Sulfinylmethyl phosphines as chiral ligands in the intermolecular pauson - Khand reaction

Article abstract of DOI:10.1021/om900438v

A new family of enantiomerically pure p-tolyl and tert-butyl sulfinylmethyl phosphine ligands is described. Ligands with an extra chiral center in the central carbon atom were prepared by phosphinylation of benzyl and homobenzyl sulfoxides. Ligand exchang

Full text of DOI:10.1021/om900438v

Organometallics 2009, 28, 4571–4576 4571
DOI: 10.1021/om900438v
Sulfinylmethyl Phosphines as Chiral Ligands in the Intermolecular
Pauson-Khand Reaction
Catalina Ferrer, Antoni Riera,* and Xavier Verdaguer*
´
ꢀ
Unitat de Recerca en Sıntesi Asimetrica (URSA-PCB), Institute for Research in Biomedicine
´
ꢀ
(IRB Barcelona), and Departament de Quımica Organica, Universitat de Barcelona,
c/Baldiri Reixac 10, E-08028 Barcelona, Spain
Received May 25, 2009
A new family of enantiomerically pure p-tolyl and tert-butyl sulfinylmethyl phosphine ligands is
described. Ligands with an extra chiral center in the central carbon atom were prepared by
phosphinylation of benzyl and homobenzyl sulfoxides. Ligand exchange reaction of these com-
pounds with Co2-alkyne complexes afforded up to 6:1 dr. The resulting bridged complexes were
tested in the intermolecular Pauson-Khand reaction to provide up to 97% ee.
Introduction
The main feature of these bidentate ligands is that the
phosphorus atom provides metal affinity, while the sulfur
moiety is the source of chirality. However, few examples of
phosphorus-sulfoxide bidentate ligands have been described
in the literature.9,10 One of the few examples of phosphorus-
sulfoxide bidentate ligands described is the p-tolylsulfinyl-
methyl phosphine 1 (Figure 1). When pure, compound 1 is
stable toward oxygen migration, although it can be prepared
in only 23% yield.11
Considering the success achieved with the use of PNSO
ligands in the asymmetric intermolecular PKR, we thought it
important to study the effect of changing the central nitrogen
for a carbon atom and the introduction of an extra chiral
center in the ligand. Thus, here we describe the synthesis of a
family of ligands of general formula III (PCSO ligands), their
coordination behavior toward alkyne-dicobalt complexes,
and the intermolecular asymmetric PKR of the resulting
complexes.
Since its discovery in 1973, the ability to synthesize cyclo-
pentenones in a straightforward way aroused interest in the
Pauson-Khand reaction (PKR)1 and has led to the devel-
opment of new complexes and catalysts capable of perform-
ing the reaction in an enantioselective fashion.2 Apart from
cobalt, other metals, such as Ru,3 Ir,4 Ni,5 or Rh,6 have also
been successfully used in the intramolecular version of this
reaction. Currently, one of the major challenges still to be
tackled is the development of an efficient catalyst for the
asymmetric intermolecular version of the PKR. In our
efforts to find efficient ligands for the asymmetric PKR,7
we have recently reported a new family of N-phosphine
sulfinamide (PNSO) ligands that give high yields and
high ee’s in the asymmetric intermolecular PKR (Figure 1).8
*Corresponding author. E-mail: antoni.riera@irbbarcelona.org;
xavier.verdaguer@irbbarcelona.org.
(1) Khand, I. U.; Knox, G. R.; Pauson, P. L.; Watts, W. E.; Foreman,
M. I. J. Chem. Soc., Perkin Trans. 1 1973, 977–981.
Results and Discussion
(2) For general reviews see: (a) Laschat, S.; Becheanu, A.; Bell, T.;
Baro, A. Synlett 2005, 2547–2570. (b) Gibson, S. E.; Mainolfi, N. Angew.
Chem., Int. Ed. 2005, 44, 3022–3037. (c) Gibson, S. E.; Stevenazzi, A.
Angew .Chem., Int. Ed. 2003, 42, 1800–1810. (d) Bonaga, L. V. R.; Krafft,
M. E. Tetrahedron 2004, 60, 9795–9833. (e) Shibata, T. Adv. Synth. Catal.
2006, 348, 2328–2336. (f) Rivero, M. R.; Adrio, J.; Carretero, J. C. Synlett
2005, 26–41. (g) Struebing, D.; Beller, M. Top. Organomet. Chem. 2006,
18, 165–178.
The general strategy for the preparation of PCSO ligands
was the reaction of the corresponding R-sulfinyl carbanions
with Ph2PCl (Scheme 1). Thus, ligand 1 was prepared by
alkylation of commercially available (R)-p-tolyl methyl sulf-
oxide (2) with chlorodiphenyl phosphine at -78 °C, followed
by protection in situ with borane to prevent oxygen migra-
tion. Using this strategy, the yield of compound 1-BH3 was
improved from 23% to 43%.
(3) Morimoto, T.; Chatani, N.; Fukumoto, Y.; Murai, S. J. Org.
Chem. 1997, 62, 3762–3765.
(4) Shibata, T.; Takagi, K. J. Am. Chem. Soc. 2000, 122, 9852–9853.
ꢀ
(5) Pages, L.; Llebaria, A.; Camps, F.; Molins, E.; Miravitlles, C.;
For the preparation of PCSO ligands bearing an addi-
tional chiral center on the central carbon atom, benzyl
and homobenzyl sulfoxides 3 and 5 were used as starting
Moreto, J. M. J. Am. Chem. Soc. 1992, 114, 10449–10461.
(6) Jeong, N.; Sung, B. K.; Choi, Y. K. J. Am. Chem. Soc. 2000, 122,
6771–6772.
ꢀ
(7) (a) Verdaguer, X.; Moyano, A.; Pericas, M. A.; Riera, A.;
Maestro, M. A.; Mahia, J. J. Am. Chem. Soc. 2000, 122, 10242–10243.
(b) Verdaguer, X.; Pericas, M. A.; Riera, A.; Maestro, M. A.; Mahia, J.
