Allylation of imines with allyltrimethylsilane and experimental evidences for a fluoride-triggered autocatalysis mechanism of the Sakurai- Hosomi reaction

Article abstract of DOI:10.1021/jo980767y

This article reports the reaction of allyltrimethylsilane 1 with aldimines 2 in the presence of tetra-n-butylammonium fluoride to give the corresponding homoallylamines 3 in moderate to excellent yields. The allylation mechanism of imines as well as that of aldehydes can be reasonably interpreted by a fluoride-triggered autocatalytic procedure.

Full text of DOI:10.1021/jo980767y

J . Org. Chem. 1999, 64, 4233-4237
4233
Allyla tion of Im in es w ith Allyltr im eth ylsila n e a n d Exp er im en ta l
Evid en ces for a F lu or id e-Tr igger ed Au toca ta lysis Mech a n ism of
th e Sa k u r a i-Hosom i Rea ction
De-Kun Wang, Yong-Gui Zhou, Yong Tang, Xue-Long Hou,* and Li-Xin Dai
Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry,
Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China
Received April 23, 1998
This article reports the reaction of allyltrimethylsilane 1 with aldimines 2 in the presence of tetra-
n-butylammonium fluoride to give the corresponding homoallylamines 3 in moderate to excellent
yields. The allylation mechanism of imines as well as that of aldehydes can be reasonably interpreted
by a fluoride-triggered autocatalytic procedure.
In tr od u ction
reaction with a CdO bond, little is known about its aza
analogue, that is, the reaction between allylsilane and
aldimine. Although the reactions of allyltrifluorosilane
and allyltrimethylsilane with imines mediated by fluo-
rides were reported by Sakurai and very recently by
The allylation of carbonyl compound is one of the most
1
important C-C bond forming reactions. In addition to
the widely used allyl organometallic reagents,1 the use
-4
of allylsilane compounds opens a new facet in the
7
DeSheng, respectively, excess florides have to be used
5
allylation reaction. The reaction of an allylsilane with a
(3-4 equiv of CsF and 10 equiv of tetrabutylammonium
carbonyl compound under Lewis acid conditions or in the
presence of fluoride ions, known as the Sakurai-Hosomi
reaction,6g has been extensively studied and applied
triphenyldifluorosilicate was used respectively). To our
knowledge the reactions of allylsilane with imines in the
presence of a catalytic amount of fluoride anion has never
been reported. In this paper, we disclose our research
results for this problem: the facile synthesis of homo-
allylamines from allyltrimethylsilane and imines under
mild conditions triggered by a catalytic amount of fluoride
ion and the experimental evidences for its mechanism.
6
successfully in organic synthesis. In contrast to the
(1) For recent reviews, see: (a) Yamamoto, Y.; Asao, N. Chem. Rev.
1
993, 93, 2207. (b) Roush, W. R. In Comprehensive Organic Synthesis;
Trost, B. M., Fleming, I., Eds. (Vol. 2 editor C. H. Heathcock);
Pergamon Press: Oxford, 1991; pp 1-53. (c) Fleming, I. In Compre-
hensive Organic Synthesis; Trost, B. M., Fleming, I. Eds.(Vol. 2 editor
C. H. Heathcock); Pergamon Press: Oxford, 1991; pp 563-593. (d)
Masse, C. E.; Panek, J . S. Chem. Rev. 1995, 95, 1293. (e) Nishigaichi,
Y.; Takuwa, A.; Naruta, Y.; Maruyama, K. Tetrahedron 1993, 49, 7395.
Resu lts a n d Discu ssion
(2) (a) Yasuda, M.; Fujibayashi, T.; Shibata, I.; Baba, A.; Matsuda,
H.; Sonada, N. Chem. Lett. 1995, 167. (b) J ephcote, V. J .; Thomas, E.
