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1
. Ph
3 3
PCH Br
MeO
MeO
Br
MeO
MeO
CHO
n-BuLi
Tanaka, K.; Mori, H.; Yamamoto, M.; Katsumura, S. J. Org. Chem
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Nakashima, M.; Hakogi, T.; Tanaka, K.; Katsumura, S. Org. Lett.
2. n-BuLi then
DMF
CHO
10
11
72%
OMe
85%
2
006, 8, 3809–3812; (f) Kobayashi, T.; Hasegawa, F.; Tanaka, K.;
MeO
Ph
Katsumura, S. Org. Lett. 2006, 8, 3813–3816; (g) Tanaka, K.;
Masuyama, T.; Hasegawa, K.; Tahara, T.; Mizuma, H.; Wada, Y.;
Watanabe, Y.; Fukase, K. Angew. Chem., Int. Ed. 2008, 47, 102–
105.
8
, DMSO
O
1
20 ºC, 16h
MeO
MeO
MgBr
N
76%
5
. Asao, N.; Yudha, S. S.; Nogami, T.; Yamamoto, Y. Angew. Chem.,
Int. Ed. 2005, 44, 5526–5528.
1
2 1S
:1R
= 93 : 7
OMe
OMe
N
6. (a) Asao, N.; Iso, K.; Yudha, S. S. Org. Lett. 2006, 8, 4149–4151; (b)
Iso, K.; Yudha, S.; Menggenbateer, S.; Asao, N. Heterocycles 2007,
MeO
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7
4, 649–660.
1
. H , PtO
OH
Ph
2
2
7
. For reviews on the asymmetric synthesis of isoquinolines, see: (a)
2. HCHO
MeO
MeO
MeO
MeO
Me
Chrzanowska, M.; Rozwadowska, M. D. Chem. Rev. 2004, 104,
N
NaBH
4
3
341–3370; (b) Bracca, A. B. J.; Kaufman, T. S. Tetrahedron 2004, 60,
57%
10575–10610 and references therein.
8
. For recent examples of 6p-azaelectrocyclization for synthesis of
benzene-fused heterocycles, see: (a) Kuwabara, N.; Hayashi, H.;
Hiramatsu, N.; Choshi, T.; Kumemura, T.; Nobuhiro, J.; Hibino, S.
Tetrahedron 2004, 60, 2943–2952; (b) Kumemura, T.; Choshi, T.;
Yukawa, J.; Hirose, A.; Nobuhiro, J.; Hibino, S. Heterocycles 2005,
13 1S
:1
R
= 98 : 2
(
S
)-cryptostyline II 14
9
6%ee
Scheme 4.
6
6, 87–90; (c) Kumemura, T.; Choshi, T.; Hirata, A.; Sera, M.;
Takahashi, Y.; Nobuhiro, J.; Hibino, S. . Chem. Pharm. Bull. 2005,
3, 393–397. and references therein.
cyclization protocol using ortho-vinylbenzaldehyde and
-aminopropanols. The present method was applied to
5
3
9. Beke, D.; Harsanyi, K.; Korbonits, D. Acta Chim. Hung. 1959, 19,
259–266.
the synthesis of chiral (S)-cryptostyline II by using (R)-phen-
ylglycinol as a chiral auxiliary. It is believed that the reac-
tion proceeds through the thermal 6p-azaelectrocyclization
and cyclic N,O-acetal formation. The obtained products
are known as versatile intermediates for various kinds of
bioactive tetrahydroisoquinoline alkaloids. Further studies
to extend the scope of synthetic utility are in progress in
our laboratory.
1
0. For reviews, see: (a) Sammes, P. G.; Weller, D. J. Synthesis 1995,
1
205–1222; (b) Jung, M. E.; Piizi, G. Chem. Rev. 2005, 105, 1735–
1
766.
1
1. Pedrosa, R.; Andr e´ s, C.; Iglesias, J. M. J. Org. Chem. 2001, 66, 243–
250.
