Imine allylations by allylic trichlorotins derived from α,α-diisopropylhomoallylic alcohols with tin(II) chloride and N-chlorosuccinimide

Article abstract of DOI:10.1055/s-2002-35581

Allylic trichlorotins, prepared in situ from α,α-diisopropylhomoallylic alcohols with tin(II) chloride and N-chlorosuccinimide in dichloromethane at -40°C, cause nucleophilic addition to N-tosylimines or N-tosyliminiums to afford the corresponding α-subst

Full text of DOI:10.1055/s-2002-35581

LETTER
2113
Imine Allylations by Allylic Trichlorotins Derived from , -Diisopropylhomo-
allylic Alcohols with Tin(II) Chloride and N-Chlorosuccinimide
Imine Allylations
by
,
-Diisop
s
ropylhom
h
oallylic alco
i
hols ro Masuyama,* Naoko Yamamoto, Yasuhiko Kurusu
Department of Chemistry, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan
Fax +81(3)32383361; E-mail: y-masuya@sophia.ac.jp
Received 4 October 2002
SnCl2
NCS
iPr
OH
iPr
iPr
iPr
Abstract: Allylic trichlorotins, prepared in situ from , -diisopro-
pylhomoallylic alcohols with tin(II) chloride and N-chlorosuccin-
imide in dichloromethane at –40 ºC, cause nucleophilic addition to
SnCl3
+
O
CH2Cl2
1
N-tosylimines or N-tosyliminiums to afford the corresponding
-
substituted homoallylic amines.
Method A
R1
Method B
R2
Key words: nucleophilic additions, allylations, organometallic
reagents, allylic tins, homoallylic amines
SnCl2
NCS
R2CHO
+
TsNH2
H
N
N+
Ts
CH2Cl2
2
Ts
4
Grignard-type (non-Barbier-type) allylation of imines and
their analogues (imine allylation) with allylic metal re-
agents has been well established,1,2 while Barbier-type
imine allylation with allylic halides and reducing agents
NHTs
R
3, R = R1 or R2
has made little progress.3 The imine allylation by allylic Scheme 1
halides, esters and alcohols with tin(II) halides cannot be
achieved under the same Barbier conditions as those for
in Scheme 1, entry 1 in Table 1): To the solution of 1 (2.0
mmol), N-benzylidenetosylamide (2, R1 = Ph, 1.0 mmol)
and tin(II) chloride (4.0 mmol) in dichloromethane (3 mL)
was added NCS (4.0 mmol) at –40 ºC. After 1 hour, the
cooling bath was removed, and the reaction mixture was
stirred for 24 h at ambient temperature. After the usual
work-up, purification by column chromatography (silica
gel, hexane–ethyl acetate = 10:1) and then HPLC (Japan
Analytical Industry Co. Ltd., LC-908; JAIGEL-2H; chlo-
roform) afforded 0.23 g (76%) of N-tosyl-1-phenyl-3-
butenylamine (3, R = Ph). This imine allylation needs
more than two equimolar amounts of tin(II) chloride and
NCS each to 1; the allylation of 2 (R1 = Ph) does not pro-
ceed with one equimolar amount of tin(II) chloride and
NCS each to 1. The results are summarized in Table 1 (en-
tries 1–9). Readily prepared and relatively moisture-stable
N-tosylaldimines can be employed for this imine allyl-
ation, except for the aldimines bearing strongly coordinat-
ing or chelating ligands (entries 6 and 7). This imine
allylation could not be applied to straight-chain aldimines,
because of the difficulty in preparing them and their insta-
bility. Thus, we hoped that N-tosyliminiums 4, prepared
in situ (without isolation) from aldehydes and tosylamide
with SnCl2–NCS,9 could be employed for the imine ally-
lation by 1 with SnCl2–NCS (Method B in Scheme 1).
The in situ preparation of 4 with some different types of
aldehydes was applied to the imine allylation by 1, as
summarized in Table 1 (entries 10–19). The instability of
iminium ions seems to be relative to yields of homoallylic
amines 3; relatively high yields in cases of iminiums bear-
ing electron-withdrawing groups (entries 10–13), while
low yields in cases of iminiums derived from , -unsatur-
the carbonyl allylation by allylic halides, esters and alco-
hols with tin(II) halides, which is one of the most conve-
nient methods for introduction of allylic functions.4 The
failure of the imine allylation that needs polar solvents
such as THF, DMF and 1,3-dimethylimidazolidin-2-one
to dissolve tin(II) halides can probably be ascribed to in-
stability of imines and iminiums to slight moisture.5 Bar-
bier-type imine allylation may need water-immiscible
nonpolar solvents such as dichloromethane, chloroform
and toluene, which cannot be usually used because of the
insolubility of tin(II) halides. Thus, a new methodology
will be required for in situ preparation of allylic tin species
in the nonpolar solvents. We have found that trichlorotin
homoallyloxides, derived from sterically hindered , -di-
isopropylhomoallylic alcohols with tin(II) chloride and
NCS in dichloromethane,6 cause retro-allylation7 to
produce allylic trichlorotin species, which can be applied
to carbonyl allylation.8 We here report that allylic tri-
chlorotins, prepared from , -diisopropylhomoallylic al-
cohols with tin(II) chloride and NCS in dichloromethane,
cause nucleophilic addition to N-tosylimines or N-tosyl-
iminiums (imine allylation) to produce the corresponding
homoallylic amines.
A typical procedure in Barbier-type allylation of N-tosyl-
aldimines 2 with , -diisopropylhomoallyl alcohol (1)8 is
as follows using the optimum conditions of the carbonyl
allylation by 1 with tin(II) chloride and NCS (Method A
Synlett 2002, No. 12, Print: 02 12 2002.
Art Id.1437-2096,E;2002,0,12,2113,2115,ftx,en;U06002ST.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0936-5214

