Rhodium-catalyzed asymmetric arylation of imines with organostannanes. Asymmetric synthesis of diarylmethylamines [14]

Full text of DOI:10.1021/ja9927220

976
J. Am. Chem. Soc. 2000, 122, 976-977
Scheme 1
Rhodium-Catalyzed Asymmetric Arylation of Imines
with Organostannanes. Asymmetric Synthesis of
Diarylmethylamines
Tamio Hayashi* and Mitsuo Ishigedani
Department of Chemistry, Graduate School of Science
Kyoto UniVersity, Sakyo, Kyoto 606-8502, Japan
ReceiVed August 2, 1999
Although enantiomerically pure diarylmethylamines constitute
many biologically important compounds,1 their preparation by
asymmetric synthesis has not been well developed.2 Especially,
the synthesis by asymmetric catalysis is a formidable challenge
in synthetic organic chemistry. To our knowledge, there have been
no successful reports on catalytic asymmetric synthesis of
diarylmethylamines either by asymmetric reduction of imines of
diaryl ketones or by asymmetric arylation of aldehyde imines.3,4
We have made efforts to find a new chiral catalyst system for
the asymmetric addition of arylmetal reagents to imines derived
from aromatic aldehydes and found that some rhodium complexes
coordinated with chiral monodentate phosphine ligands, MOP’s,5
catalyze the addition of arylstannanes to N-alkylidenesulfonamides
to give sulfonamide of diarylmethylamines with high enantio-
selectivity (up to 96% ee). Here we wish to report the preliminary
results of the new catalytic asymmetric addition reaction.
fluoride7 in dioxane at 110 °C for 12 h gave 82% yield of
(+)-[N-(4-trifluoromethylphenyl)phenylmethyl]-4-nitrobenzene-
sulfonamide (5am) ([R]20 +7.2 (c 1.00, chloroform)), whose
D
In numerous studies carried out in this laboratory, we have
found that N-alkylidenesulfonamides (Ar1CHdNSO2Ar3), readily
accessible by condensation of aromatic aldehydes (Ar1CHdO)
with arenesulfonamides (H2NSO2Ar3) in the presence of triethoxy-
silane,6 undergo asymmetric arylation with arylstannanes under
the catalysis by a rhodium complex coordinated with a chiral
monodentate phosphine ligand (Scheme 1). The reactivity of
sulfonamides 1-3 toward the rhodium-catalyzed arylation is
dependent on the substituents at the 4 position on the phenyl ring
Ar3 of sulfonamides. Sulfonamide 1a containing nitro group at
the 4 position gave higher yields of arylation product 5am in the
reaction with phenyltrimethylstannane (4m) than that containing
4-chloro (2a) or 4-methyl (3a). The enantioselectivity is also
higher with the 4-nitro group than with the 4-chloro or 4-methyl
group. Thus, for example, the reaction of 1a with 4m in the
presence of 3 mol % of a rhodium catalyst, generated from Rh-
(acac)(C2H4)2 and (R)-MeO-MOP5 (Rh/P ) 1/2), and lithium
enantiomeric purity was determined to be 92% by HPLC analysis
with a chiral stationary phase column (entry 1 in Table 1). On
the other hand, the reaction of 2a and 3a with 4m gave the
corresponding arylation products 6am and 7am, in 66% yield
(87% ee) and 64% yield (75% ee), respectively (entries 2 and 3).
In addition to the higher reactivity and higher enantioselectivity,
4-nitrobenzenesulfonamide has another important advantage over
others in that it is readily removed from diarylmethylamine moiety
without loss of enantiomeric purity. Treatment of (+)-5am (92%
ee) with benzenethiol and potassium carbonate in DMF8 gave
(+)-(4-trifluoromethylphenyl)phenylmethylamine (8am)9 of 92%
ee ([R]20D +13.4 (c 1.00, ethanol)) in 80% yield. The enantiomeric
purity was determined by the HPLC analysis of toluenesulfona-
mide 7am obtained by treatment of 8am9 with toluenesulfonyl
chloride, triethylamine, and 4-(dimethylamino)pyridine (Scheme
2).
The choice of the MOP ligand is essential for the present
catalytic asymmetric arylation. With chelating bisphosphine
ligands the arylation was very slow, the yields of 5am being 6%
and 10%, with rhodium catalysts of binap10 and diop,11 respec-
tively (entries 5 and 6). Higher yield and enantioselectivity were
observed with newly developed MOP ligand, (R)-Ar*-MOP,12
which gave 90% yield of 5am with 96% ee (entry 4).
(1) For examples: (a) Bishop, M. J.; McNutt, R. W. Bioorg. Med. Chem.
Lett. 1995, 5, 1311. (b) Spencer, C. M.; Foulds, D.; Peters, D. H. Drugs 1993,
46, 1055. (c) Sakurai, S.; Ogawa, N.; Suzuki, T.; Kato, K.; Ohashi, T.; Yasuda,
S.; Kato, H.; Ito, Y. Chem. Pharm. Bull. 1996, 44, 765.
