1730-37-6Relevant academic research and scientific papers
Palladium-catalyzed synthesis of fluorenes by intramolecular c(sp 2)-h activation at room temperature
Fujihara, Tetsuaki,Tanji, Yutaka,Tsuji, Yasushi
, p. 805 - 808 (2020)
The synthesis of fluorenes by intramolecular Pd-catalyzed C(sp 2)-H activation of 2-arylbenzyl chlorides was conducted at room temperature by using commercially available triphenylphosphine and pivalic acid as ligands. The desired reactions proceeded efficiently at room temperature, and various substrates were converted into the corresponding fluorene derivatives in excellent yields.
Conformational Preference for the Binding of Biaryl Substrates and Inhibitors to the Active Site of Phenylethanolamine N-Methyltransferase
Grunewald, Gary L.,Carter, Anne E.,Sall, Daniel J.,Monn, James A.
, p. 60 - 65 (1988)
We have previously described regions of steric bulk tolerance in the aromatic-ring binding site of phenylethanolamine N-methyltransferase (PNMT, EC 2.1.1.28) for phenylethanolamine substrates and α-methylbenzylamine inhibitors.For bound substrates, this region is located in the vicinity of the para position of the aromatic ring, while for bound α-methylbenzylamine inhibitors, it is located in the region complementary to the meta position.In the present study, we sought to determine the preferred conformation of the biaryl portion of (m-phenylphenyl)- and (p-phenylphenyl)ethanolamine (4 and 5, respectively) as well as for m-phenyl and p-phenyl-α-methylbenzylamine (7 and 8, respectively) for PNMT active site interactions.Planar derivatives of 4,5,7, and 8 were obtained through the synthesis of 2-(1-fluorenyl)-2-hydroxyethylamine (9), 2-(2-fluorenyl)-2-hydroxyethylamine (10), 1-(1-fluorenyl)ethylamine (11), and 1-(2-fluorenyl)ethylamine (12).The four fluorene derivatives were examined for in vitro activity as substrates and inhibitors of the PNMT-catalyzed reaction.As in case of 4, 5, 7, and 8, we have observed a positional preference for the alkylamine side chain with respect to the biphenyl skeleton present in 9-12.Thus, fluorenylethanolamine 10 ("p-biphenyl") displays a Michaelis constant (Km = 26 μM) that is approximately 10 times lower than that for 9 ("m-bipenyl", Km = 297 μM); in the α-methylbenzylamine inhibitors, fluorenyl derivative 11 ("m-biphenyl", Ki = 4.14 μM) is approximately 40 times better than 12 ("p-biphenyl", Ki =185 μM) for in vitro inhibition of PNMT.In each case, conformational restriction of the biaryl system present in 4, 5, 7, and 8, such that the aromatic rings are coplanar, resulted in enhanced affinity for thr PNMT active site.Thus, conformational restriction of ethanolamine 5 (Km = 82 μM) and α-methylbenzylamine 7 (Ki = 89 μM) as in 11 (Ki = 4.14 μM) leads, in each case, to a stronger enzyme-ligand dissociable complex.These results, in conjunction with others from these laboratories, indicate that the PNMT active site beyond the zone that interacts with the central aromatic ring portion of phenylethanolamine substrates and α-methylbenzylamine inhibitors is essentially a flat, hydrophobic pocket.
A denitrogenative palladium-catalyzed cascade for regioselective synthesis of fluorenes
Fu, Wai Chung,Kwong, Fuk Yee
, p. 1411 - 1417 (2020)
We herein report a denitrogenative palladium-catalyzed cascade for the modular and regioselective synthesis of polysubstituted fluorenes. Hydrazone facilitates the Pd(ii) to Pd(iv) oxidative addition in a Catellani pathway and is also the methylene synthon in the proposed reaction. Aryl iodides and 2-bromoarylaldehyde hydrazones undergo a norbornene-controlled tandem reaction sequence to give a broad scope of fluorenes in the presence of a palladium catalyst. The method described is scalable and adaptable to a three-component reaction with in situ generation of the hydrazone group. Preliminary mechanistic investigations have been conducted.
