نتایج جستجو برای: diels alder and 1 3 dipolar cycloaddition reactions

تعداد نتایج: 17429646  

Journal: :Molecules 2017
Ana F R Cerqueira Vítor A S Almodôvar Maria G P M S Neves Augusto C Tomé

This review covers the synthesis of coumarin-porphyrin, coumarin-phthalocyanine and coumarin-corrole conjugates and their potential applications. While coumarin-phthalocyanine conjugates were obtained almost exclusively by tetramerization of coumarin-functionalized phthalonitriles, coumarin-porphyrin and coumarin-corrole conjugates were prepared by complementary approaches: (a) direct synthesis...

Journal: :Bulletin of the Chemical Society of Japan 1978

2007
REINER SUSTMANN

A reactivity model for concerted cycloaddition reactions is presented which allows a systematization of substituent effects. The treatment is based on the frontier electron theory of Fukui. The consideration of the energy separations of HOMOs (Highest Occupied Molecular Orbitals) and LUMOs (Lowest Unoccupied Molecular Orbitals) leads to three reactivity types in these cycloadditions. For the Di...

2010
Mohit L Deb Pulak J Bhuyan

Some novel annulated pyrido[2,3-d]pyrimidines 6 and 7 were synthesized stereoselectively by intramolecular hetero Diels-Alder reactions involving 1-oxa-1,3-butadienes.

Journal: :Chemistry: A European Journal 2021

The first immobilization of a pyrene-tagged chromium salen complex through π-π noncovalent interactions on reduced graphene oxide (rGO) is described. A very robust supported catalytic system obtained to promote asymmetric catalysis in repeated cycles, without loss activity or enantioselectivity. This specific behavior was demonstrated two different reactions (up ten reuses) promoted by complexe...

2014
Jillian E. Spangler Yajing Lian Sandeep N. Raikar Huw M. L. Davies

Treatment of (E)-1-(methoxymethylene)-1,2,3,4-tetrahydronaphthalene with styryl diazoacetates in the presence of catalytic amounts of the dirhodium complex Rh2(S-DOSP)4 provides a highly enantioenriched hexacyclic product with 10 new stereogenic centers. The transformation proceeds by a cascade sequence starting with a double cyclopropanation of a benzene ring, followed by a Cope rearrangement ...

Journal: :Journal of the American Chemical Society 2006
Ciby J Abraham Daniel H Paull Michael T Scerba James W Grebinski Thomas Lectka

In this Communication, we report a system in which an achiral Lewis acid (activating the diene) works in concert with a chiral nucleophile (dienophile) to effect the first highly enantio- and regioselective catalytic inverse electron demand Diels-Alder [4 + 2] cycloaddition reaction to form biologically active quinoxalinones from ketene enolates and o-benzoquinone diimides in good to excellent ...

Journal: :Beilstein Journal of Organic Chemistry 2008
Deniz Akalay Gerd Dürner Jan W Bats Michael W Göbel

C(2)-symmetric bisamidines 8 have been tested as chiral Brønsted bases in the Diels-Alder reaction of anthrones and N-substituted maleimides. High yields of cycloadducts and significant asymmetric inductions up to 76% ee are accessible. The proposed mechanism involves proton transfer between anthrone and bisamidine, association of the resulting ions and finally a cycloaddition step stereoselect...

Journal: :Green Chemistry 2021

Catechyl monomers 1-electron-oxidize and undergo radical coupling to produce benzodioxane units in lignin. Derived o -quinones Diels–Alder reactions giving oxatricyclo new products, but does this occur lignification?.

Journal: :The Journal of organic chemistry 2006
Douglass F Taber Karen V Taluskie

Diels-Alder cycloaddition of 10 followed by Wittig homologation and intramolecular diene cyclozirconation of the resulting triene under equilibrating conditions led to the tricyclic 6-6-5 ketone 5 with high diastereocontrol. The derived alpha-azido ketone 16 cyclized efficiently to the heptacyclic pyrazine core of ritterazine N.

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