- Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone
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Highly substituted fluorenones are readily prepared in mostly fair to good yields via metal- and additive-free TBHP-promoted cross-dehydrogenative coupling (CDC) of readily accessible N-methyl-2-(aminomethyl)biphenyls and 2-(aminomethyl)biphenyls. This methodology is compatible with numerous functional groups (methoxy, cyano, nitro, chloro, and SEM and TBS-protective groups for phenols) and was further utilized in the first total synthesis of the natural product nobilone.
- Bracher, Franz,Jourjine, Ilya A. P.,Krau?, Jürgen,Zeisel, Lukas
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supporting information
p. 2668 - 2679
(2021/11/30)
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- Pd-Catalyzed Assembly of Fluoren-9-ones by Merging of C-H Activation and Difluorocarbene Transfer
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We disclose a novel Pd-catalyzed assembly of fluoren-9-ones by merging of C-H activation and difluorocarbene transfer. ClCF2COONa served as a difluorocarbene precursor to be harnessed as a carbonyl source in this transformation. The current protocol enables us to afford fluoren-9-ones in high yields with excellent functional group compatibility, which also represents the first example of using difluorocarbene as a coupling partner in transition-metal-catalyzed C-H activation.
- Liu, Xiaobing,Sheng, Heyun,Zhou, Yao,Song, Qiuling
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supporting information
p. 2543 - 2547
(2021/05/05)
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- General method for functionalized polyaryl synthesis via aryne intermediates
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A method for base-promoted arylation of arenes and heterocycles by aryl halides and aryl triflates is described. Additionally, in situ electrophilic trapping of ArLi intermediates generated in the reaction of benzyne with deprotonated arenes or heterocycles has been developed, providing rapid and easy access to a wide range of highly functionalized polyaryls. Base-promoted arylation methodology complements transition-metal-catalyzed direct arylation and allows access to structures that are not easily accessible via other direct arylation methods. The reactions are highly functional-group tolerant, with alkene, ether, dimethylamino, trifluoromethyl, ester, cyano, halide, hydroxyl, and silyl functionalities compatible with reaction conditions.
- Truong, Thanh,Mesgar, Milad,Le, Ky Khac Anh,Daugulis, Olafs
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supporting information
p. 8568 - 8576
(2014/07/07)
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- Efficient synthesis of fluoren-9-ones by the palladium-catalyzed annulation of arynes by 2-haloarenecarboxaldehydes
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(Chemical Equation Presented) Fluoren-9-ones and derivatives are readily prepared in good yields by the annulation of in situ generated arynes by 2-haloarenecarboxaldehydes in the presence of a palladium catalyst.
- Waldo, Jesse P.,Zhang, Xiaoxia,Shi, Feng,Larock, Richard C.
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p. 6679 - 6685
(2008/12/22)
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- Photoinduced C-Br homolysis of 2-bromobenzophenones and Pschorr ring closure of 2-aroylaryl radicals to fluorenones
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(Chemical Equation Presented) A variety of diversely substituted 2-aroylaryl radicals, generated by photoinduced homolysis of 2-bromoarylketones, is shown to undergo Pschorr cyclization to yield fluorenones in moderate to excellent yields. The photochemical results illustrate that the substituents in the two phenyl rings of the 2-bromobenzophenone skeleton exert a dramatic influence on the reactivity of the derived 2-aroylaryl radicals. The disubstitution by methoxy groups in the radical ring renders the aryl σ-radical highly electrophilic and unreactive for hydrogen abstraction and cyclization. On the other hand, the substituents in the non-radical ring that strongly stabilize the hydrofluorenyl π-radical, formed subsequent to the attack of the 2-aroylaryl radical on the non-radical ring, promote cyclization to furnish fluorenones in excellent isolated yields.
- Moorthy, Jarugu Narasimha,Samanta, Subhas
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p. 9786 - 9789
(2008/03/17)
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- Mimicking the biological activity of diazobenzo[b]fluorene natural products with electronically tuned diazofluorene analogs
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Under appropriate electronic modulation, simple diazofluorene analogs recapitulate the DNA cleavage activity of kinamycin D under thiol-based reducing conditions. Achieving DNA cleavage under these reducing conditions is key to anticancer activity, as the most active compound, 1-methoxydiazofluorene, inhibits the proliferation of HeLa cells.
- Zeng, Wei,Eric Ballard,Tkachenko, Alexander G.,Burns, Virginia A.,Feldheim, Daniel L.,Melander, Christian
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p. 5148 - 5151
(2007/10/03)
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- Palladium-catalyzed annulation of arynes by 2-halobenzaldehydes: Synthesis of fluoren-9-ones
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(Chemical Equation Presented) Arynes, generated in situ from 2-(trimethylsilyl)aryl triflates and CsF, undergo annulation by o-haloarenecarboxaldehydes in the presence of a Pd catalyst, providing a useful new method for the synthesis of fluoren-9-ones in good yields.
- Zhang, Xiaoxia,Larock, Richard C.
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p. 3973 - 3976
(2007/10/03)
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- Structure-activity relationships and optimisation of the selective MDR modulator 2-(3,4-dimethoxyphenyl)-5-(9-fluorenylamino)-2-(methylethyl) pentanenitrile and its N-methyl derivative
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Several ring-substituted derivatives of previously studied MDR inhibitors 2-(3,4-dimethoxyphenyl)-5-(9-fluorenylamino)-2-(methylethyl)pentanenitrile and 2-(3,4-dimethoxyphenyl)-5-[(9-fluorenyl)-N-methylamino]-2-(methylethyl) pentanenitrile have been synthesised and studied with the aim of optimising activity and selectivity. The results show that MDR inhibition is scarcely sensitive to modulation of the electronic properties of the fluorene ring. Even if dramatic improvement was not obtained, one of the compounds (2) showed improved potency and selectivity with respect to the leads and appears to be a better candidate for drug development.
- Dei,Teodori,Garnier-Suillerot,Gualtieri,Scapecchi,Budriesi,Chiarini
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p. 2673 - 2682
(2007/10/03)
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- The directed ortho metalation - Palladium catalyzed cross coupling connection. A general regiospecific route to 9-phenanthrols and phenanthrenes. Exploratory further metalation
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A new general and regiospecific synthesis of 9-phenanthrols (1 + 2 → 3 → 4, Scheme 1, Table 1) proceeding by a Directed ortho Metalation (DoM), Suzuki-Miyaura crocs coupling, and a new LDA-mediated Directed remote Metalation sequence is described. The facile Pd-catalyzed hydrogenolysis of the phenanthrols 4 into the corresponding phenanthrenes 5 via their triflates 18 translates the original DoM regioselectivity also into a general synthesis of phenanthrenes (Table 2). Further DoM (19 → 20, 21; 24 → 25), cross coupling (20c → 23), as well as oxidation - ring contraction (4b, 4f → 28a, 28b) chemistry of phenanthrene derivatives is reported.
- Fu, Jian-Min,Snieckus, Victor
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p. 905 - 919
(2007/10/03)
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