1
356
T. Imamoto et al.
PAPER
1
H NMR (CDCl ): d = 0.31–1.04 (br q, 3 H), 1.22 (d, JH–P = 14.3 Hz,
mixture was allowed to warm to 0 °C during 1 h, sulfur powder (9.6
g, 0.30 mmol) was added to the reaction mixture in one portion. The
resulting solution was allowed to warm to r.t., and stirring was con-
3
9
1
H), 2.05 (m, 2 H), 2.22 (m, 2 H), 2.35 (m, 1 H), 2.55 (m, 1 H).
3
C NMR (CDCl ): d = 17.8 (d, JC–P = 38.6 Hz), 17.9 (t, JC–P = 18.9
3
tinued for 2 h. H O (200 mL) was then slowly added to quench the
2
Hz), 24.3, 28.2 (d, J = 18.9 Hz), 32.2 (d, JC–P = 34.5 Hz).
3
C–P
reaction. The organic layer was washed with H O (200 mL) and
2
1
P NMR (CDCl ): d = 64.7 (br q).
3
brine (200 mL), dried (Na SO ), and concentrated. The resulting
2
4
pasty solid was passed through an alumina column, followed by re-
crystallization from n-hexane to give colorless crystals; yield: 15.6
g (48%); mp 120–121 °C.
(
1S,1¢S,2R,2¢R)-1,1¢-Di-tert-butyl-2,2¢-diphosphetanyl Dibo-
rane (3) and (1S,1¢R,2R,2¢S)-1,1¢-Di-tert-butyl-2,2¢-diphospheta-
nyl Diborane (4)
s-BuLi (53 mL, 0.99 M, 52.5 mmol) was added to a solution of (–)-
sparteine (14.06 g, 60 mmol) in Et O (100 mL) at –78 °C. After stir-
–
1
IR (KBr): 2960, 1462, 1362, 945, 718, 678 cm .
1
3
H NMR (CDCl ): d = 1.30 (d, J = 16.4 Hz, 9 H), 1.95–2.15 (m,
3 H–P
2
ring for 30 min, 1-tert-butylphosphetane 1-borane (2; 7.20 g, 50
2 H), 2.25–2.65 (m, 1 H), 2.45–2.65 (m, 2 H), 2.60–2.80 (m, 2 H).
mmol) in Et O (100 mL) was slowly added to the solution, and the
13
2
= 21.1 Hz), 23.86 (d, 2J
2
C NMR: d = 14.15 (d, J
= 2.7 Hz),
C–P
C–P
mixture was kept at the same temperature for 5 h. CuCl (10.1 g, 75
2
3
0.97 (d, J = 45.35 Hz), 33.92 (d, JC–P = 34.71 Hz).
C–P
mmol), dried in vacuo at 130 °C for 2 h, was added in one portion
with vigorous stirring. The cooling bath was removed and the mix-
ture was allowed to warm to r.t. during 2 h, and stirring was contin-
ued for another 12 h before quenching the reaction with aq NH3
3
1
1
P NMR ( H decoupled, CDCl ): d = 82.07.
3
+
HRMS: m/z calcd for C H PS (M ): 162.0632; found: 162.0631.
7
15
(
25%, 250 mL). To this mixture was added EtOAc (150 mL) and the
(
(
1R,1¢R,2R,2¢R)-1,1¢-Di-tert-butyl-2,2¢-diphosphetanyl Disulfide
8) and (1R,1¢S,2R,2¢S)-1,1¢-Di-tert-butyl-2,2¢-diphosphetanyl
organic layer was separated. The aqueous layer was extracted with
EtOAc (3 × 150 mL). The combined organic layers were washed
with 5% aq NH , 2 M HCl, and brine, dried (Na SO ) and concen-
trated. Purification of the residual solid by flash column chromatog-
raphy on silica gel afforded the C -symmetric product 3 (94.7% ee)
Disulfide (9)
3
2
4
s-BuLi (37 mL, 0.98 M, 36 mmol) was added to a solution of (–)-
sparteine (8.44 g, 36 mmol) in Et O (70 mL) at –78 °C. After stir-
ring for 30 min, 1-tert-butylphosphetane sulfide (7; 4.86 g, 30
mmol) in toluene (30 mL) was slowly added to the solution, and the
mixture was kept at the same temperature for 5 h. CuCl (6.05 g, 45
mmol) was added in one portion with vigorous stirring. The cooling
bath was removed and the mixture was allowed to warm to r.t. over
2
2
(
1.73 g, 24%) and the meso isomer 4 (2.23 g, 31%). Several recrys-
tallizations from EtOAc furnished pure 3 (>99% ee); yield: 1.1 g
15%).
2
(
3
2
h, and the stirring was continued for another 12 h before quench-
2
5
Mp 147–149 °C (dec); [a]D –96.9 (c = 1.01, CHCl ); HPLC anal-
ysis: Daicel Chiralcel OD-H, i-PrOH–hexane = 1:99, 0.5 mL/min,
UV 210 nm, (1R,1¢R,2S,2¢S) t = 12.1 min, (1S,1¢S,2R,2¢R) t = 13.5
min, (meso) t = 18.6 min.
3
ing the reaction with aq NH (25%, 150 mL). To this mixture was
added EtOAc (100 mL) and organic layer was separated. The aque-
ous layer was extracted with EtOAc (3 × 100 mL). The combined
organic layers were washed with 5% aq NH , 2 M HCl, and brine,
3
1
2
3
3
–
1
dried (Na SO ) and concentrated. Purification of the yellow solid by
IR (KBr): 2965, 2860, 2365, 1460, 1365, 1060 cm .
