Synthesis of allylamines from alkynes and iminium ions

Article abstract of DOI:10.1055/s-2003-41028

The iminium salt Bn₂N⁺=CH₂ SnCl ₅^- undergoes ene reactions with inverse electron demand with alkynes and with the triple bond of enynes to give benzylideneammonium ions in aprotic solvents. Their hydr

Full text of DOI:10.1055/s-2003-41028

1790
PAPER
Synthesis of Allylamines from Alkynes and Iminium Ions
Synthesis of
A
u
llylamines fr
s
om
A
lkyn
a
es and Imi
n
nium Ions ne Rehn,1 Armin R. Ofial, Herbert Mayr*
Department Chemie der Ludwig-Maximilians-Universität München, Butenandtstr. 5-13 (Haus F), 81377 München, Germany
Fax +49(89)218077717; E-mail: Herbert.Mayr@cup.uni-muenchen.de
Received 10 June 2003; revised 3 July 2003
Dedicated to Professor Wolfgang Steglich on the occasion of his 70th birthday.
Abstract: The iminium salt Bn2N+=CH2 SnCl5– undergoes ene re-
actions with inverse electron demand with alkynes and with the tri-
ple bond of enynes to give benzylideneammonium ions in aprotic
solvents. Their hydrolysis yields N-benzylallylamines in good
yields. Mannich reaction products, which are the main products un-
der more nucleophilic reaction conditions, have not been detected.
Key words: electrophilic additions, ene reactions, enynes, pericy-
clic reactions
Scheme 1 Ene reaction of alkynes with iminium ions
Introduction
We now report that the synthetic value of this method can
greatly be enhanced by employing N,N-dibenzyliminium
pentachlorostannates which give rise to a variety of N-
benzyl protected allylamines.
Allylamines are versatile building blocks for the synthesis
of numerous organic compounds. Their synthesis via elec-
trophilic aminations of non-functionalized alkenes having
allylic C–H bonds is particularly attractive because the al-
lylic functionality is readily introduced in one step.2 Apart
from metal-catalyzed electrophilic aminations with ni-
trenes and ArNHX compounds, the ene reactions of alk-
enes with aza enophiles3 have been employed for the
synthesis of allylamines.4 However, highly reactive aza
enophiles usually carry activating substituents which have
to be removed from the initially formed ene products in
additional reaction steps.5
Results
When solutions of the readily accessible N,O-acetal 111,12
in dichloromethane or 1,2-dichloroethane were treated
with 1 equivalent of chlorotrimethylsilane and 1 equiva-
lent of tin(IV) chloride (Equation 1), a colorless precipi-
tate formed which was separated by filtration. This
precipitate dissolved in acetonitrile and was characterized
by 1H, 13C, and 119Sn NMR spectroscopy.13 The resonanc-
es for the N+=CH2 group14 at H = 7.95 and C = 169.7
which showed couplings to 14N (I = 1) were consistent
with the structure of N,N-dibenzylmethyleneammonium
pentachlorostannate 2.15
Previously, only ene reactions with normal electron de-
mand have been employed for the synthesis of allyl-
amines.2 However, interchanging the roles of ene and
enophile is possible,6 and recently a stereoselective syn-
thesis of allylic amines by ene reactions of alkynes with
preformed iminium salts has been reported that proceeds
with inverse electron demand (Scheme 1).7 Hydrolytic
workup of the reaction mixture gave secondary allyl-
amines, while reductive workup yielded tertiary allyl-
amines.
