D
Y.-L. Tseng et al.
Letter
Synlett
(9) At the time, the isolation of paniculidine C had not been dis-
closed; See Ref. 2.
(10) Selvakumar, N.; Rajulu, G. G. J. Org. Chem. 2004, 69, 4429.
(11) Cheskis, B. A.; Alekseev, I. G.; Moiseenkov, A. M. Zh. Org. Khim.
1990, 26, 425.
(12) (a) Tanner, M. E. Nat. Prod. Rep. 2015, 32, 88. (b) Li, S.-M. Nat.
Prod. Rep. 2010, 27, 57.
(13) For a leading review, see: Lindel, T.; Marsch, N.; Adla, S. K. Top.
Curr. Chem. 2012, 309, 67.
(14) For leading examples, see: (a) Casanati, G.; Francioni, M.;
Guareschi, A.; Pochini, A. Tetrahedron Lett. 1969, 10, 2485.
(b) Bocchi, V.; Casanati, G.; Marchelli, R. Tetrahedron 1978, 34,
929. (c) Wenkert, E.; Angell, E. C.; Ferreira, V. F.; Michelotti, E. L.;
Piettre, S. R.; Sheu, J.-H.; Swindell, C. S. J. Org. Chem. 1986, 51,
2343. (d) Zhu, X.; Ganesan, A. J. Org. Chem. 2002, 67, 2705.
(e) Müller, J. M.; Stark, C. B. W. Angew. Chem. Int. Ed. 2016, 55,
4798. (f) Trost, B. M.; Chan, W. H.; Malhotra, S. Chem. Eur. J. 2017,
23, 4405. (g) Tanaka, S.; Shiomi, S.; Ishikawa, H. J. Nat. Prod. 2017,
80, 2371; and references cited therein.
(15) For conceptually relevant examples, see: (a) Austin, J. F.; Kim,
S.-G.; Sinz, C. J.; Xiao, W.-J.; MacMillan, D. W. C. Proc. Natl. Acad.
Sci. U. S. A. 2004, 101, 5482. (b) Spessard, S. J.; Stoltz, B. M. Org.
Lett. 2002, 4, 1943. (c) De, S.; Rigby, J. H. Tetrahedron Lett. 2013,
54, 4760.
mixture, presumably generated via alkene isomerization of 5
under the hydrogenation conditions.
IR (CHCl3): 3688, 1603, 1460 cm–1 1H NMR (400 MHz, CDCl3):
.
δ = 7.58 (ddd, J = 7.9, 1.0, 1.0 Hz, 1 H), 7.41 (ddd, J = 8.2, 0.9, 0.9
Hz, 1 H), 7.24 (ddd, J = 8.1, 7.1, 1.1 Hz, 1 H), 7.11 (ddd, J = 8.0,
7.1, 1.0 Hz, 1 H), 7.06 (d, J = 1.0 Hz, 1 H), 4.05 (s, 3 H), 3.57 (dd,
J = 10.4, 5.8 Hz, 1 H), 3.50 (dd, J = 10.0, 6.3 Hz, 1 H), 2.82 (dddd,
J = 14.7, 10.0, 5.6, 1.0 Hz, 1 H), 2.72 (dddd, J = 14.7, 9.8, 6.3, 0.9
Hz, 1 H), 1.91–1.83 (m, 1 H), 1.79–1.70 (m, 1 H), 1.53 (dddd,
J = 13.4, 9.8, 8.0, 5.6 Hz, 1 H), 1.40 (br s, 1 H), 1.03 (d, J = 6.7 Hz, 3
H). 13C NMR (100 MHz, CDCl3): δ = 132.79, 123.96, 122.31,
120.43, 119.37, 119.13, 112.96, 108.32, 68.21, 65.44, 35.50,
33.41, 22.43, 16.53. HRMS (EI): m/z [M+] calcd for C14H19NO2:
233.1416; found: 233.1410.
(21) (a) Cheng, K.-F.; Kong, Y.-C.; Chan, T.-Y. J. Chem. Soc., Chem.
Commun. 1985, 48. (b) Wenkert, E.; Moeller, P. D. R.; Piettre, S.
R.; McPhail, A. T. J. Org. Chem. 1988, 53, 3170. (c) Sheu, J.-H.;
Chen, Y.-K.; Hong, Y.-L. V. Tetrahedron Lett. 1991, 32, 1045.
