22410-97-5Relevant academic research and scientific papers
Boryl Radical Activation of Benzylic C-OH Bond: Cross-Electrophile Coupling of Free Alcohols and CO2via Photoredox Catalysis
Jiang, Yi-Qian,Lan, Yu,Li, Shi-Jun,Li, Wen-Duo,Li, Yan-Lin,Wu, Yang,Xia, Ji-Bao
, (2022/04/19)
A new strategy for the direct cleavage of the C(sp3)-OH bond has been developed via activation of free alcohols with neutral diphenyl boryl radical generated from sodium tetraphenylborate under mild visible light photoredox conditions. This strategy has been verified by cross-electrophile coupling of free alcohols and carbon dioxide for the synthesis of carboxylic acids. Direct transformation of a range of primary, secondary, and tertiary benzyl alcohols to acids has been achieved. Control experiments and computational studies indicate that activation of alcohols with neutral boryl radical undergoes homolysis of the C(sp3)-OH bond, generating alkyl radicals. After reducing the alkyl radical into carbon anion under photoredox conditions, the following carboxylation with CO2 affords the coupling product.
Palladium-Catalyzed α-Arylation of Carboxylic Acids and Secondary Amides via a Traceless Protecting Strategy
He, Zhi-Tao,Hartwig, John F.
supporting information, p. 11749 - 11753 (2019/08/26)
A novel traceless protecting strategy is presented for the long-standing challenge of conducting the palladium-catalyzed α-arylation of carboxylic aids and secondary amides with aryl halides. Both of the presented coupling processes occur with a variety of carboxylic acids and amides and with a variety of aryl bromides containing a broad range of functional groups, including base-sensitive functionality like acyl, alkoxycarbonyl, nitro, cyano, and even hydroxyl groups. Five commercial drugs were prepared through this method in one step in 81-96% yield. Gram-scale synthesis of medication Naproxen and Flurbiprofen with low palladium loading further highlights the practical value of this method.
Construction of a visible light-driven hydrocarboxylation cycle of alkenes by the combined use of Rh(i) and photoredox catalysts
Murata, Kei,Numasawa, Nobutsugu,Shimomaki, Katsuya,Takaya, Jun,Iwasawa, Nobuharu
supporting information, p. 3098 - 3101 (2017/03/17)
A visible light driven catalytic cycle for hydrocarboxylation of alkenes with CO2 was established using a combination of a Rh(i) complex as a carboxylation catalyst and [Ru(bpy)3]2+ (bpy = 2,2′- bipyridyl) as a photoredox catalyst. Two key steps, the generation of Rh(i) hydride species and nucleophilic addition of π-benzyl Rh(i) species to CO2, were found to be mediated by light.
Rhodium-Catalyzed Hydrocarboxylation of Olefins with Carbon Dioxide
Kawashima, Shingo,Aikawa, Kohsuke,Mikami, Koichi
supporting information, p. 3166 - 3170 (2016/07/19)
The catalytic hydrocarboxylation of styrenes derivatives and α,β-unsaturated carbonyl compounds with CO2(101.3 kPa) in the presence of an air-stable rhodium catalyst was explored. The combination of [RhCl(cod)]2(cod = cyclooctadiene) as a catalyst and diethylzinc as a hydride source allowed for effective hydrocarboxylation and provided the corresponding α-aryl carboxylic acids in moderate to excellent yields. In this catalytic process with carbon dioxide, intervention of the RhI–H species, which could be generated from the RhIcatalyst and diethylzinc, was clarified. Significantly, the catalytic asymmetric hydrocarboxylation of α,β-unsaturated esters with carbon dioxide was also performed by employing a cationic rhodium complex possessing (S)-(–)-4,4′-bi-1,3-benzodioxole-5,5′-diylbis(diphenylphosphine) [(S)-SEGPHOS] as a chiral diphosphine ligand. A plausible model for asymmetric induction was proposed by determination of the absolute configuration of the product.
Beyond benzyl grignards: Facile generation of benzyl carbanions from styrenes
Grigg, R. David,Rigoli, Jared W.,Van Hoveln, Ryan,Neale, Samuel,Schomaker, Jennifer M.
supporting information; experimental part, p. 9391 - 9396 (2012/08/29)
Benzylic functionalization is a convenient approach towards the conversion of readily available aromatic hydrocarbon feedstocks into more useful molecules. However, the formation of carbanionic benzyl species from benzyl halides or similar precursors is far from trivial. An alternative approach is the direct reaction of a styrene with a suitable coupling partner, but these reactions often involve the use of precious-metal transition-metal catalysts. Herein, we report the facile and convenient generation of reactive benzyl anionic species from styrenes. A CuI-catalyzed Markovnikov hydroboration of the styrenic double bond by using a bulky pinacol borane source is followed by treatment with KOtBu to facilitate a sterically induced cleavage of the C-B bond to produce a benzylic carbanion. Quenching this intermediate with a variety of electrophiles, including CO2, CS2, isocyanates, and isothiocyanates, promotes C-C bond formation at the benzylic carbon atom. The utility of this methodology was demonstrated in a three-step, two-pot synthesis of the nonsteroidal anti-inflammatory drug (±)-flurbiprofen. Make or break: The facile generation of benzyl anion equivalents from styrenes has been achieved by using a Cu-catalyzed hydroboration in conjunction with sterically induced cleavage of the C-B bond with tBuOK. Quenching this reactive intermediate with heteroallene electrophiles yields benzylic C-C bond formation (see scheme), and the utility of this methodology has been demonstrated by a synthesis of the nonsteroidal anti-inflammatory drug (±)-flurbiprofen. Copyright
Nickel-catalyzed reductive carboxylation of styrenes using CO2
Williams, Catherine M.,Johnson, Jeffrey B.,Rovis, Tomislav
supporting information; experimental part, p. 14936 - 14937 (2009/03/12)
A nickel-catalyzed reductive carboxylation of styrenes using CO2 has been developed. The reaction proceeds under mild conditions using diethylzinc as the reductant. Preliminary data suggests the mechanism involves two discrete nickel-mediated catalytic cycles, the first involving a catalyzed hydrozincation of the alkene followed by a second, slower nickel-catalyzed carboxylation of the in situ formed organozinc reagent. Importantly, the catalyst system is very robust and will fixate CO2 in good yield even if exposed to only an equimolar amount introduced into the headspace above the reaction. Copyright