J . Tetrahedron Lett. 1985, 26, 5327. (c) Yamamoto, Y.; Maruyama, K.;
Naruta, Y.; Yatagai, H. J . Am. Chem Soc. 1980, 102, 7101. (d)
Yamamoto, Y.; Yatagai, H.; Ishihara, Y.; Maeda, N.; Maruyama, K.
Tetrahedron 1984, 40, 2239. (e) J ephcote, V. J .; Pratt, A. J .; Thomas,
E. J . J . Chem. Soc., Chem. Commun. 1984, 800. (f) Yanngisawa, A.;
Morodome, M.; Nakashima, H.; Yamamoto, H. Synlett 1997, 1309. (g)
Yanagisawa, A.; Inoun, H.; Morodome, M.; Yamamoto, H. J . Am. Chem.
Soc. 1993, 115, 10356 and references therein.
I. Syn th esis of Hom oa llyla m in es 3. To cleave the
C-Si bond efficiently, several fluoride compounds, CsF,
4 4
NH F, and n-Bu NF, were tested as catalysts for the
reaction of allyltrimethylsilane (1) with benzylidene-
aniline (2a ). The reaction gave no allylation product in
the presence of 10 mol % of CsF while a 40% yield of
homoallylamine 3a was afforded when 10 mol % of NH F
4
was used. According to the yields of homoallylamine 3a ,
(3) (a) Chen, D. L.; Li, C. J . Tetrahedron Lett. 1996, 37, 295. (b)
Chan, T. H.; Li, C. J . J . Chem. Soc., Chem. Commun. 1992, 747. (c)
Kim, E.; Gordon, D. M.; Schmid, W.; Whitesides, G. M. J . Org. Chem.
TBAF is the most efficient and suitable reagent for the
1
993, 58, 5500. (d) Li, C. J . Chem. Rev. 1993, 93, 2023. (e) For an
allylation of aldimine in comparison with CsF and NH
vide infra). The solubility of fluoride in THF may be a
decisive factor.
4
F
excellent book, see: Li, C. J .; Chan, T. H. In Organic Reaction in
Aqueous Media; J ohn Wiley & Sons, Inc.: 1997; p 75 and references
therein.
(
(
4) For some leading references, see: (a) Roush, W. R.; Ando, K.;
Powers, D. B.; Palkowitz, A. D.; Halterman, R. L. J . Am. Chem. Soc.
990, 112, 6339. (b) Roush, W. R.; Palkowitz, A. D.; Ando, K. J . Am.
Various homoallylamines 3 can be prepared by the
reaction of allyltrimethylsilane 1 with aldimines 2 in the
presence of 1 mol % of TBAF (Scheme 1), and the results
are summarized in Table 1. The addition of allylsilane 1
to the simple aldimines 2, which derive from aryl
aldehydes and aryl amines (entries 1 and 3-5) proceeded
very smoothly under reflux in the presence of as little as
1 mol % of TBAF or even 0.1 mol % (entries 1 and 3,
respectively). Many organometallic reactions used in
organic syntheses require strictly anhydrous reaction
1
Chem. Soc. 1990, 112, 6348. (c) Corey, E. J .; Yu, C. M.; Kim, S. S. J .
Am. Chem. Soc. 1989, 111, 1, 5495. (d) Corey, E. J .; Huang, H. C.
Tetrahedron Lett. 1989, 30, 5235 and references therein.
(5) For reviews, see: (a) Furin, G. G.; Vyazankina, O. A.; Gostevsky,
B. A.; Vyazankin, N. S. Tetrahedron 1988, 44, 2675. (b) Sakurai, H.
Pure Appl. Chem. 1985, 57, 1759. (c) Sakurai, H. Pure Appl. Chem.
1
982, 54, 1. (d) Hosomi, A. Acc. Chem. Res. 1988, 21, 200.