Following the previously described protocol (Scheme 1),
only activated alkynes could be converted into the corre-
sponding ene products, mainly because of the poor solu-
bility of the iminium hexachloroantimonates which
resulted in low effective concentrations of the iminium
ions in the biphasic reaction mixtures. Furthermore, the
original method produced only allylamines carrying N-
alkyl groups, which cannot easily be exchanged. Related
syntheses of allylamines have also been described.8–10
Equation 1 Generation of iminium salt 2
For the ene reactions (Scheme 2), usually 1–3 equivalents
of the alkyne 3 were added to suspensions of 2 in dichlo-
romethane or 1,2-dichloroethane freshly prepared from
equimolar amounts of the N,O-acetal 1, chlorotrimethylsi-
lane and tin(IV) chloride. The suspension was stirred at
25–83 °C (see Table 1) until the complete dissolution of 2
was observed. Hydrolytic workup of the resulting N-ben-
zyl-N-allylalkylidene ammonium salts 4 with 2 M NaOH
Synthesis 2003, No. 12, Print: 02 09 2003. Web: 13 08 2003.
Art Id.1437-210X,E;2003,0,12,1790,1796,ftx,en;Z08003SS.pdf.
DOI: 10.1055/s-2003-41028
© Georg Thieme Verlag Stuttgart · New York

PAPER
Synthesis of Allylamines from Alkynes and Iminium Ions
1791
N,N-dialkyliminium hexachloroantimonates gave rise to
higher effective concentrations of the ene component in
the reaction mixtures. As a consequence, the reaction of
phenyl(trimethylsilyl)acetylene (3e) with Et2N+=CH2
SbCl6– was reported7 to proceed within 19 hours whereas
–
the reaction of 3e with Bn2N+=CH2 SnCl5 (2) was now
found to be complete within 3 hours under analogous con-
ditions (25 °C, CH2Cl2).
Scheme 2
Terminal as well as internal alkynes 3a–f gave secondary
amines 5a–f in 57–83% yield (Table 1).
and distillation of the crude product gave the N-benzyl
substituted allylamines 5.
The silylated propargyl ether 3g gave product 5g in 72%
yield within 3 hours at 75 °C, whereas corresponding
The higher solubility of the N,N-dibenzyliminium pen- products of the propargyl ethers 3h–j could not be ob-
tachlorostannate (2) compared with the previously used tained analogously.
Table 1 Products 5 of the Ene Reactions of Iminium Salt 2 with Alkynes 3a–k in 1,2-Dichloroethane
Alkyne
R1C CR2
Temp (°C) Time (h)
Product
Yield (%)
73a
3a
25
24
5a
3a
3b
83
75
0.75
5a
5b
75
71
8
3c
83
75
1.5
5c
83
57
3d
8
5d
3e
3f
25
75
75
3
5
3
5e
5f
76a
66
3g
5g
72
b
3h
3i
75
83
24
–
5h
5i
–
–
c
2
2
–
c
3j
83
25
–
5j
–
b
3k
120
–
5k
0a
a In CH2Cl2.
b No reaction, starting materials were recovered.
c Decomposition.
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S. Rehn et al.
PAPER
When propargyl methyl ether (3h) was heated with the In contrast to the reactions under Mannich conditions and
iminium salt 2 in 1,2-dichloroethane in a pressure tube at in analogy to previous experiments with N,N-diethylimin-
75 °C for 24 hours, compound 3h and dibenzylamine ium hexachloroantimonates7 we now find that also N,N-
were isolated after hydrolytic workup indicating the lower dibenzylmethyleneammonium pentachlorostannate (2) is
reactivity of 3h compared to 3g. Iminium salt 2 dissolved capable of undergoing ene reactions with alkynes when a
within 2 hours when heated with the tertiary propargyl solvent of low nucleophilicity is used.
ethers 3i or 3j in 1,2-dichloroethane at 83 °C and yielded
red solutions that did not decolorize during hydrolysis.
NMR analysis of the crude products showed the presence
of complex mixtures of compounds which are probably
formed via Lewis acid induced ionization of 3i and 3j.
(3d), and trimethylsilylacetylene (3f) with Et2N+=CH2
Table 2 demonstrates that the conjugated enynes 3l–n also SbCl6 have previously not been reported.
The formation of the allylamines 5b, 5c, 5d, and 5f from
the alkynes 3b–d,f and the iminium salt 2 exemplifies the
enhanced synthetic potential of this procedure since reac-
tions of hex-1-yne (3b), 1-phenylpropyne (3c), hex-3-yne
–
underwent imino ene reactions at the CC triple bond and
yielded the dienylamines 5l–n under analogous condi-
tions as discussed before. Attack at the CC double bond
Stereoselectivity
could not be detected in any of these cases.
