1,721,049 research outputs found
Diastereoselective Tri-step Route to o-(6-Nitrocyclohex-3-en-1-yl)phenol and Tetrahydro-6H-benzo[c]chromen-6-ol Derivatives from Salicylaldehydes
No full textHeterogeneous Bisoxazoline/Copper Complex: A Green Catalyst for the Enantioselective Reaction of Nitromethane with Substituted Benzaldehydes
No full textPolystyrene-supported chiral 2,2′-methylenebis[(4S)-4-tert-butyl-2-oxazoline] is a promising heterogeneous catalyst for the enantioselective Henry reaction of nitromethane with substituted benzaldehydes. The process is carried out in ethanol as a green solvent, and the corresponding chiral β-nitroalcohols are obtained in 56–95 % yield with 49–88 % ee
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Synthesis and characterization of novel polystyrene-supported TBD catalysts and their use in the Michael addition for the synthesis of Warfarin and its analogues
No full textIn the search for efficient and polymeric supports for organic bases to be used in environmentally friendly media and conditions, novel polystyrene-bound 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) has been prepared and characterized. Their catalytic properties have been tested in the Michael additions of 4-hydroxycoumarin to alpha,beta-unsaturated ketones as a representative useful process for the syntheses of 4-hydroxy-3-(3-oxo-1-phenylbuty1)-2H-chromen-2-one (Warfarin (TM)), 4-hydroxy-3-(1-(4-nitropheny1)-3-oxobuty1)-2H-chromen-2-one (Acenocumarol (TM)), 4-hydroxy-3-(1-(4-chloropheny1)-3-oxobuty1)-2 H-chromen-2-one (Coumachlor (TM)), and 4-hydroxy-3-(1-(4-methoxypheny1)-3-oxobutyI)-2H-chromen-2-one. Products were obtained in high to quantitative conversion yields. The novel catalytic systems showed promising catalytic properties, and they could be all easily recovered by filtration and have been reused for three representative consecutive runs without any significant lowering of their activity. (C) 2013 Elsevier Inc. All rights reserved
Synthesis of enantiopure angularly condensed [2.2]paracyclophanes containing five-membered rings
No full textOptically active angularly condensed [2.2]paracyclophanes containing five-membered rings have been synthesized by a two-step approach based on the Diels-Alder cycloaddition of (S)-(+)-4-vinyl[2.2]paracyclophane. Structural analysis by NMR spectroscopy is presented. These helicenophanes containing a cyclopentane ring show extraordinarily high specific rotations. This phenomenon has been discussed in terms of structural modifications caused by the replacement of the benzene unit with a cyclopentane ring. © 2003 Elsevier Science Ltd. All rights reserved
- …
