Asymmetric synthesis of 1-(9-anthracenyl)ethylamine and its trifluoromethyl analogue via nucleophilic addition to an N -(tert -butylsulfinyl)imine

Article abstract of DOI:10.1055/s-0030-1260153

Asymmetric synthesis of the 9-anthracenyl analogues of 1-phenylethylamine and 2,2,2-trifluoro-1-phenylethylamine was achieved via nucleophilic addition to the corresponding N-(tert-butylsulfinyl)imine. Georg Thieme Verlag Stuttgart, New York.

Full text of DOI:10.1055/s-0030-1260153

PAPER
2817
Asymmetric Synthesis of 1-(9-Anthracenyl)ethylamine and Its Trifluoro-
methyl Analogue via Nucleophilic Addition to an N-(tert-Butylsulfinyl)imine
A
M
symmetric Synthesis
a
of Chiral
A
r
mines
w
c
itha 9-Ant
o
hracenyl
G
ro
s
up Hernández-Rodríguez,* Tania Castillo-Hernández, Karla Elisa Trejo-Huizar
Instituto de Química, Universidad Nacional Autónoma de México, Circuito Exterior, Ciudad Universitaria, Del. Coyoacán, C. P. 04510,
México, D.F., Mexico
Fax +52(55)56224402; E-mail: marcoshr@unam.mx
Received 21 April 2011; revised 7 June 2011
Then, we focused on the addition of an organometallic re-
Abstract: Asymmetric synthesis of the 9-anthracenyl analogues of
agent to obtain amine 1. The addition of methylmagne-
1
-phenylethylamine and 2,2,2-trifluoro-1-phenylethylamine was
achieved via nucleophilic addition to the corresponding N-(tert-bu-
tylsulfinyl)imine.
O
S
O
S
O
Key words: amines, asymmetric synthesis, chiral auxiliaries, tert-
butanesulfinamide, trifluoromethyl compounds
H2N
t-Bu
N
t-Bu
CH3
CH3
Ti(OEt)4
THF, reflux, 48 h
1
5%
The synthesis of chiral amines is an important endeavor
due to the many uses of chiral amines in medicinal chem-
istry. In asymmetric synthesis such amines are also a pri-
mary target because of their uses as ligands and
organocatalysts. In this regard, we sought to obtain chiral
amines 1 and 2 (Figure 1) in order to incorporate them
3
O
S
O
S
O
H2N
t-Bu
N
t-Bu
H
H
1
into (thio)ureas for two purposes: as organocatalysts and
Ti(OEt)4
2
THF, r.t., 17 h
for the chiral recognition of carboxylates. Amine 1 has
8
9%
3
been used previously as a chiral solvating agent and in
4
asymmetric synthesis as a higher analogue of 1-phenyl-
4
5
ethylamine.
Scheme 1 Synthesis of N-sulfinyl ketimine 3 and aldimine 4
NH2
CH3
NH2
CF3
Table 1 Addition of the Grignard or Organolithium Reagent to
N-Sulfinylimine 4
*
*
O
S
O
S
O
S
M-CH3
N
t-Bu
HN
t-Bu + HN
Ar
t-Bu
1
2
Ar
H
Ar
CH3
(S,RS)-5
CH3
4
(R,RS)-5
Figure 1 Chiral 1-(9-anthracenyl)ethylamine and its trifluoro-
methyl analogue
Entrya Reagent
Tempb
Solvent
Yield
dr
[(S,R )/(R,R )]
(
°C)
(%)
92
50
93
98
25
65
79
S
S
One of the successful methodologies for the synthesis of
1
CH MgI
THF
–45
–45
–45
–78
–78
–78
–78
70:30
3
chiral amines is the use of Ellman’s tert-butanesulfin-
6
amide. Useful from the synthetic viewpoint of high dia-
2
CH MgI
toluene
toluene
toluene
toluene
THF
68:32
58:42
22:78
62:38
13:87
9:91
3
stereomeric ratios of the products and easy removal of the
auxiliary, we deemed to obtain chiral amines 1 and 2 em-
ploying this methodology. The reported one-pot conden-
3c
4
CH MgI
3
CH Li
3
7
sation and reduction was not successful with 9-
5c
6
CH Li
3
acetylanthracene as the substrate. When we tried to isolate
ketimine 3, only 15% yield was obtained (Scheme 1).
This difficulty due to the anthracene moiety was circum-
vented through the use of the more reactive 9-anthracene-
carbaldehyde, resulting in aldimine 4.