(2) For recent examples of asymmetric synthesis of diarylmethylamines:
(a) Corey, E. J.; Helal, C. J. Tetrahedron Lett. 1996, 37, 4837. (b) Delorme,
D.; Berthelette, C.; Lavoie, R.; Roberts, E. Tetrahedron Asym. 1998, 9, 3963.
(c) Pridgen, L. N.; Mokhallalati, M. K.; Wu, M. J. J. Org. Chem. 1992, 57,
1237.
(3) For a recent pertinent review on catalytic enantioselective addition to
imines: Kobayashi, S.; Ishitani, H. Chem. ReV. 1999, 99, 1069.
(4) Catalytic asymmetric alkylation and allylation of imines and Mannich-
type reaction have been reported. For recent examples: (a) Inoue, I.; Shindo,
M.; Koga, K.; Kanai, M.; Tomioka, K. Tetrahedron Asym. 1995, 6, 2527. (b)
Denmark, S. E.; Nakajima, N.; Nicaise, O. J.-C. J. Am. Chem. Soc. 1994,
116, 8797. (c) Gittins ne´e Jones, C. A.; North, M. Tetrahedron Asym. 1997,
8, 3789. (d) Guijarro, D.; Pinho, P.; Andersson, P. G. J. Org. Chem. 1998,
63, 2530. (e) Nakamura, H.; Nakamura, K.; Yamamoto, Y. J. Am. Chem.
Soc. 1998, 120, 4242. (f) Ishitani, H.; Ueno, M.; Kobayashi, S. J. Am. Chem.
Soc. 1997, 119, 7153. (g) Fujiidera, H.; Kanai, M.; Kambara, T.; Iida, A.;
Tomioka, K. J. Am. Chem. Soc. 1997, 119, 2060. (h) Hagiwara, E.; Fujii, A.;
Sodeoka, M. J. Am. Chem. Soc. 1998, 120, 2474. (i) Ferraris, D.; Young, B.;
Dudding, T.; Lectka, T. J. Am. Chem. Soc. 1998, 120, 4548.
The present catalytic asymmetric arylation was also successful
for the reaction of imines derived from benzaldehyde 1e and
aromatic aldehydes substituted with electron-withdrawing groups,
methoxycarbonyl (1b), fluoro (1c), and chloro (1d), on the phenyl.
(7) The present arylation was found to proceed with high reproducibility
on addition of LiF though the addition is not essential.
(8) Fukuyama, T.; Jow, C.-K.; Cheung, M. Tetrahedron Lett. 1995, 36,
6373.
(9) Diarylmethylamines 8 undergo slow decomposition on exposure to the
air or silica gel. Attempts to determine the enantiomeric purity of amines 8
themselves were not successful.
(10) Takaya, H.; Mashima, S.; Koyano, K.; Yagi, M.; Kumobayashi, H.;
Taketomi, T.; Akutagawa, S.; Noyori, R. J. Org. Chem. 1986, 51, 629.
(11) Kagan, H. B.; Dang, T. P. J. Am. Chem. Soc. 1972, 94, 6429.
(12) (R)-Ar*-MOP was prepared in 58% yield by cross-coupling of (R)-
2′-(trifluoromethanesulfonyloxy)-2-diphenylphosphino-1,1′-binaphthyl with
3,5-dimethyl-4-methoxyphenylmagnesium bromide catalyzed by NiCl2-
(5) (a) Uozumi, Y.; Hayashi, T. J. Am. Chem. Soc. 1991, 113, 9887. (b)
Uozumi, Y.; Tanahashi, A.; Lee, S.-Y.; Hayashi, T. J. Org. Chem. 1993, 58,
1945. (c) Uozumi, Y.; Suzuki, N.; Ogiwara, A.; Hayashi, T. Tetrahedron 1994,
50, 4293.
20
(6) Love, B. E.; Raje, P. S.; Williams, T. C., II Synlett 1994, 493.
(dppe): [R]D +183 (c 1.00, chloroform).