ꢀ
(9) (a) Hiroi, K.; Suzuki, Y.; Kawagishi, R. Tetrahedron Lett. 1999,
40, 715–718. (b) Wenschuh, E.; Fritzsche, B. J. Prakt. Chem. 1970, 312,
129–134.
ꢁ
ꢁ
Organometallics 2003, 22, 1868–1877. (c) Verdaguer, X.; Lledo, A.; Lopez-
ꢀ
Mosquera, C.; Maestro, M. A.; Pericas, M. A.; Riera, A. J. Org. Chem. 2004,
69, 8053–8061. (d) Sola, J.; Riera, A.; Verdaguer, X.; Maestro, M. A. J. Am.
ꢀ
ꢁ
(10) For general reviews on chiral sulfoxides see: (a) Fernandez, I.;
Chem. Soc. 2005, 127, 13629–13633.
Khiar, N. Chem. Rev. 2003, 103, 3651–3705. (b) Mellah, M.; Voituriez, A.;
Schulz, E. Chem. Rev. 2007, 107, 5133–5209.
(11) Alcock, N. W.; Brown, J. M.; Evans, P. L. J. Organomet. Chem.
ꢀ
ꢁ
(8) (a) Sola, J.; Reves, M.; Riera, A.; Verdaguer, X. Angew. Chem.,
ꢁ
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Int. Ed. 2007, 46, 5020–5023. (b) Reves, M.; Achard, T.; Sola, J.; Riera, A.;
Verdaguer, X. J. Org. Chem. 2008, 73, 7080–7087.
1988, 356, 233–247.
r
2009 American Chemical Society
Published on Web 07/07/2009
pubs.acs.org/Organometallics

4572 Organometallics, Vol. 28, No. 15, 2009
Ferrer et al.
Figure 1. Phosphino-sulfinamide (PNSO) and sulfinylmethyl
phosphines (PCSO) ligands.
Figure 2. X-ray crystal structure of 6-BH3.
Scheme 1. Synthesis of p-Tolyl PCSO Ligands
Scheme 2. Synthesis of tert-Butyl PCSO Ligands
materials (Scheme 1). Enantiomerically pure sulfoxides 3
and 5 were obtained by reaction of (1R,2S,5R)-(-)-menthyl
(S)-p-toluenesulfinate with a Grignard reagent.12 Reaction
of the sulfoxide anions with chlorodiphenyl phosphine at
-78 °C and in situ protection with borane led to the desired
ligands 4-BH3 and 6-BH3. As expected, phosphinylation of
lithium R-sulfinyl carbanions with chlorodiphenyl phos-
phine proved to be highly diastereoselective, providing the
corresponding SS,CR isomer as a major product. Ligand
4-BH3 was obtained as a 13:1 mixture of diastereomers, from
which the major SS,CR compound was isolated by crystal-
lization. Moreover, the reaction with p-tolyl homobenzyl
sulfoxide was completely stereoselective. The relative con-
figuration for these compounds was firmly established by
single-crystal X-ray analysis of 6-BH3 (Figure 2).
Addition of Ph2PCl occurs with stereoselectivity similar to
the addition of D2O, MeI, ketones, and imines to lithium
R-sulfinyl carbanions.13,14 Electrophilic assistance of the
Li ion bound to the sulfoxide oxygen with concomitant
inversion of the R-sulfinyl carbanion accounts for the ster-
eochemistry observed.15 Vedejs and co-workers used the
reaction of lithium R-sulfinyl carbanions with Ph2PCl in
the synthesis of thiol esters; however, they used racemic
sulfoxides, and the intermediate phosphine-sulfoxides were
not isolated.16 Thus, with the help of borane-phosphorus
protection, optically pure phosphine-sulfoxides 4 and 6
could be isolated for the first time.
sulfoxide 7 with MeLi at -78 °C and reaction with Ph2PCl gave
the desired PCSO ligands in 65% yield as a 6:1 diastereomeric
mixture. The selectivity was increased to 20:1 using n-BuLi at
0 °C. However, the yield in this case was only 25%. The major
diastereomer SR,CS was purified by flash chromatography.
Following the same experimental procedure, the analogous
tert-butyl homobenzyl sulfoxide 10 provided only trace
amounts of the desired PCSO ligand along with diphenyl styryl
phosphine as the major reaction product (Scheme 2). The
desired product may have been unstable due to a competing
sulfoxide β-elimination pathway.
Deprotection of the borane group with DABCO and
complexation of the PCSO ligands to dicobaltalkyne com-
plexes were carried out in toluene at 75 °C in a one-pot
procedure (Table 1). Reaction of ligand 1-BH3 with tri-
methylsilylacetylene dicobaltcarbonyl gave only the corre-
sponding pentacarbonyl complex, in which only the
phosphorus atom was coordinated to cobalt, in a 1:1 mixture
of diastereomers (Table 1, entry 1). Extended heating at
higher temperature produced small amounts of bridged
complex and led to decomposition of the starting material.
Conversely, ligand exchange reaction with 4-BH3 with either
trimethylsilylacetylene dicobaltcarbonyl (Table 1, entry 2) or
phenylacetylene dicobaltcarbonyl (Table 1, entry 3) gave the
corresponding bridged complexes in good yield as a 1:1
mixture of diastereomers. Ligand 6-BH3 proved to be some-
what more selective, and complexes 13a/13b and 14a/14b
were obtained in a 2:1 diastereomeric ratio (Table 1, entries
4 and 5). Complexes 13a/13b and 14a/14b derived from
ligand 6-BH3 were more prone to decomposition than those
derived from ligand 4-BH3, and they were isolated in lower
yield. All these diastereomeric mixtures were separated by
silica gel chromatography except for complex 14b. Diaster-
eomeric complexes can also be distinguished from one
another by 1H NMR spectroscopy by means of the terminal
For the synthesis of the analogous optically pure tert-butyl
PCSO ligands, a similar methodology was pursued (Scheme 2).