CH Li
3
7d
CH Li
THF
3
a
N-Sulfinylimine 4 (0.5 mmol) was used at a concentration of 0.2 M.
In the case of the Grignard reagent, the reaction was conducted at
45 °C for 4 h and at –20 °C overnight. With methyllithium the reac-
b
–
SYNTHESIS 2011, No. 17, pp 2817–2821
x
x.
x
x
.
2
0
1
1
tion was performed at –78 °C for 4 h.
c
Advanced online publication: 08.08.2011
DOI: 10.1055/s-0030-1260153; Art ID: M40911SS
Georg Thieme Verlag Stuttgart · New York
Me Al (1 equiv) was added.
3
d
HMPA (6 equiv) was added.
©

2
818
M. Hernández-Rodríguez et al.
PAPER
sium iodide to N-sulfinylimine 4 showed good yields but
low selectivity regardless of the solvent used (Table 1,
O
S
8
N
t-Bu
entries 1 and 2). It has been reported that the addition of
9
trimethylaluminum enhances the selectivity but with our
Ar
H
substrate the result was unfavorable (Table 1, entry 3).
The use of methyllithium as nucleophile also gave good
yields with the opposite selectivity (Table 1, entries 4–7).
Experiments with additives such as trimethylaluminum
I-Mg-CH3
Li-CH3
favored the S,R -product in low selectivity (Table 1, entry
S
5
), while the use of hexamethylphosphoramide showed
improved selectivity (Table 1, entry 7).
≠
H3C-Li
≠
H
The difference in selectivity between these two reagents
can be explained by two different transition states. For the
Grignard reagent, with a more coordinating magnesium
ion, the methyl group is incorporated through a cyclic
transition state to the Si face of the imine. Meanwhile,
with methyllithium, an acyclic transition state is favored
and the methyl group is added to the Re face of the imine
S
Ar
CH3
N
H
Mg
N
O
Ar
O
(
Scheme 2). It becomes clear that trimethylaluminum,
which enhances the cyclic transition state by its coordina-
tion to the nitrogen, does not improve the selectivity be-
O
O
S
S
cause of the steric clash with C –H of the anthracenyl
1
HN
t-Bu
HN
t-Bu
group. On the other hand, hexamethylphosphoramide sol-
vates the lithium ion and favors an acyclic transition
state.
1
0
Ar
CH3
S,RS)
Ar
CH3
(R,RS)
(
For the synthesis of the trifluoromethyl analogue 2 we Scheme 2 Stereochemistry of the nucleophilic addition
employed N-sulfinylimine 4 and the Ruppert–Prakash re-
agent [trimethyl(trifluoromethyl)silane]. This type of re-
Table 2 Addition of Trimethyl(trifluoromethyl)silane to N-Sulfinylimine 4
O
S
O
S
O
S
TMSCF3
N
t-Bu
HN
t-Bu
+
HN
t-Bu
activator (1.1 equiv)
Ar
H
Ar
CF3
Ar
CF3
(R,RS)-6
4
(S,RS)-6
Entrya
Activator
TBAT
TBATb
TBAF
CsF
Solvent
THF
Temp (°C)
Time (h)
Yield (%)
90
dr [(S,R )/(R,R )]
S
S
1
2
3
4
5
6
7
8
–50
–50c
–50
20
3
3
99:1
99:1
–
THF
97
THF
3
n.r.d
87
THF–DMF (1:1)
THF–DMF (1:1)
THF
2
93:7
92:8
n.d.f
95:5
95:5
96:4
CsF
–20
20
24
24
60
24
3
33
e
K CO
>10
64
2
3
3
3
K CO
DMF
20
2
g
K CO
DMF
20
67
2
b
–50c
9
Bu NOAc
THF
61
4
a
N-Sulfinylimine 4 (0.5 mmol) was used at a concentration of 0.3 M.
b
c
d
e
f
0
.2 equiv used.
The reaction mixture was warmed to –20 °C and stirred for 20 h.
n.r. = no reaction.
0.1 equiv used.
n.d. = not determined.