6) (a) Hosomi, A.; Shirahata, A.; Sakurai, H. Tetrahedron Lett. 1978,
(
1
1
9, 3043. (b) Sarker, T. K.; Andersen, N. H. Tetrahedron Lett. 1978,
9, 3513. (c) Deleris, G.; Dunogues, J .; Calas, R.; Pisciotti, F. J .
Organomet. Chem. 1974, 69, C 15. (d) Deleris, G.; Dunogues, J .; Calas,
R.; Pisciotti, F. J . Organomet. Chem. 1975, 93, 43. (e) Able, E. W.;
Rowley, R. J . J . Organomet. Chem. 1975, 84, 199. (f) Hosomi, A.;
Sakurai, H. Tetrahedron Lett. 1976, 1295. (g) Generally, the Lewis acid-
catalyzed allylation of carbonyl compound with allyl silane is known
as the Sakurai-Hosomi reaction (Majetich suggested to name this
reaction as Hosomi reaction, see ref 16a); here we further extended
the name of this reaction to include the fluoride-triggered reaction.
(7) (a) Kira, M.; Hino, T.; Sakurai, H. Chem. Lett. 1991, 277. They
suggested that the pentacoordinate allylsilicate complexes might be
involved when the following molar ratio of reagents was used:
crotyltrifluorosilane/aldimine/CsF ) 2/1/3-4. (b) Pilcher, A. S.; De-
Shong, P. J . Org. Chem. 1996, 61, 6901.
1
0.1021/jo980767y CCC: $18.00 © 1999 American Chemical Society
Published on Web 05/22/1999

4
234 J . Org. Chem., Vol. 64, No. 12, 1999
Wang et al.
may also be involved. Recently, Bottoni and Tagliavini8b
reported computational and experimental evidence for
the mechanism of the Sakurai-Hosomi reaction in the
Sch em e 1
presence of BF
3
. They found that the reaction of alde-
afforded
hydes with allyltrimethylsilane promoted by BF
3
fluorotrimethylsilane and a borylated homoallylic alcohol
in a noncatalytic fashion, but they did not study the
mechanism of fluoride-catalyzed allylation of aldehydes.
Ta ble 1. Ad d ition of Allyltr im eth ylsila n e to Ald im in es
in th e P r esen ce of a Ca ta lytic Am ou n t of TBAF a
9
An alternative autocatalytic mechanism was proposed
entry
R1
R2
reaction conditions
yield (%)b
for an isopropenylation reaction of benzophenone, which
took place quantitatively at 50 °C (Scheme 3). In this
mechanism, the fluoride ion just served as an initiator
of the reaction and was not involved in the catalytic cycle.
The strongly basic alkoxide 6 reacted with allylsilane and
then regenerated the active species and completed the
catalytic cycle. The intermediate 6 acted as a key species
in the catalytic cycle, and autocatalysis was named for
this mechanism. The authors, however, did not preclude
1
2
3
4
5
6
7
Ph
Ph
Ph
Ph
Ph
Ph
1 mol % TBAF, 5 h
1 mol % TBAF, 5 h
0.1 mol % TBAF, 9 h 85 (3a )
92 (3a )
0
c
p-MeOPh Ph
furyl
Ph
1 mol % TBAF, 3 h
p-MeOPh 1 mol % TBAF, 3 h
Me 1 mol % TBAF, 2 d
CH(CH3)- 1 mol % TBAF, 2 d
Ph (R)
91 (3b)
93 (3c)
74 (3d )
30 (60:40)
(3e)d
p-ClPh
8
9
Ph
Ph
tert-butyl 1 mol % TBAF, 2 d
Ts
1 mol % TBAF, 2 d
the possibility of the participation of a hypervalent silicon
a
The reaction was run on a 0.5 mmol scale, the ratio of reagents
-
intermediate [CH
2
dCHCH
2
Si(F)Me
3
] . These two mech-
was allylsilane/aldimine ) 1.2:1, and 200 mg of 4 Å MS was added.
b
Isolated yields based on aldimine. c No 4 Å MS was added. d Ratio
anisms appear in the authors’ review article as two
possible alternatives,5 and no further validation has
appeared.
b,c
1
of diastereoisomers (300 MHz HNMR analysis) was obtained and
is shown in parentheses. The configuration of the homoallylamine
was not determined.
