- Redox-neutral decarboxylative photocyclization of anthranilic acids
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A mild metal-, catalyst-, and oxidant-free photoredox neutral system has been found to efficiently enable intramolecular decarboxylative cyclization of anthranilic acids. This facile protocol provides an alternative method for the synthesis of carbazoles. Mechanistic studies reveal a key photoinduced 6π-electrocyclization process and formic acid was released as the sole byproduct.
- Huang, Huawen,Deng, Kun,Deng, Guo-Jun
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p. 8243 - 8247
(2020/12/29)
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- Palladium-catalyzed C-H bond activation for the assembly of: N -aryl carbazoles with aromatic amines as nitrogen sources
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A convenient and efficient palladium-catalyzed C-H bond activation for the assembly of N-aryl carbazole is reported, in which two C-N bonds were formed under one set of conditions. The desired carbazoles were achieved in decent yields with a wide substrate scope by utilizing readily available 2-iodo biphenyls and aromatic amines as starting materials.
- Liu, Xiaobing,Sheng, Heyun,Zhou, Yao,Song, Qiuling
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supporting information
p. 1665 - 1668
(2020/02/18)
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- Palladium-Catalyzed Methylation of Aryl, Heteroaryl, and Vinyl Boronate Esters
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A method for the direct methylation of aryl, heteroaryl, and vinyl boronate esters is reported, involving the reaction of iodomethane with aryl-, heteroaryl-, and vinylboronate esters catalyzed by palladium and PtBu2Me. This transformation occurs with a remarkably broad scope and is suitable for late-stage derivatization of biologically active compounds via the boronate esters. The unique capabilities of this method are demonstrated by combining carbon-boron bond-forming reactions with palladium-catalyzed methylation in a tandem transformation.
- Haydl, Alexander M.,Hartwig, John F.
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supporting information
p. 1337 - 1341
(2019/02/26)
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- Trimethylphosphate as a Methylating Agent for Cross Coupling: A Slow-Release Mechanism for the Methylation of Arylboronic Esters
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A methyl group on an arene, despite its small size, can have a profound influence on biologically active molecules. Typical methods to form a methylarene involve strong nucleophiles or strong and often toxic electrophiles. We report a strategy for a new, highly efficient, copper and iodide co-catalyzed methylation of aryl- and heteroarylboronic esters with the mild, nontoxic reagent trimethylphosphate, which has not been used previously in coupling reactions. We show that it reacts in all cases tested in yields that are higher than those of analogous copper-catalyzed reactions of MeOTs or MeI. The combination of C-H borylation and this methylation with trimethylphosphate provides a new approach to the functionalization of inert C-H bonds and is illustrated by late-stage methylation of four medicinally active compounds. In addition, reaction on a 200 mmol scale demonstrates reliability of this method. Mechanistic studies show that the reaction occurs by a slow release of methyl iodide by reaction of PO(OMe)3 with iodide catalyst, rather than the typical direct oxidative addition to a metal center. The low concentration of the reactive electrophile enables selective reaction with an arylcopper intermediate, rather than nucleophilic groups on the arylboronate, and binding of tert-butoxide to the boronate inhibits reaction of the electrophile with the tert-butoxide activator to form methyl ether.
- He, Zhi-Tao,Li, Haoquan,Haydl, Alexander M.,Whiteker, Gregory T.,Hartwig, John F.
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supporting information
p. 17197 - 17202
(2018/12/14)
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- Photochemical Synthesis of Carbazoles Using an [Fe(phen)3](NTf2)2/O2 Catalyst System: Catalysis toward Sustainability
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An increasingly sustainable photochemical synthesis of carbazoles was developed using a catalytic system of Fe(phen)3(NTf2)2/O2 under continuous flow conditions and was demonstrated on gram-scale using a numbering-up strategy. Photocyclization of triaryl and diarylamines into the corresponding carbazoles occurs in general in higher yields than with previously developed photocatalysts.
- Parisien-Collette, Shawn,Hernandez-Perez, Augusto C.,Collins, Shawn K.
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supporting information
p. 4994 - 4997
(2016/10/14)
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- Visible Light-Mediated Ullmann-Type C-N Coupling Reactions of Carbazole Derivatives and Aryl Iodides
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The combined use of an iridium-based photocatalyst and a copper salt under blue light emitting diode irradiation enables the Ullmann-type C-N cross-coupling reaction between carbazole derivatives and aryl iodides to proceed under mild conditions.
- Yoo, Woo-Jin,Tsukamoto, Tatsuhiro,Kobayashi, Shu
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supporting information
p. 3640 - 3642
(2015/07/28)
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- "transition-metal-free" synthesis of carbazoles by photostimulated reactions of 2′-halo[1,1′-biphenyl]-2-amines
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An efficient and simple protocol for the preparation of a series of 9H-carbazoles by photostimulated SRN1 substitution reactions is presented. Substituted 9H-carbazoles were synthesized in low to excellent yields (up to 96%) through an intramolecular C-N bond formation of 2′-halo[1,1′-biphenyl]-2-amines by the photoinitiated SRN1 mechanism under mild and "transition-metal-free" conditions. The biphenylamines used as substrates were obtained with isolated yields ranging from 21% to 84% by two approaches: (A) the cross-coupling Suzuki-Miyaura reaction and (B) the radical arylation of anilines. Some key aspects of the proposed mechanism were evaluated at the B3LYP/6-311+G? level.
- Guerra, Walter D.,Rossi, Roberto A.,Pierini, Adriana B.,Barolo, Silvia M.
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p. 928 - 941
(2015/01/30)
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- Reactions of arynes with nitrosoarenes - An approach to substituted carbazoles
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No transition metals are necessary in the reaction of in situ generated arynes with nitrosoarenes to give substituted carbazoles. Depending on the fluoride source and the solvent, either N-arylated carbazoles or NH-carbazoles are obtained (see scheme; DME=dimethoxyethane, OTf=trifluoromethanesulfonate). In these cascades a C-C and one or two C-N bonds are formed. The reactions are easy to conduct and proceed under mild conditions. Copyright
- Chakrabarty, Shyamal,Chatterjee, Indranil,Tebben, Ludger,Studer, Armido
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p. 2968 - 2971
(2013/03/29)
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- A visible-light-mediated synthesis of carbazoles
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The photosynthetic preparation of N-aryl- and N-alkyl-bearing carbazoles utilizes continuous flow, visible light, and an in situ formed Cu-based sensitizer (see picture). The method is mild and efficient, and allows the straightforward synthesis of a variety of carbazoles with different substituents, heterocycles, and complex carbon architectures. Copyright
- Hernandez-Perez, Augusto C.,Collins, Shawn K.
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supporting information
p. 12696 - 12700
(2013/12/04)
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