135969-65-2Relevant articles and documents
Tuning Triplet Energy Transfer of Hydroxamates as the Nitrene Precursor for Intramolecular C(sp3)-H Amidation
Chang, Sukbok,Jung, Hoimin,Keum, Hyeyun,Kweon, Jeonguk
, p. 5811 - 5818 (2020/04/10)
Reported herein is the design of a photosensitization strategy to generate triplet nitrenes and its applicability for the intramolecular C-H amidation reactions. Substrate optimization by tuning physical organic parameters according to the proposed energy transfer pathway led us to identify hydroxamates as a convenient nitrene precursor. While more classical nitrene sources, representatively organic azides, were ineffective under the current photosensitization conditions, hydroxamates, which are readily available from alcohols or carboxylic acids, are highly efficient in accessing synthetically valuable 2-oxazolidinones and γ-lactams by visible light. Mechanism studies supported our working hypothesis that the energy transfer path is mainly operative.
Versatile Cp*Co(III)(LX) Catalyst System for Selective Intramolecular C-H Amidation Reactions
Chang, Sukbok,Jung, Hoimin,Kim, Dongwook,Lee, Jeonghyo,Lee, Jia,Park, Juhyeon
, p. 12324 - 12332 (2020/08/06)
Herein, we report the development of a tailored cobalt catalyst system of Cp*Co(III)(LX) toward intramolecular C-H nitrene insertion of azidoformates to afford cyclic carbamates. The cobalt complexes were easy to prepare and bench-stable, thus offering a convenient reaction protocol. The catalytic reactivity was significantly improved by the electronic tuning of the bidentate LX ligands, and the observed regioselectivity was rationalized by the conformational analysis and DFT calculations of the transition states. The superior performance of the newly developed cobalt catalyst system could be broadly applied to both C(sp2)-H and C(sp3)-H carbamation reactions under mild conditions.
Visible-Light-Mediated Liberation and In Situ Conversion of Fluorophosgene
Petzold, Daniel,Nitschke, Philipp,Brandl, Fabian,Scheidler, Veronica,Dick, Bernhard,Gschwind, Ruth M.,K?nig, Burkhard
supporting information, p. 361 - 366 (2018/11/23)
The first example for the photocatalytic generation of a highly electrophilic intermediate that is not based on radical reactivity is reported. The single-electron reduction of bench-stable and commercially available 4-(trifluoromethoxy)benzonitrile by an organic photosensitizer leads to its fragmentation into fluorophosgene and benzonitrile. The in situ generated fluorophosgene was used for the preparation of carbonates, carbamates, and urea derivatives in moderate to excellent yields via an intramolecular cyclization reaction. Transient spectroscopic investigations suggest the formation of a catalyst charge-transfer complex-dimer as the catalytic active species. Fluorophosgene as a highly reactive intermediate, was indirectly detected via its next downstream carbonyl fluoride intermediate by NMR. Furthermore, detailed NMR analyses provided a comprehensive reaction mechanism including a water dependent off-cycle equilibrium.
Synthesis of oxazolidinones: Rhodium-catalyzed C-H amination of: N -mesyloxycarbamates
Lebel, Hélène,Mamani Laparra, Laura,Khalifa, Maroua,Trudel, Carl,Audubert, Clément,Szponarski, Mathieu,Dicaire Leduc, Cédric,Azek, Emna,Ernzerhof, Matthias
, p. 4144 - 4158 (2017/07/10)
N-Mesyloxycarbamates undergo intramolecular C-H amination reactions to afford oxazolidinones in good to excellent yields in the presence of rhodium(ii) carboxylate catalysts. The reaction is performed under green conditions and potassium carbonate is used, forming biodegradable potassium mesylate as a reaction by-product. This method enables the production of electron-rich, electron-deficient, aromatic and heteroaromatic oxazolidinones in good to excellent yields. Conformationally restricted cyclic secondary N-mesyloxycarbamates furnish cis-oxazolidinones in high yields and selectivity; DFT calculations are provided to account for the observed selectivity. trans-Oxazolidinones were prepared from acyclic secondary N-mesyloxycarbamates using Rh2(oct)4. The selectivity was reverted with a cytoxazone N-mesyloxycarbamate precursor using large chiral rhodium(ii) carboxylate complexes, affording the corresponding cis-oxazolidinone. This orthogonal selectivity was used to achieve the formal synthesis of (-)-cytoxazone.
