10.1002/chem.202002581
Chemistry - A European Journal
COMMUNICATION
By enabling cooperativity of substituent and solvent effects, the
concept of
a photochemically triggered two-carbon ring
expansion was implemented to open a modular synthetic access
to cyclohepta[b]indole-type buildings blocks.
[1] a) W. Treibs, Justus Liebigs Ann. Chem. 1952, 576, 110–115. b) J. H.
Boyer, J. De Jong, J. Am. Chem. Soc. 1969, 91, 5929–5930.
[2] a) C. Kuehm-Caubère, P. Caubère, B. Jamart-Grégoire, B. Pfeiffer, B.
Guardiola-Lemaître, D. Manechez, P. Renard, Eur. J. Med. Chem.
1999, 34, 51–61. b) A. D. Napper, J. Hixon, T. McDonagh, K. Keavey,
J.-F. Pons, J. Barker, W. T. Yau, P. Amouzegh, A. Flegg, E. Hamelin, R.
J. Thomas, M. Kates, S. Jones, M. A. Navia, J. O. Saunders, P. S.
DiStefano, R. Curtis, J. Med. Chem. 2005, 48, 8045–8054. c) T. Barf, F.
Lehmann, K. Hammer, S. Haile, E. Axen, C. Medina, J. Uppenberg, S.
Svensson, L. Rondahl, T. Lundbäck, Bioorg. Med. Chem. Lett. 2009, 19,
1745–1748. d) E. Yamuna, R. A. Kumar, M. Zeller, R. P. K.
Jayarampillai, Eur. J. Med. Chem. 2012, 47, 228–238.
[3] For a recent example, see: P. Krishnan, F.-K. Lee, K.-W. Chong, C.-W. Mai,
A. Muhamad, S.-H. Lim, Y.-Y. Low, K.-N. Ting, K.-H. Lim, Org. Lett.
2018, 20, 8014–8018.
[4] X.-X. Zhu, Y.-Y. Fan, L. Xu, Q.-F. Liu, J.-P. Wu, J.-Y. Li, J. Li, K. Gao, J.-M.
Yue, Org. Lett. 2019, 21, 1471–1474.
[5] E. Stempel, T. Gaich, Acc. Chem. Res. 2016, 49, 2390–2402.
[6] For selected recent examples, see: a) J. Kaufmann, E. Jäckel, E. Haak,
Angew. Chem. Int. Ed. 2018, 57, 5908–5911. b) M. A. Kroc, A.
Prajapati, D. J. Wink, L. L. Anderson, J. Org. Chem. 2018, 83, 1085–
1094. c) A. S. Jadhav, Y. A. Pankhade, R. Vijaya Anand, J. Org. Chem.
2018, 83, 8615–8626. d) Q. Zeng, K. Dong, J. Huang, L. Qiu, X. Xu,
Org. Biomol. Chem. 2019, 17, 2326–2330. e) L. Zhang, Y. Zhang, W. Li,
X. Qi, Angew. Chem. Int. Ed. 2019, 58, 4988–4991.
[7] For selected recent examples, see: a) T. Takeda, S. Harada, A. Okabe, A.
Nishida, J. Org. Chem. 2018, 83, 11541–11551. b) C. Gelis, G. Levitre,
J. Merad, P. Retailleau, L. Neuville, G. Masson, Angew. Chem. Int. Ed.
2018, 57, 12121–12125. c) Z. Wang, Y. Addepalli, Y. He, Org. Lett.
2018, 20, 644–647. d) A. N. Parker, M. C. Martin, R. Shenje, S. France,
Org. Lett. 2019, 21, 7268–7273. e) J. Xu, V. H. Rawal, J. Am. Chem.
Soc. 2019, 141, 4820–4823.
Figure 2. (TD)DTF (u)B3LYP/def2-TZVP calculated (relative) electronic plus
zero-point energies (ΔE) at 298.15 K in kcal/mol.
[8] For selected recent examples, see: a) G. Xu, L. Chen, J. Sun, Org. Lett.
2018, 20, 3408–3412. b) M. Häfner, Y. M. Sokolenko, P. Gamerdinger,
E. Stempel, T. Gaich, Org. Lett. 2019, 21, 7370–7374.
[9] For the initial example, see: D. Tymann, D. C. Tymann, U. Bednarzick, L.
Iovkova-Berends, J. Rehbein, M. Hiersemann, Angew. Chem. Int. Ed.
2018, 130, 15779–15783.
Acknowledgements
Financial support by the TU Dortmund is gratefully
acknowledged.
[10] Conditions adapted from: E. N. Agbo, T. J. Makhafola, Y. S. Choong, J. M.
Mphatele, P. Ramasami, Molecules 2016, 21, 28.
[11] T. Mukaiyama, J.-i. Matsuo, H. Kitagawa, Chem. Lett. 2000, 29, 1250–
1251.
Keywords: cascade reaction • cyclohepta[b]indole • indole[2,3-
d]tropone • photochemistry • ring expansion
[12] CCDC 1991297 and 1985305 (9a and 10b) contain the supplementary
crystallographic data. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre.
[13] Structural assignment in solid state and in solution is in accordance with
the notion of 9 as cyclohepta[b]indol-8(5H)-one and not as tautomeric
cyclohepta[b]indol-8-ol.
Entry for the Table of Contents
[14] To the best of our knowledge, parent indolo[2,3-d]tropone has been
mentioned only once, see: T. Nozoe, H. Horino, T. Toda, Tetrahedron
Lett. 1967, 8, 5349–5353.
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