400747-55-9Relevant articles and documents
Olefin Cyclopropanation by Radical Carbene Transfer Reactions Promoted by Cobalt(II)/Porphyrinates: Active-Metal-Template Synthesis of [2]Rotaxanes
Alcantara, Arthur F. P.,Fontana, Liniquer A.,Rigolin, Vitor H.,Andrade, Yuri F. S.,Ribeiro, Marcos A.,Barros, Wdeson P.,Ornelas, Catia,Megiatto, Jackson D.
, p. 8979 - 8983 (2018)
A CoII/porphyrinate-based macrocycle in the presence of a 3,5-diphenylpyridine axial ligand functions as an endotopic ligand to direct the assembly of [2]rotaxanes from diazo and styrene half-threads, by radical-carbene-transfer reactions, in excellent 95 % yield. The method reported herein applies the active-metal-template strategy to include radical-type activation of ligands by the metal-template ion during the organometallic process which ultimately yields the mechanical bond. A careful quantitative analysis of the product distribution afforded from the rotaxane self-assembly reaction shows that the CoII/porphyrinate subunit is still active after formation of the mechanical bond and, upon coordination of an additional diazo half-thread derivative, promotes a novel intercomponent C?H insertion reaction to yield a new rotaxane-like species. This unexpected intercomponent C?H insertion illustrates the distinct reactivity brought to the CoII/porphyrinate catalyst by the mechanical bond.
Control over the Redox Cooperative Mechanism of Radical Carbene Transfer Reactions for the Efficient Active-Metal-Template Synthesis of [2]Rotaxanes
Alcantara, Arthur F. P.,Fontana, Liniquer A.,Almeida, Marlon P.,Rigolin, Vitor H.,Ribeiro, Marcos A.,Barros, Wdeson P.,Megiatto, Jackson D.
, p. 7808 - 7822 (2020)
A 5,15-bis(1,1′-biphenyl)porphyrin-based molecular clip covalently connected to a ditopic aliphatic ester loop moiety yields a semi-rigid macrocycle with a well-defined cavity. The resulting macrocycle fits the structural requirements for the preparation of porphyrinates capable of promoting formation of C?C bonds. To demonstrate the usefulness of porphyrin-based macrocycles, an active-metal-template synthesis of rotaxanes through a redox non-innocent carbene transfer reaction is described. Coordination of CoII ions into the porphyrin subunit followed by addition of appropriate monodentate nitrogen-based additives to function as axial ligands enables the radical carbene transfer reactions to styrene derivatives to occur exclusively through the cavity of the macrocycle to afford cyclopropane-linked rotaxanes in excellent 95 % yield. Investigation of the product distribution afforded from the rotaxane assembly reaction reveals how the redox cooperative action between the carbene species and the CoII ions can be manipulated to gain control over the radical-type mechanism to favor the productive rotaxane forming process.
Asymmetric synthesis of functionalized tetrahydrofluorenones via an NHC-catalyzed homoenolate Michael addition
Shu, Tao,Li, Sun,Chen, Xiang-Yu,Liu, Qiang,Von Essen, Carolina,Rissanen, Kari,Enders, Dieter
, p. 7661 - 7664 (2018)
The first example of an N-heterocyclic carbene-catalyzed asymmetric desymmetrization of enal-tethered cyclohexadienones via an intramolecular homoenolate Michael addition/esterification reaction is described. This new protocol offers a direct entry to various functionalized tetrahydrofluorenones with three contiguous stereocenters in high yields, good diastereoselectivities and excellent enantioselectivities.
Photochromic phenoxyl-imidazolyl radical complexes with decoloration rates from tens of nanoseconds to seconds
Yamashita, Hiroaki,Ikezawa, Takahiro,Kobayashi, Yoichi,Abe, Jiro
, p. 4952 - 4955 (2015)
We report a novel photochromic molecular system, phenoxyl-imidazolyl radical complex (PIC), in which both a phenoxyl radical site and an imidazolyl radical site are reversibly and simultaneously generated upon UV light irradiation. PIC consists of the three parts: an aromatic linker, a diarylimidazole moiety, and a 4H-cyclohexadienone ring. Upon UV light irradiation, the C-N bond between the 4H-cyclohexadienone ring and the imidazole ring in the colorless closed-ring isomer of PIC undergoes a homolytic cleavage, leading to the formation of the transient colored open-ring isomer. Based on the substituents on the imidazoyl/4H-cyclohexadienone rings and the nature of the aromatic linker, the half-life of the colored open-ring isomer can be varied between tens of nanoseconds and seconds. PIC derivatives containing a 1,2-phenylene linker exhibit high fatigue resistance toward repeated photochromic reactions. Analysis using laser flash photolysis reveals that the absorption spectra of the open-ring isomers are not readily rationalized by a straightforward superposition of the spectra of the two component radical fragments and the photogenerated radicals are electronically coupled through the aromatic linker. Furthermore, the open-ring isomer can be treated as a hybrid of the pure open-shell biradical and closed-shell quinoid resonance structures.
Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical
Kobayashi, Yoichi,Mamiya, Yukie,Mutoh, Katsuya,Sotome, Hikaru,Koga, Masafumi,Miyasaka, Hiroshi,Abe, Jiro
, p. 2369 - 2379 (2019)
Visible-light sensitized photoswitches have been paid particular attention in the fields of life sciences and materials science because long-wavelength light reduces photodegradation, transmits deep inside of matters, and achieves the selective excitation
Asymmetric transfer hydrogenation of acetophenone derivatives using 2-benzyl-tethered ruthenium (II)/TsDPEN complexes bearing η6-(p-OR) (R = H, iPr, Bn, Ph) ligands
Knighton, Richard C.,Vyas, Vijyesh K.,Mailey, Luke H.,Bhanage, Bhalchandra M.,Wills, Martin
, p. 72 - 79 (2018/09/22)
A series of 4′-OR (R = H, iPr, Bn, Ph) substituted ruthenium (II) biphenyl TsDPEN complexes are described; the complexes are accessed via an operationally simple and reliable two-step ligand synthesis followed by ligation to the ruthenium (II) centre. We report the preliminary asymmetric transfer hydrogenation (ATH) results on a range of primarily acetophenone derivatives with these new complexes using FA/TEA (5:2) as a reducing agent; the results confirm that these catalysts are capable of reducing the substrates within 48 h with excellent enantioselectivities.
Silver-Catalyzed Tandem C=C Bond Hydroazidation/Radical Addition/Cyclization of Biphenyl Acetylene: One-Pot Synthesis of 6-Methyl Sulfonylated Phenanthridines
Tang, Jiawei,Sivaguru, Paramasivam,Ning, Yongquan,Zanoni, Giuseppe,Bi, Xihe
supporting information, p. 4026 - 4029 (2017/08/14)
A silver-catalyzed tandem carbon-carbon triple bond hydroazidation, radical addition, and cyclization of biphenyl acetylene is described under mild conditions, leading to the formation of 6-methyl sulfonylated phenanthridines in good yields. In this novel cascade reaction, most of the atoms are incorporated into the product without cleavage of the C=C bond. Mechanistic studies suggest the reaction should proceed through an iminyl radical reactive intermediate.
Palladium salt and functional reduced graphene oxide complex: in situ preparation of a generally applicable catalyst for C-C coupling reactions
Wang, Sheng,Hu, Donghua,Hua, Wenwen,Gu, Jiangjiang,Zhang, Qiuhong,Jia, Xudong,Xi, Kai
, p. 53935 - 53939 (2015/06/30)
A novel Pd catalyst was designed by affording Pd2+ salt on the surface of functional reduced graphene oxide (FRGO), providing a new cheap and stable in situ prepared palladium catalyst for C-C coupling reactions, including the Heck reaction, Suzuki reaction, C-H bond functionalization reactions of thiophenes, and terminal alkyne C-H activation and homocoupling.
Desymmetrization of cyclohexadienones via intramolecular stetter reaction to construct tricyclic carbocycles
Jia, Min-Qiang,You, Shu-Li
supporting information, p. 1201 - 1204 (2013/07/19)
N-Heterocyclic carbene catalyzed desymmetrization of cyclohexadienones to construct tricyclic carbocycles via an intramolecular enantioselective Stetter reaction was realized. With 10 mol% of d-camphor-derived triazolium salt E and 10 mol% of KOAc, various substituted tricyclic carbocycles bearing a quaternary carbon stereogenic center and two contiguous stereocenters were obtained in excellent yields with up to 89% ee. Georg Thieme Verlag Stuttgart New York.