In this case, addition of the Grignard reagents to Ellman’s (R)-
tert-butanethiosulfinate gave the corresponding enantiomeri-
cally pure sulfoxides 7 and 10.17 Metalation of tert-butyl benzyl
(12) Maitro, G.; Vogel, S.; Sadaoui, M.; Prestat, G.; Madec, D.; Poli,
G. Org. Lett. 2007, 9, 5493–5496.
(13) Solladie, G.; Moine, G. J. Am. Chem. Soc. 1984, 106, 6097–6098.
(14) Crucianelli, M.; Bravo, P.; Arnone, A.; Corradi, E.; Meille, S. V.;
Zanda, M. J. Org. Chem. 2000, 65, 2965–2971.
(15) Marsh, M.; Massa, W.; Harms, K.; Baum, G.; Boche, G. Angew.
Chem., Int. Ed. Engl. 1986, 25, 1011–1012.
(16) Vedejs, E.; Meier, G. P.; Powell, D. W.; Mastalerz, H. J. Org.
Chem. 1981, 46, 5253–5254.
(17) Cogan, D. A.; Liu, G.; Kim, K.; Backes, B. J.; Ellman, J. A. J.
Am. Chem. Soc. 1998, 120, 8011–8019.

Article
Organometallics, Vol. 28, No. 15, 2009 4573
Table 1. Complexation of p-Tolyl PCSO Ligands
Table 2. Pauson-Khand Reaction of Optically Pure Complexes
with Norbornadiene
entry ligand
R
H
X
t (h) yield (%)
d.r.a
complex
entry
complex
L
X
t (h)
yield (%)
eea
product
1
2
3
4
5
1-BH3
TMS 16
1:1b
1.2:1
1:1
2:1
2:1
1
2
3
4
5
6
7
8b
11a
11b
12a
12b
13a
13b
14a
16b
4
4
4
4
6
6
6
9
TMS
TMS
Ph
16
16
6
84
87
79
90
77
94
98
75
75
66
88
97
83
96
87
88
(þ)-17
(-)-17
(þ)-18
(-)-18
(þ)-17
(-)-17
(þ)-18
(-)-18
4-BH3 Ph TMS
4-BH3 Ph Ph
6-BH3 Bn TMS
6-BH3 Bn Ph
1
6
1
1
62
60
36
33
11a/11b
12a/12b
13a/13b
14a/14b
Ph
1
TMS
TMS
Ph
0.5
0.5
0.5
5
a As determined by 1H NMR spectroscopy. b Only the pentacar-
bonylic complex was obtained.
Ph
a Enantiomeric excess determined by either chiral GC or HPLC.
Scheme 3. Complexation of Ligand 8-BH3
b Reaction carried out at room temperature.
Scheme 4. Isomerization of Ligand 8-BH3 and Complexation of
Ligand 9-BH3 with Phenylacetylene Dicobaltcarbonyl
alkyne resonance. In the Xa series of diastereomers this
proton appears at lower field than the one corresponding
to the Xb series.18
the complexation reaction. A 6:1 diastereomeric mixture of
ligands 8-BH3 and 9-BH3 was treated with MeLi at 0 °C for
1 h and then quenched with water (Scheme 4). This treat-
ment resulted in the isomerization of ligand 8-BH3 to give a
1:1 mixture of diastereomers 8-BH3 and 9-BH3, which
were separated by chromatography. The reaction of ligand
9-BH3 with phenylacetylene dicobaltcarbonyl proved to be
quite selective, and a 1:6 mixture of complexes 16a/16b was
obtained in 30% yield (Scheme 4). Ligand 9 provided a trans
disposition between the tert-butyl and the phenyl groups in
16a/16b, which allowed the coordination of the sulfinyl
fragment to the cobalt center. Nevertheless, the pentacar-
bonylic complex, in which the sulfur moiety is not coordi-
nated, was isolated in 27% yield.
Similar results to those for the complexation of ligand
1-BH3 were obtained in the reaction of ligand 8-BH3 with
phenylacetylene dicobaltcarbonyl. Only coordination of the
phosphorus atom was observed, which yielded a 1:1 mixture
of pentacarbonylic complexes 15a/15b (Scheme 3). In this
case, complexes 15a and 15b were quite stable and were
isolated in 92% yield; however, they could not be separated
by either crystallization or chromatography. Extended heat-
ing for longer periods or higher temperature led only to
the decomposition of materials. Treatment of 15a/15b with
N-methylmorpholine N-oxide (NMO) in CH2Cl2 at room
temperature to create a coordinative vacancy at the cobalt
atom that would be occupied by a sulfur atom led only to
oxidation of the latter.
Finally, diastereomerically and optically pure complexes
obtained in the complexation reactions were tested in the
intermolecular PKR with norbornadiene under thermal
activation in toluene at 80 °C (Table 2). Complexes contain-
ing PCSO ligands are very active in this process, since all the
corresponding product enones were obtained in good yield
and good to excellent enantiomeric excess. As a general
trend, complexes of the Xa series provided dextrorotatory
product enones, while Xb complexes gave levorotatory
ones. This observation allowed us to establish the absolute
configuration of the bridged series of complexes Xa and Xb.
In a similar fashion to that for N-phosphino sulfinamide
ligands, dextrorotatory products are indicative of sulfoxide
The difficulty in the coordination of sulfur to the metal
center in complexes 15a/15b may be attributed to the steric
hindrance found in the closed bridged complexes (Scheme 3).
When PCSO ligands 4-8 act as a bridged P,S ligands on the
dicobalt complexes, the substituents on sulfur and carbon
adopt a cis disposition. While this is not an obstacle for
p-tolyl PCSO ligands, the extra bulk of the tert-butyl analo-
gue 8-BH3 prevents the formation of the bridged species. In
order to check this hypothesis, we tested ligand 9-BH3 in
(18) The stereochemistry of the bridged complexes was assigned on
the basis of the optical rotation of the resulting Pauson-Khand adducts
(vide infra).

