26945-93-7Relevant articles and documents
Palladium-Catalyzed Oxidation of β-C(sp3)-H Bonds of Primary Alkylamines through a Rare Four-Membered Palladacycle Intermediate
Bunescu, Ala,Ernst, Martin,Hartwig, John F.,Qiu, Yehao,Su, Bo,Zuend, Stephan J.
supporting information, p. 7912 - 7919 (2020/05/22)
Site-selective functionalizations of C-H bonds are often achieved with a directing group that leads to five- or six-membered metallacyclic intermediates. Analogous reactions that occur through four-membered metallacycles are rare. We report a challenging palladium-catalyzed oxidation of primary C-H bonds β to nitrogen in an imine of an aliphatic amine, a process that occurs through a four-membered palladacyclc intermediate. The success of the reaction relies on the identification, by H/D exchange, of a simple directing group (salicylaldehyde) capable of inducing the formation of this small ring. To gain insight into the steps of the catalytic cycle of this unusual oxidation reaction, a series of mechanistic experiments and density functional theory (DFT) calculations were conducted. The experimental studies showed that cleavage of the C-H bond is rate-limiting and formation of the strained four-membered palladacycle is thermodynamically uphill. DFT calculations corroborated these conclusions and suggested that the presence of an intramolecular hydrogen bond between the oxygen of the directing group and hydroxyl group of the ligating acetic acid is crucial for stabilization of the palladacyclic intermediate.
Coumaraz-2-on-4-ylidene: Ambiphilic N-Heterocyclic Carbenes with a Tunable Electronic Structure
Song, Hayoung,Kim, Hyunho,Lee, Eunsung
supporting information, p. 8603 - 8607 (2018/07/14)
Herein, a coumaraz-2-on-4-ylidene (1) as a new example of an ambiphilic N-heterocyclic carbene, having electronic properties that can be fine-tuned, is reported. The N-carbamic and aryl groups on the carbene carbon center provide exceptionally high electrophilicity and nucleophilicity simultaneously to the carbene center, as evidenced by the 77Se NMR chemical shifts of their selenoketone derivatives and the CO stretching strengths of their rhodium carbonyl complexes. Since the precursors of 1 could be synthesized from various functionalized Schiff bases in a practical and scalable manner, the electronic properties of 1 can be fine-tuned in a quantitative and predictable way by using the Hammett σ constant of the functional groups on aryl ring. The facile electronic tuning capability of 1 may be applicable to eliciting novel properties in main-group and transition-metal chemistry.
Oxazine Ring-Related Vibrational Modes of Benzoxazine Monomers Using Fully Aromatically Substituted, Deuterated, 15N Isotope Exchanged, and Oxazine-Ring-Substituted Compounds and Theoretical Calculations
Han, Lu,Iguchi, Daniela,Gil, Phwey,Heyl, Tyler R.,Sedwick, Victoria M.,Arza, Carlos R.,Ohashi, Seishi,Lacks, Daniel J.,Ishida, Hatsuo
, p. 6269 - 6282 (2017/09/01)
Polymerization of benzoxazine resins is indicated by the disappearance of a 960-900 cm-1 band in infrared spectroscopy (IR). Historically, this band was assigned to the C-H out-of-plane bending of the benzene to which the oxazine ring is attach
