Search results for "Michael"
showing 10 items of 171 documents
ChemInform Abstract: E,Z-Stereodivergent Synthesis of N-Tosyl α,β-Dehydroamino Esters via a Mukaiyama-Michael Addition
2016
The stereodivergent synthesis of N-tosyl α,β-dehydroamino esters via a Mukaiyama–Michael addition is reported. The reaction of silylketene acetals with N-tosylimines derived from β,γ-unsaturated α-keto esters in dichloromethane provided the corresponding (Z)-α,β-dehydroamino esters while the (E)-isomers were obtained when the reaction was carried out in the presence of 10 mol% copper(II) triflate.
A New Versatile Synthesis of N,N′,N″,N″′-Tetra-(2-carboxyethyl)-and N,N′,N″,N″′-Tetra-(3-aminopropyl)-tetraazacycloalkanes by Michael Addition of Pol…
1996
Abstract A smooth and convenient one step synthesis of N,N′,N″,N″′-tetra-(2-carboxyethyl)-tetraazacycloalkanes is reported. These compounds are synthesized by Michael addition of tetraazacycloalkanes to acrylic acid. The same Michael addition of tetraazacycloalkanes to an excess of acrylonitrile also leads to the corresponding tetracyanoethylated derivatives. The reduction of such tetracyanoethylated compounds is a new way of preparation for the corresponding primary amines.
Novel 2-pyrone synthesis via Michael addition of mandelic acid enolate to trans-1,2-diaroylethenes
2005
4-Aroyl-6-aryl-3-phenyl-2-pyrones are prepared in a three-step procedure involving the Michael addition of a cis-2,5-disubstituted-1,3-dioxolan-4-one, derived from mandelic acid, to trans-1,2-diaroylethenes, cyclisation to a furan under acidic conditions and lactonisation. The 2-pyrones can be also obtained directly from the Michael products under prolonged or strong acidic treatment with little decrease in yield.
Enantioselective LaIII-pyBOX-Catalyzed Nitro-Michael Addition to (E)-2-Azachalcones
2013
A [La(OTf)3] complex with a new pyBOX ligand bearing a bulky 1-naphthylmethyl substituent at the 4′-position of the oxazoline ring catalyzes the conjugate addition of nitroalkanes to a broad range of (E)-2-azachalcones, providing the expected nitro-Michael products with good yields and enantiomeric excesses up to 87 %. The optical purity of the products can be increased by a single crystallization. A plausible stereochemical model to account for the observed stereochemistry has been proposed.
ChemInform Abstract: A New Versatile Synthesis of N,N′,N′′,N′′′-Tetra(2-carboxyethyl)- and N,N′,N′′,N′′′-Tetra(3-aminopropyl)-tetraazacycloalkanes by…
2010
Abstract A smooth and convenient one step synthesis of N,N′,N″,N″′-tetra-(2-carboxyethyl)-tetraazacycloalkanes is reported. These compounds are synthesized by Michael addition of tetraazacycloalkanes to acrylic acid. The same Michael addition of tetraazacycloalkanes to an excess of acrylonitrile also leads to the corresponding tetracyanoethylated derivatives. The reduction of such tetracyanoethylated compounds is a new way of preparation for the corresponding primary amines.
Cyclam-strapped porphyrins and their iron(III)-copper(II) complexes as models for the resting state of cytochrome c oxidase
1999
International audience; The ESR study of two cyclam-strapped porphyrins in which, on one side, the cyclam is attached with a variable length linker to the porphyrin and, on the other side, a non-coordinating strap protects the iron from any intermolecular interaction, is reported. Variation of the linker length is made possible by the use of either a Michael reaction or a nucleophilic substitution, leading respectively to three or two carbon atom links. It is shown that in the case of the shortest link, the oxidized ironÈcopper complex exhibits a spin interaction. The distance between thetwo metal centers is evaluated to be around 4.5 Å, a value consistent with the one found in the natural …
Organocatalytic Domino Oxa-Michael/1,6-Addition Reactions: Asymmetric Synthesis of Chromans Bearing Oxindole Scaffolds.
2016
An asymmetric organocatalytic domino oxa-Michael/1,6-addition reaction of ortho-hydroxyphenyl-substituted para-quinone methides and isatin-derived enoates has been developed. In the presence of 5 mol % of a bifunctional thiourea organocatalyst, this scalable domino reaction affords 4-phenyl-substituted chromans bearing spiro-connected oxindole scaffolds and three adjacent stereogenic centers in good to excellent yields (up to 98 %) and with very high stereoselectivities (up to >20:1 d.r., >99 % ee).
Lesson 7: Enzymatic kinetics
2022
Este documento ha sido revisado por el Servicio de política Linguística. Su labor ha sido muy importante para la correción del documento. Este documento contiene un pdf con las diapositivas utilizadas en el tema 7 de los alumnos de primero del Grado de Medicina, dentro de la asignatura Bioquímica y Biología Molecular. Se describen los conceptos de cinética enzimática y la ecuación de Michaelis Menten. También se describe el fenómeno de cooperatividad y el alosterismo enzimático. This document contains a pdf doc with the slides used in lesson 7 for first-year students of the Medicine Degree, within the Biochemistry and Molecular Biology subject. This lesson describes the concepts of enzyme k…
Species–area relationships in continuous vegetation: Evidence from Palaearctic grasslands
2019
Aim Species-area relationships (SARs) are fundamental scaling laws in ecology although their shape is still disputed. At larger areas, power laws best represent SARs. Yet, it remains unclear whether SARs follow other shapes at finer spatial grains in continuous vegetation. We asked which function describes SARs best at small grains and explored how sampling methodology or the environment influence SAR shape. Location Palaearctic grasslands and other non-forested habitats. Taxa Vascular plants, bryophytes and lichens. Methods We used the GrassPlot database, containing standardized vegetation-plot data from vascular plants, bryophytes and lichens spanning a wide range of grassland types throu…