نتایج جستجو برای: ring opeing of epoxides
تعداد نتایج: 21176018 فیلتر نتایج به سال:
b-Lactones are important intermediates for ring-opening polymerization to form poly(b-hydroxyalkanoates), a naturally occurring biodegradable and thermoplastic polyester. Many synthetic methods are available for preparing b-lactones, among which catalytic ring-opening carbonylation of epoxides has received considerable attention because of its ability to produce enantiopure b-lactones. Over the...
A stereocontrolled synthesis of benzannulated spiroketals has been developed using solvent-dependent Sc(OTf)3-mediated spirocyclizations of exo-glycal epoxides having alcohol side chains. In THF, the reaction proceeds via Lewis acid catalysis under kinetic control with inversion of configuration at the anomeric carbon. In contrast, in CH2Cl2, Brønsted acid catalysis under thermodynamic control ...
A cholate derivative with three epoxide groups was synthesized from cholic acid by allylation followed by epoxidation. Ring opening of the epoxides by various nucleophiles yielded facial amphiphiles with anionic, cationic, or nonionic functional groups. The critical micelle concentrations of these amphiphiles largely depend on the number of charged groups on the molecule. A facial amphiphile wi...
Supported ionic liquid-like phases (SILLPs) containing Rose Bengal (RB) units are used to develop organocatalytic systems for the cycloaddition of CO2 epoxides. The activity supported RB fragments can be fine-tuned by controlling nature SILLPs (i.e., substitution at imidazolium ring, cross-linking degree polymeric matrix, loading, etc.). Such a catalytic system prepared from cheap, simple, and ...
این پایان نامه به تشریح و تبیین نتایج مقاله ی زیر می پردازد: g. zeng, henselian valuations and orderings of a commutative ring, proc. amer. math. soc. 135(2007), 929- 938. هدف اصلی در مقاله فوق بررسی ارتباط بین ارزیاب های هنسلی و ترتیب ها(یا نیم ترتیب ها) روی یک حلقه می باشد. نتیجه اصلی این است که برای ارزیاب هنسلی v روی حلقه r شرایط زیر معادلند: ارزیاب v با هر نیم ترتیب روی r سازگار است؛...
Dibenzo(a,e)fluoranthene (DBF), a powerful carcinogenic nonalternant aromatic hydrocarbon, has been metabolized in vitro by incubation in mouse and rat liver microsomal homogenates. Five major stable metabolites were separated by highpressure liquid chromatography and then analyzed by spectroscopic procedures and comparison with synthetic model com pounds. Three of them are phenols correspondin...
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