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イリジウム触媒によるエナチオセレクティブC (sp) -Hビサイクロ[1.1.0]ブタンのボリレーション

  • 0State Key Laboratory of Low Carbon Catalysis and Carbon Dioxide Utilization, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China.
Journal of the American Chemical Society +

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2025年12月5日

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2025年12月5日

まとめ

No abstract available on PubMed

関連する概念動画

Electrophilic 1,2- and 1,4-Addition of X<sub>2</sub> to 1,3-Butadiene 01:14

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Electrophilic addition of halogens to alkenes proceeds via a cyclic halonium ion to form a 1,2-dihalide or a vicinal dihalide.

Conjugated dienes react with halogens in a similar manner. However, in addition to the 1,2-dihalide, they also form a 1,4-dihalide. The mechanism involves two steps.
First, a nucleophilic attack by one of the diene π bonds on the electrophilic center of the polarized halogen molecule forms a halonium ion intermediate. This is followed by a nucleophilic attack of the...

Electrophilic 1,2- and 1,4-Addition of HX to 1,3-Butadiene 01:17

7.4K

The electrophilic addition of hydrogen halides such as HBr to alkenes and nonconjugated dienes gives a single product as per Markovnikov’s rule.

With conjugated systems like 1,3-butadiene, the addition of one equivalent of HBr yields a mixture of products: 1,2 and 1,4-addition products. As shown below, the mechanism involves the addition of H+ across one of the double bonds of the conjugated diene to form a resonance stabilized allyl cation. This is followed by the nucleophilic attack of...

Regioselectivity and Stereochemistry of Hydroboration 02:36

9.3K

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 stereochemistry.

The observed...

Hydroboration-Oxidation of Alkenes 03:08

11.0K

In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.

Borane as a reagent is very reactive, as the...

Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration 02:34

9.4K

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...

Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation 02:47

20.6K

Introduction
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.

Mechanism
The hydroboration-oxidation reaction is a two-step...