2932
J . Org. Chem. 1996, 61, 2932-2933
Sch em e 1
Asym m etr ic [2,3]Sigm a tr op ic
Rea r r a n gem en t of Ch ir a l Allylic
Selen im id es
Noriyuki Kurose, Tamiko Takahashi, and
Toru Koizumi*
Faculty of Pharmaceutical Sciences,
Toyama Medical & Pharmaceutical University,
2630 Sugitani, Toyama 930-01, J apan
Received February 13, 1996
In contrast to the many reports on asymmetric reac-
tions using chiral sulfinyl compounds, few applications
of chiral seleninyl compounds to asymmetric synthesis
have been described.1 Recently, some groups have
reported the asymmetric [2,3]sigmatropic rearrangement
of chiral selenoxides.1 Uemura and co-workers have
succeeded in the asymmetric [2,3]sigmatropic rearrange-
ment of chiral selenimides giving the chiral sulfonamide
with up to 87% enantiomeric excess.2 However, the
stereochemical course of the reaction was not described.
The key steps of these asymmetric reactions are enantio-
or diastereoselective oxidation or imination of the se-
lenides and transfer of the chirality of the selenium atom
to C-3 of the resulting allylic alcohols or amines. We
recently reported the first synthesis of optically pure
haloselenuranes using the 2-exo-hydroxy-10-bornyl group
as a chiral ligand.3 Alkaline hydrolysis of the (RSe)-
chloroselenurane proceeds with retention of configuration
to give (RSe)-selenoxide as the sole product.3,4 This
selenoxide is stable at room temperature due to the
bulkiness of the bornyl group as well as in intramolecular
hydrogen bond between the seleninyl oxygen and the
secondary hydroxy group.5 Nucleophilic reaction of the
corresponding chiral allylic chloroselenurane with an
N-protected amine should also occur with complete
retention of configuration. If [2,3]sigmatropic rearrange-
ment of the resulting allylic selenimide proceeded ste-
reoselectively, a chiral N-protected allylic amine would
be obtained with high enantioselectivity. We report here
that the nucleophilic reaction of the allylic chloro-
selenuranes with N-protected amines followed by the
[2,3]sigmatropic rearrangement of the resulting chiral
allylic selenimides proceeds in a highly stereoselective
manner to afford chiral N-protected allylic amines. [2,3]-
Sigmatropic rearrangement of the allylic selenimides was
evidenced to progress selectively via an endo transition
state.
Sch em e 2
verted to the corresponding MOM ether 2. Reaction of
2 with sodium selenolate7 followed by hydrolysis of the
resulting diselenide 3 gave the deprotected diselenide 4.
Allylic selenides 5 and 6 were obtained by reaction of
cinnamyl chloride or allylic mesylate with selenolate
anion which was prepared in situ from 4 and sodium
borohydride.8 Treatment of the allylic selenides 5 and 6
with t-BuOCl gave allylic chloroselenuranes 7 and 8 as
an exclusive product.9 We selected benzyl carbamate,
tert-butyl carbamate, p-tosylamide, and diphenylphos-
phinamide as an N-protected amine for selenimide
formation (Scheme 2 and Table 1). Nucleophilic reaction
of 7 and 8 with lithium N-protected amides afforded
chiral allylic selenimides, 9a -d and 10a -d , in situ, with
retention of configuration. [2,3]Sigmatropic rearrange-
ment of 9a -d and 10a -d gave chiral N-protected allylic
amines 11a -d and 12a -d . These results are shown in
Table 1. The ee values of allylic amines 11 and 12 were
determined by HPLC using a Daicel Chiralcel OJ or a
Chiralpak AS column. Determination of the absolute
configuration of 11 and 12 is summarized in the footnote
of Table 1.
Allylic selenides were prepared by a route shown in
Scheme 1. (1S)-10-Bromo-2-exo-borneol (1)6 was con-
(1) For asymmetric [2,3]sigmatropic rearrangement of chiral
selenoxides: (a) Nishibayashi, Y.; Singh, J . D.; Fukuzawa, S.; Uemura,
S. J . Org. Chem. 1995, 60, 4114. (b) Komatsu, N.; Nishibayashi, Y.;
Uemura, S. Tetrahedron Lett. 1993, 34, 2339. (c) Davis, F. A.; Reddy,
R. T. J . Org. Chem. 1992, 57, 2599. (d) Reich, H. J .; Yelm, K. E. J .
Org. Chem. 1991, 56, 5672. For asymmetric â-elimination of chiral
selenoxides: ref 1a and references cited therein.
(2) Nishibayashi, Y.; Chiba, T.; Ohe, K.; Uemura, S. J . Chem. Soc.,
Chem. Commun. 1995, 59, 3262.
(3) Takahashi, T.; Kurose, N.; Kawanami, S.; Arai, Y.; Koizumi, T.;
Shiro, M. J . Org. Chem. 1994, 59, 3262.
(4) Nucleophilic reaction of the (RSe)-chloroselenurane with active
methylene compounds also proceeds with retention of configuration
to afford (SSe)-selenonium ylides exclusively: Takahashi, T.; Kurose,
N.; Kawanami, S.; Nojiri, A.; Arai, Y.; Koizumi, T.; Shiro, M. Chem.
Lett. 1995, 379.
(5) We have applied this selenoxide to an asymmetric protonation
reaction: Takahashi, T.; Nakao, N.; Koizumi, T. Chem. Lett. 1996, 207.
(6) Poth, N. Rev. Tech. Luxemb. 1976, 68, 195; Chem. Abstr. 1977,
87, 135965k.
(7) Syper, L.; Młochowski, J . Synthesis 1984, 439.
(8) Scaborough, R. M., J r.; Toder, B. H.; Smith, A. B., III. J . Am.
Chem. Soc. 1980, 102, 3904.
(9) The structure of chloroselenuranes was confirmed by comparison
of their 1H-NMR spectra with that of (1S,RSe)-5-chloro-10,10-dimethyl-
5-phenyl-5λ4-selena-4-oxatricyclo[5.2.1.03,7]decane (ref 3).
(10) Moriwake, T.; Hamano, S.; Saito, S.; Torii, S.; Kashino, S. J .
Org. Chem. 1989, 54, 4114.
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