Solid-state construction of zigzag periphery: Via intramolecular C-H insertion induced by alumina-mediated C-F activation
Akhmetov, Vladimir,Amsharov, Konstantin,F?rtsch, Andreas,Feofanov, Mikhail
, p. 12325 - 12328 (2021/11/30)
Caryl-F bond activation has become an important and quickly developing method for construction of carbon-based materials. We report that alumina-mediated C-F bond activation (AmCFA) enables construction of PAHs with zigzag periphery. This method includes
Decarbonylative Methylation of Aromatic Esters by a Nickel Catalyst
Okita, Toshimasa,Muto, Kei,Yamaguchi, Junichiro
, p. 3132 - 3135 (2018/05/28)
A Ni-catalyzed decarbonylative methylation of aromatic esters was achieved using methylaluminums as methylating agents. Dimethylaluminum chlorides uniquely worked as the methyl source. Because of the Lewis acidity of aluminum reagents, less reactive alkyl esters could also undergo the present methylation. By controlling the Lewis acidity of aluminum reagents, a chemoselective decarbonylative cross-coupling between alkyl esters and phenyl esters was successful.
Palladium-Catalyzed Formal [4 + 1] Annulation via Metal Carbene Migratory Insertion and C(sp2)-H Bond Functionalization
Xu, Shuai,Chen, Ri,Fu, Zihao,Zhou, Qi,Zhang, Yan,Wang, Jianbo
, p. 1993 - 1997 (2017/08/14)
A highly efficient and operationally simple palladium-catalyzed formal [4 + 1] annulation reaction has been developed. The reaction is featured by the formation of two different C-C bonds on a carbenic center. It represents a concise method for the synthesis of a wide range of polycyclic aromatic hydrocarbons (PAHs) and 1H-indenes with easily available (trimethylsilyl)diazomethane as the carbene source. Metal carbene migratory insertion and C(sp2)-H bond activation are proposed as the key steps in this transformation. The reaction further demonstrates the versatility of the carbene-based coupling in combination with various transition-metal-catalyzed transformations.
Efficient palladium-catalyzed C(sp2)-H activation towards the synthesis of fluorenes
Song, Juan,Li, Yali,Sun, Wei,Yi, Chenglong,Wu, Hao,Wang, Haotian,Ding, Keran,Xiao, Kang,Liu, Chao
, p. 9030 - 9033 (2016/11/11)
A facile protocol for the synthesis of fluorene derivatives has been developed through palladium-catalyzed cyclization of 2′-halo-diarylmethanes via activation of arylic C-H bonds. The reactions occurred smoothly and allowed both electron-rich and electron-deficient substrates to convert into their corresponding fluorenes in good to excellent yields. Studies revealed that this Pd-catalyzed cyclization was also available for the substrates of 2′-chloro-diarylmethanes and no catalyst poisoning occurred for 2′-iodo-diphenylmethane.
Halogen-Adjusted Chemoselective Synthesis of Fluorene Derivatives with Position-Controlled Substituents
Song, Juan,Sun, Wei,Li, Yali,Wei, Fuliang,Liu, Chao,Qian, Yan,Chen, Shufen
supporting information, p. 211 - 215 (2016/03/01)
Fluorenes have been synthesized through an efficient novel Pd-catalyzed tandem cross-coupling reaction; these substrates are fascinating building blocks found in organic photoelectric materials. The position of the substituent on fluorenes could be conveniently tuned by changing the halogen in the ortho-halobenzyl bromide substrates when coupled with various arylboronic acids. This newly developed synthetic approach could achieve the potential diversity in fluorene-based molecular architectures.
Palladium-Catalyzed Reaction of Haloarenes with Diarylethynes: Synthesis, Structural Analysis, and Properties of Methylene-Bridged Arenes
Lee, Che-Wei,Liu, En-Chih,Wu, Yao-Ting
, p. 10446 - 10456 (2015/11/18)
Fluorenes and methylene-bridged polyarenes were easily and efficiently synthesized from haloarenes (or aryl triflates) and diarylethynes by a one-pot, two-step procedure. This protocol involves the palladium-catalyzed cycloisomerization and a subsequent base-mediated retro-aldol condensation. A major advantage is that the starting materials need not have ortho functional groups to complete the annulation. The backbone of the designed products was enlarged using dihaloarenes, highly π-conjugated haloarenes, or diarylalkynes. The mechanism of the formation of benzo[a]fluorene was investigated. The bowl-shaped structure of methylene-bridged indenocorannulene was verified by X-ray crystallography. The photophysical and electrochemical properties of the products thus prepared were investigated.
Br?nsted acid-mediated intramolecular cyclization of biaryl triazenes for the synthesis of fluorenes and 9,10-dihydro-phenanthrenes
Xu, Lijun,Yang, Weijun,Zhang, Lili,Miao, Maozhong,Yang, Zhigen,Xu, Xin,Ren, Hongjun
, p. 9206 - 9221 (2015/01/08)
The efficient synthesis of fluorenes from biaryl triazenes is successfully developed. Up to 27 examples of biaryl triazenes are converted into their corresponding fluorene derivatives in the presence of CF3COOH (4.0 equiv). Mechanism research i