2114
Y. Masuyama et al.
LETTER
ated cinnamaldehyde and 4-methoxybenzaldehyde bear- Regioselectivity and diastereoselectivity using , -diiso-
ing an electron-donating group (entries 15 and 16). propyl- -methylhomoallyl alcohol (5)8 were investigated
Unstable aliphatic iminiums can be used for this imine al- under the same conditions as those for the allylations of 2
lylation, though the yields are not high (entries 17–19). A or 4 respectively by 1. The allylations of 2 by 5 proceeded
typical procedure is as follows (entry 10): To the solution regioselectively and diastereoselectively to produce 1-
of 4, prepared from benzaldehyde (1.0 mmol) and tosyla- substituted N-tosyl-2-methyl-3-butenylamines 6 (R1 = Ph,
mide (1.0 mmol) with tin(II) chloride (1.2 mmol) and 19 h, 43%, syn/anti = 83:17; R1 = 4-ClC6H4, 20 h, 43%,
NCS (1.2 mmol) at 0 °C in dichloromethane (2 mL), was syn/anti = 84:16; R1 = 4-MeOOCC6H4, 27 h, 53%, syn/
added the solution of 2-propenyltrichlorotin, prepared anti = 82:18; R1 = 4-MeOC6H4, 30 h, 35%, syn/anti =
from 1 (2.0 mmol) with tin(II) chloride (4.0 mmol) and 83:17) (Scheme 2).10 No allylation of 4 by 5 occurred in
NCS (4.0 mmol) at –40 °C in dichloromethane (2 mL), at cases of the same substituents R1 as those of 2. A plausible
0 °C. The reaction mixture was stirred for 41 h. After the mechanism, which explains the syn-diastereoselection in
mixture had been worked up and purified, 0.22 g (73%) of the allylation of 2 by 5, is shown in Scheme 3. An E,Z
N-tosyl-1-phenyl-3-butenylamine (3, R = Ph) was ob- mixture of 2-butenyltrichlorotin (A), derived from 5 with
tained.
tin(II) chloride and NCS, probably forms an acyclic anti-
periplanar transition state (B) with N-tosylimines 2, which
coordinate to excess tin(IV) species, to produce syn ad-
duct 6s preferentially.11
Table 1 Allylation of 2 or 4 by 1 with Tin(II) Chloride and NCS
Entry
1
R
Method Time (h)
3, Yield (%)a
iPr
OH
iPr
Ph
A
A
A
A
A
A
A
A
A
B
B
B
B
B
B
B
B
B
B
24
24
24
24
24
50
27
24
24
41
23
17
15
21
21
48
23
45
24
76
71
68
79
63
27
9
SnCl2
NCS
SnCl3
2
4-ClC6H4
4-MeOOCC6H4
4-MeC6H4
4-MeOC6H4
4-O2NC6H4
2-Furyl
-iPr2C=O
A
3
5
SnCl2/NCS
2
4
5
Cl3Sn
H
NHTs
R1
R1
6
H3C
Ts
H
7
N+
SnCl3
6s
8
PhCH=CH
Me3C
83
62
73
58
77
73
35
14
11
39
30
36
B
9
Scheme 3
10
11
12
13
14
15
16
17
18
19
Ph
Acknowledgment
4-ClC6H4
4-NCC6H4
4-MeOOCC6H4
4-MeC6H4
4-MeOC6H4
PhCH=CH
PhCH2CH2
C6H13
This work was supported by a Grant-in-Aid for Scientific Research
(No. 12640573) from the Japan Society for the Promotion of Sci-
ence (JSPS).
References
(1) For a review, see: Yamamoto, Y.; Asao, N. Chem. Rev.
1993, 93, 2207.
(2) For recent non-Barbier-type imine allylations using imines,
iminiums, oximes, hydrazones and so on, see: (a) Kise, N.;
Yamazaki, H.; Mabuchi, T.; Shono, T. Tetrahedron Lett.
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Shankweiler, J. M.; Klinekole, B. W. III Tetrahedron Lett.
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1994, 59, 2674. (d) Basile, T.; Bocoum, A.; Savoia, D.;
Umani-Ronchi, A. J. Org. Chem. 1994, 59, 7766.
(e) Bellucci, C.; Cozzi, P. G.; Umani-Ronchi, A.
Tetrahedron Lett. 1995, 36, 7289. (f) Wang, D.-K.; Dai,
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(g) Veenstra, S. J.; Schmid, P. Tetrahedron Lett. 1997, 38,
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1997, 1099. (i) Billet, M.; Klotz, P.; Mann, A. Tetrahedron
Lett. 2001, 42, 631. (j) Hirabayashi, R.; Ogawa, C.; Sugiura,
M.; Kobayashi, S. J. Am. Chem. Soc. 2001, 123, 9493.
(k) Aspinall, H. C.; Bissett, J. S.; Greeves, N.; Levin, D.
Tetrahedron Lett. 2002, 43, 323.
c-C6H11
a Isolated yields.
SnCl2
NCS
iPr
OH
iPr
NHTs
R1
+
N
R1
CH2Cl2
Ts
5
2
6
Scheme 2
Synlett 2002, No. 12, 2113–2115 ISSN 0936-5214 © Thieme Stuttgart · New York