4574 Organometallics, Vol. 28, No. 15, 2009
Ferrer et al.
(or sulfide) bonding to the Pro-S metal center (Xa series),
while levorotatory products entail sulfoxide coordination to
the Pro-R cobalt atom (Xb series).7b,19 Complexes of the Xb
series tended to provide a more stereoselective reaction
(>95% ee) than the Xa series (Table 2, entries 4 and 6)
except for complexes 11a and 11b (75% and 66% ee,
respectively). In general, we may conclude that p-tolyl PCSO
ligands proved to be more selective than their PNSO analo-
gues (II). In contrast, the tert-butyl PCSO ligands proved to
be more difficult to synthesize and were less selective than
their PNSO analogues (I) in the asymmetric intermolecular
PKR.8
(0.13 mL, 0.71 mmol) was added. After 5 min the solution was
warmed to room temperature and left for 2 h. Then BH3 SMe2
3
(0.07 mL, 0.71 mmol) was added, and the reaction was left
for 30 min more. The solution was quenched with water, and
after extractive workup (water/EtOAc) and silica gel chromato-
graphy (10:1 hexane/EtOAc) 97 mg (43%) of 1-BH3 was obtained
as a white solid. Mp: 141-142 °C. IR (film): νmax 1046, 1436,
2387 cm-1. 1H NMR (400 MHz, CDCl3): δ 0.77-1.62 (br, 3H,
BH3), 2.36 (s, 3H), 3.55 (dd, J=14 and 6 Hz, 1H), 3.84 (dd, J=
14 and 8 Hz, 1H), 7.21 (d, J=8 Hz, 2H), 7.36-7.53 (m, 8H), 7.64-
7.83 (m, 4H) ppm. 13C NMR (75 MHz, CDCl3): δ 21.3 (CH3),
56.3 (d, JP=27 Hz, CH2), 124.1 (2CH), 126.9 (d, JP=56 Hz, C),
127.1 (d, JP=56 Hz, C), 128.9 (d, JP=10 Hz, 2CH), 129.0 (d, JP=
10 Hz, 2CH), 130.0 (2CH), 131.6 (d, JP=2 Hz, CH), 131.9 (d, JP=
2 Hz, CH), 132.6 (d, JP=12 Hz, 2CH), 132.7(d, JP=12 Hz, 2CH),
141.6 (d, JP =6 Hz, C), 142.2 (C) ppm. 31P NMR (121 MHz,
CDCl3): δ 13.8 (s) ppm. HRMS-ESI: m/z calcd for C20H23BOPS
353.1300, found 353.1291 [Mþ þ H].
Conclusions
Here we have synthesized a new family of enantiomerically
pure p-tolyl and tert-butyl sulfinylmethyl phosphine (PCSO)
ligands. Selective phosphinylation of benzyl and homoben-
zyl sulfoxides allowed the preparation of ligands with an
extra chiral center in the central carbon atom. The ligand
exchange reaction of these ligands to Co2-alkyne complexes
afforded moderate diastereoselectivities (up to 6:1). The
relevance of the relative stereochemistry on the sulfur and
carbon centers for the formation of bridged complexes has
been disclosed. Thus, for the tert-butyl PCSO analogue, only
the SR,CR diastereomer provides the desired bridged com-
plex 16a/16b. Finally, the resulting PCSO cobalt complexes
have been tested in the intermolecular PKR, in which the
p-tolylsulfinyl ligands 4 and 6 provided up to 97% and
96% ee.
General Procedure for the Alkylation of Optically Pure Sulf-
oxides with Chlorodiphenyl Phosphine. A solution of 1 equiv of
the sulfoxide in THF (volume necessary to make the concentra-
tion of the sulfoxide 0.5 M) was cooled at -78 °C, and 1.3 equiv
of MeLi (1.6 M solution in diethyl ether) was added dropwise.
After 30 min the solution was added via cannula very slowly to a
solution of 1.1 equiv of Ph2PCl in THF (volume necessary to
make the concentration of the phosphine 0.5 M) at -78 °C.
After 30 min 1.3 equiv of BH3 SMe2 was added, and the
3
reaction was slowly warmed to room temperature for 3 h. The
solution was quenched with water, and after extractive workup
(water/EtOAc) and silica gel chromatography (10:1 hexane/
EtOAc) the PCSO ligands were obtained.
Diphenyl((1R)-phenyl-(S)-(p-tolylsulfinyl)methyl)phosphine,
Borane Complex 4-BH3. Following the general procedure, (R)-
benzyl p-tolylsulfoxide (3)12 (100 mg, 0.43 mmol), MeLi (0.35 mL
of a 1.6 M solution, 0.57 mmol), Ph2PCl (0.09 mL, 0.48 mmol),
Experimental Section
and BH3 SMe2 (0.05 mL, 0.57 mmol) were reacted to give 55 mg
3
General Methods. All reactions were carried out under a
nitrogen atmosphere in dried solvents. THF was dried over
sodium/benzophenone, toluene over sodium, and dichloro-
methane over CaH2. Thin-layer chromatography was carried
out using TLC-aluminum sheets with silica gel (Merk 60 F254).
Chromatography purifications were carried out using flash grade
silica gel (SDS Chromatogel 60 ACC, 35-70 μm). NMR spectra
were recorded at 23 °C on a Varian Mercury 400 and on a Varian
Unity 300 apparatus. 1H NMR and 13C NMR spectra were
referenced either to relative internal TMS or to residual solvent
peaks. 31P NMR spectra were referenced to phosphoric acid.
Signal multiplicities in the 13C spectra have been assigned by
DEPT and HSQC experiments. Optical rotations were recorded
on a Perkin-Elmer polarimeter at the sodium D line at room
temperature (concentration in g/mL). Melting points were deter-
(30%) of 4-BH3 as a 13:1 diastereomeric mixture as a white solid.