The NMR spectra of the isolated iminium salts 419 and of
the allylamines 5 reveal that R1 and R2 of the former sub-
stituents of the CC triple bond are exclusively cis posi-
tioned at the new CC double bond, in accord with
previous results.7
The NMR resonances of the allylamines 5a–g and the
conjugated dienylamines 5l–m are summarized in
Tables 3 and 4, respectively. For further analytical data,
see the Experimental section.
Since concerted as well as stepwise ene reactions give rise
to products with the substituents R1 and R2 in cis position
(Scheme 3), the syn-stereoselectivity does not provide in-
formation on the reaction mechanism.
Discussion
As already described by Mannich in the 1930s,16 the reac-
tion of terminal alkynes with iminium ions generated in
situ from formaldehyde and secondary amines usually
yields propargyl amines (Equation 2).17 These reaction
conditions are comparable to those of the well known
Mannich aminomethylations of other CH acidic com-
pounds, e.g., enolizable carbonyl and dicarbonyl com-
pounds, which are among the most important CC bond
forming reactions.18
Equation 2
Scheme 3
Table 2 Products 5l–n of the Ene Reactions of Iminium Salt 2 with Enynes 3l–n
Enyne
R1C CR2
Temp (°C) Time (h)
Product
Yield (%)
68a
3l
83
2
5l
3m
3n
25
25
20
5m
5n
86b,c
72b
0.5
a In 1,2-dichloroethane.
b In dichloromethane.
c Only 1.2 equiv of enophile 3m was used.
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PAPER
Synthesis of Allylamines from Alkynes and Iminium Ions
1793
Table 3 1H and 13C NMR Chemical Shifts ( ), and Coupling Constants (J in Hz) of Allylamines 5a–g in CDCl3
Pro-
duct
1 -H NH
1-H
R1
3-H
Other H
C-1
C-1
R1
–
C-3
Other C
5a
3.80 2.60 3.39
6.28
6.51
7.16–7.39
52.9
(t)
50.8
(t)
131.8 126.2, 127.0,
(d)
(dd, J = 6.4, (dt, J = 15.9, (d, J = 15.9) (m, 10 H)
127.3, 127.6,
1.3)
6.3)
128.2, 128.36,
128.43 (7 d),
136.9, 139.4 (2 s)
a
5b
3.75 2.09 3.19
5.47–5.63
(m, 2 H)
0.88 (t, J = 7.1, 3 52.9
50.8
(t)
–
–
13.8 (q), 22.0 (t),
31.3 (t), 31.9 (t),
126.7, 127.7,
128.1, 128.2,
133.0 (5 d), 139.9
(s)
(d, J = 4.8)
H), 1.24–1.37
(m, 4 H), 1.98–
2.05 (m, 2 H),
7.17–7.38
(t)
(m, 5 H)
5c
5d
5e
3.79 2.89 3.31
(d, J = 1.0)
1.88
(d, 3 H, J =
1.4, CH3)
6.45 (s)
7.02–7.40
(m, 10 H)
52.7
(t)
57.1
(t)
16.5
(q)
126.1 126.1, 126.9,
(d)
127.9, 128.1,
128.2, 128.7 (6
d), 136.4, 137.8,
139.8 (3 s)
b
a
3.72 1.64 3.16
(d, J = 1.0)
–
5.28
(t, J = 7.2)
0.96 (t, 3 H, J = 53.0
7.6), 0.97 (t, 3 H, (t)
J = 7.7), 2.07
(mc, 4 H), 7.16–
7.33 (m, 5 H)
54.3
(t)
–
127.6 13.3, 14.5 (2 q),
(d)
20.6, 21.8 (2 t),
126.6, 128.0,
128.2 (3 d),
138.4, 140.5 (2 s)
b
3.92 2.50 3.55
(d, J = 1.5)
0.08
[s, 9 H,
Si(CH3)3]
–
7.28–7.47
(m, 11 H)
53.0
(t)
56.8
(t)
0.3
(q)
142.1 126.8, 126.9,
(d)
127.7, 128.2,
128.3, 128.4
