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COMMUNICATION
Journal Name
aforementioned methodology, we have synthesized dimeric 2- 3725. (b) M. Movassaghi, M. A. Schmidt, J. A. ADsOhIe: h10u.r1s0t3, 9A/nCg8eCwC.0C4h3e3m8H.,
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oxindoles sharing vicinal all-carbon quaternary stereocentres in only
steps, which is structural feature of many naturally occurring
alkaloids. Further investigation on mechanistic details and synthetic
applications of our method are currently underway.
4
2
010, 132, 14376.
(
8) For the use of homodimerization approach, see: (a) C. Pérez-Balado,
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9) M. Movassaghi, O. K. Ahmad, S. P. Lathrop, J. Am. Chem. Soc. 2011,
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10) E. Iwasa, Y. Hamashima, S. Fujishiro, E. Higuchi, A. Ito, M. Yoshida,
M. Sodeoka, J. Am. Chem. Soc. 2010, 132, 4078.
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1
(
(
(
(
12) R. Liu, J. Zhang, Org. Lett. 2013, 15, 2266.
13) H. Mitsunuma, M. Shibasaki, M. Kanai, S. Matsunaga, Angew.
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(
(
14) B. M. Trost, M. Osipov, Angew. Chem., Int. Ed. 2013, 52, 9176.
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2
014, 50, 2434. (b) S. Ghosh, S. Chaudhuri, A. Bisai, Chem. Eur. J. 2015,
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16) (a) S. Ma, X. Han, S. Krishnan, S. C. Virgil, B. M. Stoltz, Angew.
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Scheme 5. Formal total synthesis of ()-folicanthine 1b and H. Kang, R. Wang, J. Am. Chem. Soc. 2013, 135, 14098. (e) A base
rationale of observe diastereoselectivity.
promoted formation of o-azaxylylene from 3-halo 2-oxindole was the
crucial for efficient enantioselective malonate addition.
(
17) For Lewis acid catalyzed reactions of 3-hydroxy-2-oxindoles with a
Financial supports from the SERB, DST [EMR/2016/000214] and
CSIR [02(0295)/17/EMR-II], Govt. of India, are gratefully variety of nucleophiles, see; (a) S. Ghosh, L. K. Kinthada, S. Bhunia, A.
acknowledged. K.N.B. and L.K.K., thank the CSIR for senior research Bisai,Chem. Commun. 2012, 48, 10132. (b) L. K. Kinthada, S. Ghosh, S.
fellowships (SRFs). We sincerely thank Prof. R. N. Mukherjee, IIT De, S. Bhunia, D. Dey, A. Bisai, Org. Biomol. Chem. 2013, 11, 6984. (c)
Kanpur for helpful discussion pertaining to CV and EPR studies of
Cu(II)-PHOX complexes.
Electron-donating affinity of indole ring at C-3 position of 3-hydroxy 2-
oxindole makes them as an attractive substrate for Lewis-acid catalyzed
substitution reactions.
Notes and references
(
18) PHOX ligands: (a) G. Helmchen, A. Pfaltz, Acc. Chem. Res. 2000, 33,
(
1) For a general method for the construction of quaternary carbon 336. (b) M. R. Krout, J. T. Mohr, B. M. Stoltz, Org. Synth. 2009, 86, 181.
stereocentres, see: (a) A. Y. Hong, B. M. Stoltz, Eur. J. Org. Chem. 2013, (19) Trost Ligands L5-L7: (a) B. M. Trost, D. L. Van Vranken, Angew.
2
1
1
3
745. (b) C. J. Douglas, L. E. Overman, Proc. Natl. Acad. Sci. U.S.A. 2004, Chem., Int. Ed. 1992, 31, 228. (b) B. M. Trost, D. A. Thaisrivongs, J.
01, 5363. (c) J. Christoffers, A. Baro, Angew. Chem., Int. Ed. 2003, 42, Hartwig, J. Am. Chem. Soc. 2011, 133, 12439.
688. (d) E. J. Corey, A. Guzman-Perez, Angew. Chem., Int. Ed. 1998, 37, (20) For a review on the p-stacking effect in asymmetric synthesis, see:
88.
(a) G. B. Jones, B. J. Chapman, Synthesis 1995, 475. (b) E. A. Meyer, R. K.
(
2) (a) E. J. Corey, S. Lin, J. Am. Chem. Soc. 1996, 118, 8765. (b) E. A. Castellano, F. Diederich, Angew. Chem., Int. Ed. 2003, 42, 1210.
Peterson, L. E. Overman, Proc. Natl. Acad. Sci. U.S.A. 2004, 101, 11943.
(
21) (a) Absolute configuration of malonate addition product was
(
(
7
c) A. Steven, L. E. Overman, Angew. Chem., Int. Ed. 2007, 119, 5584.
3) B. M. Trost, S. Malhotra, W. H. Chan, J. Am. Chem. Soc. 2011, 133,
328.
confirmed by transforming 4f into known C -symmetric diol 12 (see,
2
Scheme 4). (b) Reaction of 5a with t-butyl acetoacetate and ethyl 2-
oxo-cyclopentane carboxylate afforded racemic products clearly
depicting the reversible nature of our process, which is relatively slow
with malonates, but fast with the more acidic ketoesters (see, SI for
details).
(
4) For racemic approaches, see: (a) C.-L. Fang, S. Horne, N. Taylor, R.
Rodrigo, J. Am. Chem. Soc. 1994, 116, 9480. (b) H. Ishikawa, H.
Takayama, N. Aimi, Tetrahedron Lett. 2002, 43, 5637. (c) Y.-X. Li, H.-X.
Wang, S. Ali, X.-F. Xia, Y.-M. Liang, Chem. Commun. 2012, 2343. For
total synthesis of meso-chimonanthine and meso-calycanthine, see: (d)
J. T. Link, L. E. Overman, J. Am. Chem. Soc. 1996, 118, 8166. (e) C.
Menozzi, P. I. Dalko, J. Cossy, Chem. Commun. 2006, 4638. Total
(
22) The enantioselectivity of (+)-4f was found to be 98%, when the
reaction was carried out in 0.25 g scale of 3-hydroxy 2-oxindole (0
ºC, 24 h, 83% yield). However, the enantioselectivity was dropped
to 90%, when the reaction was performed on 0.5 g scale (0 ºC, 32 h,
synthesis of hodgkinsine
B
via desymmetrization of meso-
7
(
9% yield).
23) Alkylation from above face (Re-face) is retarded because of steric
clash imposed by bulky benzylester group.
chimonanthine, see; (f) R. H. Snell, R. L. Woodward, M. C. Willis, Angew.
Chem., Int. Ed. 2011, 50, 9116. (g) R. H. Snell, M. J. Durbin, R. L.
Woodward, M. C. Willis, Chem. Eur. J. 2012, 18, 9116.
(
5) For a recent review, see: P. Ruis-Sanchis, S. A. Savina, F. Alberecio,
M. Álvarez, Chem. Eur. J. 2011, 17, 1388 and references cited.
6) (a) L. E. Overman, D. V. Paone, Sterns, B. A. J. Am. Chem. Soc. 1999,
21, 7702. (b) L. E. Overman, J. F. Larrow, B. A. Stearns, J. M. Vance,
Angew. Chem., Int. Ed. 2000, 39, 213.
(
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