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調整されたリガンドによって,α-アザリル-α-ヒドロキシエステルへの非対称な触媒的1,2-アザレンの移行

  • 0Shanghai Frontiers Science Center for Drug Target Identification and Delivery, National Key Laboratory of Innovative Immunotherapy and Shanghai Key Laboratory for Molecular Engineering of Chiral Drugs, School of Pharmaceutical Sciences, Shanghai Jiao Tong University, Shanghai, 200240, China.
Angewandte Chemie (International ed. in English) +

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Reduction of Alkenes: Asymmetric Catalytic Hydrogenation 02:17

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Catalytic hydrogenation of alkenes is a transition-metal catalyzed reduction of the double bond using molecular hydrogen to give alkanes. The mode of hydrogen addition follows syn stereochemistry.
The metal catalyst used can be either heterogeneous or homogeneous. When hydrogenation of an alkene generates a chiral center, a pair of enantiomeric products is expected to form. However, an enantiomeric excess of one of the products can be facilitated using an enantioselective reaction or an...

[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement 01:21

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The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.

From a molecular orbital perspective, the rearrangement can be viewed as the interaction between the ground state frontier orbitals of the allyl anion and cation. Under thermal conditions, the...

Preparation of 1° Amines: Hofmann and Curtius Rearrangement Mechanism 01:26

3.6K

The Hofmann and Curtius rearrangement reactions can be applied to synthesize primary amines from carboxylic acid derivatives such as amides and acyl azides. In the Hofmann rearrangement, a primary amide undergoes deprotonation in the presence of a base, followed by halogenation to generate an N-haloamide. A second proton abstraction produces a stabilized anionic species, which rearranges to an isocyanate intermediate via an alkyl group migration from the carbonyl carbon to the neighboring...

Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration 02:34

8.6K

The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.

The reaction proceeds with the slow protonation of an alkene by a hydronium ion to form a carbocation, which is the rate-determining step.
The reaction involving a tertiary carbocation intermediate is faster than a reaction proceeding through a secondary or primary carbocation. This can be justified by comparing their...

Regioselectivity and Stereochemistry of Hydroboration 02:36

8.4K

A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn...

Preparation of 1° Amines: Hofmann and Curtius Rearrangement Overview 01:07

3.3K

In the presence of an aqueous base and a halogen, primary amides can lose the carbonyl (as carbon dioxide) and undergo rearrangement to form primary amines. This reaction, called the Hofmann rearrangement, can produce primary amines (aryl and alkyl) in high yields without contamination by secondary and tertiary amines.

In the Curtius rearrangement, acyl azides are converted into primary amines under thermal conditions, accompanied by the loss of gaseous N2 and CO2. The loss of nitrogen acts as...