- Ligand-Free Nickel-Catalyzed Reductive Allylic Defluorinative Cross-Coupling of α-Trifluoromethyl Alkenes with Epoxides
-
We report a reductive allylic defluorinative reaction of α-trifluoromethyl alkenes with terminal epoxides, which consists of an iodide-mediated regioselective ring opening and a nickel-catalyzed radical-type cross-coupling, providing diverse tertiary gem -difluorobishomoallylic alcohols in moderate to high yields. Notably, this reaction is conducted under mild conditions and requires no external ligand or proton donor.
- Lin, Zhiyang,Lan, Yun,Wang, Chuan
-
-
Read Online
- Spirocyclohexadienones: VIII. 1-R-3,3-Dimethyl-2-azaspiro[5.5]undeca-1,7, 10-trien-9-ones
-
1-R-3,3-Dimethyl-2-azaspiro[5.5]undeca-1,7,10-trien-9-ones were synthesized by condensation of 4-(p-methoxyphenyl)-2-methylbutan-2-ol with nitriles RCN in the presence of a concn. sulfuric acid. Nauka/Interperiodica 2006.
- Glushkov,Vetoshkina,Kolgashev,Maiorova,Shurov,Shklyaev
-
-
Read Online
- 8-Hydroxyquinolin-2(1H)-one analogues as potential β2-agonists: Design, synthesis and activity study
-
β2-Agonists that bind to plasmalemmal β2-adrenoceptors causing cAMP accumulation are widely used as bronchodilators in chronic respiratory diseases. Here, we designed and synthesized a group of 8-hydroxyquinolin-2(1H)-one analogues and studied their β2-agonistic activities with a cellular cAMP assay. Compounds B05 and C08 were identified as potent (EC50 2-agonists among the compounds tested. They behaved as partial β2-agonists in non-overexpressed HEK293 cells, and possessed rapid smooth muscle relaxant actions and long duration of action in isolated guinea pig tracheal strip preparations. In summary, B05 and C08 are β2-agonists with potential applicability in chronic respiratory diseases.
- Xing, Gang,Zhi, Zhengxing,Yi, Ce,Zou, Jitian,Jing, Xuefeng,Yiu-Ho Woo, Anthony,Lin, Bin,Pan, Li,Zhang, Yuyang,Cheng, Maosheng
-
-
- Aqueous phase semihydrogenation of alkynes over Ni-Fe bimetallic catalysts
-
Bimetallic Ni-Fe catalysts (Ni/Fe, 1?:?1, 1?:?3, and 3?:?1) are synthesized and explored for their catalytic activity in semihydrogenation of internal alkynes using H2 gas in water-ethanol solution. Our findings revealed that over the Ni1Fe3 catalyst a high diastereoselectivity for Z-alkenes with a high conversion for a wide range of internal alkynes can be achieved at moderate reaction temperature (40 °C). Notably, the selectivity for the Z-alkenes is enhanced in the presence of n-butyl amine as an additive. Deuterium labeling experiments evidenced that H2 gas becomes dissociated homolytically over the catalyst surface to hydrogenate alkynes to alkenes. Synthesized catalysts were successfully characterized by HR-TEM, SEM, XPS, EDS, P-XRD and H2-TPD.
- Awasthi, Mahendra K.,Barman, Sudipta Roy,Behrens, Silke,Rai, Rohit K.,Singh, Sanjay K.,Singh, Vipin K.
-
p. 4968 - 4980
(2020/08/19)
-
- Design, synthesis and biological evaluation of 8-(2-amino-1-hydroxyethyl)-6-hydroxy-1,4-benzoxazine-3(4H)-one derivatives as potent β2-adrenoceptor agonists
-
A series of β2-adrenoceptor agonists with an 8-(2-amino-1-hydroxyethyl)-6-hydroxy-1,4-benzoxazine-3(4H)-one moiety is presented. The stimulatory effects of the compounds on human β2-adrenoceptor and β1-adrenoceptor were characterized by a cell-based assay. Their smooth muscle relaxant activities were tested on isolated guinea pig trachea. Most of the compounds were found to be potent and selective agonists of the β2-adrenoceptor. One of the compounds, (R)-18c, possessed a strong β2-adrenoceptor agonistic effect with an EC50 value of 24 pM. It produced a full and potent airway smooth muscle relaxant effect same as olodaterol. Its onset of action was 3.5 min and its duration of action was more than 12 h in an in vitro guinea pig trachea model of bronchodilation. These results suggest that (R)-18c is a potential candidate for long-acting β2-AR agonists.
