229-95-8Relevant academic research and scientific papers
Visible light mediated synthesis of 6H-benzo[c]chromenes: transition-metal-free intramolecular direct C-H arylation
Budén, María E.,Heredia, Micaela D.,Puiatti, Marcelo,Rossi, Roberto A.
, p. 228 - 239 (2021/12/29)
A synthetic approach towards the 6H-benzo[c]chromene ring under visible light and transition-metal-free conditions has been developed. Benzochromenes are synthesized from the corresponding (2-halobenzyl) phenyl ethers or (2-halophenyl) benzyl ethers using
N-Methylanilines as Simple and Efficient Promoters for Radical-Type Cross-Coupling Reactions of Aryl Iodides
Yang, Huan,Zhang, Li,Jiao, Lei
supporting information, p. 65 - 69 (2017/01/09)
Activation of the carbon–halogen bonds in aryl halides is a key step in transition-metal-free cross-coupling reactions. In this paper, a new and efficient radical initiation system for the activation of iodoarenes to produce aryl radicals was discovered, which employs the combination of N-methylanilines and tBuOK. This radical initiation system is robust and versatile, enabling various types of aryl-radical-related reactions.
Tandem C-H activation/arylation catalyzed by low-valent iron complexes with bisiminopyridine ligands
Salanouve, Elise,Bouzemame, Ghania,Blanchard, Sebastien,Derat, Etienne,Desage-El Murr, Marine,Fensterbank, Louis
, p. 4754 - 4761 (2014/05/06)
Tandem C-H activation/arylation between unactivated arenes and aryl halides catalyzed by iron complexes that bear redox-active non-innocent bisiminopyridine ligands is reported. Similar reactions catalyzed by first-row transition metals have been shown to involve substrate-based aryl radicals, whereas our catalytic system likely involves ligand-centered radicals. Preliminary mechanistic investigations based on spectroscopic and reactivity studies, in conjunction with DFT calculations, led us to propose that the reaction could proceed through an inner-sphere C-H activation pathway, which is rarely observed in the case of iron complexes. This bielectronic noble-metal-like behavior could be sustained by the redox-active non-innocent bisiminopyridine ligands. A radical choice! A low-valent iron complex with non-innocent bisiminopyridine ligands performs C-H activation/arylation of unactivated aryl compounds (see figure). The reaction likely involves ligand-based radicals, whereas previously reported iron-based systems imply substrate-based radicals.
Organic super-electron-donors: Initiators in transition metal-free haloarene-arene coupling
Zhou, Shengze,Anderson, Greg M.,Mondal, Bhaskar,Doni, Eswararao,Ironmonger, Vicki,Kranz, Michael,Tuttle, Tell,Murphy, John A.
, p. 476 - 482 (2014/01/17)
Recent papers report transition metal-free couplings of haloarenes to arenes to form biaryls, triggered by alkali metal tert-butoxides in the presence of various additives. These reactions proceed through radical intermediates, but understanding the origin of the radicals has been problematic. Electron transfer from a complex formed from potassium tert-butoxide with additives, such as phenanthroline, has been suggested to initiate the radical process. However, our computational results encouraged us to search for alternatives. We report that heterocycle-derived organic electron donors achieve the coupling reactions and these donors can form in situ in the above cases. We show that an electron transfer route can operate either with phenanthrolines as additives or using pyridine as solvent, and we propose new heterocyclic structures for the respective electron donors involved in these cases. In the absence of additives, the coupling reactions are still successful, although more sluggish, and in those cases benzynes are proposed to play crucial roles in the initiation process.
Ultrasound-promoted intramolecular direct arylation in a capillary flow microreactor
Zhang, Lei,Geng, Mei,Teng, Peng,Zhao, Dan,Lu, Xi,Li, Jian-Xin
, p. 250 - 256 (2012/04/23)
An intramolecular direct arylation of various aryl bromides was performed using ultrasonic irradiation and a continuous flow capillary microreactor. The present procedure provided a higher functional group tolerance, ligand-free, milder reaction condition
Neocuproine-KOtBu promoted intramolecular cross coupling to approach fused rings
Sun, Chang-Liang,Gu, Yi-Fan,Huang, Wei-Ping,Shi, Zhang-Jie
, p. 9813 - 9815 (2011/10/11)
Polycycles can be produced with different linkages (A, B = O, N, C, S) by constructing biaryl C-C bonds via neocuproine-KOtBu promoted cross coupling between C-Xs and C-Hs.
Potassium tert-butoxide promoted intramolecular arylation via a radical pathway
Roman, Daniela Sustac,Takahashi, Yoko,Charette, Andre B.
supporting information; scheme or table, p. 3242 - 3245 (2011/08/02)
Potassium tert-butoxide mediated intramolecular cyclization of aryl ethers, amines, and amides was efficiently performed under microwave irradiation to provide the corresponding products in high regioisomeric ratios. The reaction proceeds via single-electron transfer to initiate the formation of an aryl radical, followed by a kinetically favored 5-exo-trig and subsequent ring expansion.
Catalytic direct arylation with aryl chlorides, bromides, and iodides: Intramolecular studies leading to new intermolecular reactions
Campeau, Louis-Charles,Parisien, Mathieu,Jean, Annie,Fagnou, Keith
, p. 581 - 590 (2007/10/03)
A catalyst for the intramolecular direct arylation of a broad range of simple and heterocyclic arenes with aryl iodides, bromides, and chlorides has been developed. These reactions occur in excellent yield and are highly selective. Studies with aryl iodides substrates revealed that catalyst poisoning occurs due to the accumulation of iodide in the reaction media. This can be overcome by the addition of silver salts which also permits these reactions to occur at lower temperature. The utility of the methodology is illustrated by a rapid synthesis of a carbazole natural product and by the synthesis of sterically encumbered tetra-ortho-substituted biaryls via ring-opening reactions of the direct arylation products. Mechanistic investigations have provided insight into the catalyst's mode of action and show the presence of a kinetically significant C-H bond cleavage in palladium-catalyzed direct arylation of simple arenes. Knowledge garnered from these studies has led to the development of new intermolecular arylation reactions with previously inaccessible arenes, opening the door for the development of other new direct arylation processes.
Direct arylation reactions catalyzed by Pd(OH)2/C: Evidence for a soluble palladium catalyst
Parisien, Mathieu,Valette, Damien,Fagnou, Keith
, p. 7578 - 7584 (2007/10/03)
Palladium hydroxide on carbon (Pearlman's catalyst) effectively catalyzes direct arylation reactions of aryl iodides and bromides, providing excellent arylation-to-hydrodehalogenation ratios (>30:1) with broad scope for both intra- and intermolecular arylation processes. Studies aimed at determining the nature of the active catalyst indicate that an active homogeneous palladium species is produced under the reaction conditions.
A new cascade radical reaction for the synthesis of biaryls and triaryls from benzyl iodoaryl ethers
Harrowven, David C.,Nunn, Michael I.T.,Newman, Nicola A.,Fenwick, David R.
, p. 961 - 964 (2007/10/03)
The paper describes a new method of synthesizing biaryls and triaryls through an intramolecular ipso-substitution reaction initiated by the addition of an aryl radical to a benzyl ether. A tandem variant of the reaction has also been demonstrated. A short synthesis of isoaucuparin 27, a natural product found in the sapwood tissue of Sorbus aucuparia, is also described.