(6 d), 140.00,
140.03, 142.6
(3 s)
5f
3.88 1.60 3.50
(m)
0.25
[s, 9 H,
Si(CH3)3]
5.54, 5.87
(2 mc)
7.13–7.61
(m, 5 H)
53.3
(t)
54.5
(t)
–1.6
(q)
123.9 126.6, 127.9,
(t)
128.1 (3 d),
140.0, 140.4 (2 s)
5g
3.83 1.80 3.40
(s)
0.28
[s, 9 H,
Si(CH3)3]
6.33
(t, J = 6.5)
3.42 (s, 3 H),
53.2
56.6
(t)
0.0
(q)
139.1 58.0 (q), 71.4 (t),
4.10 (d, 2 H, J = (t)
6.5), 7.29–7.45
(m, 5 H)
(d)
126.7, 128.1,
128.2 (3 d),
140.4, 142.2 (2 s)
a For relevant signals, see the column ‘other C’.
b For relevant signals, see the column ‘other H’.
The -silyl effect20 offers another possibility to stabilize
the transition state as demonstrated by the reaction of phe-
nyl(trimethylsilyl)acetylene (3e) which yields amine 5e in
76% yield within 3 hours at ambient temperature while
the corresponding reaction with phenylacetylene (3a) re-
quires 24 hours under the same conditions. However, the
silyl substitution in the propargyl carbonate 3k was not
sufficient to compensate for the destabilizing effect of the
electron-withdrawing carbonate group: No conversion
was observed even after several days at ambient tempera-
ture.
Structure Reactivity Relationships
The regioselectivities of the ene reactions in this work can
be rationalized when one assumes that C-2 of the triple
bond carries a partial positive charge in the transition state
of the ene reaction (Scheme 3).
Electron-donating substituents R2 (alkyl or phenyl) stabi-
lize the transition state. Since phenyl stabilizes positive
charge better than alkyl, the ene reaction of phenylacetyl-
ene (3a) proceeds faster than the analogous reaction with
hex-1-yne (3b) (Table 1).
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S. Rehn et al.
PAPER
Table 4 1H and 13C NMR Chemical Shifts ( ) and Coupling Constants (J in Hz) of Dienylamines 5l–n in CDCl3
1 -H 1-H
3.71 3.26
R1
3-H
R2
5-H
Other H
1.50
C-1
C-1
C-3
R2
C-5
Other C
5l
5.71
6.23
1.81
4.90
53.0
50.7
(t)
133.9 18.3
(d) (q)
115.4 126.5, 127.7,
(t)
(s)
(dd, J = (dt, 1 H,
(J =16) (s, 3 H) (br s, 2 H) (s, 1 H, NH), (t)
127.8, 128.0
(4 d), 139.9,
141.2 (2 s)
6.4, 1.0) J = 16, 6.4)
7.16–7.40
(m, 5 H)
5m 3.90 3.47
(s) (d, J =
1.5)
0.34
(s, 9 H)
6.73
(m)
1.94
5.00, 5.04 7.37–7.50
53.2
(t)
56.9
(t)
144.5 22.8
113.6 0.4 [q,
(t) Si(CH3)3],
(mc, 3 H) (2 m, 2 H) (m, 5 H)
(d)
(q)
126.6, 128.0,
128.1 (3 d),
139.3, 140.6,
144.7 (3 s)
a
b
5n 3.75 3.28
5.62
6.15
(J = 16)
–
5.68
(mc)
1.49
53.1
51.2
(t)
135.1
(d)
-
128.6 22.3, 22.4,
(s)
(dd, J = (dtd, J =
(s, 1 H, NH), (t)
1.54–1.68
(m, 4 H),
2.07–2.14
(m, 4 H),
(d)
24.4, 25.6
(4 t),
6.5, 1.0) 16, 6, 0.6)
123.9 (d, C-2),
127.9, 128.0,
128.2 (3 d),
135.2, 140.2
(2 s)
7.18–7.38
(m, 5 H)
a For relevant signals, see the column ‘other H’.
b For relevant signals, see the column ‘other C’.
