Synlett 2016; 27(14): 2105-2112
DOI: 10.1055/s-0035-1562720
© Georg Thieme Verlag Stuttgart · New York

Aromatic Rings and Aromatic Rods: Nonplanar Character of an Indeno-dehydro[14]annulene

Kévin Cocq
a  CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP44099, 31077 Toulouse Cedex 4, France   Email:   Email:
b  Université de Toulouse, UPS, ICT-FR 2599, 31062 Toulouse Cedex 9, France
Nathalie Saffon-Merceron
c  Université de Toulouse, UPS, Institut de Chimie de Toulouse ICT-FR-2599, 118 Route de Narbonne, 31062 Toulouse Cedex 9, France
Albert Poater
d  Institut de Química Computacional i Catàlisi and Departament de Química, Universitat de Girona, Campus Montilivi, 17003 Girona, Catalonia, Spain
Valérie Maraval*
a  CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP44099, 31077 Toulouse Cedex 4, France   Email:   Email:
b  Université de Toulouse, UPS, ICT-FR 2599, 31062 Toulouse Cedex 9, France
Remi Chauvin*
a  CNRS, LCC (Laboratoire de Chimie de Coordination), 205 route de Narbonne, BP44099, 31077 Toulouse Cedex 4, France   Email:   Email:
b  Université de Toulouse, UPS, ICT-FR 2599, 31062 Toulouse Cedex 9, France
› Author Affiliations
Further Information

Publication History

Received: 11 May 2016

Accepted after revision: 04 July 2016

Publication Date:
20 July 2016 (online)


Since the concept of aromaticity has been proposed to be generalizable to acetylenic rods (‘linear ring’ of [2]annulene), p-diisopropyl-tetraphenyl-carbo-benzene (C48H34) and an indenone-fused isopropyl-triphenyloctadehydro[14]annulene (C42H26O) can be regarded as based on heptacyclic aromatic cores. The formation and X-ray crystal structures of both products are described. The latter has been obtained as a reductive rearrangement product of a transient isopropyl-pentaoxy[5]pericyclyne devised as a putative precursor of a carbo-fulvene target. A mechanism accounting for this peculiar transformation is proposed. Deviation from global planarity is measured by a 6° angle between the mean plane of the indenone bicycle and that of 13 atoms of the [14]annulenic macrocycle, forming dihedral angles with the local plane of the isopropyl-substituted sp2 vertex of 16° and 15°, respectively. The magnetic aromaticity of the carbo-benzene and indeno-octadehydro[14]annulene products is evaluated by NICS calculations.

Supporting Information

  • References and Notes

  • 1 The larger the number of atoms prone to undergo slight strains vs. the ideal VSEPR configuration (Gillespies’ valence shell electron pair repulsion model), the larger the allowed global out-of-plane deformation of the ring, the angular strain being spread out over all the endocyclic atoms.

    • For general references on carbo-mers, see:
    • 2a Chauvin R. Tetrahedron Lett. 1995; 36: 397
    • 2b Maraval V, Chauvin R. Chem. Rev. 2006; 106: 5317
    • 2c Cocq K, Lepetit C, Maraval V, Chauvin R. Chem. Soc. Rev. 2015; 44: 6535

