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1.
Alex F. Meindertsma Michael M. Pollard Ben L. Feringa Johannes G. de Vries Adriaan J. Minnaard 《Tetrahedron: Asymmetry》2007,18(24):2849-2858
This paper describes the enantioselective hydrogenation of vinylthioethers. We show that thioether derivatives of maleic esters can be hydrogenated with full conversion and up to 60% ee, and that α-thioether cinnamic acids can be hydrogenated in 51% ee with modest conversion. 相似文献
2.
Peña D López F Harutyunyan SR Minnaard AJ Feringa BL 《Chemical communications (Cambridge, England)》2004,(16):1836-1837
Highly enantioselective Cu-catalysed 1,4-addition of diphenylzinc to cyclohexenone has been achieved for the first time using a monodentate phosphoramidite ligand. 相似文献
3.
Fingering instabilities in films moving along wetted surfaces, dimpling in horizontal liquid films, and the drainage of vertical soap films by marginal regeneration are caused by surface tension gradients along the perimeter of the thin film. These gradients lead to a mechanical instability which involves Marangoni type liquid flow. It is possible to describe the conditions for the onset of marginal regeneration with a critical number of the ratio between the driving force for the Marangoni flow and the friction of film elements that move relative to their surroundings. This ratio is called the Mysels number. A linear stability analysis leads to a scaling relation lambda approximately h(Ca)(-1/3) between the wavelength lambda of the instability and the capillary number Ca (Ca=/etaV(s)/gamma. In experiments with several Marangoni-driven instabilities this scaling relation has been found; it illustrates the general applicability in the understanding of flow phenomena of this type. Copyright 2001 Academic Press. 相似文献
4.
The use of (certified) reference materials and quality control materials can form a suitable basis for evaluating measurement uncertainty of routine measurements. In particular when these materials are used for quality control purposes, it is not always evident how the quality control data can be used in the uncertainty budget of a routine measurement. Current guidance documents on the evaluation of measurement uncertainty and the use of reference materials treat this subject only in part, or in very generic terms. ISO/REMCO has established a new working group that will provide practical guidance and examples on how to use quality control data in the evaluation of measurement uncertainty. A short introduction to the subject is given.
相似文献
Adriaan M. H. van der VeenEmail: Phone: +31-15-2691733Fax: +31-15-2691670 |
5.
Barbier-type Zn and In-mediated allylations of an N,N-(dimethylsulfamoyl)-protected aldimine with different allyl bromides were investigated for the preparation of N-homoallylic sulfamides. The desired N,N-(dimethylsulfamoyl)-protected products were obtained in moderate to high yields in THF as the optimal solvent. Their further derivatization was demonstrated by a facile preparation of a functionalized dehydropiperidine by an allylation/olefin metathesis reaction sequence. A high yielding deprotection of the N,N-dimethylsulfamoyl group was likewise demonstrated. 相似文献
6.
López F Harutyunyan SR Minnaard AJ Feringa BL 《Journal of the American Chemical Society》2004,126(40):12784-12785
A highly enantioselective Cu-catalyzed addition of Grignard reagents to acyclic aliphatic enones is described. In the presence of 5 mol % of CuBr.SMe2 and 6 mol % of JosiPhos diphosphine aliphatic enones react with Grignard reagents to provide beta-substituted linear ketones with high yields, regio-, and enantioselectivities. 相似文献
7.
Accreditation and Quality Assurance - 相似文献
8.
Dr. María Francisco M.Sc. Adriaan van den Bruinhorst Prof. Dr. Maaike C. Kroon 《Angewandte Chemie (International ed. in English)》2013,52(11):3074-3085
A new generation of designer solvents emerged in the last decade as promising green media for multiple applications, including separation processes: the low‐transition‐temperature mixtures (LTTMs). They can be prepared by mixing natural high‐melting‐point starting materials, which form a liquid by hydrogen‐bond interactions. Among them, deep‐eutectic solvents (DESs) were presented as promising alternatives to conventional ionic liquids (ILs). Some limitations of ILs are overcome by LTTMs, which are cheap and easy to prepare from natural and readily available starting materials, biodegradable, and renewable. 相似文献
9.
Adriaan M. H. van der Veen Hugo Ent Annarita Baldan Valnei S. da Cunha Romeu J. Daroda Brian Lang Michele Schantz Manuela Ulberth-Buchgraber Andrea Held Ruth Hearn Richard J. C. Brown Paul J. Brewer 《Accreditation and quality assurance》2013,18(1):41-50
The main objective of the reference materials for biofuel specifications (BIOREMA) project is the development of two test materials (one bio-ethanol material and one biodiesel material) with well-established reference values. Of a series of three papers, this part describes the material preparation, homogeneity study, stability study, and characterisation of the bio-ethanol material. The test material thus obtained was used in an interlaboratory comparison (ILC) to assess current practices and comparability amongst laboratories providing bio-ethanol testing services. Only 13 participants provided data, resulting in a small dataset for evaluation. Further, it appeared that for a number of laboratories, there was not sufficient material for the determination of all requested parameters. In most cases, as far as the data permit, it can be concluded that the consensus values (based on participant’s results) are in good agreement with the reference or the BIOREMA values (obtained by NMIs participating in the project). For three parameters, namely ethanol content, water content, and density, there is good agreement between the reference and consensus values. For these parameters, the reproducibility standard deviation is close to, or even smaller than, the expanded uncertainty associated with the reference value. A number of parameters show very poor reproducibility, for example, pHe, electrolytic conductivity, and acidity. The same applies to sodium and copper content, which are very low and therefore challenging parameters to measure accurately. The results of the ILC underpin the need for certified reference materials and demonstrate the requirement for more robust quality control to improve the precision and trueness of the results from testing laboratories. 相似文献
10.
Mikhail Iakovlev Xiang You Adriaan van Heiningen Herbert Sixta 《Cellulose (London, England)》2014,21(3):1419-1429
SO2–ethanol–water (SEW) fractionation process is a highly attractive platform for future lignocellulosic Biorefineries. Its governing advantages include high flexibility in the selection of the raw material, simple and efficient recovery of fractionation chemicals, absence of carbohydrate degradation (both cellulose and hemicelluloses), and high reaction rates. The process is suitable for production of various carbohydrate- and lignin-based products including papermaking pulp, glucose, bioalcohols and lignosulfonates. The present paper addresses the possibility of producing dissolving pulp from spruce using SEW fractionation followed by ECF bleaching with and without hot caustic extraction. Comprehensive characterisation of chemical and macromolecular properties of the SEW dissolving pulps was complemented by determining the quality of viscose. The comparison with conventional viscose-grade acid sulfite pulps revealed close proximity in all properties. Therefore, considering the advantages of SEW process, it is suggested as a possible replacement for acid sulfite process in dissolving pulp manufacturing. 相似文献