نتایج جستجو برای: asymmetric transformation

تعداد نتایج: 285010  

Journal: :Physical review letters 2018
Shengfeng Yang Naixie Zhou Hui Zheng Shyue Ping Ong Jian Luo

First-order interfacial phaselike transformations that break the mirror symmetry of the symmetric ∑5 (210) tilt grain boundary (GB) are discovered by combining a modified genetic algorithm with hybrid Monte Carlo and molecular dynamics simulations. Density functional theory calculations confirm this prediction. This first-order coupled structural and adsorption transformation, which produces tw...

Journal: :Organic letters 2015
Sílvia Orgué Thierry León Antoni Riera Xavier Verdaguer

The asymmetric intermolecular and catalytic Pauson-Khand reaction has remained an elusive goal since Khand and Pauson discovered this transformation. Using a novel family of P-stereogenic phosphanes, we developed the first catalytic system with useful levels of enantioselection for the reaction of norbornadiene and trimethylsilylacetylene. The results demonstrate that Co-bisphosphane systems ar...

Journal: :Organic & biomolecular chemistry 2011
Helmut Haning Carles Giró-Mañas Victoria L Paddock Christian G Bochet Andrew J P White Gerald Bernardinelli Inderjit Mann Wolfang Oppolzer Alan C Spivey

Two syntheses of the Amaryllidaceae alkaloid clivonine (1) are described. Both employ previously reported 7-arylhydrindane 6 as an intermediate but differ in the method employed for subsequent introduction of what becomes the ring-B lactone carbonyl carbon (C7). The synthesis featuring a Bischler-Napieralski reaction for this transformation constitutes the first asymmetric synthesis of natural ...

Journal: :Organic & biomolecular chemistry 2015
Edward Richmond Kenneth B Ling Nicolas Duguet Lois B Manton Nihan Çelebi-Ölçüm Yu-Hong Lam Sezen Alsancak Alexandra M Z Slawin K N Houk Andrew D Smith

The reaction of L-serine derived N-arylnitrones with alkylarylketenes generates asymmetric 3-alkyl-3-aryloxindoles in good to excellent yields (up to 93%) and excellent enantioselectivity (up to 98% ee) via a pericyclic cascade process. The optimization, scope and applications of this transformation are reported, alongside further synthetic and computational investigations. The preparation of t...

Journal: :Molecules 2017
Giulia Rainoldi Matteo Faltracco Claudia Spatti Alessandra Silvani Giordano Lesma

This work describes the synthesis of enantioenriched spiro compounds, incorporating the azetidine and the oxindole motifs. The preparation relies on a formal [2 + 2] annulation reaction of isatin-derived N-tert-butylsulfonyl ketimines with allenoates. The asymmetric induction is secured by an organocatalytic strategy, exploiting a bifunctional cinchona-type β-isocupridine-based catalyst. Some p...

2012
Sanjay E. Sarma Isaac M. Ehrenberg Bae-Ian Wu

Related Articles Spin-wave propagation and transformation in a thermal gradient Appl. Phys. Lett. 101, 192406 (2012) GaP based terahertz time-domain spectrometer optimized for the 5-8 THz range Appl. Phys. Lett. 101, 181101 (2012) An oversized X-band transit radiation oscillator Appl. Phys. Lett. 101, 173504 (2012) Millimeterwave Schottky diode on grapene monolayer via asymmetric metal contacts...

Journal: :The Journal of organic chemistry 2017
Danijel Glavač Chao Zheng Irena Dokli Shu-Li You Matija Gredičak

Asymmetric addition of indoles to cyclic α-diaryl-substituted N-acyl imines, which are generated in situ from 3-aryl 3-hydroxyisoindolinones, is described. The transformation proceeds smoothly with a broad range of indoles and isoindolinone alcohols using a SPINOL-derived chiral Brønsted acid catalyst to afford α-tetrasubstituted (3-indolyl)(diaryl)methanamines in excellent yields and enantiose...

Journal: :Angewandte Chemie 2015
Yiyang Liu Scott C Virgil Robert H Grubbs Brian M Stoltz

The direct α-vinylation of carbonyl compounds to form a quaternary stereocenter is a challenging transformation. It was discovered that δ-oxocarboxylic acids can serve as masked vinyl compounds and be unveiled by palladium-catalyzed decarbonylative dehydration. The carboxylic acids are readily available through enantioselective acrylate addition or asymmetric allylic alkylation. A variety of α-...

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