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

1. TransannularCyclization of Dehydrobenzo[12]annulene Induced by Nucleophilic Attack TobeLab AyumiYoshizaki

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

3. 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

4. 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

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

6. 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

7. 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

8. 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.

9. 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

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

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-stepsynthesis rout is required. • I have studied to synthesize a dibenzoindacenewith transannularcyclization.

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

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

14. Identification by NMR 5 2 3 4 1

15. 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.

16. Identification by NMR 3

17. 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.

18. Future Work ２ • Bergman Cycloaromatization W. M. Dai, et al. J. Am. Chem. Soc. 1992, 114, 7360-7371.

19. Future Work ２ • Bergman Cycloaromatizationof 3

20. 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.