123732-09-2Relevant articles and documents
peri-Xanthenoxanthene (PXX): a Versatile Organic Photocatalyst in Organic Synthesis
Pezzetta, Cristofer,Folli, Andrea,Matuszewska, Oliwia,Murphy, Damien,Davidson, Robert W. M.,Bonifazi, Davide
supporting information, p. 4740 - 4753 (2021/04/09)
Recent years have witnessed a continuous development of photocatalysts to satisfy the growing demand of photophysical and redox properties in photoredox catalysis, with complex structures or alternative strategies devised to access highly reducing or oxidising systems. We report herein the use of peri-xanthenoxanthene (PXX), a simple and inexpensive dye, as an efficient photocatalyst. Its highly reducing excited state allows activation of a wide range of substrates, thus triggering useful radical reactions. Benchmark transformations such as the addition of organic radicals, generated by photoreduction of organic halides, to radical traps are initially demonstrated. More complex dual catalytic manifolds are also shown to be accessible: the β-arylation of cyclic ketones is successful when using a secondary amine as organocatalyst, while cross-coupling reactions of aryl halides with amines and thiols are obtained when using a Ni co-catalyst. Application to the efficient two-step synthesis of the expensive fluoro-tetrahydro-1H-pyrido[4,3-b]indole, a crucial synthetic intermediate for the investigational drug setipiprant, has been also demonstrated. (Figure presented.).
Palladium-catalyzed redox cascade for direct β-arylation of ketones
Huang, Zhongxing,Dong, Guangbin
supporting information, p. 3253 - 3265 (2018/05/04)
Herein we report a full article about the detailed design and development of two palladium-catalyzed redox cascade methods that enable direct β-arylation of ketones. Palladium-catalyzed ketone dehydrogenation, aryl-X bond activation and conjugate addition were merged into a redox-neutral catalytic cycle. Non-metal-based aryl electrophiles were used as both the oxidant and the aryl source. The β-arylation with aryl iodides was achieved site-selectively with Pd(TFA)2/P(i-Pr)3 as the precatalyst and AgTFA as the iodide scavenger. Both cyclic and linear ketones can react to give β-aryl ketones with excellent functional group tolerance. The β-arylation with diaryliodonium salts was realized without stoichiometric heavy metal additives, and proved to be redox-neutral. A wider substrate scope regarding aryl groups and ketones was obtained for the arylation with diaryliodonium salts, and the possible involvement of palladium nanoparticles as the active catalyst was examined and discussed.
DIRECT B-ARYLATION OF CARBONYL COMPOUNDS
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Paragraph 0117; 0119, (2016/09/12)
Disclosed is a method for the β-C—H H functionalization of carbonyl compounds that is both selective and broadly applicable. The methods provide direct β-arylation of carbonyl compound with a diverse array of aryl or heteroaryl halides, aryl or heteroryl tosylate, aryl or heteroaryl triflates, or diaryliodonium salts, by palladium catalysis in the presence of a ligand and promoter.
The direct arylation of allylic sp3 C-H bonds via organic and photoredox catalysis
Cuthbertson, James D.,MacMillan, David W. C.
, p. 74 - 77 (2015/03/18)
The direct functionalization of unactivated sp3 C-H bonds is still one of the most challenging problems facing synthetic organic chemists. The appeal of such transformations derives from their capacity to facilitate the construction of complex organic molecules via the coupling of simple and otherwise inert building blocks, without introducing extraneous functional groups. Despite notable recent efforts, the establishment of general and mild strategies for the engagement of sp3 C-H bonds in C-C bond forming reactions has proved difficult. Within this context, the discovery of chemical transformations that are able to directly functionalize allylic methyl, methylene and methine carbons in a catalytic manner is a priority. Although protocols for direct oxidation and amination of allylic C-H bonds (that is, C-H bonds where an adjacent carbon is involved in a C = C bond) have become widely established, the engagement of allylic substrates in C-C bond forming reactions has thus far required the use of pre-functionalized coupling partners. In particular, the direct arylation of non-functionalized allylic systems would enable access to a series of known pharmacophores (molecular features responsible for a drug's action), though a general solution to this long-standing challenge remains elusive. Here we report the use of both photoredox and organic catalysis to accomplish a mild, broadly effective direct allylic C-H arylation. This C-C bond forming reaction readily accommodates a broad range of alkene and electron-deficient arene reactants, and has been used in the direct arylation of benzylic C-H bonds.
