Asymmetric Synthesis of a New Bidentate As/P=S Ligand
were removed and the residue was extracted with dichloromethane
and water and the organic layer was dried with MgSO4. Removal
of the solvent gave 4 as a solid, which was then recrystallized from
dichloromethane/acetonitrile to give the product as orange yellow
crystals (0.075 g, 96%); m.p. 131–132 °C. C28H29AsBr2NPPdS
(783.69): calcd. C 42.9, H 3.7, N 1.8, S 4.1; found C 42.7, H 3.4,
N 1.7, S 4.3. 31P{1H} NMR (CD2Cl2): δ = 51.4 ppm. 1H NMR
(CD2Cl2): δ = 1.59 (s, 3 H, =CCH3), 1.67 (s, 3 H, =CCH3), 2.12
Conclusions
The cycloaddition reaction between DMPA and di-
phenylvinylphosphane sulfide was promoted by a chiral
palladium complex, however, both the resulting dia-
stereomers 2 and the corresponding dihalogen complexes 3
and 4 could not be separated into their enantiomeric coun-
terparts via column chromatography or fractional crystalli-
zation. When the chiral metal promoter was changed from
palladium to platinum, the reaction selectivity is similar al-
though the rate improved drastically. However, the major
isomer (Sc,RAs)-7 and the dichloro complex (–)-8 could be
separated via fractional crystallization and column
chromatography. Alternatively they could be converted into
the corresponding iodo complexes (Sc,RAs)-9 and (–)-10.
The two iodo complexes were readily separated by means
of column chromatography. The optically pure As/P=S li-
gand (+)-11 could be liberated by treatment of (–)-9 with
KCN. The arsanylidene elimination reaction was observed
on the racemic or chiral free ligand 9.
3
2
(dd, JHH = 11.0, JPH = 25.8 Hz, 1 H, PCH), 2.85 (m, 1 H,
3
CHCH2), 3.39 (d, JHH = 4.8 Hz, 1 H, AsCH), 3.41 (m, 1 H,
CHCH2), 3.55 (s, 1 H, AsCH), 7.43–8.28 (m, 15 H, arom.) ppm.
Preparation of Compound 5: Dibromo complex
4 (0.16 g,
0.22 mmol) in dichloromethane (30 mL) was treated with potas-
sium cyanide (0.2 g) in water (30 mL) for 3 min at room tempera-
ture in air. The solution changed from red to colorless. The organic
layer was washed with water (3ϫ30 mL), dried (MgSO4), and the
solvent was removed. The residue was purified by column
chromatography with dichloromethane to give compound 5 as a
white solid (0.06 g, 84%); m.p. 94–95 °C. 31P{1H} NMR (CDCl3):
1
δ = 49.0 ppm. H NMR (CDCl3): δ = 1.54 (s, 3 H, =CCH3), 1.70
3
3
(s, 3 H, =CCH3), 2.15 (m, 1 H, PCH), 2.78 (dd, JHH = 16.2, JPH
3
3
= 32.3 Hz, 1 H, CHCH2), 3.58 (dd, JHH = 10.0, JPH = 15.2 Hz,
1 H, CHCH2), 5.37 (s, 1 H, =CH), 5.39 (s, 1 H, =CH), 7.42–7.95
(m, 10 H, arom.) ppm. 13C NMR (CDCl3): δ = 19.0 (CH3), 19.9
(d, 4JPC = 7.3 Hz, CH3), 22.6 (d, 2JPC = 6.7 Hz, CH2), 37.1 (d, 1JPC
Experimental Section
3
2
= 220.7 Hz, PCH), 116.1 (d, JPC = 20.4 Hz, =CH), 120.6 (d, JPC
= 53.7 Hz, =CH), 128.0, 128.1, 128.4, 128.6, 129.9, 130.9, 131.1,
131.19, 131.2, 131.3, 131.4, 131.9, 132.3, 132.4, 132.9 (arom.), 133.4
General Methods: Reactions involving air-sensitive compounds
were performed under inert argon using standard Schlenk tech-
niques. Solvents were dried and freshly distilled according to stan-
dard procedures and degassed prior to use when necessary. NMR
spectra were recorded at 25 °C on Bruker Avance 300, 400, and 500
spectrometers. Optical rotations were measured on the specified
solution in a 0.1 dm cell at 20 °C with a Perkin–Elmer 341 polari-
meter. Elemental analysis was performed by the Elemental Analysis
Laboratory of the Division of Chemistry and Biological Chemistry
at Nanyang Technological University. Melting points were mea-
sured with a Stanford Research Systems OptiMelt MPA 100 instru-
ment and are uncorrected. Diphenylvinylphosphane sulfide,[20] (+)-
1[15] and (+)-6[16] were prepared following literature procedures.
4
3
(d, JPC
= 14.8 Hz, =CCH3), 137.8 (d, JPC = 47.5 Hz,
=CCH3) ppm. EI-MS: m/z (%)= 325.1 [M]+.