The diastereomers were separated by precipitation with hexane
and EtOAc. Mp: 149-150 °C. [R]D=þ1.36 (c 0.05, CHCl3). IR
(film): νmax 1057, 1435, 2362 cm-1. 1H NMR (400 MHz, CDCl3):
δ 1.04-1.64 (br, 3H, BH3), 2.29 (s, 3H), 4.22 (d, J=11 Hz, 1H),
6.84 (d, J=7 Hz, 2H), 6.93 (d, J=8 Hz, 2H), 7.03 (d, J=8 Hz, 2H),
7.07-7.11 (m, 2H), 7.19-7.23 (m, 1H), 7.34-7.38 (m, 2H), 7.42-
7.49 (m, 3H), 7.54-7.58 (m, 1H), 7.62-7.67 (m, 2H), 7.87-7.91
(m, 2H) ppm. 13C NMR (75 MHz, CDCl3): δ 21.6 (CH3), 70.0 (d,
JP=26 Hz, CH), 124.5 (2CH), 126.4 (d, JP=55 Hz, C), 127.0 (d,
JP=5 Hz, C), 127.3 (d, JP=55 Hz, C), 127.9 (CH), 128.7 (d, JP=
1 Hz, 2CH), 128.9 (d, JP=10 Hz, 2CH), 129.0 (d, JP=10 Hz,
2CH), 129.5 (2CH), 131.7 (d, JP=2 Hz, CH), 131.8 (d, JP=4 Hz,
2CH), 132.2 (d, JP=2 Hz, CH), 133.3 (d, JP=9 Hz, 2CH), 134.3
(d, JP = 9 Hz, 2CH),139.8 (d, JP = 7 Hz, C), 141.8 (C) ppm.
31P NMR (121 MHz, CDCl3): δ 23.0 (s) ppm. HRMS-ESI: m/z
calcd for C26H27BOPS 429.1613, found 429.1615 [MþþH].
Diphenyl((1R)-2-phenyl-1-(S)-(p-tolylsulfinyl)ethyl)phosphine,
Borane Complex 6-BH3. Following the general procedure, (R)-
2-phenylethyl p-tolylsulfoxide (5)21 (600 mg, 2.46 mmol), MeLi
(2.30 mL of a 1.6 M solution, 3.69 mmol), Ph2PCl (0.50 mL,
€
mined using a Buchi melting point apparatus and were not
corrected. IR spectra wererecordedin a FT-IRapparatus. HRMS
were recorded using an electrospray ionization spectrometer.
HPLC chromatography was performed on an Agilent Technolo-
gies Series 1100 chromatograph with UV detector. Enantiomeric
purity of sulfoxides 3 and 5 was checked by HPLC chromato-
graphy (Chiralcel OD-H) and was shown to be higher than
98% ee, as compared to a racemic standard. Sulfoxide 1020 has
been previously described in the literature.
(R)-Diphenyl(p-tolylsulfinylmethyl)phosphine, Borane Complex
1-BH3. To a solution of (R)-methyl p-tolylsulfoxide (100 mg,
0.65 mmol) in diethyl ether at -10 °C was added a 1.8 M solution
of PhLi (0.39 mL, 0.71 mmol). After stirring for 30 min at
this temperature, the solution was cooled to -78 °C and Ph2PCl
2.70 mmol), and BH3 SMe2 (0.30 mL, 3.19 mmol) were reacted
to give 430 mg (40%) of 6-BH3 as a single diastereomeras a white
solid. Mp: 108-109 °C. [R]D=þ0.56 (c 0.02, CHCl3). IR (film):
3
νmax 1056, 1436, 2388 cm-1 1H NMR (400 MHz, CDCl3):
.
δ 0.78-1.63 (br, 3H, BH3), 2.34 (s, 3H), 3.02-3.18 (m, 2H),
4.12 (ddd, J=10, 7, and 5 Hz, 1H), 6.81-6.83 (m, 2H), 7.04-
7.05 (m, 3H), 7.08 (d, J=8 Hz, 2H), 7.15 (d, J=8 Hz, 2H), 7.20
(td, J=8 and 2 Hz, 2H), 7.31-7.35 (m, 1H), 7.51-7.60 (m, 5H),
8.11 (dd, J=8 and 2 Hz, 1H), 8.13 (dd, J=8 and 2 Hz, 1H) ppm.
13C NMR (75 MHz, CDCl3): δ 21.4 (CH3), 31.78 (d, JP=4 Hz,
ꢁ
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Article
Organometallics, Vol. 28, No. 15, 2009 4575
CH2), 64.2 (d, JP =22 Hz, CH), 125.5 (2CH), 125.7 (d, JP =
55 Hz, C), 126.48 (CH), 127.0 (d, JP=55 Hz, C), 128.3 (2CH),
128.4 (d, JP=10 Hz, 2CH), 128.6 (2CH), 128.8 (d, JP=10 Hz,
2CH), 129.5 (2CH), 131.1 (d, JP=2 Hz, CH), 131.9 (d, JP=2 Hz,
CH), 132.9 (d, JP=9 Hz, 2CH), 134.1 (d, JP=9 Hz, 2CH), 137.8
(d, JP = 2 Hz, C),137.9 (d, JP = 7 Hz, C), 141.8 (C) ppm.
31P NMR (121 MHz, CDCl3): δ 22.8 (s) ppm. HRMS-ESI:
m/z calcd for C27H29BOPS 443.1770, found 443.1770 [Mþ þ H].
HPLC analysis of 6-BH3 performed with a Chiralcel OD-H
column, eluting with 2% i-PrOH in heptane at 1.0 mL/min and
monitored by UV at 254 nm, gave peaks at 25.1 min (minor
enantiomer) and 34.5 min (major enantiomer), which integrated
to reveal 99% ee (as compared to a racemic standard).
under vacuum and purified by silica gel chromatography
(20:1 hexane/EtOAc or toluene) to give the PCSO complexes
as red solids.
Co2(μ-TMSC2H)(CO)4(μ-C26H23OPS) (11a/11b). Following
the general procedure, diphenyl((1R)-phenyl-(S)-(p-tolylsul-
finyl)methyl) phosphine borane complex (4-BH3) (400 mg,
0.94 mmol), DABCO (157 mg, 1.40 mmol), and trimethylsilyla-
cetylene dicobalt complex (395 mg, 1.03 mmol) were reacted.
