Imine allylation by allylic trimethylsilanes via in situ formation of N-tosyliminium species from carbonyl compounds and toluene-p-sulfonamide with SnCl2 and N-chlorosuccinimide: Regioselection and diastereoselection

Article abstract of DOI:10.1039/a902789k

N-Tosyliminium species, prepared in situ from carbonyl compounds and TsNH₂ with SnCl₂ and N-chlorosuccinimide, undergo nucleophilic addition of allylic silanes (imine allylation) to produce the corresponding homoallylic amines; the i

Full text of DOI:10.1039/a902789k

Imine allylation by allylic trimethylsilanes via in situ formation of
N-tosyliminium species from carbonyl compounds and toluene-p-sulfonamide
with SnCl2 and N-chlorosuccinimide: regioselection and diastereoselection
Yoshiro Masuyama,* Jiro Tosa and Yasuhiko Kurusu
Department of Chemistry, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan.
E-mail: y-masuya@hoffman.cc.sophia.ac.jp
Received (in Cambridge, UK) 8th April 1999, Accepted 5th May 1999
N-Tosyliminium species, prepared in situ from carbonyl
compounds and TsNH2 with SnCl2 and N-chlorosuccini-
mide, undergo nucleophilic addition of allylic silanes (imine
allylation) to produce the corresponding homoallylic
amines; the imine allylation by but-2-enyltrimethylsilane
with aldehydes and TsNH2 leads to regio- and diastereo-
selection to produce anti 1-substituted 2-methylbut-3-enyl-
amines.
including aromatic aldehydes bearing either an electron-
withdrawing group (entries 2 and 3) or an electron-donating
group (entries 4–6), aliphatic aldehydes (entries 8–10) and an
a,b-unsaturated aldehyde (entry 11) can be used in the imine
allylation. In the cases of aldehydes bearing a coordinate group,
O
NCS
TsNH2
TsNHSnCl3
+
NSnCl3
Lewis acid-catalysed allylations of imines or iminium species
with allylic silane or tin reagents are one of the most effective
methods for the introduction of an amino group into carbon
skeletons.1, 2 However, some imines and iminium species are
unstable to water or heat, and their purification is difficult via
recrystallization, distillation and chromatography. The allyla-
tion of imines or iminium species, prepared in situ from
carbonyl compounds and amines, would therefore be a
synthetically useful strategy.3–7 We have reported that N-
chlorosuccinimide (NCS) and SnCl2 can be utilized for the
aldol-type reaction of isopropenyl acetate with oxycarbenium
ions derived from either aldehydes with alcohols or lactols.8 A
key step in the aldol-type reaction is probably the formation of
alkoxytrichlorotins, which react with aldehydes to form oxy-
carbenium ions. We hoped that, using NCS–SnCl2, aldehydes
could be transformed into N-tosyliminium species with TsNH2,
in analogy to alcohols giving oxycarbenium ions, and that the
N-tosyliminium species could undergo nucleophilic addition
with allylic silanes (imine allylation).9
O
SnCl2
B
O
NH
O
A
RCHO
R
OSnCl3
NHTs
H
C
H
R
H
O=SnCl2
SiMe3
Cl–
N+
SiMe3
4
Ts
D
H
H
R
SiMe3
CH3
+
1
N
As a consequence of the investigation of imine allylation by
allyltrimethylsilane 1 with benzaldehyde and some amines
under various conditions, it was proved that starting with a
solution of SnCl2 (1.1 mmol), TsNH2 (1 mmol) and benzalde-
hyde (2; R1 = Ph, R2 = H, 1 mmol) in CH2Cl2 (3 ml) in an ice-
bath, the addition of NCS (1.1 mmol) in CH2Cl2 (5 ml) followed
by allyltrimethylsilane (1, 1.5 mmol) after 2 h afforded N-tosyl-
1-phenylbut-3-enylamine (3; R1 = Ph, R2 = H) in a 96% yield
(Scheme 1). Benzylamine, benzamide, and tert-butyl carbamate
were ineffective in the reaction under the same conditions as
those used with TsNH2. This allylation probably needs amines
or amides bearing an acidic proton on nitrogen for the formation
of the trichlorotin amide; as shown in Scheme 2, TsNH2 reacts
with A, derived from NCS and SnCl2, to form B, which
undergoes nucleophilic addition to benzaldehyde (R = Ph) to
form C followed by D. The imine allylation by 1 with various
carbonyl compounds and TsNH2 was carried out under the same
conditions as those for benzaldehyde described above. Repre-
sentative results are summarized in Table 1. Any aldehyde,
Ts
H
NHTs
E
NHTs
R
R
5a
3
Scheme 2
Table 1 Imine allylation by 1 with 2, TsNH2, NCS and SnCl2 to give 3
Entry
R1
R2
t/h
Yielda (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Ph
H
H
H
H
H
H
H
H
H
H
H
6
6
6
96
90
92
81
75
47
28
64
70
86
52
26
38
17
4-ClC6H4
4-NCC6H4
4-MeC6H4
4-MeOC6H4
3,4-(CH2O2)C6H3
2-Furyl
C6H13
c-C6H11
PhCH2CH2
PhCH = CH
(CH2)4
8
10
15
15
15
15
10
15
20
20
20
TsNH2
NHTs
R2
R1
NCS/SnCl2
SiMe3
R2
R1
+
CH2Cl2
O
(CH2)5
ice-bath
Ph
Me
1
2
3
a Isolated yields.
Scheme 1
Chem. Commun., 1999, 1075–1076
1075