We deem that the first fluoride-catalyzed reaction
probably does not occur, not only because of the low
conditions, and the allylation reaction of allylsilane with
imines is not an exception especially due to the easy
hydrolysis of imines. Since the commercially available
TBAF contains a certain amount of water, the addition
of 4 Å MS was invoked. In the presence of anhydrous 4
Å MS, the reaction can take place efficiently. None of the
desired product could be obtained in the absence of 4 Å
MS (entry 2). In the cases of aldimines derived from alkyl
amines, the reactions gave lower chemical yields (entries
3
boiling point of Me SiF but also since the bond energy of
Si-F (561 kJ /mol) is much higher than that of the Si-O
10
bond (442 kJ /mol) and the Si-N bond (∼316 kJ /mol).
3
So the metathesis between Me SiF and the alkoxy anion
3
is not favorable thermodynamically even if Me SiF could
exist as a solvent complex in the reaction mixture. In
other words, we doubt that the fluoride ion could be
11
regenerated under the reaction conditions. To clarify
this point, we synthesized the high-boiling triethylsilicon
6
and 7) even under reflux for an appropriate period of
12
fluoride and the key intermediate alkoxy anions 7 and
time. When a hindered aldimine (entry 8) and an N-
electron deficient aldimine (entry 9) were used, no
addition took place under the same conditions, even for
a prolonged time period.
8
which were included in both the fluoride-catalyzed
mechanism and the autocatalytic mechanisms and tried
to find further evidence about the mechanism of this
reaction.
II. Mech a n ism of th e Ad d ition of Allylsila n e w ith
CdO a n d CdN Dou ble Bon d s. As DeShong reported
in his paper,7b fluoride-promoted condensation of imines
and allytrimethylsilane is an unprecedented reaction, but
the reaction is not catalytic in the silicate salt. On the
contrary, we found that the reaction of allyltrimethylsi-
lane and imines can proceed smoothly with high yields
in the presence of a catalytic amount of TBAF (Table 1).
The reaction of allylsilane with an imine bears close
analogy to that of the reaction with a carbonyl compound.
For the later reaction, the so-called Sakurai-Hosomi
reaction,5 two possible mechanisms have been proposed.
3
First, when Et SiF and tetrabutylammonium alkoxy
anion salt were mixed together in THF, no triethylsilyl
alkyl ether formed even on refluxing for a prolonged
period of time (eq 1 in Scheme 4). This indicates that the
trimethylsilyl fluoride formed in the reaction cycle could
not be regenerated to TBAF as shown in Scheme 2.
Furthermore, when a catalytic amount of alkoxy anion
(
10 mol %) in place of fluoride ion was used for the
Sakurai-Hosomi reaction (eq 2 in Scheme 4) and the
reaction of allylsilane with imine 2a (eq 3 in Scheme 4),
both homoallyl alcohol and homoallylamine 3a could be
,6
13
obtained in 76% and 65% yields, respectively. Therefore,
The first mechanism is a fluoride ion catalyzed
the autocatalytic reaction seems to be the most probable
mechanism. Up to this point, we may extrapolate this
autocatalytic mechanism to the aza analogue of the
Sakurai-Hosomi reaction. But one still may argue as to
reaction5
c,6a
(Scheme 2). The released trimethylsilyl
fluoride reacts again with the tetrabutylammonium
alkoxide 5 to regenerate tetrabutylammonium fluoride
in the catalytic cycle. This same author expressed concern
3
about this mechanism due to the low boiling point of Me -
(
9) Sakurai, H.; Hosomi, A.; Saito, M.; Sasaki, K.; Iguck, H.; Sasata,
J .; Araki, Y. Tetrahedron 1983, 39, 883.