Asymmetric synthesis of N-stereogenic molecules: Diastereoselective double aza-Michael reaction
Lauber, Alex,Zelenay, Benjamin,Cvengros, Jan
, p. 1195 - 1197 (2014/02/14)
A novel approach towards the asymmetric synthesis of N-stereogenic molecules via double aza-Michael addition was developed. The diastereomeric ratio can be increased by a thermodynamically controlled isomerization mechanism. Simple separation and functionalization of the products afford N-stereogenic compounds in high enantiomeric purity.
Ethyl imidazole-1-carboxylate (EImC) as a carbonylating agent: Efficient synthesis of oxazolidin-2-ones from amino alcohols
Veeraswamy,Reddy, K. Indrasena,Ragavan, R. Venkat,Yennam, Satyanarayana,Jayashree
, p. 109 - 111 (2013/03/14)
Various substituted oxazolidin-2-ones were synthesized from the corresponding amino alcohols using ethyl imidazole- 1-carboxylate (EImC). Highly substituted and sterically hindered amino alcohols and amino alcohols having a free hydroxy group were cyclized to oxazolidin-2-ones efficiently. This method is simple and produces oxazolidin-2-ones in very good yield.
Catalytic, enantioselective N-acylation of lactams and thiolactams using amidine-based catalysts
Yang, Xing,Bumbu, Valentina D.,Liu, Peng,Li, Ximin,Jiang, Hui,Uffman, Eric W.,Guo, Lei,Zhang, Wei,Jiang, Xuntian,Houk,Birman, Vladimir B.
supporting information, p. 17605 - 17612 (2013/01/15)
In contrast to alcohols and amines, racemic lactams and thiolactams cannot be resolved directly via enzymatic acylation or classical resolution. Asymmetric N-acylation promoted by amidine-based catalysts, particularly Cl-PIQ 2 and BTM 3, provides a convenient method for the kinetic resolution of these valuable compounds and often achieves excellent levels of enantioselectivity in this process. Density functional theory calculations indicate that the reaction occurs via N-acylation of the lactim tautomer and that cation-π interactions play a key role in the chiral recognition of lactam substrates.
Desulfurization-oxygenation of chiral 1,3-thiazolidine-2-thiones and 1,3-oxazolidine-2-thiones using propylene oxide and microwave irradiation
Minor-Villar, Leticia,Tello-Aburto, Rodolfo,Olivo, Horacio F.,Fuentes, Aydee,Romero-Ortega, Moises
, p. 2835 - 2839 (2013/02/21)
An efficient method for the desulfurization-oxygenation of 1,3-thiazolidine-2-thiones and 1,3-oxazolidine-2-thiones using propylene oxide and employing microwave irradiation is described. This strategy of oxygenation of the thiocarbonyl group provides an attractive methodology to prepare chiral 1,3-thiazolidin-2-ones and 1,3-oxazolidin-2-ones from the corresponding precursors in good yields. Copyright
Copper-catalyzed intramolecular C-H amination
Barman, Dipti N.,Nicholas, Kenneth M.
supporting information; experimental part, p. 908 - 911 (2011/04/26)
The amino-functionalization of tertiary, secondary and benzylic C-H bonds of tethered carbamates and sulfamates by iodosobenzene is catalyzed by Cu I-diimine complexes in moderate to good yield. Employing homochiral imine-Cucatalysts affords oxazolidinones and oxathiazinanes with modest enantioselectivity.
