*. Gingras, Information The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.7b07622. Detailed experimental procedures, characterization of compounds, computational details, structural, spectroscopic , and enantiomerization data (PDF) Crystallographic data for racemic 2 (CIF) INFORMATION Corresponding Authors *yoann, pp.0-0003

?. M. Acknowledgments-we-thank-dr and . Giorgi, ) for X-ray structural analysis, Pr Ste?phaneSte?phane Viel and Mrs Roselyne Rosas (Aix-Marseille Universite?)Universite?) for assistance with NMR spectrometry , Pr. Paola Ceroni (Univ. of Bologna) for photophysics, the Centre Re?gionalRe?gional de Compe?tencesCompe?tences en Modeíisation Mole?culaireMole?culaire (Aix-Marseille Universite?)Universite?) for computing facilities. Financial supports from, CNRS), and CNRS PICS (No. PICS07573) with the University of Bologna are gratefully acknowledged. M.V. is thankful to the French-Italian University (Vinci Program) for a Ph.D. contract (No. C3-141)

. P. Appl, L. Ma, J. Wang, F. C. Ding, A. Scarso et al., Books and Reviews: (a), Chirality at the Nanoscale, Nanoparticles, Surfaces, Materials and More 29?65. (b) Molecular Switches, pp.47-54, 2009.

. R. Soc, M. Gingras, G. Feíix, R. Peresutti, Y. Shen et al., ) For some laterally ?-extended helicenes: (a) Fujikawa, Chem. Soc. Rev. Chem. Soc. Rev. Chem. Soc. Rev. Chem. Rev. J. Org. Chem, vol.45, issue.82, pp.1463-1535, 1051.

G. Naulet, H. Gallardo, P. Dechambenoit, H. Bock, F. Durola et al., For recent elongated helicenes: (g), 6847?6851. (h) Sehnal, 2017.

M. Szymonski, I. Cisarova, I. Stary, D. V. Preda, Y. Segawa et al., For extended and configurationally stable helicenes: (a) Corannulene-helicene: Fujikawa, 3992?3995. (b) Quadruple helicenes 3587?3595. (c) Double [7]heterohelicene: Wang, pp.13169-13174, 2009.

K. Itami, (f) Core-extended terrylene tetracarboxdiimide: Lu? tke Eversloh, J. Am. Chem. Soc. 2015 C Z.; Mu? ller, B, vol.137, pp.7763-7768

M. Stangl, C. Li, K. Mu?-llen, . Org, and . Lett, (g) Perylene diimide helicenes, pp.5528-5531, 2011.

F. Ng, M. L. Steigerwald, C. Nuckolls, H. Saito, A. Uchida et al., In the following studies, double [5]helicenes were possibly configurationally stable by modelisation (DFT calculations), but their separation into enantiomers was not reported: (i) Kashihara, 13519?13523. (h) Triple [5]helicene, pp.5663-5668, 2015.

S. Pe?rezpe?rez, D. Pen?-a, D. Guitia?nguitia?n, E. 5. Pe?rezpe?rez, D. Guitia?nguitia?n et al., For hexabenzotriphenylene: (a) Pen? a, Eur. J. Org. Chem. Angew. Chem., Int. Ed, vol.134, issue.378, pp.2659-2661, 1998.

L. Castedo, . Org, Y. Lett-wang, A. D. Stretton, M. C. Mcconnell et al., For higher triphenylenes, J. Am. Chem. Soc, vol.1, issue.129, pp.13193-13200, 1999.

T. K. Shah, A. E. Goetz, N. K. Garg, K. N. Houk, A. Pradhan et al., For alternative synthetic approaches: (e), 2266?2274. See also reference 5h. (9) (a) Ru? diger, E.; Rominger, F.; Steuer, 2011.

C. Ru?-diger, E. C. Porz, M. Schaffroth, M. Rominger, F. Bunz et al., 10) From the experimental barrier, t 1/2 = 100 000 years at 25 °C (considering the barrier independent of temperature, Chem. -Eur. J. Z.-h J. Organomet. Chem. M, vol.81, issue.41411, pp.119-127, 1991.

U. Baumeister, S. Ho?-ger, and R. J. Kuroda, Helicene Chemistry, From Synthesis to Applications, J. Am. Chem. Soc. Chem. Soc., Perkin Trans, vol.139, issue.2114, pp.4429-4434, 1982.