TBAB (1 equiv) was added.
g
Synthesis 2011, No. 17, 2817–2821 © Thieme Stuttgart · New York

PAPER
Asymmetric Synthesis of Chiral Amines with a 9-Anthracenyl Group
2819
action has been reported with different fluoride sources as on a Varian Inova (300 MHz) or a Bruker Avance (300 MHz) spec-
trometer. Chemical shifts (d) are in ppm downfield from TMS and
coupling constants are in hertz. Optical rotations were measured at
r.t. on a Perkin-Elmer 343 polarimeter. Mass spectra were obtained
with a Jeol JMS-SX 102A or a Jeol JMS-AX 505 HA mass spec-
trometer.
activators, such as stoichiometric quantities of tetrabutyl-
1
1
ammonium difluorotriphenylsilicate (TBAT) or tetra-
1
2
methylammonium fluoride. We followed the described
procedure with TBAT which afforded excellent diaste-
reoselectivity. Nevertheless, because of the high cost of
TBAT on a preparative scale, we screened conditions and (R,E)-N-[(9-Anthracenyl)methylene]-tert-butanesulfinamide (4)
found that 20% TBAT with prolonged time and higher In a 250-mL round-bottomed flask was placed 9-anthracenecarbal-
dehyde (7.94 g, 38.5 mmol) dissolved in anhyd THF (70 mL) under
temperature are the optimal conditions (Table 2, entry 2).
Then, we explored different sources of fluoride or Lewis
base; with tetrabutylammonium fluoride (Table 2, entry
N atmosphere. Ti(OEt) (16 mL, 77 mmol) and (R)-tert-butane-
2
4
sulfinamide (4.24 g, 35 mmol) were added to the mixture which was
then stirred at r.t. for 17 h. Then, the mixture was poured into brine
3
) no reaction was observed, while cesium fluoride af-
(
100 mL) with stirring and the flask was washed with EtOAc
®
forded lower selectivity even at low temperature (Table 2, (2 × 20 mL). The suspension was filtered over Celite and the solid
entries 4 and 5). The use of potassium carbonate in the ad- was washed with EtOAc (2 × 60 mL). The phases were separated
and the aqueous phase was extracted with EtOAc (2 × 40 mL). The
dition of trimethyl(trifluoromethyl)silane to ketones has
1
3
combined organic phases were dried (Na SO ) and concentrated.
been reported but with our substrate poor activation was
2
4
The product was purified by flash chromatography (hexane–
EtOAc, 100:0 to 75:25) to afford a yellow solid; yield: 9.68 g
observed, even with N,N-dimethylformamide as solvent
(
Table 2, entries 6–8). With tetrabutylammonium bro-
(
89%).
mide the reaction was accelerated (Table 2, entry 8). Fi-
nally, tetrabutylammonium acetate was found to be the
best activator of the explored alternatives (Table 2, entry
2
5
Mp 137–138 °C; [a]D –80.8 (c 1, CHCl3).
Rf = 0.33 (hexanes–EtOAc, 8:2).
1
4
1
9
).
H NMR (300 MHz, CDCl ): d = 9.92 (s, 1 H), 8.88 (d, J = 9.0 Hz,
3
2
1
H), 8.54 (s, 1 H), 8.04 (d, J = 8.4 Hz, 2 H), 7.48–7.65 (m, 4 H),
The liberation of the chiral amines was performed under
acidic conditions, affording both enantiomers of amine 1
and the S-enantiomer of amine 2 (Scheme 3). Configura-
.38 (s, 9 H).
1
3
C NMR (75 MHz, CDCl ): d = 161.0, 131.7, 130.4, 130.3, 128.3,
3
1
27.1, 124.7, 123.7, 123.4, 56.8, 21.9.
1
2,15
tions were assigned from the optical rotations.
+
MS (EI, 70 eV): m/z (%) = 309 (8) [M ], 253 (95), 205 (100), 178
(45), 151 (10), 57 (23).
O
S
HCl
N-[1-(9-Anthracenyl)ethyl]-tert-butanesulfinamide (5)
In a round-bottomed flask was placed N-sulfinylimine 4 (1.85 g, 6
mmol) dissolved in anhyd THF (36 mL) under argon atmosphere.
HN
*
t-Bu
NH2
CX3
MeOH
r.t., 1 h
Ar
CX3
Ar
*
The mixture was cooled to –45 °C and 2.75 M CH MgI in Et O
(2.62 mL, 7.2 mmol) was added; the solution was stirred at –45 °C
for 4 h and at –20 °C for 20 h. The reaction was quenched by the
(S,RS)-5
(R,RS)-5
(S,RS)-6
(S)-1, X = H, 94%
(R)-1, X = H, 91%
(S)-2, X = F, 93%
3
2
addition of sat. aq NH Cl soln (20 mL) and the phases were separat-
4
Scheme 3 Acidic removal of the chiral auxiliary to obtain enantio-
pure amines 1 and 2
ed. The aqueous layer was extracted with EtOAc (3 × 30 mL), and
the combined organic extracts were dried (Na SO ) and concentrat-
2
4
ed. The product was purified by flash chromatography (hexane–
EtOAc, 9:1 to 3:7).