Table 2 Diastereoselective imine allylation by but-2-enyltrimethylsilane 4
to give 5a
thylbut-3-enylamines 5a in good yields, as summarized in Table
2 (Scheme 3).‡ The g-anti-addition probably occurs via an
acyclic antiperiplanar transition state (E) between 4 and D
(Scheme 2), due to steric hindrance between the tosyl group and
the methyl group (Fig. 1).4,9
Entry
R
t/h
Yieldb (%)
5s : 5ac
1
2
3
4
5
Ph
6
15
15
15
15
91
87
73
48
62
11:89
11:89
10:90
8:92
4-ClC6H4
4-MeC6H4
C6H13
Notes and references
c-C6H11
9:91
† But-2-enyltrimethylsilane (4; E:Z = 86:14) was prepared by the reaction
of but-2-enyltrichlorosilane, derived from 1-chlorobut-2-ene and tri-
chlorosilane with CuCl and Et3N, with MeMgI (ref. 10).
‡ The stereochemistry was determined by comparison of 1H NMR data of
primary homoallylic amines (R = Ph, C6H13), which were produced by
removal of the tosyl group (ref. 9), with those in the literature (ref. 11).
a
The imine allylation by 4 (1.5 mmol) was carried out with aldehydes (1
mmol), TsNH2 (1 mmol), SnCl2 (1.1 mmol) and NCS (1.1 mmol) in CH2Cl2
(3 ml) by the same method as that for the allylation by 1. b Isolated yields.
c The ratio was determined by 1H NMR (JEOL GX-270).
1 For a review, see: Y. Yamamoto and N. Asao, Chem. Rev., 1993, 93,
2207.
Me3Si
2 For recent papers, see: D.-K. Wang, L.-X. Dai and X.-L. Hou,
Tetrahedron Lett., 1995, 36, 8649; C. Bellucci, P. G. Cozzi and A.
Umani-Ronchi, Tetrahedron Lett., 1995, 36, 7289; T. Basile, A.
Bocoum, D. Savoia and A. Umani-Ronchi, J. Org. Chem., 1994, 59,
7766.
3 For the reaction of allylic silane and tin reagents with formaldehyde and
amines, see: S. D. Larsen, P. A. Grieco and W. F. Fobare, J. Am. Chem.
Soc., 1986, 108, 3512; P. A. Grieco and A. Bahsas, J. Org. Chem., 1987,
52, 1378.
H
R
H3C
H
+
N
Ts
H
Fig. 1 Antiperiplanar transition state of 4
4 For the reaction of allylic silanes with aldehydes and carbamates, see:
S. J. Veenstra and P. Schmid, Tetrahedron Lett., 1997, 38, 997; J. S.
Panek and N. F. Jain, J. Org. Chem., 1994, 59, 2674.
5 For the reaction of allyltributyltin with aldehydes and arylamines, see:
S. Kobayashi, S. Iwamoto and S. Nagayama, Synlett, 1997, 1099.
6 For the allylation of iminiums prepared in situ from a-alkox-
ymethylcarbamate, see: Y. Yamamoto and M. Schmid, J. Chem. Soc.,
Chem. Commun., 1989, 1310; N. Kise, H. Yamazaki, T. Mabuchi and T.
Shono, Tetrahedron Lett., 1994, 35, 1561.
7 For the allylation of iminium species prepared in situ from N-alkyl-N-
trifluoromethanesulfonyloxyamide, see: R. V. Hoffman, N. K. Nayar,
J. M. Shankweiler and B. W. Klinekole III, Tetrahedron Lett., 1994, 35,
3231.
NHTs
SiMe3
5s
TsNH2
R
syn
4
NCS/SnCl2
+
+
CH2Cl2
NHTs
R
RCHO
ice-bath
5a
anti
2
Scheme 3
8 Y. Masuyama, Y. Kobayashi, R. Yanagi and Y. Kurusu, Chem. Lett.,
1992, 2039; Y. Masuyama, Y. Kobayashi and Y. Kurusu, J. Chem. Soc.,
Chem. Commun., 1994, 1123.
9 For the allylation of only aromatic sulfonimines, prepared beforehand,
with allylic bromides and indium, see: T. H. Chan and W. Lu,
Tetrahedron Lett., 1998, 39, 8605.
10 N. Furuya and T. Sukawa, J. Organomet. Chem., 1975, 96, C1.
11 R. W. Hoffmann and A. Endersfelder, Liebigs Ann. Chem., 1987,
215.
3,4-methylenedioxybenzaldehyde and furan-2-carbaldehyde
exhibited low yields (entries 6 and 7), and pyridine-2-carbalde-
hyde did not react under the given conditions. Ketones can also
undergo the imine allylation to be converted into the corre-
sponding homoallylic amines in unsatisfactory yields (entries
12–14).
The imine allylation of but-2-enyltrimethylsilane (4)† with
some aldehydes and TsNH2 under the same conditions as those
of 1 caused g-anti-addition to afford anti 1-substituted 2-me-
Communication 9/02789K
1076
Chem. Commun., 1999, 1075–1076