      For early results on carbo-benzenes, see:
    • 3a Kuwatani Y, Watanabe N, Ueda I. Tetrahedron Lett. 1995; 36: 119
    • 3b Chauvin R. Tetrahedron Lett. 1995; 36: 401
    • 4a Jensen FR, Noyce DS, Sederholm CH, Berlin AJ. J. Am. Chem. Soc. 1960; 82: 1256
    • 4b Anet FA.L, Bourn AJ. R. J. Am. Chem. Soc. 1967; 89: 760
    • 5a Scott LT, DeCicco GJ, Hyunn JL, Reinhardt G. J. Am. Chem. Soc. 1985; 107: 6546
    • 5b Houk KN, Scott LT, Rondan NG, Spelleyer DC, Reinhardt G, Hyunn JL, DeCicco GJ, Weiss R, Chen MH. M, Bass LS, Clardy J, Jorgensen FS, Eaton TA, Sarkozi V, Petit CM, Ng L, Jordan KD. J. Am. Chem. Soc. 1985; 107: 6556
  • 6 Lepetit C, Silvi B, Chauvin R. J. Phys. Chem. A 2003; 107: 464
  • 7 Chauvin R, Lepetit C, Maraval V, Leroyer L. Pure Appl. Chem. 2010; 82: 769
  • 8 Suzuki R, Tsukuda H, Watanabe N, Kuwatani Y, Ueda I. Tetrahedron 1998; 54: 2477
    • 9a Godard C, Lepetit C, Chauvin R. Chem. Commun. 2000; 1833
    • 9b Lepetit C, Godard C, Chauvin R. New J. Chem. 2001; 25: 572
    • 10a Chauvin R, Lepetit C. Phys. Chem. Chem. Phys. 2013; 15: 3855
    • 10b Cocq K, Maraval V, Saffon-Merceron N, Chauvin R. Chem. Rec. 2015; 15: 347
  • 11 Cocq K, Maraval V, Saffon-Merceron N, Saquet A, Lepetit C, Poidevin C, Chauvin R. Angew. Chem. Int. Ed. 2015; 54: 2703
  • 12 The term ‘carbo-fulvene’ is employed here for the first time. The actual nomenclature of B is: 1,4,7,10-tetraphenyl-13-(propan-2-ylidene)cyclopentadeca-1,2,3,7,8,9-hexaen-5,11,14-triyne.
  • 13 In tentative efforts aiming at accessing the carbo-quinoid A, conditions for a selective reaction of the ene-di(ynone) 9 with TMS-C≡C–Li could not be found. In an alternative approach, attempts at mesylation–elimination at the isopropylcarbinol vertices of the [6]periclynediol 2 also failed to produce A.
    • 14a Leroyer L, Lepetit C, Rives A, Maraval V, Saffon-Merceron N, Kandaskalov D, Kieffer D, Chauvin R. Chem. Eur. J. 2012; 18: 3226
    • 14b Baglai I, de Anda-Villa M, Barba-Barba RM, Poidevin C, Ramos-Ortíz G, Maraval V, Lepetit C, Saffon-Merceron N, Maldonado J.-L, Chauvin R. Chem. Eur. J. 2015; 21: 14186
  • 15 The parent tetraphenyl-carbo-benzene, was, however, obtained in the presence of an undetermined impurity evidenced by 1H NMR spectroscopy, see ref. 10b.
  • 16 CCDC 1479480 (1) and 1479481 (12) contain the supplementary crystallographic data for this paper. The data can be obtained free of charge from The Cambridge Crystallographic Data Centre via
    • 17a Maurette L, Tedeschi C, Sermot E, Soleilhavoup M, Hussain F, Donnadieu B, Chauvin R. Tetrahedron 2004; 60: 1077
    • 17b Leroyer L, Zou C, Maraval V, Chauvin R. C. R. Chim. 2009; 12: 412
  • 18 The conversion of 10 to 12 proceeded in three steps. (i) First Step A solution of impure 10 (74 mg) in CH2Cl2 (15 mL) was treated at 0 °C with Et3N (0.32 mL, 2.30 mmol) and mesyl chloride (0.18 mL, 2.33 mmol). The resulting mixture was stirred for 2 h at 0 °C, before dilution with CH2Cl2 (20 mL). After successive treatments with distilled water, sat. aq solution of NaHCO3, 1 N aq solution of HCl, and extractions with CH2Cl2, the combined organic layers were washed with brine, dried over MgSO4, and concentrated under reduced pressure without going to dryness. (ii) Second Step The concentrated solution resulting from the first step was diluted with CHCl3 (20 mL) and treated at r.t. with silica (2 g). The mixture was stirred for 4 h at r.t., before filtration through Celite® and concentration under reduced pressure without going to dryness. (iii) Third Step The concentrated solution obtained from the second step was diluted with CH2Cl2 (20 mL) and treated at –78 °C with SnCl2 (310 mg, 1.63 mmol). The resulting mixture was stirred for 20 min at –78 °C and for 2.5 h at r.t., before filtration through Celite® and silica gel and concentration under reduced pressure. Purification by silica gel chromatography (pentane–CH2Cl2, 8:2) afforded 12 as orange crystals (4 mg, 7.3 mmol, 6% yield from 4 or 11). Analytical Data for Compound 12 1H NMR (400 MHz, 298 K, CDCl3): δ = 1.85 (d, 3 J H–H = 6.7 Hz, 6 H, CH(CH 3)2), 5.80 (m, 1 H, –CH(CH3)2), 7.40–7.81 (m, 12 H, m-, p-C6 H 5 and -C 1,2,3H), 8.30 (d, 3 J H–H = 7.6 Hz, 1 H, -C 4 H), 8.64, 8.71, 8.78 (3 d, 3 3 J H–H = 7.4 Hz, 3 × 2 H, o-C6 H 5, without assignment). 