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[1] [2] Hence, the reaction is sometimes referred to as the Huisgen cycloaddition (this term is often used to specifically describe the 1,3-dipolar cycloaddition between an organic azide and an alkyne to generate 1,2,3-triazole). 1,3-dipolar cycloaddition is an important route to the regio-and stereoselective synthesis of five-membered ...
A (4+3) cycloaddition [1] is a cycloaddition between a four-atom π-system and a three-atom π-system to form a seven-membered ring. Allyl or oxyallyl cations (propenylium-2-olate) are commonly used three-atom π-systems, while a diene (such as butadiene ) plays the role of the four-atom π-system.
As a class of addition reaction, cycloadditions permit carbon–carbon bond formation without the use of a nucleophile or electrophile. Cycloadditions can be described using two systems of notation. An older but still common notation is based on the size of linear arrangements of atoms in the reactants.
In organic chemistry, syn-and anti-addition are different ways in which substituent molecules can be added to an alkene (R 2 C=CR 2) or alkyne (RC≡CR). The concepts of syn and anti addition are used to characterize the different reactions of organic chemistry by reflecting the stereochemistry of the products in a reaction.
In this partial synthesis of the BC rings of Taxol, the framework buildup utilized an intramolecule [4+4] photocycloaddition of a relatively linear and simple 2-pyridone derivative, folding it into the desired fused rings with correct stereochemistry at C3, C8, and C15 (compare with Taxol on the right) and two double bonds on the B ring ready ...
Vicinal difunctionalization refers to a chemical reaction involving transformations at two adjacent centers (most commonly carbons). This transformation can be accomplished in α,β-unsaturated carbonyl compounds via the conjugate addition of a nucleophile to the β-position followed by trapping of the resulting enolate with an electrophile at the α-position.
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Cyclohexene derivatives, such as imines, epoxides, and halonium ions, react with nucleophiles in a stereoselective fashion, affording trans-diaxial addition products. The term “Trans-diaxial addition” describes the mechanism of the addition, however the products are likely to equilibrate by ring flip to the lower energy conformer, placing the new substituents in the equatorial position.