The similarity of the reaction conditions required for the long as they are not easily ionized under the reaction con-
conversion of hex-3-yne (3d) and trimethylsilylacetylene ditions.
(3f) illustrates that the -stabilizing effect of an alkyl and
the -stabilizing effect of a trimethylsilyl group are simi-
lar in the transition states of these ene reactions.
All reactions were performed under dry N2 at r.t. 1,2-Dichloro-
ethane and CH2Cl2 were dried over P4O10 and freshly distilled from
CaH2 prior to use. N,O-Acetal 1 was prepared from dibenzylamine,
paraformaldehyde, and MeOH following the method described by
Stewart and co-workers.11,12 Enynes 3l and 3n were obtained by de-
hydration of the corresponding alcohols according to methods de-
scribed in the literature.23 Alkyne 3a and enyne 3l were silylated
according to a standard Grignard procedure to give 3e and 3m, re-
spectively.24 2-Methoxy-2-phenylbut-3-yne (3i) was prepared by
methylation of 2-phenylbut-3-yn-2-ol using NaNH2 and dimethyl
sulfate as described in Ref.25 Propargyl ethers 3h and 3i were treated
The activating effect of silyl substitution at the triple bond
was also found in the reactions of the propargylic ethers
3g and 3h: whereas the propargyl methyl ether (3h) did
not react, its trimethylsilylated analogue 3g gave the ene
product 5g in 72% yield.
The good yields obtained from the reactions of 2 with
enynes 5l–n are surprising in view of the low nucleophil-
icities of enynes previously observed in their reactions
with benzhydrylium ions.21,22 The formation of products
5l–n may, therefore be interpreted by the operation of a
concerted mechanism. The conjugated dienylamines 5l–n
may be used as dienes in Diels–Alder reactions, which
will be published separately.
with BuLi and chlorotrimethylsilane following
a standard
procedure26 to give the silylated derivatives 3g and 3j, respectively.
Methyl(3-(trimethylsilyl)prop-2-ynyl)carbonate (3k) was synthe-
sized according to a literature method.27 All other chemicals are
commercially available.
1H NMR spectra (300 or 400 MHz) refer to CDCl3 ( H = 7.24) or
CD3CN ( H = 1.93). 13C NMR spectra (75.5 or 100.6 MHz) were
calibrated to CDCl3 ( C = 77.00) or CD3CN ( C = 1.30). DEPT ex-
periments were used to obtain information about the multiplicity of
the 13C resonances. Further 1H,13C-HETCOR, and NOESY experi-
ments were performed for an unambiguous assignment of the NMR
signals. 119Sn NMR spectra (100.7 MHz) refer to Me4Sn ( Sn = 0.0).
Mass spectra were obtained on a Finnigan MAT 95 Q.