In conclusion, the condensation of Ellman’s sulfinamide
was more efficient with 9-anthracenecarbaldehyde than
with 9-acetylanthracene. Depending on the organometal-
lic reagent used in the addition to N-sulfinylimine 4, both
diastereomers of the product could be obtained selective-
ly. Several activators promoted the addition of the
Ruppert–Prakash reagent to N-sulfinylimine 4 with good
(
S,R )-5 (Major Diastereomer)
S
The major diastereomer, (S,R )-5, was obtained as a yellow foam
S
that solidified under reduced pressure; yield: 1.26 g (64%).
2
5
Mp 80–82 °C; [a]D –60.2 (c 1, CHCl3).
Rf = 0.24 (hexanes–EtOAc, 1:1).
selectivity, with TBAT being the optimal activator. The 1H NMR (300 MHz, CDCl
): d = 8.62 (br, 2 H), 8.41 (s, 1 H), 7.97–
.02 (m, 2 H), 7.39–7.53 (m, 4 H), 6.19 (q, J = 7.0 Hz, 1 H), 3.84
3
8
synthesis of amines 1 and 2 via the chiral N-sulfinylimine
can be regarded as an example of a sterically hindered
substrate in which the acyclic transition state is by far
more selective than the cyclic counterpart.
(
br, 1 H), 1.91 (d, J = 7.0 Hz, 3 H), 1.09 (s, 9 H).
1
3
C NMR (75 MHz, CDCl ): d = 134.2, 133.6, 132.3, 131.9, 129.5,
3
1
28.6, 127.3, 124.9, 55.2, 49.0, 22.6.
+
MS (EI, 70 eV): m/z (%) = 325 (14) [M ], 269 (15), 205 (100), 178
(
45), 57 (18).
Starting materials were purchased from Aldrich; solvents were re-
agent grade. Anhyd THF and toluene were freshly distilled from so-
+
HRMS–FAB: m/z [M ] calcd for C H NOS: 325.1500; found:
3
20 23
25.1499.
dium ketyl. HMPA and DMF were dried over CaH and distilled
2
under reduced pressure. Methyllithium was titrated with diphenyl-
acetic acid. Flash column chromatography was carried out with sil-
ica gel 60 (0.40–0.63 mm, 230–400 mesh). TLC was performed
with silica gel F254 plates. Melting points (uncorrected) were deter-
(
R,R )-5 (Minor Diastereomer)
S
The minor diastereomer, (R,R )-5, was obtained as a yellow foam
that solidified under reduced pressure; yield: 538 mg (28%).
S
1
13
2
5
mined with a Fisher-Johns melting point apparatus. H and
C
Mp 50–53 °C; [a]D –53.9 (c 1, CHCl3).
NMR spectra were recorded at 300 MHz and 75 MHz, respectively,
Synthesis 2011, No. 17, 2817–2821 © Thieme Stuttgart · New York

2
820
M. Hernández-Rodríguez et al.
PAPER
Rf = 0.47 (hexanes–EtOAc, 1:1).
was stirred at r.t. for 1 h, then CH Cl (30 mL) was added and the
2
2
1
mixture was washed with 10% aq NaOH soln (30 mL). The organic
layer was separated and the aqueous layer was extracted with
CH Cl (2 × 20 mL). The combined organic layers were dried
H NMR (300 MHz, CDCl ): d = 8.57 (br, 2 H), 8.42 (br, 1 H),
3
7
.98–8.03 (m, 2 H), 7.43–7.53 (m, 4 H), 6.17 (qd, J = 5.0, 1.0 Hz, 1
2
2
H), 3.73 (br, 1 H), 1.94 (d, J = 5.0 Hz, 3 H), 1.28 (s, 9 H).
1
(
Na SO ) and concentrated. The product was purified by flash chro-
2 4
3
C NMR (75 MHz, CDCl ): d = 134.2, 134.0, 131.9, 129.6, 129.4,
3
matography (hexane–EtOAc, 1:1 + 1% Et N) to afford a yellowish
3
1
28.6, 127.3, 126.5, 125.0, 55.8, 44.4, 22.9.
solid; yield: 320 mg (94%).
