Transannular cyclization of dehydrobenzo 12 annulene induced by nucleophilic attack
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Transannular Cyclization of Dehydrobenzo [12] annulene Induced by Nucleophilic Attack. Tobe Lab Ayumi Yoshizaki. Contents. Introduction - π-Conjugated compounds Application Frame-work Dibenzoindacene Motivation Experiments & Results Future Work Summary. π-Conjugated compounds.

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Transannular Cyclization of Dehydrobenzo [12] annulene Induced by Nucleophilic Attack

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Transannular cyclization of dehydrobenzo 12 annulene induced by nucleophilic attack

TransannularCyclization of Dehydrobenzo[12]annulene Induced by Nucleophilic Attack

TobeLab

AyumiYoshizaki


Contents

Contents

  • Introduction - π-Conjugated compounds

    Application

    Frame-work

    Dibenzoindacene

  • Motivation

  • Experiments & Results

  • Future Work

  • Summary


Conjugated compounds

π-Conjugated compounds

2D π-conjugated compounds have attracted attention as organic semiconductors.

E

・・・

N=1

N=2

N=3

N=4

N=5

N→∞

Pentadienyl Radical

Ethylene

AllylRadical

Butadiene

Energy bands of olefins


Application

Application

Pentacenehas already been put to practical use in thin-film transistor. But, it unfortunately is prone toward oxidative degradation.

There is demand for alternative, acene-like topologies.

Pentacene


Frame work

Frame-work

  • Acenes

    condensed benzene ring in a line

  • Dibenzopentalene

  • Dibenzoindacene

Pentalene

Attractive Structural Motifs

Indacene


Dibenzoindacene

Dibenzoindacene

  • Antiaromatic (20 π-electorons)

  • p-Xylylenecore

  • More resistant to degrade acenes

    It does not possess any internal s-cisdiene linkage.

    Fully conjugated dibenzoindacenesare extremely rare.

p-Xylylene

s-cisdiene


The h ckel rule

The HückelRule

  • Aromatic

    (4n+2) π-electrons (n = 0, 1, 2, 3, …)

  • Antiaromatic

    (4n) π-electrons (n = 0, 1, 2, 3, …)

E

x

Cyclic π-Conjugated Polyene

1,3-Cyclobutadiene

(4n) π

Benzene

(4n+2) π


Example of dibenzoindacene

Example1of Dibenzoindacene

  • TransannularCyclization is induced by Iodine, electrophilic.

  • Tetraiodides

    These rapidly oxidized to the corresponding diones upon exposure to air.

R = H, Decane, Dodecane

Tetraiodides

T. M. Swager, et al. J. Org. Chem. 1994, 59, 1294-1301.


Example 2 of dibenzoindacene

Example 2 of Dibenzoindacene

  • The Synthesis of StableDibenzoindacenes

    MultipleSteps

2 or 3 months

1: R = H

2 : R = Decane

M. M. Haley, et al. Angew. Chem. Int. Ed.ASAP


Electronic absorption spectra

Electronic Absorption Spectra

pentacene

2

1

M. M. Haley, et al. Angew. Chem. Int. Ed.ASAP


Motivation

Motivation

  • The dibenzoindacene (tetraiodides) synthesized in a single step is unstable.

  • Multiple steps are required to synthesize the stable one.

  • For easy synthesis, a short-stepsynthesis rout is required.

  • I have studied to synthesize a dibenzoindacenewith transannularcyclization.


Transannular cyclization

TransannularCyclization

J.Otera, et al. Chem. Lett. 2008, 37, 1296-1297.


Synthesis of dehydrobenzo 12 annulene

Synthesis of Dehydrobenzo[12]annulene

Dehydrobenzo[12]annulene


Identification by nmr

Identification by NMR

5

2

3

4

1


Transannular cyclization of dehydrobenzo 12 annulene

TransannularCyclization of Dehydrobenzo[12]annulene

3

Various reaction conditions were investigated.

(concentration of material, equivalent of BuLi, reaction time, reaction temperature)

Reaction conditions were optimized.


Identification by nmr1

Identification by NMR

3


Future work 1

Future Work 1

  • I will study reaction conditions for the next transannularcyclization.

  • Then I will mesure its physical properties, and tune them by using other reagents instead of BuLi and BuI.


Future work

Future Work 2

  • Bergman Cycloaromatization

W. M. Dai, et al. J. Am. Chem. Soc. 1992, 114, 7360-7371.


Future work1

Future Work 2

  • Bergman Cycloaromatizationof 3


Summary

Summary

  • Dibenzoindacene are rare fully conjugated species.

  • The reaction conditions for transannularcyclizationof dehydrobenzo[12]annulene were optimized.

  • Future works are transannularcyclization of the next step and bergmancycloaromatization to synthesize π-conjugated compounds with short-steps.


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