نتایج جستجو برای: diels alder reaction

تعداد نتایج: 415019  

2005
Alessandro Gandini

The furan heterocycle is a dienic reagent particularly suitable for the Diels-Alder reaction and maleimides represent a typical family of complementary reagents because of their strong dienophilic character. This paper reviews critically the studies devoted to the exploitation of the Diels Alder reaction between those moieties to synthesise macromolecular materials possessing different structur...

2009
Taro Nomura Yoshio Hano Toshio Fukai

Many isoprenylated flavonoids have been isolated from Japanese mulberry tree (Moraceae). Among them, kuwanons G (1) and H (2) were the first isolated active substances exhibiting a hypotensive effect. These compounds are considered to be formed through an enzymatic Diels-Alder type reaction between an isoprenyl portion of an isoprenylphenol as the diene and an alpha, beta-double bond of chalcon...

Journal: :Science 2010
Justin B Siegel Alexandre Zanghellini Helena M Lovick Gert Kiss Abigail R Lambert Jennifer L St Clair Jasmine L Gallaher Donald Hilvert Michael H Gelb Barry L Stoddard Kendall N Houk Forrest E Michael David Baker

The Diels-Alder reaction is a cornerstone in organic synthesis, forming two carbon-carbon bonds and up to four new stereogenic centers in one step. No naturally occurring enzymes have been shown to catalyze bimolecular Diels-Alder reactions. We describe the de novo computational design and experimental characterization of enzymes catalyzing a bimolecular Diels-Alder reaction with high stereosel...

Journal: :Yakugaku zasshi : Journal of the Pharmaceutical Society of Japan 2001
T Nomura

Many isoprenylated flavonoids have been isolated from mulberry trees and related plants (Moraceae). Among them, kuwanons G (13) and H (14) were the first isolated active substances exhibiting a hypotensive effect from the Japanese Morus root bark. These compounds are considered to be formed through an enzymatic Diels-Alder reaction of a chalcone (15) and dehydro-kuwanon C (16) or its equivalent...

Journal: :Angewandte Chemie 2007
Konrad Tiefenbacher Vladimir B Arion Johann Mulzer

A fascinating aspect of the Diels–Alder reaction is its endo selectivity. This endo preference is much less pronounced in intermolecular cases compared with the intramolecular and transannular Diels–Alder (IMDA and TADA) reactions. Nevertheless, high endo selectivity is observed in the Diels– Alder additions of (E)-1-O-substituted dienes catalyzed by Lewis acids that lead to cis-1,6-disubstitut...

Journal: :Organic & biomolecular chemistry 2012
Sompong Boonsri Christian Gunawan Elizabeth H Krenske Mark A Rizzacasa

The methyl ether derivatives 2, 4 and 6 of the mulberry Diels-Alder adducts chalcomoracin (1) and mulberrofuran C (3) and kuwanon J (5) respectively have been synthesized by a thermal [4 + 2]-cycloaddition reaction between a chalcone and dehydroprenyl diene. A H-bonded ortho OH substituent on the chalcone was found to be essential for Diels-Alder reactivity. Density functional theory calculatio...

Journal: :The Journal of organic chemistry 2007
Aitor Landa Bo Richter Rasmus Lyng Johansen Anna Minkkilä Karl Anker Jørgensen

A general catalytic oxo-hetero-Diels-Alder reaction for pro-chiral aldehyde and ketone N-oxy-pyridines is presented. The catalytic and asymmetric oxo-hetero-Diels-Alder reaction of electron-rich dienes with N-oxy-pyridine-2-carbaldehyde and ketone derivatives, catalyzed by chiral copper(II)-bisoxazoline complexes, gives optically active six-membered oxygen heterocycles in moderate to good yield...

Journal: :Chemical communications 2015
Zhe Ji Ji Chen Liang Huang Gaoquan Shi

On the basis of the Diels-Alder reaction of graphite and tetracyanoethylene, graphite has been mechanically exfoliated into graphene adducts in a yield up to 38%. The graphene adduct can restore its conjugated structure via retro-Diels-Alder reaction under mild conditions, exhibiting a high conductivity of 1035 S m(-1).

Journal: :Organic letters 2006
Michael T Crimmins Aaron C Smith

The conversion of a substituted dioxinone to a pyrone was used in an improved synthesis of the AB spiroketal subunit of the spongistatins. This transformation occurred via a hetero-Diels-Alder reaction of an acyl ketene with butyl vinyl ether. A double diastereoselective Mukaiyama aldol reaction is used to provide the hetero-Diels-Alder precursor.

2012
Aleksandra Pałasz

ABSTRACT Knoevenagel condensation of barbituric acids with aromatic aldehydes containing one or two formyl groups was carried out. 5-Arylidenebarbituric acids underwent smooth hetero-Diels-Alder (HDA) reactions with enol ethers to afford cis and trans diastereoisomers of pyrano[2,3-d]pyrimidine-2,4-diones and 5,5'-(1,4-phenylene)bis[2H-pyrano[2,3-d]pyrimidine-2,4(3H)-dione] derivatives in excel...

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