10) Pauling, L. The Nature of the Chemical Bond, 3rd ed.; Cornell
University Press: New York, 1960; Chapter 3.
11) For the fluoride-catalyzed Aldol reaction of enol silyl ethers with
SiF (16.4 °C) which might not exist in the reaction system
at the refluxing temperature. However, this mechanism
is mentioned even in a recent monograph review book.8
The reviewer adopted this mechanism and modified it
by the assumption that a pentacoordinated silicon species
(
a
(
aldehydes, see: (a) Noyori, R.; Nishida, I.; Sakata, J . J . Am. Chem.
Soc. 1981, 103, 2106. (b) Nakmura, E.; Shimizu, M.; Kuwajima, I.;
Sakata, J .; Yokoyama, K.; Noyori, R. J . Org. Chem. 1983, 48, 932.
(
12) DiGiorgio, P. A.; Strong, W. A.; Sommer, L. H.; Whitmore, F.
(
8) (a) For a recent book, see: Majetich, G. In Organic Synthesis
Theory and Application; Hudlicky, T., Ed.; J AI Press Ltd.: 1989; Vol.
, p 173. (b) Bottoni, A.; Costa, A. L.; Tommaso, D. D.; Rossi, I.;
Tagliavini, E. J . Am. Chem. Soc. 1997, 119, 12131.
C. J . Am. Chem. Soc. 1946, 68, 1380.
(13) For an example of an alkoxide-induced reaction between an
imine and a benzylsilane derivative, see: Shimizu, S.; Ogata, M. Synth.
Commun. 1989, 19, 2219.
1

Allylation of Imines with Allyltrimethylsilane
J . Org. Chem., Vol. 64, No. 12, 1999 4235
Sch em e 2
Sch em e 3
and the π-allyl species A-1, the countercation being tetra-
n-butylammonium. π-Allyl species A-1 then reacts with
imine to afford intermediate A-2. The key species A-2
then reacts with allylsilane again to regenerate active
species A-1 and a catalytic cycle is complete.
Interaction between A-2 and allylsilane 1 gives the
π-allylic anion A-1 and the silyl homoallylamine. When
the substituents on the nitrogen atom are bulky alkyl
groups, such as tert-butyl (entry 7 of Table 1) or second-
ary alkyl (entry 6), the hindered structure causes the
addition of A-1 to be difficult. When the substituent was
a strongly electron withdrawing tosyl group, it stabilized
and reduced the nucleophlicity of the intermediate A-2,
and hence stopped the catalytic cycle (entry 9).
According to the current pentacoordinated silicon
chemistry,14 probably a pentacoordinated species may
also be involved during the reaction of A-2 with allyl-
trimethylsilane 1 (from A-2 to A-1). To probe the exist-
ence of this pentacoordinated species, a model reaction
was carried out (Scheme 6). The tetrabutylammonium
alkoxide of benzyl alcohol was prepared (eq 5) and
subjected to a reaction with allyltrimethylsilane 1 at
room temperature in THF (eq 6). After 1 h, the Si NMR
showed only two peaks at 0.06 and 17.25 ppm. The
former one belongs to the chemical shift of allyltrimeth-
ylsilane 1 and the downfield one is the signal of the silyl
ether which was confirmed by comparison with an
authentic sample prepared by the reaction of benzyl
whether the amide anion intermediate 8 (analogue to 7)
is basic enough to do the same job. Similarly, with a
catalytic amount of amide anion 8 (10 mol %) used
instead of an alkoxy anion to catalyze this reaction,
homoallylic amine could be obtained in 80% isolated yield
2
9
(
eq 3 in Scheme 4). Accordingly, a catalytic amount of
amide anion generated in situ from the reaction product
a , NaH, and n-Bu NCl can also initiate this reaction
eq 4 in Scheme 4) in a one-pot manner, and no fluoride
3
(
4
3
alcohol and TMSCl in the presence of Et N. There was
no signal indicating the presence of a pentacoordinated
species in the background of the glass Si of the NMR tube
ion is further invoked.
