14804-34-3Relevant articles and documents
Determining the Conformational Landscape of σ and π Coupling Using para-Phenylene and "Aviram-Ratner" Bridges
Stasiw, Daniel E.,Zhang, Jinyuan,Wang, Guangbin,Dangi, Ranjana,Stein, Benjamin W.,Shultz, David A.,Kirk, Martin L.,Wojtas, Lukasz,Sommer, Roger D.
, p. 9222 - 9225 (2015)
The torsional dependence of donor-bridge-acceptor (D-B-A) electronic coupling matrix elements (HDA, determined from the magnetic exchange coupling, J) involving a spin SD = 1/2 metal semiquinone (Zn-SQ) donor and a spin SA
Desymmetric enantioselective reduction of cyclic 1,3-diketones catalyzed by a recyclable p-chiral phosphinamide organocatalyst
Qin, Xu-Long,Li, Ang,Han, Fu-She
supporting information, p. 2994 - 3002 (2021/03/01)
The P-stereogenic phosphinamides are a structurally novel skeletal class which has not been investigated as chiral organocatalysts. However, chiral cyclic 3-hydroxy ketones are widely used as building blocks in the synthesis of natural products and bioactive compounds. However, general and practical methods for the synthesis of such chiral compounds remain underdeveloped. Herein, we demonstrate that the P-stereogenic phosphinamides are powerful organocatalysts for the desymmetric enantioselective reduction of cyclic 1,3-diketones, providing a useful method for the synthesis of chiral cyclic 3-hydroxy ketones. The protocol displays a broad substrate scope that is amenable to a series of cyclic 2,2-disubstituted five- and six-membered 1,3-diketones. The chiral cyclic 3-hydroxy ketone products bearing an all-carbon chiral quaternary center could be obtained with high enantioselectivities (up to 98% ee) and diastereoselectivities (up to 99:1 dr). Most importantly, the reactions could be practically performed on the gram scale and the catalysts could be reused without compromising the catalytic efficiency. Mechanistic studies revealed that an intermediate formed from P-stereogenic phosphinamide and catecholborane is the real catalytically active species. The results disclosed herein bode well for designing and developing other reactions using P-stereogenic phosphinamides as new organocatalysts.
Multi-faceted reactivity of alkyltellurophenols towards peroxyl radicals: Catalytic antioxidant versus thiol-depletion effect
Amorati, Riccardo,Valgimigli, Luca,Diner, Peter,Bakhtiari, Khadijeh,Saeedi, Mina,Engman, Lars
, p. 7510 - 7522 (2013/07/19)
Hydroxyaryl alkyl tellurides are effective antioxidants both in organic solution and aqueous biphasic systems. They react by an unconventional mechanism with ROO. radicals with rate constants as high as 107 M-1 s-1 at 303 K, outperforming common phenols. The reactions proceed by oxygen atom transfer to tellurium followed by hydrogen atom transfer to the resulting RO. radical from the phenolic OH. The reaction rates do not reflect the electronic properties of the ring substituents and, because the reactions occur in a solvent cage, quenching is more efficient when the OH and TeR groups have an ortho arrangement. In the presence of thiols, hydroxyaryl alkyl tellurides act as catalytic antioxidants towards both hydroperoxides (mimicking the glutathione peroxidases) and peroxyl radicals. The high efficiency of the quenching of the peroxyl radicals and hydroperoxides could be advantageous under normal cellular conditions, but pro-oxidative (thiol depletion) when thiol concentrations are low. Anti- and pro-oxidants: Hydroxyaryl alkyl tellurides are unconventional antioxidants able to quench chain-carrying peroxyl radicals with rate constants as high as 107 M-1 s-1 by a mechanism involving oxygen atom transfer to tellurium followed by reaction of the RO. radical with the phenol (see figure). They can also catalytically decompose both the ROO. radical and H2O2 in the presence of excess thiols. Copyright