13C{1H} NMR (100 MHz, 298K, CDCl3): δ = 25.12 (CH(CH3)2), 31.49 (CH(CH3)2), 124.17, 124.28, 129.19, 129.31, 129.43, 129.68, 129.82, 129.88, 130.51, 134.43, 135.60 135.95, 137.40, 137.98, 149.33 (o-, m-, p-C 6H5 and -C1,2,3,4 H, not assigned), 196.40 (>C=O). MS (DCI/CH4): m/z (%) = 546.3 (100) [M]+. HRMS (DCI/CH4): m/z [M]+ calcd for C42H26O: 546.1984; found: 546.2006. UV-vis: λmax (toluene) = 421 nm. FT-IR: ν = 730 (s), 1262 (s), 1723 (s), 2924 (s) cm–1.
  • 19 Chauvin R. J. Phys. Chem. 1992; 96: 9194
  • 20 Liebeskind LS, South MS. J. Org. Chem. 1980; 45: 5426
  • 21 Eakins GL, Alford JS, Tiegs BJ, Breyfogle BE, Stearman CJ. J. Phys. Org. Chem. 2011; 24: 1119
  • 22 Maraval V, Leroyer L, Harano A, Barthes C, Saquet A, Duhayon C, Shinmyozu T, Chauvin R. Chem. Eur. J. 2011; 17: 5086
    • 23a Granovsky, A. A. Firefly version 8 (http://classic.chem.msu. su:gran:firefly:index.html) which is partially based on the GAMESS (US) source code.
    • 23b Schmidt MW, Baldridge KK, Boatz JA, Elbert ST, Gordon MS, Jensen JH, Koseki S, Matsunaga N, Nguyen KA, Su S, Windus TL, Dupuis M, Montgomery JA. J. Comput. Chem. 1993; 14: 1347
  • 24 DFT calculations at the B3PW91/6-31G(d,p) level on the crude crystallographic nuclear geometry of 12 (without re-optimization of the C–H bond lengths), give an indicative HOMO–LUMO gap of 0.090 Ha, corresponding to a one-electron excitation wavelength of 506 nm (see Supporting Information). The transition associated to the observed lower λmax value (421 nm) thus likely involves excitations of higher energy, such as HOMO – 1 → LUMO or HOMO → LUMO + 1 as in the Gouterman model shown to apply to carbo-benzene systems (see ref. 14). The HOMO and LUMO here also involve the main π system and are spread out over both the cyclopentadienone and [14]annulene rings of 12 (see Figures in Supporting Information).
  • 25 The calculation of the formal ‘total oxidation level’ ζ of an organic molecule proceeds in two steps. First, the carbon skeleton is fully saturated (to sp3 C centers only) by hydration (addition of H2O) of all the insaturations, and fully oxygenated by replacement of all the C–heteroatom bonds by a C–O bond if the heteroatom is more electronegative than C or by a C–H bond in the contrary case. Then ζ is equated to the total number of (single) C–O bonds.
  • 26 Chen B, Xie X, Lu J, Wang Q, Zhang J, Tang S, She X, Pan X. Synlett 2006; 259
  • 27 Frisch MJ, Trucks GW, Schlegel HB, Scuseria GE, Robb MA, Cheeseman JR, Scalmani G, Barone V, Mennucci B, Petersson GA, Nakatsuji H, Caricato M, Li X, Hratchian HP, Izmaylov AF, Bloino J, Zheng G, Sonnenberg JL, Hada M, Ehara M, Toyota K, Fukuda R, Hasegawa J, Ishida M, Nakajima T, Honda Y, Kitao O, Nakai H, Vreven T, Montgomery JA. Jr, Peralta JE, Ogliaro F, Bearpark M, Heyd JJ, Brothers E, Kudin KN, Staroverov VN, Kobayashi R, Normand J, Raghavachari K, Rendell A, Burant JC, Iyengar SS, Tomasi J, Cossi M, Rega N, Millam NJ, Klene M, Knox JE, Cross JB, Bakken V, Adamo C, Jaramillo J, Gomperts R, Stratmann RE, Yazyev O, Austin AJ, Cammi R, Pomelli C, Ochterski JW, Martin RL, Morokuma K, Zakrzewski VG, Voth GA, Salvador P, Dannenberg JJ, Dapprich S, Daniels AD, Farkas Ö, Foresman JB, Ortiz JV, Cioslowski J, Fox DJ. Gaussian 09, Revision A.01. Gaussian, Inc; Wallingford CT: 2009
  • 28 Schleyer Pv. R, Maerker C, Dransfeld A, Jiao HJ, Hommes JR. V. J. Am. Chem. Soc. 1996; 118: 6317
  • 29 Wolinski K, Hinton JF, Pulay P. J. Am. Chem. Soc. 1990; 112: 8251
  • 30 Poater J, Duran M, Solà M, Silvi B. Chem. Rev. 2005; 105: 3911
  • 31 Corminboeuf C, Heine T, Seifert G, Schleyer Pv. R, Weber J. Phys. Chem. Chem. Phys. 2004; 6: 273
  • 32 Turias F, Poater J, Chauvin R, Poater A. Struct. Chem. 2016; 27: 240