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Related Concept Videos

Aromatic Hydrocarbon Cations: Structural Overview01:18

Aromatic Hydrocarbon Cations: Structural Overview

Cycloheptatriene is a neutral monocyclic unsaturated hydrocarbon that consists of an odd number of carbon atoms and an intervening sp3 carbon in the ring. The three double bonds in the ring correspond to 6 π electrons, which is a Huckel number, and therefore satisfies the criteria of 4n + 2 π electrons. However, the intervening sp3 carbon disrupts the continuous overlap of p orbitals. As a result, cycloheptatriene is not aromatic.
Removing one hydrogen from the intervening CH2 group with both...
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.
[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.
Structure of Conjugated Dienes01:16

Structure of Conjugated Dienes

Introduction
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
Stability of Conjugated Dienes01:28

Stability of Conjugated Dienes

Introduction
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
Aromatic Hydrocarbon Anions: Structural Overview01:18

Aromatic Hydrocarbon Anions: Structural Overview

Neutral hydrocarbons like cyclopentadiene with an odd number of carbon atoms and one intervening CH2 group in the ring are not aromatic. Cyclopentadiene with 4 π electrons does not satisfy the 4n + 2 π electron rule. Additionally, the intervening CH2 group is sp3 hybridized and lacks a vacant p orbital, thereby interrupting the overlap of p orbitals in a continuous manner and preventing the delocalization of π electrons throughout the ring.
Due to the absence of continuous overlap of p...

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Related Experiment Video

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Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units
09:35

Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

Published on: September 18, 2016

A versatile synthesis of functionalized pentahelicenes.

Olivier Songis1, Jirí Mísek, Markus B Schmid

  • 1Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic.

The Journal of Organic Chemistry
|September 25, 2010
PubMed
Summary

A new method synthesizes functionalized helicenes using organometallic addition, cobalt-catalyzed cyclization, and acid elimination. This approach yields various substituted pentahelicenes, including those for Suzuki-Miyaura coupling.

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Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
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Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene

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Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)
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Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)

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Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene
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Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)
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Synthesis of Antiviral Tetrahydrocarbazole Derivatives by Photochemical and Acid-catalyzed C-H Functionalization via Intermediate Peroxides (CHIPS)

Published on: June 20, 2014

Area of Science:

  • Organic Chemistry
  • Synthetic Methodology
  • Heterocyclic Chemistry

Background:

  • Helicenes are chiral polycyclic aromatic hydrocarbons with unique structural and photophysical properties.
  • Developing efficient synthetic routes to functionalized helicenes is crucial for their application in materials science and catalysis.
  • Existing methods often lack generality or require harsh conditions.

Purpose of the Study:

  • To develop a general and versatile synthetic methodology for preparing functionalized (hetero)helicenes.
  • To demonstrate the synthesis of various substituted pentahelicenes and their derivatives.
  • To explore post-synthetic modification of helicenes via cross-coupling reactions.

Main Methods:

  • A multi-step synthesis involving double propargyl organometallic addition to a dialdehyde intermediate.
  • Cobalt-catalyzed [2 + 2 + 2] cycloisomerization of a triyne intermediate.
  • Silica gel-assisted acetic acid elimination for helicene formation.
  • Suzuki-Miyaura coupling for diarylhelicene synthesis.

Main Results:

  • Successful preparation of pentahelicene, 1,14-diazapentahelicene, and several substituted pentahelicenes (dichloro-, dichloro-trimethylsilyl-, di-tert-butyl-).
  • Demonstration of Suzuki-Miyaura coupling on 3,12-dichloropentahelicene to yield 3,12-diarylpentahelicenes.
  • The developed methodology offers a general route to diverse functionalized helicene structures.

Conclusions:

  • A robust and general synthetic strategy for functionalized (hetero)helicenes has been established.
  • The method allows for the introduction of various substituents and heteroatoms into the helicene core.
  • The synthesized helicenes are amenable to further functionalization, expanding their synthetic utility.