2
4
flash column chromatography on silica gel using hexane–EtOAc
5:1) as the eluent afforded a mixture of C -symmetric compound 8
1
H NMR (CDCl ): d = 0.80–1.13 (m, 6 H), 1.23 (d, JH–P = 15 Hz, 18
3
(
2
H), 1.72 (m, 2 H), 2.08 (m, 4 H), 2.43 (m, 2 H), 3.21 (m, 2 H).
and meso compound 9 (1.94 g, 40%). The mixture was again puri-
fied by flash column chromatography on silica gel using hexane–
acetone (5:1) as the eluent to give the crude product 8 (95% ee, 1.51
g, 30%). Several recrystallizations from EtOAc furnished enantio-
merically pure 8; yield: 0.49 g (10%); >99% ee. HPLC analysis:
Daicel Chiralcel OD-H, hexane–i-PrOH (95:5), 0.5 mL/min,
1
3
C NMR (CDCl ): d = 13.7 (d, JC–P = 39.4 Hz), 22.9 (t, JC–P = 14.7
3
Hz), 24.9, 29.7 (d, JC–P = 16.4 Hz), 32.2 (d, JC–P = 34.5 Hz).
3
1
P NMR (CDCl ): d = 67.8 (d, JP–B = 55.8 Hz).
3
Anal. Calcd for C H B P : C, 58.79; H, 11.98. Found: C, 58.77;
H, 12.07.
14
34
2 2
(
1S,1¢S,2S,2¢S) t = 10.8 min, (1R,1¢R,2R,2¢R) t = 11.9 min, (meso)
1
2
t3 = 16.8 min.
4
Mp 166–168 °C (dec.).
8
2
5
–
1
C
o
l
o
r
l
e
s
s
n
e
e
d
l
e
s
;
m
p
2
1
2
–
2
1
4
°
C
;
[
a
]
–
1
7
7
(
c
=
0
.
9
8
,
C
H
C
l
)
.
IR (KBr): 2960, 2360, 1460, 1365, 1060 cm .
D
3
–
1
1
IR (KBr): 2970, 2947, 2364, 1460, 1366, 896, 808, 708, 646 cm .
H NMR (CDCl ): d = 0.32–1.10 (m, 6 H), 1.20 (d, J = 14.0 Hz,
3
H–P
9
2
1
H), 1.32 (d, JH–P = 13.3 Hz, 9 H), 1.94 (m, 2 H), 2.02 (m, 2 H),
.20 (m, 1 H), 2.35 (m, 1 H), 2.48 (m, 1 H), 2.77 (m, 1 H), 2.88 (m,
H), 3.35 (m, 1 H).
1
3
H NMR (CDCl ): d = 1.30 (d, J = 17.0 Hz, 18 H), 1.95–2.15
m, 4 H), 2.25–2.50 (m, 2 H), 2.55–2.75 (m, 2 H), 3.60–3.84 (m, 2
3
H–P
(
H).
13
1
3
C NMR (CDCl ): d = 14.2 (d, JC–P = 37.7 Hz), 15.5 (t, JC–P = 36.9
2
3
3
C NMR (CDCl ): d = 19.53 (dd, J = 21.7 Hz, J = 18.3 Hz),
3
C–P
C–P
Hz), 24.8, 26.4, 28.4 (d, JC–P = 16.4 Hz), 28.9 (d, JC–P = 18.0 Hz),
4
24.25 (s), 25.85 (dd, J
= 47.2 Hz, J = 1.8 Hz), 35.41 (dd,
C–P
C–P
2
4
9.8 (d, JC–P = 16.4 Hz), 32.9 (d, JC–P = 6.8), 33.3 (d, JC–P = 6.6 Hz,
0.2 (d, JC–P = 32.8 Hz).
4
J
= 34.1 Hz, JC–P = 2.5 Hz), 38.02 (dd, JC–P = 44.7 Hz,
C–P
2
JC–P = 6.8 Hz).
3
1
P NMR (CDCl ): d = 71.5, 78.0.
31
1
3
P NMR ( H decoupled, CDCl ): d = 90.3.
3
Anal. Calcd for C H B P : C, 58.79; H, 11.98. Found: C, 58.92;
H, 12.10.
+
14
34
2
2
HRMS: m/z calcd for C H P S (M + H ): 323.1186; found:
14 29 2 2
3
23.1198.
Anal. Calcd for C H P S : C, 52.15; H, 8.75. Found: C, 52.24; H,
1
4
28 2 2
1
-tert-Butylphosphetane Sulfide (7)
8
.80.
t-Butylphosphine (150 g of 12% n-hexane solution, 0.200 mol) was
added to a solution of 1,3-dichloropropane (22.6 g, 0.200 mol) and
THF (1 L) under argon via syringe. To this mixture was slowly add-
ed n-BuLi (277 mL of 1.59 M hexane solution, 0.440 mol) at –78 °C
and the mixture was kept at the same temperature for 1 h. After the
9
Colorless needles; mp 250–252 °C.
–
1
IR (KBr): 2969, 2360, 1460, 1363, 893, 811, 731, 668 cm .
Synthesis 2004, No. 9, 1353–1358 © Thieme Stuttgart · New York