Chromatography on silica gel (10:1 hexane/EtOAc) afforded
430 mg (62%) of a 1:1 diastereomeric mixture of complexes
11a/11b. The diastereomers could be partially separated by silica
gel chromatography (toluene). 11a: IR (film): νmax 1970, 1998,
2027 cm-1. 1H NMR (400 MHz, C6D6): δ 0.43 (s, 9H), 1.73 (s,
3H), 4.37 (d, J=7 Hz, 1H), 6.52 (br s, 2H), 6.58-6.62 (m, 4H),
6.70-6.74 (m, 1H), 6.94-6.96 (m, 3H), 7.00 (d, J=8 Hz, 1H),
7.04-7.06 (m, 3H), 7.52-7.58 (m, 4H), 7.81-7.86 (m, 2H) ppm.
13C NMR (75 MHz, C6D6): δ 0.8 (3CH3), 20.8 (CH3), 90.6 (d,
JP=8 Hz, CH), 93.4 (d, JP=9 Hz, CH), 97.8 (d, JP=9 Hz, C),
125.1 (2CH), 127.4 (2CH), 127.9 (CH), 128.1 (d, JP=7 Hz, 2CH),
128.8 (d, JP=9 Hz, 2CH), 129.3 (2CH), 130.2 (d, JP=2 Hz, CH),
130.7 (d, JP=2 Hz, CH), 131.2 (d, JP=2 Hz, 2CH), 132.2 (d, JP=
6 Hz, C), 132.6 (d, JP=9 Hz, 2CH), 133.9 (d, JP=33 Hz, C), 135.4
(d, JP=13 Hz, 2CH), 135.6 (d, JP=38 Hz, C), 141.3 (C), 144.3 (d,
JP=11 Hz, C) ppm. 31P NMR (121 MHz, C6D6): δ 64.3 (s) ppm.
HRMS-ESI: m/z calcd for C35H33O5Co2NaPSSi 765.0111, found
Diphenyl((1S)-(R)-tert-butylsulfinyl(phenyl)methyl)phosphine,
Borane Complex (8-BH3). Following the general procedure, (S)-
benzyl tert-butylsulfoxide (7)22 (1.0 g, 5.04 mmol), MeLi (4.10 mL
of a 1.6 M solution, 6.56 mmol), Ph2PCl (1.02 mL, 5.55 mmol),
and BH3 SMe2 (0.62 mL, 6.56 mmol) were reacted to give 1.3 g
3
(65%) of 8-BH3 as a 6:1 diastereomeric mixture as a white solid.
Alternatively, when the reaction was carried out using n-BuLi
(2.73 mL of a 2.4 M solution, 6.56 mmol) at 0 °C, 495 mg (25%) of
a 20:1 diastereomeric mixture was obtained as a white solid.
The diastereomers were separated by silica gel chromatography
(15:1 toluene/EtOAc). Mp: 128-129 °C. [R]D = -0.42 (c 0.5,
CHCl3). IR (film): νmax = 1056, 1437, 2400, 2959, 3059 cm-1
.
1H NMR (400 MHz, CDCl3): δ 1.01 (s, 9H), 5.02 (d, J=10 Hz,
1H), 7.05-7.07 (m, 2H), 7.12-7.24 (m, 5H), 7.27-7.31 (m, 1H),
7.39-7.44 (m, 2H), 7.50-7.59 (m, 3H), 8.06-8.11 (m, 2H) ppm.
13C NMR (75 MHz, CDCl3): δ 24.0 (3CH3), 57.9 (d, JP=3 Hz, C),
60.1 (d, JP=24 Hz, CH), 125.7 (d, JP=54 Hz, C), 128.2 (2CH),
128.3 (2CH), 128.8 (d, JP=56 Hz, C), 128.7-128.8 (m, 4CH),
130.4 (d, JP=1 Hz, C), 130.6 (d, JP=4 Hz, CH), 130.83 (d, JP=
2 Hz, CH), 132.0 (d, JP=6 Hz, CH), 132.7 (d, JP=9 Hz, 2CH),
134.8 (d, JP=10 Hz, 2CH) ppm. 31P NMR (121 MHz, CDCl3):
δ 27.8 (s) ppm. HRMS-ESI: m/z calcd for C23H27BOPS 393.1613,
found 393.1622 [M--H].
765.0116 [Mþ þ Na]. 11b: IR (film): νmax 1974, 2000, 2031 cm-1
.
1H NMR (400 MHz, C6D6): δ 0.44 (s, 9H), 1.72 (s, 3H), 4.62 (d,
J=8 Hz, 1H), 5.90 (d, J=10 Hz, 1H), 6.45 (br s, 2H), 6.56 (t, J=
7 Hz, 2H), 6.62 (d, J=8 Hz, 2H), 6.65-6.69 (m, 1H), 6.92-6.99
(m, 6H), 7.30 (d, J=8 Hz, 2H), 7.34-7.39 (m, 2H), 7.77-7.82 (m,
2H) ppm. 13C NMR (75 MHz, C6D6): δ 1.0 (3CH3), 20.9 (CH3),
84.0 (d, JP=12 Hz, CH), 85.0 (d, JP=10 Hz, CH), 95.8 (d, JP=
10 Hz, C), 124.9 (2CH), 127.3 (2CH), 127.9 (CH), 128.1 (d, JP=
7 Hz, 2CH), 128.5 (d, JP=9 Hz, 2CH), 129.0 (2CH), 129.9 (d,
JP=1 Hz, CH), 130.7 (d, JP=2 Hz, CH), 130.8 (d, JP=6 Hz, C),
131.6 (d, JP=2 Hz, 2CH), 132.3 (d, JP=11 Hz, 2CH), 132.8 (d,
JP=31 Hz, C), 134.8 (d, JP=38 Hz, C), 135.2 (d, JP=13 Hz,
2CH), 141.2 (C), 144.9 (d, JP = 10 Hz, C) ppm. 31P NMR
(121 MHz, C6D6): δ 57.0 (s) ppm. HRMS-ESI: m/z calcd for
C35H33O5Co2NaPSSi 765.0111, found 765.0108 [MþþNa].