+
HRMS–FAB: m/z [M ] calcd for C H NOS: 325.1500; found:
3
Mp 113–115 °C (Lit.15 110–113 °C for the R-enantiomer); [a]D
25
2
0
23
25.1503.
15
–
16.7 (c 1, CHCl ) [Lit. [a] +18 (c 1, CHCl ) for the R-enan-
3
D
3
tiomer].
(
S,R )-N-[1-(9-Anthracenyl)-2,2,2-trifluoroethyl]-tert-butane-
S
R = 0.1 (hexanes–EtOAc–Et N, 1:1:0.01).
f
3
sulfinamide [(S,R )-6]
S
1
The optimized conditions (Table 2, entry 2) were scaled up for this
preparative procedure: In a round-bottomed flask under N atmo-
H NMR (300 MHz, CDCl ): d = 8.72 (br d, J = 7 Hz, 2 H), 8.36 (s,
3
1 H), 7.97–8.02 (m, 2 H), 7.40–7.51 (m, 4 H), 5.79 (q, J = 6.9 Hz, 1
2
sphere were suspended N-sulfinylimine 4 (2.47 g, 8 mmol) and
TBAT (863 mg, 1.6 mmol) in anhyd THF (25 mL) (some TBAT re-
mains suspended). The mixture was cooled to –50 °C, then trimeth-
yl(trifluoromethyl)silane (1.42 mL, 9.6 mmol) was added and the
mixture was stirred for 4 h. The reaction mixture was warmed to
H), 2.29 (br, 2 H), 1.85 (d, J = 6.9 Hz, 3 H).
13
C NMR (75 MHz, CDCl ): d = 137.4, 131.9, 129.4, 129.1, 127.4,
3
1
25.2, 125.0, 124.7, 46.5, 23.9.
+
MS (EI, 70 eV): m/z (%) = 221 (41) [M ], 206 (100), 178 (35).
–
20 °C and stirred for 20 h. The reaction was quenched by the addi-
+
HRMS–FAB: m/z [M ] calcd for C H N: 221.1204; found:
1
6
15
tion of sat. aq NH Cl soln (30 mL) and extracted with EtOAc
4
221.1208.
(
3 × 30 mL). The combined organic extracts were dried (Na SO )
2
4
and concentrated. The product was purified by flash chromatogra-
phy (hexane–EtOAc, 100:0 to 65:35) to afford a yellow solid; yield:
(
R)-1-(9-Anthracenyl)ethylamine [(R)-1]
The enantiomer (R)-1 was prepared from sulfinamide (R,R )-5 (500
S
2
.48 g (82%).
mg, 1.54 mmol) using the same procedure as for (S)-1; yield: 310
mg (91%). This compound had the same physical and spectroscop-
ic properties as (S)-1, differing only in the optical rotation.
Mp 140–142 °C; [a] –66.6 (c 2, MeOH) [Lit.12 [a] –59.3 (c 3,
2
5
D
D
MeOH)].
Mp 113–115 °C (Lit. 110–113 °C); [a]D25 +16.1 (c 1, CHCl3)
1
5
Rf = 0.29 (hexanes–EtOAc, 8:2).
1
5
[
Lit. [a] +18 (c 1, CHCl )].
1
D 3
H NMR (300 MHz, CDCl ): d = 8.56 (s, 1 H), 8.47 (d, J = 9.3 Hz,
3
1
H), 8.31 (d, J = 8.3 Hz, 1 H), 8.05 (t, J = 8.3 Hz, 2 H), 7.45–7.68
(
S)-1-(9-Anthracenyl)-2,2,2-trifluoroethylamine (2)
(m, 4 H), 6.47 (qd, J = 8.5, 3.6 Hz, 1 H), 4.24 (d, J = 3.2 Hz, 1 H),
To a suspension of sulfinamide (S,R )-6 (2.87 g, 7.56 mmol) in
S
1
.30 (s, 9 H).
MeOH (10 mL) was added 4 M HCl in dioxane (3.78 mL). After 2
min the starting material was completely soluble and the solution
became orange. The solution was stirred at r.t. for 1 h, then concen-
trated to dryness. The residue was dissolved in CH Cl (30 mL) and
1
3
C NMR (75 MHz, CDCl ): d = 132.0, 131.5, 131.3, 131.2, 130.4,
3
1
5
29.7, 128.0, 127.8, 127.1, 125.4, 125.0, 124.4, 124.0, 123.0, 57.2,
6.5 (q, J = 33 Hz), 22.6.