The above experimental evidences showed that the
fluoride ion only served as a trigger in these reactions
and could not act as a catalytic species to regenerate
(-70 to -200 ppm) as expected. However, this phenom-
enon does not exclude the presence of a transient forma-
tion of a pentacoordinated silicon intermediate.
4
n-Bu NF. It also showed that the autocatalytic cycle
formed by the alkoxide ion or the amide anion is the most
probable mechanism and the fluoride-catalyzed mecha-
nism for the Hosomi-Sakurai reaction should be rejected.
On the basis of this argument, a possible mechanism of
the allylation of imine with allyltrimethylsilane 1 is
proposed (Scheme 5), which confirmed the autocatalytic
It is claimed that a pentacoordinated silicon species
could explain the γ-attack product in the reaction with
cinnamyl- or crotyltrimethylsilane. Therefore, cinnamyl-
trimethylsilane17 was subjected to a reaction with PhCHd
9
(14) For an excellent review on reactivity of pentacoordinate silicon
compounds, see: Chuit, C. C.; Corriu, R. J .; Reye, C.; Young, J . C.
Chem. Rev. 1993, 93, 1371 and references therein.
mechanism proposed by Sakurai and Hosomi.
According to this mechanism, the interaction of allyl-
silane and fluoride ion leads to the evolution of Me
3
SiF
(15) Love, B. E.; Raje, P. S.; Williams, T. C., II. Synlett 1994, 493.

4
236 J . Org. Chem., Vol. 64, No. 12, 1999
Wang et al.
Sch em e 4
Sch em e 5
Sch em e 6
of 3-methyl-2-butenyltrimethylsilane with benzaldehyde
in a catalytic amount of TBAF: a mixture of R- and
γ-attack was obtained.18 The exclusive R-attack in our
case did not support the pentacoordinated silicon mech-
anism.
In conclusion, allylation of aldimines with allyltri-
methylsilane triggered by a catalytic amount of TBAF
under mild conditions is realized. Furthermore, experi-
mental evidences also supported the fluoride-triggered
autocatalytic mechanism of the Sakurai-Hosomi reaction
as well as its aza analogue. This method represents the
first example of a catalytic allylation of imines by
allylsilane, which is a non-Lewis acid mediated allylation
of aldimines and can be used for homoallylamine syn-
thesis.
NPh under the same conditions, and an almost linear
product (>95:5) was obtained in 83% isolated yield (eq 7
in Scheme 6). Furthermore, Sakurai reported the reaction
Exp er im en ta l Section
Ma ter ia ls a n d Gen er a l P r oced u r e. All reactions were
performed in oven-dried glassware under an atmosphere of
nitrogen unless otherwise stated. THF was distilled im-
(16) (a) Campbell, K. N.; Sommers, A. H.; Campbell, B. K. J . Am.
Chem. Soc. 1944, 66, 822. (b) Castello, J . A.; Goldmacher, J . E.; Barton,
L. A.; Kane, J . S. J . Org. Chem. 1968, 33, 3501.
(17) Slutsky, J .; Kwart, H. J . Am. Chem. Soc. 1973, 95, 8684.
(18) Sakurai, H. Synlett 1989, 1.

Allylation of Imines with Allyltrimethylsilane
J . Org. Chem., Vol. 64, No. 12, 1999 4237
mediately prior to use from sodium/benzophenone ketyl under
nitrogen, and the other solvents were treated according to
standard methods. Et SiF and N-sulfonylimine were pre-
3
(5 mL) was added NaH (5 mmol) in three portions, and after
30 min, 1.40 g (5 mmol) tetrabutylammonium chloride was
added under nitrogen and the reaction miture was stirred for
6 h at room termperature. The concentration of the resulting
solution is 1 M.