Co2(μ-PhC2H)(CO)4(μ-C26H23OPS) (12a/12b). Following
the general procedure, diphenyl((1R)-phenyl-(S)-(p-tolylsul-
finyl)methyl) phosphine borane complex (4-BH3) (200 mg,
0.47 mmol), DABCO (78 mg, 0.70 mmol), and phenylacetylene
dicobalt complex (200 mg, 0.51 mmol) were reacted. Chroma-
tography on silica gel (10:1 hexane/EtOAc) afforded 210 mg
(60%) of a 1:1 diastereomeric mixture of complexes 12a/12b.
The diastereomers could be partially separated by silica gel
chromatography (toluene). 12a: IR (film): νmax 1973, 2003,
Diphenyl((1R)-(R)-tert-butylsulfinyl(phenyl)methyl)phosphine,
Borane Complex 9-BH3. To a solution containing a 6:1 diastere-
omeric mixture of ligands 8-BH3 and 9-BH3 (790 mg, 2.01 mmol)
in THF (15 mL) was added MeLi (1.34 mL of a 3 M solution,
4.03 mmol) at 0 °C. The reaction was stirred at room temperature
for 1 h, and then it was quenched with water. After extractive
workup (water/EtOAc), a 1:1 diastereomeric mixture of ligands
8-BH3 and 9-BH3 was obtained in quantitative yield as a white
solid. The diastereomers were separated by silica gel chromato-
graphy (15:1 toluene/EtOAc). Mp: 141-142 °C. [R]D = -0.34
(c 0.5, CHCl3). IR (film): νmax 1045, 1104, 1437, 2395 cm-1. 1H
NMR (400 MHz, CDCl3): δ 1.00 (s, 9H), 4.53 (d, J=11 Hz, 1H),
7.14-7.22 (m, 5H), 7.37-7.43 (m, 2H), 7.44-7.50 (m, 3H), 7.56
(td, J=7 and 1 Hz, 1H), 7.66-7.75 (m, 2H), 7.84-7.91 (m, 2H)
ppm. 13C NMR (75 MHz, CDCl3): δ 24.0 (3CH3), 58.0 (d, JP=
28 Hz, CH), 58.2 (d, JP=7 Hz, C), 125.2 (d, JP=53 Hz, C), 127.0
(d, JP=53 Hz, C), 128.1 (d, JP=2 Hz, 2CH), 128.5 (d, JP=2 Hz,
C), 128.7 (d, JP=2 Hz, CH), 128.8 (d, JP=3 Hz, 2CH), 128.9
(d, JP=3 Hz, 2CH), 131.7 (d, JP=2 Hz, CH), 132.4 (CH), 132.5
(d, JP=5 Hz, 2CH), 133.4 (d, JP=9 Hz, 2CH), 135.1 (d, JP=
9 Hz, 2CH) ppm. 31P NMR (121 MHz, CDCl3): δ 27.3 (s) ppm.
HRMS-ESI: m/z calcd for C23H29BOPS 395.1764, found
395.1764 [Mþþ H].
1
2030 cm-1. H NMR (400 MHz, C6D6): δ 1.74 (s, 3H), 4.29
(d, J=7 Hz, 1H), 6.53 (br s, 2H), 6.58-6.65 (m, 4H), 6.72-6.76
(m, 1H), 6.81 (d, J=7 Hz, 1H), 6.95-6.97 (m, 3H), 7.02-7.13
(m, 6H), 7.47 (d, J=8 Hz, 2H), 7.56-7.61 (m, 2H), 7.85 (d, J=
7 Hz, 2H), 7.87-7.92 (m, 2H) ppm. 13C NMR (75 MHz, C6D6):
δ 20.7 (CH3), 78.0 (d, JP=13 Hz, CH), 90.4 (d, JP=5 Hz, CH),
103.8 (C), 124.8 (2CH), 127.2 (CH), 127.3 (2CH), 128.1 (d, JP=
9 Hz, 2CH), 128.6 (d, JP = 9 Hz, 2CH), 128.8 (2CH), 129.2
(2CH), 130.0 (d, JP=3 Hz, 2CH), 130.2 (CH), 130.6 (CH), 131.3
(d, JP=2 Hz, 2CH), 131.8 (d, JP=6 Hz, C), 132.7 (d, JP=12 Hz,
2CH), 133.8 (d, JP=32 Hz, C), 134.8 (d, JP=22 Hz, C), 135.0 (d,
JP=13 Hz, 2CH), 141.2 (C), 141.5 (C), 143.9 (d, JP=11 Hz, C)
ppm (one carbon signal is missing). 31P NMR (121 MHz, C6D6):
δ 64.9 (s) ppm. HRMS-ESI: m/z calcd for C38H29O5Co2NaPS
769.0029, found 769.0022 [Mþ þ Na]. 12b: IR (film): νmax 1976,
General Procedure for the Preparation of the Dicobalt-Tetra-
carbonyl Complexes of Optically Pure PCSO Ligands. To a
Schlenk tube containing 1 equiv of the corresponding borane-
protected PNSO ligand in toluene (volume necessary to make
the concentration of the ligand 0.1 M) was added 1.5 equiv of
DABCO and 1.1 equiv of the corresponding dicobalt-hexacar-
bonyl acetylene complex. The mixture was kept at 75 °C for the
time indicated in Table 1. The crude product was concentrated
1
2004, 2033 cm-1. H NMR (400 MHz, C6D6): δ 1.78 (s, 3H),
4.50 (d, J=8 Hz, 1H), 5.71 (d, J=9 Hz, 1H), 6.51 (br s, 2H),
6.62-6.73 (m, 5H), 6.99-7.09 (m, 8H), 7.35-7.43 (m, 5H),
7.86-7.92 (m, 4H) ppm. 13C NMR (75 MHz, C6D6): δ 21.3
(CH3), 71.8 (d, JP = 10 Hz, CH), 82.4 (d, JP = 13 Hz, CH),
104.4 (d, JP=16 Hz, C), 125.3 (2CH), 127.7 (2CH), 127.8 (CH),
(22) Kelly, P.; Lawrence, S. E.; Maguire, A. R. Eur. J. Org. Chem.