(d) Sheu, J.-H.; Chen, C.-A.; Chen, B.-H. Chem. Commun. 1999,
203. (e) Abe, T.; Komatsu, H.; Ikeda, T.; Hatae, N.; Toyota, E.;
Ishikura, M. Heterocycles 2012, 86, 505.
(22) Sheu, J.-H.; Chen, Y.-K.; Hong, Y.-L. V. J. Org. Chem. 1993, 58,
5784.
(23) For the purpose of comparison, we adopted Sheu’s conditions
that effected the transformation of 3-(1-hydroxy-3-methylbut-
3-enyl)indole into yuehchukene (Table 1, entry 1); see Ref. 22.
(24) For the isolation of 4 from natural sources, see: Kruber, O.;
Marx, A. Chem. Ber. 1938, 71, 2478.
(25) Lu and co-workers have reported the palladium-catalyzed syn-
thesis of 2-methylcarbazole (4) from 3-(3-methyl-3-bute-
nyl)indole in 40% yield; see: Kong, A.; Han, X.; Lu, X. Org. Lett.
2006, 8, 1339.
(16) Kimura, M.; Futamata, M.; Mukai, R.; Tamaru, Y. J. Am. Chem.
Soc. 2005, 127, 4592.
(17) (a) Kawasaki, T.; Tabata, M.; Nakagawa, K.; Kobayashi, K.;
Kodama, A.; Kobayashi, T.; Hasegawa, M.; Tanii, K.; Somei, M.
Heterocycles 2015, 90, 1038. (b) Kawasaki, T.; Kodama, A.;
Nishida, T.; Shimizu, K.; Somei, M. Heterocycles 1991, 32, 221.
(18) Chatterjee, A. K.; Choi, T.-L.; Sanders, D. P.; Grubbs, R. H. J. Am.
Chem. Soc. 2003, 125, 11360.
(19) When the hydrogenation reaction was carried out in either
MeOH or a mixture of EtOAc and hexanes, the formation of
paniculidine C (2) in various amounts could not be circum-
vented.
(26) Wilsdorf, M.; Leichnitz, D.; Reissig, H.-U. Org. Lett. 2013, 15,
2494.
(27) β-Hydroxysulfonic acid-functionalized silica gel (HO-SAS; Chro-
matorex-DPR, 0.5 mmol/g of SO3H) has been commercially
developed by Fuji Silysia Chemical Ltd. For applications of
HO-SAS as a catalyst in organic synthesis, see: (a) Furuta, A.;
Fukuyama, T.; Ryu, I. Bull. Chem. Soc. Jpn. 2017, 90, 607.
(b) Furuta, A.; Hirobe, Y.; Fukuyama, T.; Ryu, I.; Manabe, Y.;
Fukase, K. Eur. J. Org. Chem. 2017, 1365. (c) Fujii, H.; Yamada, T.;
Hayashida, K.; Kuwada, M.; Hamasaki, A.; Nobuhara, K.; Ozeki,
S.; Nagase, H. Heterocycles 2012, 85, 2685.
(28) For a Brønsted acid-catalyzed synthesis of functionalized carba-
zoles from 2-substituted indoles, see: Li, Q.; Peng, X.-S.; Wong,
H. N. C. Org. Chem. Front. 2014, 1, 1197.
(29) Zhao, J.; Li, P.; Xia, C.; Li, F. Chem. Eur. J. 2015, 21, 16383.
(30) Chakraborty, D. P. J. Indian Chem. Soc. 1989, 66, 843.
(20) Paniculidine B (1)
A mixture of compound 5 (46 mg, 0.2 mmol) and 20 mass% Pd/C
(9 mg) was stirred in THF (4 mL) under H2 (balloon) at r.t. for 6
h. The mixture was filtered through a short pad of Celite, which
was washed with THF (2 × 5 mL). To the stirred filtrate was
added NaBH4 (8 mg, 0.2 mmol) at r.t. After 3 h, the reaction was
quenched with sat. aq NH4Cl (10 mL), and the mixture was
extracted with Et2O (3 × 10 mL). The combined organic layers
were washed with brine (10 mL), dried (MgSO4), filtered, and
concentrated under reduced pressure. The residue was purified
by flash chromatography [silica gel, MeOH–CH2Cl2 (1:80)] to
give a colorless oil; yield: 42 mg (90%). Note: NaBH4 was added
in this step to reduce a minor amount of aldehyde in the crude
© Georg Thieme Verlag Stuttgart · New York — Synlett 2017, 28, A–D