- Yi, Ce,Xing, Gang,Wang, Siqi,Li, Xiaoran,Liu, Yichuang,Li, Jinyan,Lin, Bin,Woo, Anthony Yiu-Ho,Zhang, Yuyang,Pan, Li,Cheng, Maosheng
-
-
- Controllable Intramolecular Unactivated C(sp3)-H Amination and Oxygenation of Carbamates
-
Dual catalyst-controlled intramolecular unactivated C(sp3)-H amination and oxygenation of carbamates merging visible-light photocatalysis and earth-abundant transition metal catalysis have been reported. Useful amino alcohol and diol derivatives could be selectively obtained from readily available tertiary alcohol derivatives. The possible mechanisms have been proposed via a 1,5-HAT process followed by Lewis acid-controlled cyclization. The nickel and zinc catalysts inhibit the formation of oxygenation and amination products, respectively. An interesting phenomenon of chirality transfer is also observed.
- Guo, Qihang,Ren, Xiang,Lu, Zhan
-
supporting information
p. 880 - 884
(2019/05/16)
-
- Catalytic Generation and Use of Ketyl Radical from Unactivated Aliphatic Carbonyl Compounds
-
Generation of a ketyl radical from unactivated aliphatic carbonyl compounds is an important strategy in organic synthesis. Herein, catalytic generation and use of a ketyl radical for the reductive coupling of aliphatic carbonyl compounds and styrenes by organic photoredox catalysis is described. The method is applicable to both aliphatic ketones and aldehydes to afford the corresponding tertiary and secondary alcohols in continuous flow and batch. Preliminary mechanistic investigation suggests the catalytic formation of a ketyl radical intermediate.
- Seo, Hyowon,Jamison, Timothy F.
-
supporting information
p. 10159 - 10163
(2019/12/24)
-
- Dehalogenative Deuteration of Unactivated Alkyl Halides Using D2O as the Deuterium Source
-
The general dehalogenation of alkyl halides with zinc using D2O or H2O as a deuterium or hydrogen donor has been developed. The method provides an efficient and economic protocol for deuterium-labeled derivatives with a wide substrate scope under mild reaction conditions. Mechanistic studies indicated that a radical process is involved for the formation of organozinc intermediates. The facile hydrolysis of the organozinc intermediates provides the driving force for this transformation.
- Xia, Aiyou,Xie, Xin,Hu, Xiaoping,Xu, Wei,Liu, Yuanhong
-
p. 13841 - 13857
(2019/10/17)
-
- Light-Mediated Formal Radical Deoxyfluorination of Tertiary Alcohols through Selective Single-Electron Oxidation with TEDA2+.
-
The synthesis of tertiary alkyl fluorides through a formal radical deoxyfluorination process is described herein. This light-mediated, catalyst-free methodology is fast and broadly applicable allowing for the preparation of C?F bonds from (hetero)benzylic, propargylic, and non-activated tertiary alcohol derivatives. Preliminary mechanistic studies support that the key step of the reaction is the single-electron oxidation of cesium oxalates—which are readily available from the corresponding tertiary alcohols—with in situ generated TEDA2+. (TEDA: N-(chloromethyl)triethylenediamine), a radical cation derived from Selectfluor.