Allyla t ion of Im in e a n d Ald eh yd e Ca t a lyzed by t h e
Tetr a bu tyla m m on iu m Sa lt. To a solution of allyltrimeth-
ylsilane (0.6 mmol) and imine or aldehyde (0.5 mmol) in THF
(2 mL) were added 200 mg of 4 Å molecular sieves and 60 µL
of 1 M tetrabutylammonium alkoxide 7 or amide 8 (in THF).
The reaction mixture was refluxed after reaction was complete
according to TLC. The reaction mixture was filtered on a short
silica gel column, and the filtrate was concentrated and
chromatographed on a silical gel column with a mixture of light
petroleum ether (60-90 °C)/ethyl acetate (10:1) as the eluent
to give pure homoallylamines or homoallyl alcohols.
1
2
15
pared according to literature methods in reasonable yields. All
imines were prepared according to reported procedures.16
Proton magnetic resonance spectra were recorded on a Brucker
AMX-300 (300 MHz) spectromer. J values are in hertz.
Gen er a l P r oced u r e for F lu or id e-Tr igger ed Allyla tion
of Im in es. To a solution of allyltrimethylsilane (0.6 mmol) and
imine (0.5 mmol) in THF (2 mL) were added 200 mg of 4 Å
molecular sieves and 30 µL of 1 M TBAF (in THF). The
reaction mixture was refluxed. After reaction was complete
according to TLC, the reaction mixture was filtered on a short
silica gel column and the filtrate was concentrated and
chromatographied on a silica gel column with a mixture of light
petroleum ether (60-90 °C) and ethyl acetate (10:1) as the
eluent to give pure homoallylamines (showed identical spec-
R egioch em ist r y of F lu or id e-Tr igger ed R ea ct ion s of
troscopic properties to those previously reported, see lit.7
b,19a,b
).
17
Allylic Sila n es. To a solution of cinnamyltrimethylsilane
N-(P h en yl)-r-2-p r op en ylben zem eth a n a m in e (3a ):7b 1H
NMR (CDCl ) δ 7.30 (m, 5H), 7.07 (t, J ) 8.84 Hz, 2H), 6.66
t, J ) 7.20 Hz, 1H), 6.50 (m, 2H), 5.75 (m, 1H), 5.15 (m, 2H),
(0.6 mmol) and imine (0.5 mmol) in THF (2 mL) were added
3
2
00 mg of 4 Å molecular sieves and 30 µL of 1 M TBAF (in
(
THF). The reaction mixture was refluxed. After reaction was
complete according to TLC, the reaction mixture was filtered
on a short silica gel column, and the filtrate was concentrated
and chromatographied on a silica gel column with a mixture
of light petroleum ether (60-90 °C) and ethyl acetate (10:1)
as the eluent to give pure homoallylamines.
4
.40 (m, 1H), 2.55 (m, 2H).
N -(p -Me t h o x y p h e n y l)-r-2-p r o p e n y lb e n ze m e t h a n -
1
9b 1
a m in e (3b):
9
5
3
H NMR (CDCl ) δ 7.20 (m, 5H), 6.55 (d, J )
.01 Hz, 2H), 6.30 (d, J ) 9.10 Hz, 2H) 6.00-5.65 (m, 1H),
.20 (m, 2H), 4.25 (t, J ) 9.00 Hz, 1H), 3.65 (s, 3H), 2.50 (d, J
)