2
2
1
9
washed with 10% aq NaOH soln (30 mL). The organic layer was
F NMR (282 MHz, CDCl ): d = –68.39 (d, J = 8.25 Hz).
3
separated and the aqueous layer was extracted with CH Cl (2 × 20
2
2
+
MS (EI, 70 eV): m/z (%) = 379 (4) [M ], 323 (11), 259 (100), 204
(
mL). The combined organic layers were dried (Na SO ) and con-
2
4
11), 178 (60), 57 (36).
centrated. The product was purified by flash chromatography
(CH Cl –hexane, 1:1 to 3:1) to obtain a yellow solid; yield: 1.93 g
+
HRMS–FAB: m/z [M ] calcd for C H F NOS: 379.1218; found:
3
2
2
2
0
20 3
(
93%).
79.1210.
Mp 140–142 °C; [a] +26.1 (c 3, MeOH) [Lit.12 [a] +24.0 (c 3,
2
5
D
D
(
R,R )-6 (Minor Diastereomer)
S
MeOH)].
The minor diastereomer, (R,R )-6, was obtained with CsF catalysis
S
1
H NMR (300 MHz, CDCl ): d = 9.04 (d, J = 8.6 Hz, 1 H), 8.52 (s,
3
(
see Table 2, entry 5).
1
H), 8.23 (d, J = 9 Hz, 1 H), 8.03 (d, J = 8.2 Hz, 2 H), 7.45–7.63
Rf = 0.19 (hexanes–EtOAc, 8:2).
(m, 4 H), 6.11 (q, J = 9 Hz, 1 H), 2.08 (br, 2 H).
1
H NMR (300 MHz, CDCl ): d = 8.72 (d, J = 8.5 Hz, 1 H), 8.58 (s,
13
3
C NMR (75 MHz, CDCl ): d = 132.2, 131.4, 130.6, 130.3, 130.3,
3
1
H), 8.32 (d, J = 9.1 Hz, 1 H), 8.01–8.08 (m, 2 H), 7.59–7.67 (m, 1
H), 7.44–7.55 (m, 3 H), 6.53 (qd, J = 8.7, 3.6 Hz, 1 H), 4.32 (d,
J = 2.5 Hz, 1 H), 1.15 (s, 9 H).
1
29.7, 129.5, 128.8, 127.2, 126.4, 126.0, 125.1, 124.9, 123.1, 53.7
(
q, J = 30 Hz).
1
9
F NMR (282 MHz, CDCl ): d = –70.52 (d, J = 9.3 Hz).
3
1
3
C NMR (75 MHz, CDCl ): d = 132.7, 131.9, 131.5, 131.1, 129.8,
3
+
MS (EI, 70 eV): m/z (%) = 275 (56) [M ], 206 (100), 178 (23), 103
1
1
29.6, 128.1, 127.7, 127.0, 126.9, 126.1, 125.2, 125.1, 124.0, 122.7,
20.8, 56.2, 55.9 (q, J = 33.3 Hz), 22.5.
(
11).
HRMS–FAB: m/z [M ] calcd for C16
75.0913.
+
1
9
H F N: 275.0922; found:
12 3
F NMR (282 MHz, CDCl ): d = –67.76 (d, J = 8.7 Hz).
3
2
+
MS (EI, 70 eV): m/z (%) = 379 (5) [M ], 323 (10), 259 (100), 204
(12), 178 (64), 57 (45).
+
Acknowledgment
HRMS–FAB: m/z [M ] calcd for C H F NOS: 379.1218; found:
2
0
20 3
3
79.1228.
We thank I. Chávez, R. Gaviño, E. Huerta, M. A. Peña, J. Pérez, B.
Quiroz, H. Ríos and L. Velasco for their technical assistance, and
Instituto de Química, UNAM and DGAPA-UNAM (IACOD-
IA200811) for financial support.
(
S)-1-(9-Anthracenyl)ethylamine [(S)-1]
Sulfinamide (S,R )-5 (500 mg, 1.54 mmol) was dissolved in a mix-
S
ture of MeOH (5 mL) and 4 M HCl in dioxane (3 mL). The mixture
Synthesis 2011, No. 17, 2817–2821 © Thieme Stuttgart · New York

PAPER
Asymmetric Synthesis of Chiral Amines with a 9-Anthracenyl Group
(8) Even with low selectivity the difference in R of the
2821
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Synthesis 2011, No. 17, 2817–2821 © Thieme Stuttgart · New York