- Aguilar Troyano, Francisco José,Ballaschk, Frederic,Jaschinski, Marcel,?zkaya, Yasemin,Gómez-Suárez, Adrián
-
supporting information
p. 14054 - 14058
(2019/11/11)
-
- Manganese-Catalyzed Borylation of Unactivated Alkyl Chlorides
-
The use of low-cost manganese(II) bromide (MnBr2) and tetramethylethylenediamine (TMEDA) catalyzes the cross coupling of (bis)pinacolatodiboron with a wide range of alkyl halides, demonstrating the first manganese-catalyzed coupling with alkyl electrophiles. This method allows access to primary, secondary, and tertiary boronic esters from the parent chlorides, which were previously inaccessible as coupling partners. The reaction proceeds in high yield with as little as 1000 ppm catalyst loading, while 5 mol % can provide high yields in as little as 30 min. Finally, radical-clock experiments revealed that at 0 °C direct borylation outcompetes alternative radical processes, thereby providing synthetically useful, temperature-controlled reaction outcomes.
- Atack, Thomas C.,Cook, Silas P.
-
supporting information
p. 6139 - 6142
(2016/06/09)
-
- Iron-catalyzed borylation of alkyl electrophiles
-
The use of low-cost iron(III) acetoacetate (Fe(acac)3) and tetramethylethylenediamine (TMEDA) enables the direct cross-coupling of alkyl halides with bis(pinacolato)diboron. This approach allows for the borylation of activated or unactivated primary, secondary, and tertiary bromides. Moreover, even the borylation of benzylic or allylic chlorides, tosylates, and mesylates are possible. The reactions proceed under mild conditions at room temperature and show broad functional-group compatibility and "robustness" as measured by a modified Glorius robustness screen.
- Atack, Thomas C.,Lecker, Rachel M.,Cook, Silas P.
-
supporting information
p. 9521 - 9523
(2014/07/22)
-
- Oxygen versus carbon acidity in the side-chain fragmentation of 2-, 3-, and 4-arylalkanol radical cations in aqueous solution: The influence of the distance between the OH group and the aromatic ring
-
The decay of 2-, 3-, and 4-(4-methoxyphenyl) alkanol radical cations in water has been kinetically investigated by pulse radiolysis, the reaction products being determined either by steady-state γ-radiolysis experiments or by reactions promoted by potassium 12-tungstocobalt(III)ate, a bona fide one-electron oxidant. It was found that all 2-arylalkanol radical cations react with -OH at a diffusion-controlled rate leading to Cα-Cβ bond cleavage products. This suggests a reaction induced by deprotonation at the alcoholic OH group. In acidic medium (pH = 4), the rates of decay of these radical cations are much lower leading to Cα-H deprotonation (for 2-(4-methoxyphenyl)ethanol (1.+) and 1-(4-methoxyphenyl)-2-propanol (4.+)) or Cα-Cβ bond cleavage products (for 1-phenyl-2-(4-methoxyphenyl)ethanol (5.+) and 2-methyl-1-phenyl-3-(4-methoxyphenyl)-2-propanol (6.+)). The 3-(4-methoxyphenyl)propanol radical cation (2.+) reacts in acidic medium (pH = 4) at a rate close to that of 1.+, undergoing Cα-H deprotonation. In contrast, in basic medium (pH = 10) 2.+ produces 3-(4-methoxyphenyl)propanal, with a rate ~5-fold lower than that of 1.+, again indicating a reaction promoted by O - H deprotonation. With 4-(4-methoxyphenyl)-1-butanol radical cation (3.+), products of Cα - H deprotonation were observed both in the presence and in the absence of -OH. These results are discussed in terms of a mechanistic dichotomy, that is, carbon versus oxygen acidity, which appears to be operating for 2-and 3-arylalkanols whereas with 4-arylalkanol radical cations only carbon acidity is observed.
- Baciocchi, Enrico,Bietti, Massimo,Manduchi, Laura,Steenken, Steen
-
p. 6624 - 6629
(2007/10/03)
-
- Mechanism for nucleophilic substitution and elimination reactions at tertiary carbon in largely aqueous solutions: Lifetime of a simple tertiary carbocation
-
The rate constants and the yields of the products of the nucleophilic substitution and elimination reactions of 1-(4-methoxyphenyl)-3-methyl-3-butyl derivatives (1-X) have been determined in mostly aqueous solvents, and the absolute rate constant for reac
- Toteva, Maria M.,Richard, John P.
-
p. 11434 - 11445
(2007/10/03)
-