66265-99-4Relevant academic research and scientific papers
Organic photocatalysis for the radical couplings of boronic acid derivatives in batch and flow
Lima, Fabio,Grunenberg, Lars,Rahman, Husaini B. A.,Labes, Ricardo,Sedelmeier, Joerg,Ley, Steven V.
, p. 5606 - 5609 (2018)
We report an acridium-based organic photocatalyst as an efficient replacement for iridium-based photocatalysts to oxidise boronic acid derivatives by a single electron process. Furthermore, we applied the developed catalytic system to the synthesis of four active pharmaceutical ingredients (APIs). A straightforward scale up approach using continuous flow photoreactors is also reported affording gram an hour throughput.
A Lewis Base Catalysis Approach for the Photoredox Activation of Boronic Acids and Esters
Lima, Fabio,Sharma, Upendra K.,Grunenberg, Lars,Saha, Debasmita,Johannsen, Sandra,Sedelmeier, Joerg,Van der Eycken, Erik V.,Ley, Steven V.
supporting information, p. 15136 - 15140 (2017/11/20)
We report herein the use of a dual catalytic system comprising a Lewis base catalyst such as quinuclidin-3-ol or 4-dimethylaminopyridine and a photoredox catalyst to generate carbon radicals from either boronic acids or esters. This system enabled a wide range of alkyl boronic esters and aryl or alkyl boronic acids to react with electron-deficient olefins via radical addition to efficiently form C?C coupled products in a redox-neutral fashion. The Lewis base catalyst was shown to form a redox-active complex with either the boronic esters or the trimeric form of the boronic acids (boroxines) in solution.
Catalytic Ring-Opening of Cyclic Alcohols Enabled by PCET Activation of Strong O-H Bonds
Yayla, Hatice G.,Wang, Huaiju,Tarantino, Kyle T.,Orbe, Hudson S.,Knowles, Robert R.
supporting information, p. 10794 - 10797 (2016/09/09)
We report a new photocatalytic protocol for the redox-neutral isomerization of cyclic alcohols to linear ketones via C-C bond scission. Mechanistic studies demonstrate that key alkoxy radical intermediates in this reaction are generated via the direct homolytic activation of alcohol O-H bonds in an unusual intramolecular PCET process, wherein the electron travels to a proximal radical cation in concert with proton transfer to a weak Br?nsted base. Effective bond strength considerations are shown to accurately forecast the feasibility of alkoxy radical generation with a given oxidant/base pair.
Continuous UV-Flow Microsystem for Efficient Radical Generation from Organotrifluoroborates by Photoredox Catalysis
El Achi, Nassim,Penhoat, Ma?l,Bakkour, Youssef,Rolando, Christian,Chausset-Boissarie, La?titia
supporting information, p. 4284 - 4288 (2016/09/13)
An efficient continuous-flow protocol for C–O and C–C bond formation from organoborates by photoredox catalysis under UV irradiation was explored. The combination of a cyclometalated iridium photocatalyst, high-power UV light-emitting diode irradiation, and microreactor technology resulted in very efficient radical generation. The flow device enabled determination of highly accurate kinetic data that allowed the observation of good correlations with the standard Hammett σ (–0.26 to 0.227) values for a wide variety of substituents on the benzyl moiety (? = –4.70, R2= 0.98). Good to excellent yields were obtained for a variety of substrates by applying significantly short residence times.
Iron-catalyzed arene alkylation reactions with unactivated secondary alcohols
Jefferies, Latisha R.,Cook, Silas P.
supporting information, p. 2026 - 2029 (2014/05/06)
A simple, iron-based catalytic system allows for the inter- and intramolecular arylation of unactivated secondary alcohols. This transformation expands the substrate scope beyond the previously required activated alcohols and proceeds under mild reaction conditions, tolerating air and moisture. Furthermore, the use of an enantioenriched secondary alcohol provides an enantioenriched product for the intramolecular reaction, thereby offering a convenient approach to nonracemic products.
Visible light-induced selective generation of radicals from organoborates by photoredox catalysis
Yasu, Yusuke,Koike, Takashi,Akita, Munetaka
supporting information, p. 3414 - 3420 (2013/02/25)
A new strategy for the generation of carbon-centered radicals via oxidation of alkyl-, allyl-, benzyl- and arylborates by visible-light-driven single electron transfer (SET) photoredox catalysis has been established. The generated radicals smoothly react with TEMPO and electron-deficient alkenes to afford C-O and C-C coupling products, respectively. In this radical initiating system, cyclic organo(triol)borates turn out to be useful radical precursors.
Heck reaction of aryl bromides with pent-4-en-2-ol, 2-phenylpent-4-en-2-ol, or hept-6-en-3-ol catalysed by a palladium-tetraphosphine complex
Berthiol, Florian,Doucet, Henri,Santelli, Maurice
, p. 3589 - 3602 (2007/10/03)
The tetraphosphine cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl) cyclopentane in combination with [Pd(η3-C3H 5)Cl]2 affords a very efficient catalyst for the Heck reaction of aryl bromides with pent-4-en
New Intramolecular α-Arylation Strategy of Ketones by the Reaction of Silyl Enol Ethers to Photosensitized Electron Transfer Generated Arene Radical Cations: Construction of Benzannulated and Benzospiroannulated Compounds
Pandey, Ganesh,Karthikeyan,Murugan
, p. 2867 - 2872 (2007/10/03)
Efficient intramolecular α-arylation of ketones is achieved by the reaction of silyl enol ethers to photosensitized electron transfer (PET) generated arene radical cations. The arene radical cations are generated by one-electron transfer from the excited state of the methoxy-substituted arenes to ground-state 1,4-dicyanonaphthalene (DCN). This arylation strategy has provided the unique opportunity of constructing five- (23), six- (18), seven- (25) and eight-membered (27) benzannulated as well as benzospiroannulated (34) compounds. The explanation for the formation of 27 has been advanced by considering the proximity between the arene radical cation and silyl enol ether due to the self-coiling in the aqueous environment.
Zeolite β-Induced Rearrangement of Alkoxybenzyl Allyl Ethers to Aldehydes and Ketones. 5.1 Variation of the Allylic Moiety
Wennerberg, Johan,Olofsson, Charlotte,Frejd, Torbjoern
, p. 3595 - 3598 (2007/10/03)
Allylic PMB ethers rearranged in the presence of zeolite β to form 4-arylbutanals or 5-arylpentanones depending on the substituent pattern of the allylic moiety. Best results were obtained with substrates carrying simple substituents in the allylic 2-posi
Electroreductive Intramolecular Coupling of Nonconjugated Aromatic Ketones
Kise, Naoki,Suzumoto, Takeshi,Shono, Tatsuya
, p. 1407 - 1413 (2007/10/02)
The electroreduction of nonconjugated aromatic ketones gave intramolecularly coupled products.The best result was obtained using an Sn cathode in i-PrOH containing tetraalkylammonium salt as a supporting electrolyte.This reductive cyclization proceeded with remarkable stereoselectivity, and the cis isomer was obtained exclusively.A variety of new bi- and polycyclic compounds were synthesized.The reaction mechanism was studied, and it was suggested that the anion radical generated by one-electron transfer to a carbonyl group attacks an aromatic ring intramolecularly.The choice of counter cation of the anion radical was critical for the reductive cyclization.Other reductive methods employing metal reducing agents were also studied.Reduction with Na in HMPA-THF gave the same cyclized product, though the yield was lower than that with the electroreduction.
