10323-39-4Relevant articles and documents
Electronic and exchange coupling in a cross-conjugated D-B-A biradical: Mechanistic implications for quantum interference effects
Kirk, Martin L.,Shultz, David A.,Stasiw, Daniel E.,Habel-Rodriguez, Diana,Stein, Benjamin,Boyle, Paul D.
, p. 14713 - 14725 (2013)
A combination of variable-temperature EPR spectroscopy, electronic absorption spectroscopy, and magnetic susceptibility measurements have been performed on TpCum,MeZn(SQ-m-Ph-NN) (1-meta) a donor-bridge-acceptor (D-B-A) biradical that possesses a cross-conjugated meta-phenylene (m-Ph) bridge and a spin singlet ground state. The experimental results have been interpreted in the context of detailed bonding and excited-state computations in order to understand the excited-state electronic structure of 1-meta. The results reveal important excited-state contributions to the ground-state singlet-triplet splitting in this cross-conjugated D-B-A biradical that contribute to our understanding of electronic coupling in cross-conjugated molecules and specifically to quantum interference effects. In contrast to the conjugated isomer, which is a D-B-A biradical possessing a para-phenylene bridge, admixture of a single low-lying singly excited D → A type configuration into the cross-conjugated D-B-A biradical ground state makes a negligible contribution to the ground-state magnetic exchange interaction. Instead, an excited state formed by a Ph-NN (HOMO) → Ph-NN (LUMO) one-electron promotion configurationally mixes into the ground state of the m-Ph bridged D-A biradical. This results in a double (dynamic) spin polarization mechanism as the dominant contributor to ground-state antiferromagnetic exchange coupling between the SQ and NN spins. Thus, the dominant exchange mechanism is one that activates the bridge moiety via the spin polarization of a doubly occupied orbital with phenylene bridge character. This mechanism is important, as it enhances the electronic and magnetic communication in cross-conjugated D-B-A molecules where, in the case of 1-meta, the magnetic exchange in the active electron approximation is expected to be J ～ 0 cm-1. We hypothesize that similar superexchange mechanisms are common to all cross-conjugated D-B-A triads. Our results are compared to quantum interference effects on electron transfer/transport when cross-conjugated molecules are employed as the bridge or molecular wire component and suggest a mechanism by which electronic coupling (and therefore electron transfer/transport) can be modulated.
Ti-Catalyzed Synthesis of Exocyclic Allenes on Oxygen Heterocycles
Padial, Natalia M.,Hernández-Cervantes, Carmen,Mu?oz-Bascón, Juan,Roldán-Molina, Esther,García-Martínez, Mireya,Ruiz-Muelle, Ana Belén,Rosales, Antonio,álvarez-Corral, Míriam,Mu?oz-Dorado, Manuel,Rodríguez-García, Ignacio,Oltra, J. Enrique
, p. 639 - 645 (2017)
A general method for the straightforward synthesis of exocyclic allenes on five-, six-, seven-, and eight-membered oxygen heterocycles is described. A Barbier-type titanocene(III)-catalyzed cyclization of propargyl halides with a pendant carbonyl group is
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.
NOVEL COMPOUNDS, SYNTHESIS METHOD THEREOF AND USE OF SAME IN MEDICINE AND IN COSMETICS
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Paragraph 0240, (2018/01/04)
Novel compounds, synthesis methods and use of the same in medicine and in cosmetics are disclosed. Also disclosed, are novel compounds and ligands that modulate RARs.