10.1021/ja9927220 CCC: $19.00 © 2000 American Chemical Society
Published on Web 01/21/2000

Communications to the Editor
J. Am. Chem. Soc., Vol. 122, No. 5, 2000 977
Table 1. Catalytic Asymmetric Arylation of Imines 1-3 with
Arylstannanes 4 Catalyzed by Rhodium/(R)-MOP Complexesa
Scheme 2
Ar2SnMe3
yield (%)b
of amine
% eec of
amined,e
entry imine
(4)
ligand
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
1a
2a
3a
1a
1a
1a
1b
1b
1c
1c
1d
1d
1a
1a
1e
1e
1e
4m
4m
4m
4m
4m
4m
4m
4m
4m
4m
4m
4m
4n
(R)-MeO-MOP 82 (5am) 92 (+)-(S)
(R)-MeO-MOP 66 (6am) 87 (+)-(S)
(R)-MeO-MOP 64 (7am) 75 (+)-(S)
(R)-Ar*-MOP 90 (5am) 96 (+)-(S)
(R)-binap
(+)-diop
6 (5am) 91 (+)-(S)
10 (5am) 40 (-)-(R)
(R)-MeO-MOP 75 (5bm) 89 (+)-(S)
(R)-Ar*-MOP 90 (5bm) 92 (+)-(S)
(R)-MeO-MOP 61 (5 cm) 90 (+)-(S)
(R)-Ar*-MOP 69 (5 cm) 92 (+)-(S)
(R)-MeO-MOP 68 (5dm) 83 (+)-(S)
(R)-Ar*-MOP 83 (5dm) 92 (+)-(S)
(R)-MeO-MOP 82 (5an) 92 (+)-(R)
(R)-Ar*-MOP 89 (5an) 96 (+)-(R)
Scheme 3
4n
4n
4n
4o
(R)-MeO-MOP 77 (5en)
(R)-Ar*-MOP 86 (5en)
91 (+)-(R)
92 (+)-(R)
(R)-MeO-MOP 31 (5eo)f 82 (-)-(R)
a The reaction was carried out in dioxane at 110 °C for 12 h with 5
equiv of 4 in the presence of LiF (10 equiv to imine) and 3 mol % of
the catalyst generated from Rh(acac)(C2H4)2 and (R)-MOP. b Isolated
yields by column chromatography on silica gel (pretreated with
methanol and dried) using ethyl acetate as an eluent. c Determined by
HPLC analysis with a chiral stationary phase column (Daicel Chiralcel
OD-H, hexane/2-propanol ) 80/20). d Specific rotations ([R]20D (c 0.5-
1.0, chloroform)) of the products, 6am (entry 2), 7am (entry 3), 5am
(entry 4), 5bm (entry 8), 5cm (entry 9), 5dm (entry 12), 5an (entry
14), and 5en (entry 16) are +9.4, +8.0, +7.6, +6.4, +2.4, +0.4, +18.6,
and +15.9, respectively. e The absolute configuration of 5dm was
determined to be (+)-(S) by comparison of the specific rotation of
free amine 8dm (see text). For other products, the configurations were
assigned by consideration of the stereochemical reaction pathway.
f Enantiomer of 5am.
1.00, ethanol)) of (S)-(+)-4-chlorophenyl(phenyl)methylamine
(8dm), obtained by the deprotection of the sulfonamide of (+)-
5dm (Scheme 2), with the reported value.2a,13 Considering the
similarity in the stereochemical pathway where the si face of the
imine was attacked by an aryl group, other diarylamines obtained
with (R)-MOP ligands should have the same absolute configu-
ration as 5dm, which is depicted in Scheme 1.
The present catalytic asymmetric arylation can be applied to
sulfonamide of an R,â-unsaturated aldehyde, the phenylation of
9 catalyzed by rhodium-(R)-Ar*-MOP complex giving allylic
amine 10 of 93% ee14 (Scheme 3). The catalytic cycle of the
present asymmetric arylation probably involves a rhodium-aryl
species generated from arylstannane and its enantioselective
addition to the carbon-nitrogen double bond of imine. Mecha-
nistic studies are now in progress.
The phenylation with phenyltrimethylstannane (4m) gave high
yields of the corresponding sulfonamide of aryl(phenyl)methyl-
amines (+)-5bm, 5cm, and 5dm with 92% enantioselectivity in
the reaction catalyzed by the rhodium-(R)-Ar*-MOP complex
(entries 8, 10, and 12). Addition of the 4-methoxyphenyl group
to 1a and 1e also proceeded with high enantioselectivity to give
(+)-5an (96% ee) and (+)-5en (92% ee), respectively (entries
14 and 16). The reaction of imine 1e with 4-trifluoromethylphe-
nyltrimethylstannane (4o), which is a reverse combination of the
reaction of 1a with 4m, gave a lower yield of product (-)-5eo
that is an enantiomer of (+)-5am (entry 17). Absolute configu-
ration of 5 produced here in the asymmetric arylation with (R)-
MOP ligands was determined to be (S)-(+) for 5dm, which is
assigned by comparison of the specific rotation ([R]20D +10.4 (c
Acknowledgment. This work was supported by “Research for the
Future” Program, the Japan Society for the Promotion of Science, and a
Grant-in-Aid for Scientific Research, the Ministry of Education, Japan.
Supporting Information Available: Experimental procedures and
spectroscopic and analytical data for the products (PDF). This material
is available free of charge via the Internet at http://pubs.acs.org.
JA9927220
20
(13) For (S)-8dm: [R]D +10.8 (c 2.18, ethanol). (a) Clemo, G. R.;
Gardner, C.; Raper, R. J. Chem. Soc. 1939, 1958. (b) Opalka, C. J.; D’Ambra,
T. E.; Faccone, J. J.; Bodson, G.; Cossement, E. Synthesis 1995, 766.
20
(14) 10 of 93% ee: [R]D +7.4 (c 0.5, chloroform).