro-Chiral Aryl Ketosulfoxonium Ylides and Its Application in the Preparation of α-Aryl Ketones
Talero, Alexánder Garay,Martins, Bruna Sim?es,Burtoloso, Antonio C. B.
, p. 7206 - 7211 (2018/11/23)
A general, mild, and versatile synthesis of the challenging α-aryl-β-ketosulfoxonium ylides has been developed for the first time, substituting traditional methods starting from diazo compounds. The arylation of easily accessible β-ketosulfoxonium ylides using aryne chemistry allowed the preparation of a large scope of the pro-chiral ylides in very good yields (40 examples; up to 85%). As applications, these ylides were smoothly converted into α-aryl ketones after desulfurization in good yields (up to 98%) as well as in other important derivatives.
Ni/Ti Dual Catalytic Cross-Coupling of Nitriles and Organobromides to Access Ketones
Chenniappan, Vinoth Kumar,Silwal, Sajan,Rahaim, Ronald J.
, p. 4539 - 4544 (2018/05/23)
Herein, we report the development of a dual catalytic approach for the cross-coupling of nitriles with aryl- and aliphatic-bromides. A titanium(III) catalyst is used to activate nitriles enabling their coupling with organobromides through a nickel catalyst. The Ni/Ti system efficiently prepared unsymmetrical ketones with good chemoselectivity and could selectively couple a bromide in the presence of other functionalizable handles.
Palladium-Catalyzed C(sp3)-H Oxygenation via Electrochemical Oxidation
Yang, Qi-Liang,Li, Yi-Qian,Ma, Cong,Fang, Ping,Zhang, Xiu-Jie,Mei, Tian-Sheng
supporting information, p. 3293 - 3298 (2017/03/11)
Palladium-catalyzed C-H activation/C-O bond-forming reactions have emerged as attractive tools for organic synthesis. Typically, these reactions require strong chemical oxidants, which convert organopalladium(II) intermediates into the PdIII or PdIV oxidation state to promote otherwise challenging C-O reductive elimination. However, previously reported oxidants possess significant disadvantages, including poor atom economy, high cost, and the formation of undesired byproducts. To overcome these issues, we report an electrochemical strategy that takes advantage of anodic oxidation of PdII to induce selective C-O reductive elimination with a variety of oxyanion coupling partners.
Microwave role in the thermally induced SRN1 reaction for α-arylation of ketones
Caminos, Daniel A.,Garro, Alexis D.,Soria-Castro, Silvia M.,Pe?é?ory, Alicia B.
, p. 20058 - 20065 (2015/03/30)
The coupling between iodobenzene and the enolate anion of acetophenone is accelerated by microwave irradiation. This increase in reaction rate is only ascribed to thermal effects. The coupling reaction gave the corresponding substitution product 1,2-di-phenylethanone in a 50% yield when microwave irradiation was applied between 15-60 s according to the intensity of the pulse. Moreover, this reaction is effective in a temperature window of 70-120 °C. The presence of ionic and dipolar species is not involved in the initiation process as molecular radiators. The excess of tBuOK in the reaction medium may also act as an electron donor helping to generate radicals when the solution temperature increases to 70 °C. This journal is
Experimental and theoretical approaches to the influence of the addition of pyrene to a series of Pd and Ni NHC-based complexes: Catalytic consequences
Valds, Hugo,Poyatos, Macarena,Ujaque, Gregori,Peris, Eduardo
, p. 1578 - 1588 (2015/01/30)
A series of Ni and Pd complexes with three different N-heterocyclic carbene (NHC)-based ligands (imidazolylidene, benzimidazolylidene and pyrene-imidazolylidene) has been prepared and fully characterized. The influence of the addition of pyrene to solutions containing these complexes is studied by means of NMR and UV/Vis spectroscopies and by cyclic voltammetry. The addition of pyrene to the pyrene-NHC-containing Pd and Ni complexes gives rise to the formation of adducts by π-π stacking interactions between pyrene and the pyrene group of the NHC ligand. This interaction causes a modification of the electronic properties of the metal, as demonstrated by cyclic voltammetric studies of the Ni-NHC complexes. Theoretical calculations support this type of π-interactions, and justify the higher interactions observed with the pyrene-NHC containing complexes. The catalytic activities of the complexes were tested in the Suzuki-Miyaura C-C coupling and in the α-arylation of ketones. The addition of pyrene as an external π-stacking additive does not affect the activities of the complexes in the Suzuki-Miyaura coupling, but this observation may be justified due to the fact that the process is heterogeneously catalyzed, as indicated by the mercury-drop test. The addition of pyrene to the catalytic α-arylation of ketones results in a decrease in the activity of the reactions catalyzed by the pyrene-imidazolylidene palladium complex, whereas the other two catalysts do not modify their activity in the presence of this π-stacking additive.