9.00 Hz, 2H), 1.30 (br, 1H).
N -(P h e n yl)-r-(3-p h e n yl-2-p r op e n yl)b e n ze m e t h a n -
N -(p -Me t h o x y p h e n y l)-r-2-p r o p e n y lfu r y lm e t h a n -
1
a m in e: H NMR (CDCl
3
) δ 2.72 (m, 2H), 4.48 (dd, J ) 7.6,
1
9b 1
a m in e (3c):
2
6
3
H NMR (CDCl /TMS) δ 7.30 (m, 1H), 6,75 (m,
5
1
(
.4, 1H), 6.13 (dt, J ) 15.8, 7.2, 1H), 6.50 (m, 3H), 6.64 (m,
H), 7.06 (m, 2H), 7.30 (m, 10H); MS m/z 300 (M + 1, 19), 299
M , 71), 207 (56), 182 (100), 91 (7); IR 3412, 3026, 1602, 1505,
93; HRMS calcd for C22
Sp ectr oscop ic In vestiga tion s. 29Si NMR: BnOSiMe
H), 6.55 (m, 2H), 6.30 (dd, J
.10 (d, J ) 3.15 Hz, 1H) 5.70 (m, 1H), 5.15 (m, 2H), 4.45 (t,
J ) 6.35 Hz, 1H), 3.36 (s, 3H), 2.60 (t, J ) 6.78 Hz, 2H), 2.00
1
) 1.77 Hz, J
2
) 3.15 Hz, 1H),
+
+
6
H
21N (M ) 299.1674, found 299.1650.
(br, 1H).
N-Meth yl-r-2-p r op en ylben zem eth a n a m in e (3d ):19c 1H
3
(or
allyltrimethylsilane) was directly dissolved in anhydrous THF
at room termperature, the chemical shift of allyltrimethylsi-
NMR (CDCl ) δ 7.30 (m, 5H), 5.70 (m, 1H), 5.05 (m, 2H), 3.60
3
(
t, J ) 6.90 Hz, 1H), 2.45 (m, 2H), 2.30 (s, 3H).
lane is 0.06 ppm, BnOSiMe
tetrabutylammonium alkoxide BnON(n-Bu)
methylsilane was performed in an NMR tube under nitrogen
at room termperature in anhydrous THF (Me Si as the inner
3
is 19.25 ppm. The exchange of
N-(r-Meth ylben zyl)-r-2-pr open yl-p-ch lor oben zem eth an -
4
with allyltri-
1
9b
1
a m in e (3e). Isomer 1: H NMR (CDCl
3
) δ 7.25 (m, 9H), 5.65
(
2
m, 2H), 5.00 (m, 1H), 3.70 (m, 1H), 3.50 (t, J ) 6.72 Hz, 2H),
4
.45 (q, J ) 6.65, 1H), 1.80 (br, 1H), 1.35 (d, J ) 6.65 Hz, 2H).
1
standard); after 30 min, the NMR tube was transferred into
the NMR instrument set at room termperature. Recording of
Isomer 2: H NMR (CDCl
3
) δ 7.25 (m, 9H), 5.65 (m, 2H), 5.00
(
6
m, 1H), 3.70 (m, 1H), 3.40 (t, J ) 6.72 Hz, 2H), 2.25 (q, J )
2
9
Si NMR spectra showed the signals of allyltrimethylsilane
0.06 ppm) and BnOSiMe (19.17 ppm).
.65, 1H), 1.80 (br, 1H), 1.30 (d, J ) 6.65 Hz, 2H).
(
3
Syn th esis of Tetr a bu tyla m m on iu m Alk oxid e 7 a n d
Am id e 8. To a solution of alcohol or amine (5 mmol) in THF
Ack n ow led gm en t. We thank the financial support
of Chinese Academy of Sciences and the National
Natural Science Foundation of China (29790127).
(
19) (a) Wang, D.-K.; Dai, L.-X.; Hou, X.-L.; Zhang, Y. Tetrahedron
Lett. 1996, 37, 4187. (b) Wang, D.-K.; Dai, L.-X.; Hou, X.-L. Tetrahedron
Lett. 1995, 36, 8649. (c) Bhuyan, P. J .; Prajapati, D.; Sandhu, J . S.
Tetrahedron Lett. 1993, 34, 7975.
J O980767Y