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Transannular Cyclization of Dehydrobenzo[12]annulene Induced by Nucleophilic Attack Tobe Lab Ayumi Yoshizaki 1.

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Presentation on theme: "Transannular Cyclization of Dehydrobenzo[12]annulene Induced by Nucleophilic Attack Tobe Lab Ayumi Yoshizaki 1."— Presentation transcript:

1 Transannular Cyclization of Dehydrobenzo[12]annulene Induced by Nucleophilic Attack Tobe Lab Ayumi Yoshizaki 1

2 Contents Introduction - π-Conjugated compounds Application Frame-work Dibenzoindacene Motivation Experiments & Results Future Work Summary 2

3 π-Conjugated compounds 2D π-conjugated compounds have attracted attention as organic semiconductors. N=1N=2N=3N=4N=5N→∞ Ethylene ・・・・・・ Allyl RadicalButadiene E Energy bands of olefins 3 Pentadienyl Radical

4 Application Pentacene has 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 4

5 Frame-work Acenes condensed benzene ring in a line Dibenzopentalene Dibenzoindacene Attractive Structural Motifs Pentalene Indacene 5

6 Dibenzoindacene Antiaromatic (20 π-electorons) p-Xylylene core More resistant to degrade acenes It does not possess any internal s-cis diene linkage. Fully conjugated dibenzoindacenes are extremely rare. p-Xylylene s-cis diene 6

7 Benzene (4n+2) π The Hückel Rule Aromatic (4n+2) π-electrons (n = 0, 1, 2, 3, …) Antiaromatic (4n) π-electrons (n = 0, 1, 2, 3, …) Cyclic π-Conjugated Polyene E x 1,3-Cyclobutadiene (4n) π 7

8 Example 1 of Dibenzoindacene Transannular Cyclization is induced by Iodine, electrophilic. Tetraiodides These rapidly oxidized to the corresponding diones upon exposure to air. T. M. Swager, et al. J. Org. Chem. 1994, 59, R = H, Decane, Dodecane Tetraiodides 8

9 Example 2 of Dibenzoindacene The Synthesis of Stable Dibenzoindacenes Multiple Steps M. M. Haley, et al. Angew. Chem. Int. Ed. ASAP 1 : R = H 2 : R = Decane 2 or 3 months 9

10 Electronic Absorption Spectra pentacene 2 1 M. M. Haley, et al. Angew. Chem. Int. Ed. ASAP 10

11 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-step synthesis rout is required. I have studied to synthesize a dibenzoindacene with transannular cyclization. 11

12 Transannular Cyclization J.Otera, et al. Chem. Lett. 2008, 37,

13 Synthesis of Dehydrobenzo[12]annulene 13 Dehydrobenzo[12]annulene

14 Identification by NMR

15 Transannular Cyclization of Dehydrobenzo[12]annulene Various reaction conditions were investigated. ( concentration of material, equivalent of BuLi, reaction time, reaction temperature ) Reaction conditions were optimized. 3 15

16 Identification by NMR 3 16

17 Future Work 1 17 I will study reaction conditions for the next transannular cyclization. Then I will mesure its physical properties, and tune them by using other reagents instead of BuLi and BuI.

18 Future Work 2 Bergman Cycloaromatization W. M. Dai, et al. J. Am. Chem. Soc. 1992, 114,

19 Future Work 2 Bergman Cycloaromatization of 3 19

20 Summary Dibenzoindacene are rare fully conjugated species. The reaction conditions for transannular cyclization of dehydrobenzo[12]annulene were optimized. Future works are transannular cyclization of the next step and bergman cycloaromatization to synthesize π-conjugated compounds with short-steps. 20

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