12. (a) Yamato, M.; Hashigaki, K.; Ishikawa, S.; Qais, N. Tetrahedron
Lett. 1988, 29, 6949–6950; (b) Yamato, M.; Hashigaki, K.; Qais, N.;
Ishikawa, S. Tetrahedron 1990, 46, 5909–5920; (c) Hashigaki, K.;
Kan, K.; Qais, N.; Takeuchi, Y.; Yamato, M. Chem. Pharm. Bull.
1
991, 39, 1126–1131.
Acknowledgment
13. (a) Several asymmetric syntheses of cryptostyline II have been
reported, see: Ref. 10b; (b) Cho, B. T.; Han, C. K. Bull. Korean
Chem. Soc. 1990, 11, 81–82; (c) Munchhof, M. J.; Meyers, A. I. J.
Org. Chem. 1995, 60, 7086–7087; (d) Czarnocki, Z.; Mieczkowski, J.
B. Pol. J. Chem. 1995, 69, 1447–1450; (e) Suzuki, H.; Aoyagi, S.;
Kibayashi, C. Tetrahedron Lett. 1995, 36, 6709–6712.
This work was supported in part by a Grant-in-Aid
from the Sumitomo Foundation.
References and notes
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48.
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. For reviews, see: (a) Okamura, W. H.; de Lera, A. R. In Compre-
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16. Procedure for 4,5-dimethoxy-2-vinyl-benzaldehyde 11: To a solution of
methyltriphenylphosphonium bromide (8.0 g, 22.4 mmol) in THF
(50 mL) was added a 1.6 M solution of n-BuLi (14 mL, 22.4 mmol) at
0 °C and the mixture was stirred for 1 h. To the mixture was added a
solution of 6-bromoveratraldehyde (4.9 g, 20 mmol) in THF (50 mL).
After the mixture was stirred for 4 h at rt, a saturated aqueous
2
. For leading references on electrocyclic ring-closures involving 1-
azatrienes, see: (a) Okamura, W. H.; de Lera, A. R.; Reischl, W. J.
Am. Chem. Soc. 1988, 110, 4462–4464; (b) de Lera, A. R.; Reischl, W.;
Okamura, W. H. J. Am. Chem. Soc. 1989, 111, 4051–4063; (c)
Maynard, D. F.; Okamura, W. H. J. Org. Chem. 1995, 60, 1763–1771.
. (a) Hsung, R. P.; Wei, L.-L.; Sklenicka, H. M.; Douglas, C. J.;
McLaughlin, M. J.; Mulder, J. A.; Yao, L. J. Org. Lett. 1999, 1, 509–
solution of NH
Et O twice. The combined extracts were dried over MgSO
4
4
Cl was added and the mixture was extracted with
3
2
and
evaporated to leave the crude product, which was purified by column
chromatography (silica gel, hexane/AcOEt = 9/1 as eluent) to give
1-bromo-4,5-dimethoxy-2-vinylbenzene (3.8 g, 15.6 mmol) in 76%
yield as a colorless oil. To a solution of 1-bromo-4,5-dimethoxy-2-
vinylbenzene (3.56 g, 14.6 mmol) in THF (30 mL) was added a 1.6 M
solution of n-BuLi (9.5 mL, 15.2 mmol) at ꢀ78 °C and the mixture
was stirred for 40 min. To the mixture was added DMF (1.16 mL,
15.0 mmol) and the mixture was stirred for overnight at rt. A
5
12; (b) Sklenicka, H. M.; Hsung, R. P.; Wei, L.-L.; McLaughlin, M.
J.; Gerasyuto, A. I.; Degen, S. J.; Mulder, J. A. Org. Lett. 2000, 2,
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saturated aqueous solution of NH
4
Cl was added and the mixture was
2
extracted with Et O twice. The combined extracts were dried over
2