Air-stable solid aryl and heteroaryl organozinc pivalates: Syntheses and applications in organic synthesis
Manolikakes, Sophia M.,Ellwart, Mario,Stathakis, Christos I.,Knochel, Paul
supporting information, p. 12289 - 12297 (2015/03/31)
A wide range of air-stable, solid, polyfunctional aryl and heteroarylzinc pivalates were efficiently prepared by either magnesium insertion or Hal/Mg exchange followed by transmetalation with Zn(OPiv)2 (OPiv=pivalate). By reducing the amount of
Generation of functionalized aryl and heteroaryl aluminum reagents by halogen-lithium exchange
Klatt, Thomas,Groll, Klaus,Knochel, Paul
supporting information, p. 6953 - 6955 (2013/09/02)
Various functionalized aryl and heteroaryl aluminum reagents were obtained by performing I-Li or Br-Li exchange reactions with the corresponding unsaturated organic halides in the presence of i-Bu2AlCl. By means of an appropriate catalyst, the
Catalytic direct β-arylation of simple ketones with aryl iodides
Huang, Zhongxing,Dong, Guangbin
, p. 17747 - 17750 (2014/01/06)
Herein we report a direct β-arylation of simple ketones with widely available aryl iodides, combining palladium-catalyzed ketone oxidation, aryl-halide activation, and conjugate addition through a single catalytic cycle. Simple cyclic ketones with different ring-sizes, as well as acyclic ketones, can be directly arylated at the β-position with complete site-selectivity and excellent functional group tolerance.
Photoredox activation for the direct β-arylation of ketones and aldehydes
Pirnot, Michael T.,Rankic, Danica A.,Martin, David B. C.,MacMillan, David W. C.
, p. 1593 - 1596 (2013/05/09)
The direct β-activation of saturated aldehydes and ketones has long been an elusive transformation. We found that photoredox catalysis in combination with organocatalysis can lead to the transient generation of 5π-electron β-enaminyl radicals from ketones and aldehydes that rapidly couple with cyano-substituted aryl rings at the carbonyl β-position. This mode of activation is suitable for a broad range of carbonyl β-functionalization reactions and is amenable to enantioselective catalysis.
Addition reaction of arylboronic acids to aldehydes and α,β-unsaturated carbonyl compounds catalyzed by conventional palladium complexes in the presence of chloroform
Yamamoto, Tetsuya,Iizuka, Michiko,Takenaka, Hiroto,Ohta, Tetsuo,Ito, Yoshihiko
experimental part, p. 1325 - 1332 (2009/09/28)
Arylboronic acids react with aldehydes and α,β-unsaturated carbonyl compounds in the presence of a base and a catalytic amount of a palladium(0) complex with chloroform, affording the corresponding addition products in good yields, and chiral benzhydrol was obtained with up to 43% e.e. using (S,S)-bppm as a ligand. General palladium complexes have no catalytic activity without chloroform. Because chloroform is essential for this reaction, these reactions would be promoted by dichloromethylpalladium(II) species.
Organo[2-(hydroxymethyl)phenyl]dimethylsilanes as mild and reproducible agents for rhodium-catalyzed 1,4-addition reactions
Nakao, Yoshiaki,Chen, Jinshui,Imanaka, Hidekazu,Hiyama, Tamejiro,Ichikawa, Yoshitaka,Duan, Wei-Liang,Shintani, Ryo,Hayashi, Tamio
, p. 9137 - 9143 (2008/02/09)
Stable and reusable tetraorganosilicon reagents, alkenyl-, aryl-, and silyl[2-(hydroxymethyl)phenyl]-dimethylsilanes, undergo 1,4-addition reactions to α,β-unsaturated carbonyl acceptors under mild rhodium-catalysis. The reaction tolerates a diverse range of functional groups and is applicable to gram-scale synthesis. Use of a chiral diene ligand allows the achievement of the corresponding enantioselective transformations using the tetraorganosilicon reagents, providing the silicon-based approach to optically active ketones and substituted piperidones that serve as synthetic intermediates of pharmaceuticals. A rhodium alkoxide species is suggested to be responsible for a transmetalation step on the basis of the observed kinetic resolution of a racemic chiral phenylsilane in the enantioselective 1,4-addition reaction under the rhodium-chiral diene catalysis.
