Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

Regioselectivity of Electrophilic Additions-Peroxide Effect

Regioselectivity of Electrophilic Additions-Peroxide Effect

In the presence of organic peroxides, the addition of hydrogen bromide to an alkene yields the isomer that is not predicted by Markovnikov’s rule. For example, the addition of hydrogen bromide to 2-methylpropene in the presence of peroxides gives 1-bromo-2-methylpropane. This addition reaction proceeds via a free radical mechanism, which reverses the regioselectivity. The free radical reaction mechanism involves three stages: initiation, propagation, and termination.

Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule

Regioselectivity of Electrophilic Additions to Alkenes: Markovnikov's Rule

If a set of reactants can yield multiple constitutional isomers, but one of the isomers is obtained as the major product, the reaction is said to be regioselective. In such reactions, bond formation or breaking is favored at one reaction site over others.
The hydrohalogenation of an unsymmetrical alkene can yield two haloalkane products, depending on which vinylic carbon takes up the halogen. However, one product usually predominates, where hydrogen adds to the vinylic carbon bearing the...

Regioselectivity and Stereochemistry of Hydroboration

Regioselectivity and Stereochemistry of Hydroboration

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.

Acid-Catalyzed Ring-Opening of Epoxides

Acid-Catalyzed Ring-Opening of Epoxides

Epoxides that are three-membered ring systems are more reactive than other cyclic and acyclic ethers. The high reactivity of epoxides originates from the strain present in the ring. This ring strain acts as a driving force for epoxides to undergo ring-opening reactions either with halogen acids or weak nucleophiles in the presence of mild acid. The acid catalyst converts the epoxide oxygen, a poor leaving group, into an oxonium ion, a better leaving group, making the reaction feasible. The...

Cycloaddition Reactions: Overview

Cycloaddition Reactions: Overview

Cycloadditions are one of the most valuable and effective synthesis routes to form cyclic compounds. These are concerted pericyclic reactions between two unsaturated compounds resulting in a cyclic product with two new σ bonds formed at the expense of π bonds. The [4 + 2] cycloaddition, known as the Diels–Alder reaction, is the most common. The other example is a [2 + 2] cycloaddition.

Nucleophilic Acyl Substitution of Carboxylic Acid Derivatives

Nucleophilic Acyl Substitution of Carboxylic Acid Derivatives

Nucleophilic acyl substitution is an important class of substitution reactions involving a nucleophile and an acyl compound, such as carboxylic acids and their derivatives. In these reactions, the leaving group attached to the acyl group is substituted by a nucleophile. The general mechanism proceeds via two steps.

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Inducible rAAV producer cell lines yield vectors equivalent to transient transfection: a physicochemical and biological comparison.

Scientific reports·2026

Same author

Synthesis of 2,3,4,5-Tetrahydro-1,5-benzoxazepine Derivatives via Alkoxy Migration Induced by N-O Bond Cleavage of N-Aryl Isoxazolidines.

Chemical & pharmaceutical bulletin·2026

Same author

Direct electrochemical amidation of fatty acids with ammonia in liquefied ammonia.

Chemical communications (Cambridge, England)·2026

Same author

Risk-Stratified Use of Concurrent Computer-Aided Diagnosis (CAD) in Chest CT: Gains in Overall Sensitivity with Loss for CAD-Negative Nodules.

Journal of imaging informatics in medicine·2026

Same author

Altered astrocyte-neuron crosstalk in progressive supranuclear palsy: integrated evidence from proteomics and magnetic resonance spectroscopy.

Acta neuropathologica·2026

Same author

Nontarget Intrahepatic Portal Vein Embolization in Traumatic Splenic Artery Embolization.

Journal of vascular and interventional radiology : JVIR·2026

Search research articles

Related Experiment Video

Updated: Jan 10, 2026

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

Published on: January 21, 2020

Regioselectivity Inversion in the Cycloaddition Reaction between Stable Nitrile Oxides and Acylalkyne Derivatives.

Yuki Maeda¹, Yoshimitsu Hashimoto¹, Ryo Aoki¹

¹Showa Pharmaceutical University, 3-2-1 Higashi-Tamagawagakuen, Machida, Tokyo 194-8543, Japan.

Chemical & Pharmaceutical Bulletin

|November 26, 2025

Summary

Stable nitrile oxides undergo 1,3-dipolar cycloaddition with alkynyl hydrazones and carbonyl compounds. The hydrazone group reverses regioselectivity, yielding 5-iminoisoxazoles convertible to 4-acylisoxazoles.

Keywords:

cycloaddition hydrazone isoxazole nitrile oxide umpolung

More Related Videos

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

Published on: February 6, 2019

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Published on: June 21, 2017

Related Experiment Videos

Last Updated: Jan 10, 2026

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

Published on: January 21, 2020

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

Published on: February 6, 2019

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Facile Preparation of 2Z,4E-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate

Published on: June 21, 2017

Area of Science:

Organic Chemistry
Heterocyclic Chemistry

Background:

1,3-Dipolar cycloaddition is a key reaction in organic synthesis.
Nitrile oxides are versatile 1,3-dipoles used in cycloaddition reactions.
The regioselectivity of cycloadditions can be influenced by substituent electronic effects.

Purpose of the Study:

To investigate the 1,3-dipolar cycloaddition reaction of stable nitrile oxides with α,β-alkynyl hydrazones and carbonyl compounds.
To explore the influence of the hydrazone group on the regioselectivity of the cycloaddition.
To demonstrate the conversion of the resulting 5-iminoisoxazoles to 4-acylisoxazoles.

Main Methods:

Reaction of stable nitrile oxides with α,β-alkynyl hydrazones.
Reaction of stable nitrile oxides with α,β-alkynyl carbonyl compounds.
Dehydrazonation of 5-iminoisoxazoles.

Main Results:

The cycloaddition of nitrile oxides with α,β-alkynyl hydrazones yielded 5-iminoisoxazoles.
The cycloaddition of nitrile oxides with α,β-alkynyl carbonyl compounds yielded 4-acylisoxazoles.
The regioselectivity was reversed in the reaction with alkynyl hydrazones due to the electron-donating hydrazone group.
5-iminoisoxazoles were successfully converted to 4-acylisoxazoles via dehydrazonation.

Conclusions:

The 1,3-dipolar cycloaddition reaction provides a facile route to 5-iminoisoxazoles and 4-acylisoxazoles.
The electron-donating hydrazone group plays a crucial role in directing the regioselectivity of the cycloaddition.
The synthesized 5-iminoisoxazoles serve as valuable intermediates for the preparation of 4-acylisoxazoles.