Scope and Limitation
As discussed above, all types of alkyl and phenyl substi-
tuted triple bonds can be stereoselectively hydro-amino-
methylated by the iminium salt 2. The failure to observe a
reaction with the propargyl ether 3h indicates that even
weakly electron accepting groups in the vicinity of the tri-
ple bond inhibit the reaction. From the fact that the retard-
ing effect of the methoxy group can be compensated by a
suitably located electron donor one can derive that oxygen
functionalities in the enophile are in principle tolerable as
Allylamines 5 from the Iminium Salt 2 and Alkynes 3; General
Procedure
A solution of N,O-acetal 1 in anhydrous CH2Cl2 or 1,2-dichloro-
ethane (6–10 mL/mmol 1) was stirred with equimolar amounts of
chlorotrimethylsilane and SnCl4, whereby 2 was formed as a color-
less precipitate.13 After ca. 30 min, the enophile 3 was added to the
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PAPER
Synthesis of Allylamines from Alkynes and Iminium Ions
1795
suspension. The mixture was then stirred at the given temperature28
until the iminium salt 2 was completely dissolved. For the hydroly-
sis, the mixture was cooled to 0 °C, aq 2 M NaOH (20 mL) was add-
ed, and the mixture was vigorously stirred for 30 min before the
phases were separated. After extraction of the aqueous layer with
CH2Cl2 (10 mL), the combined organic layers were washed with aq
2 M NaOH (10 mL), dried (MgSO4) and concentrated in vacuo. The
secondary allylamines 5 were then obtained by bulb-to-bulb distil-
lation, whereby excess enophile and benzaldehyde could be separat-
ed in a first fraction at 100 °C (bath temp). The NMR resonances of
the allylamines 5 are listed in Tables 3 and 4.
MS (EI, 70 eV): m/z (%) = 156 (40), 141 (12), 120 (45), 91 (100),
89 (12), 73 (20).
Reaction of Iminium Salt 2 with Alkyne 3h
Heating a mixture of 2 (0.505 g 1, 2.09 mmol) with 3h (0.293 g,
4.19 mmol) for 24 h in 1,2-dichloroethane at 75 °C in a sealed tube
and hydrolysis yielded a mixture of dibenzylamine and propargyl
methyl ether 3h.
Reaction of Iminium Salt 2 with Alkyne 3i
Heating a mixture of 2 (0.528 g 1, 2.19 mmol) with 3i (0.702 g, 4.38
mmol) for 2 h at 83 °C in 1,2-dichloroethane and hydrolysis yielded
a complex mixture of unidentified compounds.
Benzyl(3-phenylallyl)amine (5a)
The reaction of 2 (1.23 g 1, 5.10 mmol) with 3a (1.12 mL, 10.2
mmol) in 1,2-dichloroethane yielded 0.852 g (75%) of 5a as a col-
orless liquid after 45 min at 83 °C; bp 250 °C/4 × 10–2 mbar (bath
temp).
Reaction of Iminium salt 2 with Alkyne 3j
Heating a mixture of 2 (0.598 g 1, 2.48 mmol) with 3j (1.15 g, 4.96
mmol) for 2 h at 83 °C in 1,2-dichloroethane and hydrolysis yielded
a complex mixture of unidentified compounds.
Anal. Calcd for C16H17N (223.3): C, 86.06; H, 7.67; N, 6.27. Found:
C, 85.60; H, 7.65; N, 6.24.
Reaction of Iminium Salt 2 and Alkyne 3k
Stirring a mixture of 2 (0.260 g 1, 1.07 mmol) with 3k (0.398 g, 2.14
mmol) in CH2Cl2 did not lead to the dissolution of the iminium salt
after 5 d at 20 °C. The hydrolysis of the filtrate yielded a complex
mixture of unidentified compounds.
Benzylhept-2-enylamine (5b)
The reaction of 2 (0.640 g 1, 2.65 mmol) with 3b (0.605 mL, 5.30
mmol) in 1,2-dichloroethane yielded 0.385 g (71%) of 5b as a col-
orless liquid after 8 h at 75 °C in a sealed tube; bp 225 °C/4 × 10–2
mbar (bath temp).
Benzyl(4-methylpenta-2,4-dienyl)amine (5l)
Anal. Calcd for C14H21N (203.3): C, 82.70; H, 10.41; N, 6.89.
Found: C, 83.27; H, 10.03; N, 6.55.
The reaction of 2 (1.22 g 1, 5.05 mmol) with 3l (0.668 g, 10.1 mmol)
in 1,2-dichloroethane yielded 0.641 g (68%) of 3l as a colorless liq-
uid after 2 h at 83 °C; bp 225 °C/4 × 10–2 mbar (bath temp).
Benzyl(2-methyl-3-phenylallyl)amine (5c)
Anal. Calcd for C13H17N (187.3): C, 83.37; H, 9.15; N, 7.48. Found:
C, 82.93; H, 9.04; N, 7.22.