Preparation of Complexes (Sc,RAs)-7, (–)-8, (–)-9, and (Sc,RAs)-10:
solution of (+)-6 (0.26 g, 0.39 mmol) in dichloromethane
A
(30 mL) was stirred for 2 h in the presence of a solution of silver
perchlorate (0.15 g) in water (1 mL). The organic layer, after the
removal of AgCl, was then washed with water (3ϫ30 mL), dried
(MgSO4), and subsequently treated with diphenylvinylphosphane
sulfide (0.10 g, 0.39 mmol) for 5 d at room temperature. The crude
diastereomeric mixture was treated with excess concentrated hydro-
chloric acid (2 mL) for 20 min at room temperature.
Caution! Perchlorate salts of metal complexes are potentially explos-
ive compounds and should be handled with care.
Method A: The mixture was washed with water (3ϫ30 mL), dried
(MgSO4), and subsequently recrystallized from dichloromethane/
diethyl ether to give (–)-8 as pale yellow crystals (0.08 g, 83%).
[α]D = –57.7 (c = 0.3, CH2Cl2); m.p. Ͼ300 °C. C26H26AsCl2PPtS
(742.43): calcd. C 42.1, H 3.5, S 4.3; found C 42.2, H 3.9, S 4.1.
Preparation of Dichloro Complex 3: A solution of (+)-1 (0.47 g,
0.82 mmol) in dichloromethane (50 mL) was stirred for 2 h in the
presence of a solution of silver perchlorate (1.0 g) in water (1 mL).
The organic layer, after the removal of AgCl, was then washed with
water (3ϫ50 mL), dried (MgSO4), and subsequently treated with
diphenylvinylphosphane sulfide (0.20 g, 0.82 mmol) for 13 d at
40 °C. The crude diastereomeric mixture was treated with excess
concentrated hydrochloric acid (2 mL) for 10 min at room tempera-
ture. The mixture was then washed with water (3ϫ50 mL), dried
(MgSO4), and subsequently recrystallized from acetonitrile to give
3 as brown yellow crystals (0.40 g, 70%); m.p. 126–127 °C.
C26H26AsCl2PPdS (653.77): calcd. C 48.4, H 4.2, N 2.0, S 4.6;
found C 48.0, H 3.9, N 1.7, S 4.5. 31P{1H} NMR (CD2Cl2): δ =
1
31P{1H} NMR (CD2Cl2): δ = 43.9 (s, JPtP = 147 Hz, 1 P) ppm. H
NMR (CD2Cl2): δ = 1.46 (s, 3 H, =CCH3), 1.59 (s, 3 H, =CCH3),
3
3
1.92 (dd, JHH = 1.5, JHH = 12.2 Hz, 1 H, CHCH2), 2.94 (m, 1
3
H, PCH), 3.16 (d, JHH = 10.6 Hz, 1 H, CHCH2), 3.38 (s, 1 H,
AsCH), 3.42 (d, JHH = 5.2 Hz, 1 H, AsCH), 7.32–8.18 (m, 15 H,
3
arom.) ppm.
The solvents from the remaining solution were removed and the
residue was isolated by column chromatography with dichloro-
methane/diethyl ether as elute to give (Sc,RAs)-7 as a yellow solid
(0.18 g, 71%). [α]D = +196.4 (c = 0.3, CH2Cl2); m.p. 160–161 °C.
C40H42AsClNO4PPtS (969.26): calcd. C 49.6, H 4.4, N 1.5, S 3.3;
found C 49.4, H 4.6, N 1.4, S 3.4. 31P{1H} NMR (CDCl3): δ =
1
51.3 ppm. H NMR (CD2Cl2): δ = 1.63 (s, 3 H, =CCH3), 1.64 (s,
3
2
3 H, =CCH3), 2.15 (dd, JHH = 10.6, JPH = 25.4 Hz, 1 H, PCH),
2.95 (m, 1 H, CHCH2), 3.40 (d, JHH = 5.0 Hz, 1 H, AsCH), 3.45
(m, 1 H, CHCH2), 3.55 (s, 1 H, AsCH), 7.42–8.29 (m, 15 H,
arom.) ppm.
3
1
47.7 (s, JPtP = 63 Hz, 1 P) ppm. H NMR (CDCl3): δ = 1.61 (s, 3
3
H, =CCH3), 1.86 (d, JHH = 6.2 Hz, 3 H, CHCH3), 2.00 (s, 3 H,
Preparation of Dibromo Complex 4: The solution of 3 (0.07 g,
0.10 mmol) in dichloromethane (50 mL) was treated with excess
=CCH3), 2.63 (m, 1 H, CHCH2), 2.71 (s, 3 H, NCH3), 2.84 (m, 1
H, CHCH2), 3.20 (d, JHH = 6.5 Hz, 1 H, AsCH), 3.37 (s, 3 H,
3
potassium bromide (0.20 g) in acetone (50 mL) and water (10 mL) NCH3), 3.70 (s, 1 H, AsCH), 3.86 (broad s, 1 H, PCH), 4.65 (q,
and stirred vigorously for 10 min at room temperature. The solvents
3JHH = 6.2 Hz, 1 H, CHCH3), 6.61–7.97 (m, 21 H, arom.) ppm.
Eur. J. Inorg. Chem. 2010, 1865–1871
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
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