LETTER
Imine Allylations by , -Diisopropylhomoallylic alcohols
2115
(3) For Barbier-type imine allylations, see: (a) Chan, T. H.; Lu,
W. Tetrahedron Lett. 1998, 39, 8605. (b) Lu, W.; Chan, T.
H. J. Org. Chem. 2000, 65, 8589. (c) Vilaivan, T.;
Winotapan, C.; Shinada, T.; Ohfune, Y. Tetrahedron Lett.
2001, 42, 9073. (d) Wallner, O. A.; Szabó, K. J. Org. Lett.
2002, 4, 1563.
(4) (a) Masuyama, Y. J. Synth. Org. Chem. Jpn. 1992, 50, 202.
(b) Masuyama, Y. In Advances in Metal-Organic
Chemistry, Vol. 3; Liebeskind, L. S., Ed.; JAI Press:
Greenwich, 1994, 255. (c) Masuyama, Y. In Recent
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Transworld Research Network: Trivandrum, India, 2000,
373; and references cited therein.
(7) (a) Tagliavini, G. Rev. Silicon, Germanium, Tin, Lead 1985,
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186; and references cited therein.
(8) Masuyama, Y.; Saeki, K.; Horiguchi, S.; Kurusu, Y. Synlett
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(9) Masuyama, Y.; Tosa, J.; Kurusu, Y. Chem. Commun. 1999,
1075.
(10) The syn-diastereoselectivity in the allylations by 5 was
confirmed by the comparison of 1H NMR spectra with
authentic samples prepared by the imine allylation by 1-
bromo-2-butene with indium.3 In addition the diastereo-
selectivity in ref.9 has been mistaken; syn adducts are major,
similarly to the imine allylation by 5.
(5) The use of imines such as N-benzylideneaniline and N-
benzylidenetosylamide in the allylation with tin(II) halides
did not afford homoallylic amines but homoallylic alcohols
in low yields.
(6) Tin(II) chloride is insoluble in dichloromethane, and
dissolves in dichloromethane containing an equimolar
amount of alcohol to the tin(II) by adding an equimolar
amount of NCS to the tin(II).
(11) The E:Z ratio of A could not be determined by the 1H NMR
observation of the reaction of 5 with SnCl2 and NCS in
CD2Cl2 either at –40 ºC or at room temperature. Since the
E:Z ratios of -adducts in the carbonyl allylation by 5 are ca.
1:1 to 1:4,8 the 2-butenyltrichlorotin intermediate is
presumed to be an E,Z mixture.
Synlett 2002, No. 12, 2113–2115 ISSN 0936-5214 © Thieme Stuttgart · New York