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Related Concept Videos

Thermal Electrocyclic Reactions: Stereochemistry01:17

Thermal Electrocyclic Reactions: Stereochemistry

The stereochemistry of electrocyclic reactions is strongly influenced by the orbital symmetry of the polyene HOMO. Under thermal conditions, the reaction proceeds via the ground-state HOMO.
Selection Rules: Thermal Activation
Conjugated systems containing an even number of π-electron pairs undergo a conrotatory ring closure. For example, thermal electrocyclization of (2E,4E)-2,4-hexadiene, a conjugated diene containing two π-electron pairs, gives trans-3,4-dimethylcyclobutene.
Thermal and Photochemical Electrocyclic Reactions: Overview01:26

Thermal and Photochemical Electrocyclic Reactions: Overview

Electrocyclic reactions are reversible reactions. They involve an intramolecular cyclization or ring-opening of a conjugated polyene. Shown below are two examples of electrocyclic reactions. In the first reaction, the formation of the cyclic product is favored. In contrast, in the second reaction, ring-opening is favored due to the high ring strain associated with cyclobutene formation.
Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry01:29

Diels–Alder Reaction Forming Bridged Bicyclic Products: Stereochemistry

Diels–Alder reactions between cyclic dienes locked in an s-cis configuration and dienophiles yield bridged bicyclic products.
Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction01:16

[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction

The Diels–Alder reaction is an example of a thermal pericyclic reaction between a conjugated diene and an alkene or alkyne, commonly referred to as a dienophile. The reaction involves a concerted movement of six π electrons, four from the diene and two from the dienophile, forming an unsaturated six-membered ring. As a result, these reactions are classified as [4+2] cycloadditions.
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry01:28

Diels–Alder Reaction Forming Cyclic Products: Stereochemistry

The Diels–Alder reaction is one of the robust methods for synthesizing unsaturated six-membered rings. The reaction involves a concerted cyclic movement of six π electrons: four π electrons from the diene and two π electrons from the dienophile.

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Related Experiment Video

Updated: May 16, 2026

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
06:46

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

Published on: June 21, 2017

Iridium-catalyzed enantioselective polyene cyclization.

Michael A Schafroth1, David Sarlah, Simon Krautwald

  • 1Eidgenössische Technische Hochschule Zürich, HCI H335, 8093 Zürich, Switzerland.

Journal of the American Chemical Society
|December 1, 2012
PubMed
Summary

A new method enables enantioselective polycyclization using iridium catalysis and Lewis acids. This approach efficiently creates diverse polycyclic compounds from simple alcohols with high stereocontrol.

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Solid-phase Synthesis of [4.4] Spirocyclic Oximes
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Solid-phase Synthesis of [4.4] Spirocyclic Oximes

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Area of Science:

  • Organic Chemistry
  • Catalysis
  • Synthetic Methodology

Background:

  • Polycyclic compounds are vital structural motifs in natural products and pharmaceuticals.
  • Developing efficient and stereoselective methods for their synthesis remains a significant challenge in organic chemistry.

Purpose of the Study:

  • To develop a novel, highly enantioselective method for constructing complex carbo- and heteropolycyclic ring systems.
  • To utilize readily available, branched racemic allylic alcohols as starting materials.

Main Methods:

  • Employed a combination of Lewis acid activation and iridium-catalyzed allylic substitution.
  • Utilized branched, racemic allylic alcohols, enabling direct use without prior resolution.

Main Results:

  • Successfully synthesized a diverse range of unique carbo- and heteropolycyclic compounds.
  • Achieved high yields and excellent enantioselectivity (≥99% ee) for the products.
  • Demonstrated the broad applicability of the developed polycyclization strategy.

Conclusions:

  • The developed method offers a powerful and efficient route to enantiomerically enriched polycyclic structures.
  • This strategy provides a valuable tool for accessing complex molecular architectures with high stereochemical fidelity.
  • The direct use of racemic starting materials simplifies synthetic pathways and enhances atom economy.