Highly enantioselective Michael addition of cyclic ketones to chalcones catalyzed by pyrrolidine-based imides
作者:Hong-Yu Xie、Shu-Rong Ban、Ju-Na Liu、Qing-Shan Li
DOI:10.1016/j.tetlet.2012.05.106
日期:2012.7
An efficient procedure for asymmetric Michaeladdition reaction of cyclic ketones with low activated chalcones catalyzed by pyrrolidine-based phthalimide and 1,8-Naphthalimide catalysts was developed. The corresponding products were obtained in high yields with high diastereoselectivities (up to 99:1 dr) and high enantioselectivities (up to 96% ee) under mild conditions.
Direct asymmetric Michael addition of ketones to chalcones catalyzed by a hydroxyphthalimide derived triazole–pyrrolidine
作者:Togapur Pavan Kumar、Mohammad Abdul Sattar、Vanka Uma Maheshwara Sarma
DOI:10.1016/j.tetasy.2013.11.002
日期:2013.12
An efficient protocol for the enantioselective Michael additions of ketones to chalcones catalyzed by a hydroxyphthalimide linked triazole-pyrrolidine derivative has been developed. The corresponding products, 1,5-dicarbonyl compounds, were obtained in good yields with high levels of stereoselectivities under mild reaction conditions employing benzoic acid as an additive. (C) 2013 Elsevier Ltd. All rights reserved.
Cohesion in science lesson discourse: clarity, relevance and sufficient information
作者:Susan Rodrigues、Ian Thompson
DOI:10.1080/09500690010025076
日期:2001.9
This paper discusses linguistics in the teaching of science, specifically the key linguistic processes through which students learn, rather than the mechanics of classroom interaction. Integrated datasets from The Classroom Learning Project contain transcripts of videotaped lessons spliced with teacher and student interviews and annotated with a researcher's comments. To illustrate the role of language in determining the effectiveness of teaching and learning, an integrated data set for one Australian Year 9 (14 year old students) science lesson on 'Fibres and Fabrics' was analysed in terms of coherence and comprehension. The analysis demonstrates the importance of communication skills in the classroom and the value of language analysis in determining the effectiveness of teacher's instructions. This paper argues the need for teachers to consider the importance of learning as a linguistic milieu especially when teaching science in context. When teaching and learning in contextually, competent communication must include adequate, genuine, clear and relevant amounts of information.
A mild and efficient procedure for asymmetric Michael additions of cyclohexanone to chalcones catalyzed by an amino acid ionic liquid
作者:Yunbo Qian、Shiyong Xiao、Lei Liu、Yongmei Wang
DOI:10.1016/j.tetasy.2008.06.022
日期:2008.7
A mild and efficient procedure for Michael additions of cyclohexanone to chalcones has been developed. In the presence of amino acid ionic liquid [EMlm][Pro] (200 mol %), cyclohexanone reacted with various chalcones to afford Michael adducts in high yields (85-98%) and moderate to good enantioselectivities (16-94% ee), accompanied by an unexpected solvent-dependent inversion of the enantioselectivity. (C) 2008 Elsevier Ltd. All rights reserved.
The Synthesis of New Organoselenium Heterocyclic Compounds: 2-aryl-4-phenyl-5,6,7,8-tetrahydro-4H-selenochromenes
AbstractWe have explored the reactions of 2‐(3‐oxo‐1‐aryl‐3‐phenylpropyl)cyclohexanone (1–3) with hydrogen selenide in situ in conditions of acid catalysis, and synthesized new 2‐aryl‐4‐phenyl‐5,6,7,8‐tetrahydro‐4H‐selenochromenes (4–6).