The reaction of 2 (0.991 g 1, 4.10 mmol) with 3c (0.952 g, 8.20
mmol) in 1,2-dichloroethane yielded 0.809 g (83%) of 5c as a col-
orless liquid after 90 min at 83 °C; bp 250 °C/3.8 × 10–2 mbar (bath
temp).
MS (EI, 70 eV): m/z (%) = 237 (M+, 18), 222 (30), 146 (33), 106
(32), 92 (15), 91 (100).
Benzyl[4-methyl-2-(trimethylsilyl)penta-2,4-dienyl]amine (5m)
Reaction of 2 (4.21 g 1, 17.4 mmol) with 3m (3.55 g, 21.1 mmol) in
CH2Cl2 yielded 3.88 g (14.9 mmol, 86%) of 5m as a colorless liquid
after 20 h at 20 °C; bp 175 °C/2.5 × 10–2 mbar (bath temp).
Anal. Calcd for C16H25NSi (259.5): C, 74.07; H, 9.71; N, 5.40.
Found: C, 73.89; H, 9.71; N, 5.35.
Benzyl(2-ethylpent-2-enyl)amine (5d)
The reaction of 2 (0.550 g 1, 2.28 mmol) with 3d (0.780 mL, 6.84
mmol) in 1,2-dichloroethane yielded 0.261 g (57%) of 5d as a col-
orless liquid after 8 h at 75 °C in a sealed tube; bp 225 °C/4 × 10–2
mbar (bath temp).
MS (EI, 70 eV): m/z (%) = 204 (14), 203 (M+, 4), 174 (25), 120 (12),
108 (21), 106 (19), 96 (19), 91 (100).
Benzyl(3-cyclohex-1-enylallyl)amine (5n)
Reaction of 2 (3.44 g 1, 14.3 mmol) with 3n (3.03 g, 28.5 mmol) in
CH2Cl2 yielded 2.34 g (72%) of 5n as a colorless liquid after 30 min
at 20 °C; bp 200 °C/3.5 × 10–2 mbar (bath temp).
MS (EI, 70 eV): m/z (%) = 228 (12), 227 (M+, 67), 226 (17), 136
(28), 132 (23), 106 (15), 92 (17), 91 (100), 79 (15), 77 (15), 65 (12).
Benzyl[3-phenyl-2-(trimethylsilyl)allyl]amine (5e)
The reaction of 2 (1.19 g 1, 4.93 mmol) with 3e (0.961 mL, 4.93
mmol) in dichloromethane yielded 1.11 g (76%) of 5e as a colorless
liquid after 3 h at 20 °C; bp 250 °C/3.9 × 10–2 mbar (bath temp).
Acknowledgments
We thank P. Mayer for the measurement of the 119Sn NMR spec-
trum and Dr. K. Karaghiosoff for helpful discussions. Financial
support by the Deutsche Forschungsgemeinschaft and the Fonds der
Chemischen Industrie is gratefully acknowledged.
Anal. Calcd for C19H25NSi (295.5): C, 77.23; H, 8.53; N, 4.74.
Found: C, 77.15; H, 8.20; N, 4.43.
Benzyl[2-(trimethylsilyl)allyl]amine (5f)
The reaction of 2 (0.650 g 1, 2.69 mmol) with 3f (1.14 mL, 8.08
mmol) in 1,2-dichloroethane yielded 0.391 g (66%) of 5f as a col-
orless liquid after 5 h at 75 °C a sealed tube; bp 200 °C/4 × 10–2
mbar (bath temp).
MS (EI, 70 eV): m/z (%) = 220 (19), 219 (M+, 5), 128 (19), 120 (68),
91 (100), 73 (11).
References
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10–2 mbar (bath temp).
Synthesis 2003, No. 12, 1790–1796 © Thieme Stuttgart · New York

1796
S. Rehn et al.
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Synthesis 2003, No. 12, 1790–1796 © Thieme Stuttgart · New York