Initially, lasubin II was synthesized diastereoselectively in racemic form [3]. Asymmetric syntheses of lasubin II were achieved based on stereoselective transformations of enantiomerically pure substrates [4] or, for example, via a diastereoselective aza-Diels-Alder reaction using a resolved chiral arylaldehyde tricarbonylchromium complex [5]. Recently, an enantioselectively catalyzed aza-Diel...

Studies toward the enantiospecific total synthesis of rhodexin A via a very hindered inverse electron demand Diels-Alder reaction are described. The C8-diastereomer of the fully elaborated tetracyclic core of rhodexin A, 23, was prepared in good yield and excellent selectivity using as the key step the stepwise Diels-Alder reaction of the very hindered dienone 3 and the silyl enol ether 4 catal...

Two catalysts, Me(2)AlNTf(2) and MeAl(NTf(2))(2), derived from the mixing of trimethylaluminum with triflimide, proved to be highly effective catalysts in hindered Diels-Alder reactions, generating the desired Diels-Alder cycloadducts from both hindered 2-silyloxydienes and hindered dienophiles. Thus reaction of 1 with 2 afforded the hindered cycloadduct 4 in excellent yield in 0.5-1.5 h at -40...

Black Africans have a higher incidence of cardiovascular disease than white Europeans. We explored potential mechanisms of this excess risk by assessing endothelium function, inflammatory status (C-reactive protein), oxidative stress (isoprostane-F2alpha), and plasma asymmetrical dimethyl arginine (ADMA; an endogenous competitive inhibitor of NO synthase) in each ethnic group. Thirty healthy bl...

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...

A large number of dienes and dienophiles have been employed in the Diels–Alder reaction to produce cyclohexene products with high facial, regio-, stereo-, and enantioselectivity. The reactions work best when the dienophile is substituted with an electron-withdrawing group. However, often in synthesis, the addition of an ethylene unit to a diene is necessary, and the normal cycloaddition with et...

Substituted 3,4-dihydro-1,8-naphthyridin-2(1H)-ones have been synthesized with the inverse electron-demand Diels-Alder reaction from 1,2,4-triazines bearing an acylamino group with a terminal alkyne side chain. Alkynes were first subjected to the Sonogashira cross-coupling reaction with aryl halides, the product of which then underwent an intramolecular inverse electron-demand Diels-Alder react...

Density Functional Theory has been used to model the Diels-Alder reactions of the fullerene fragments triindenetriphenilene and pentacyclopentacorannulene with ethylene and 1,3-butadiene. The purpose is to prove the feasibility of using Diels-Alder cycloaddition reactions to grow fullerene fragments step by step, and to dimerize fullerene fragments, as a way to obtain C₆₀. The dienophile charac...

The first successful inverse electron-demand Diels-Alder has been demonstrated with the 2-pyrone methyl coumalate in conjunction with substituted indoles. Utilizing 1-alkyl-3-chloroindoles as the electron-rich dienophile efficiently generates carbazoles without the need for additional metal catalysts. Through a thermal, one-pot Diels-Alder/decarboxylation/elimination domino sequence, access to ...

A metal-free and formal [2 + 2 + 2] cycloaddition of triynes has emerged recently as a novel methodology for the synthesis of fused tricyclic compounds via an intramolecular cascade propargylic ene reaction, Diels-Alder cycloaddition and tautomerization. DFT calculations on three model systems reveal that the ene reaction with low distortion energy makes the metal-free strategy feasible and, as...