2006, 4500–4509.

4576 Organometallics, Vol. 28, No. 15, 2009
Ferrer et al.
128.5 (CH), 128.7 (d, JP=9 Hz, 2CH), 128.9 (d, JP=9 Hz, 2CH),
129.3 (2CH), 129.4 (2CH), 130.4 (CH), 130.5 (d, JP = 4 Hz,
2CH), 131.1 (CH), 131.2 (d, JP=5 Hz, C), 132.1 (2CH), 132.7 (d,
JP=11 Hz, 2CH), 133.1 (d, JP=30 Hz, C), 134.9 (d, JP=37 Hz,
C), 135.5 (d, JP=14 Hz, 2CH),141.7 (C), 142.4 (C), 145.1 (d, JP=
11 Hz, C) ppm. 31P NMR (121 MHz, C6D6): δ 58.3 (s) ppm.
HRMS-ESI: m/z calcd for C38H29O5Co2NaPS: 769.0029, found
769.0026 [Mþ þ Na].
136.5 (d, JP=36 Hz, C), 138.4 (d, JP=4 Hz, C), 141.3 (C), 141.8 (d,
JP=7 Hz, C), 142.9 (C) ppm. 31PNMR(121MHz, C6D6):δ55.6 (s)
ppm. HRMS-ESI: m/z calcd for C39H31O5Co2NaPS 783.0191,
found 783.0209 [Mþ þ Na].
Co2(μ-PhC2H)(CO)5(C23H25OPS) (15a/15b). Following the
general procedure, diphenyl((1S)-(R)-tert-butylsulfinyl(phenyl)-
methyl) phosphine boranecomplex (8-BH3) (100 mg, 0.25 mmol),
DABCO (43 mg, 0.38 mmol), and phenylacetylene dicobalt
complex (108 mg, 0.28 mmol) were reacted. Chromatography
on silica gel (10:1 hexane/EtOAc) afforded 164 mg (92%) of a 1:1
Co2(μ-TMSC2H)(CO)4(μ-C27H25OPS) (13a/13b).Following the
general procedure, diphenyl((1R)-2-phenyl-1-(S)-(p-tolylsulfinyl)-
ethyl) phosphine borane complex (6-BH3) (30 mg, 0.07 mmol),
DABCO (12 mg, 0.1 mmol), and trimethylsilylacetylene dicobalt
complex (29 mg, 0.07 mmol) were reacted. Chromatography on silica
gel (10:1 hexane/EtOAc) afforded 19 mg (36%) of a 2:1 diastereo-
meric mixture of complexes 13a/13b. The diastereomers could be
partially separated by silica gel chromatography (50:1 hexane/
diastereomeric mixture of complexes 15a/15b: IR (film): νmax
=
2007, 2059 cm-1. 1H NMR (400 MHz, C6D6): δ 0.70 (s, 9H), 0.75
(s, 9H), 4.85 (d, J=4 Hz, 1H), 4.92 (d, J=3 Hz, 1H), 5.03 (d, J=
3 Hz, 1H), 5.24 (d, J=4 Hz, 1H), 6.79-7.08 (m, 26H), 7.24-7.37
(m, 8H), 7.43-7.48 (m, 2H), 8.06-8.10 (m, 2H), 8.39-8.43 (m,
2H) ppm. 13C NMR (75 MHz, C6D6): δ 23.7 (3CH3), 23.7
(3CH3), 57.7 (C), 57.7 (C), 61.2 (d, JP = 5 Hz, CH), 61.7 (d,
JP=8 Hz, CH), 71.5 (CH), 73.2 (CH), 85.4 (C), 87.4 (C), 126.6-
138.9 (m, 48C) ppm. 31P NMR (121 MHz, C6D6): δ 67.1, 67.8 (s)
ppm. HRMS-ESI: m/z calcd for C34H31O4Co2PS 684.0345,
found 684.0353 [M - 2CO].
1
EtOAc). 13a: IR (film): νmax 1967, 1995, 2025 cm-1. H NMR
(400 MHz, C6D6): δ 0.48 (s, 9H), 1.87 (s, 3H), 2.65-2.82 (m, 2H),
5.08-5.12 (m, 1H), 6.06 (d, J=7 Hz, 2H), 6.42 (d, J=11 Hz, 1H),
6.66-6.72 (m, 4H), 6.76-6.86 (m, 3H), 7.02-7.11 (m, 4H), 7.58-
7.63 (m, 2H), 7.83-7.88 (m, 2H), 7.99 (d, J = 8 Hz, 2H) ppm.
13C NMR (75 MHz, C6D6): δ 1.3 (3CH3), 21.3 (CH3), 33.1 (d, JP=
4Hz,CH2),83.3(d,JP=13Hz,CH),90.2(d,JP=9 Hz, CH), 97.8 (d,
JP=9 Hz, C), 126.5 (CH), 127.9 (2CH), 128.5-128.9 (m, 8CH),
129.9 (2CH), 130.1 (CH), 130.9 (CH), 133.1 (d, JP=12 Hz, 2CH),
133.5 (d, JP=31Hz, C), 135.0(d, JP=13 Hz, 2CH), 137.1 (d, JP=36
Hz, C), 138.8 (d, JP=3 Hz, C), 142.7 (d, JP=6 Hz, C), 143.4 (C) ppm.
31P NMR (121 MHz, C6D6): δ 56.1 (s) ppm. HRMS-ESI: m/z calcd
for C36H35O5Co2NaPSSi 779.0268, found 779.0274 [Mþ þ Na]. 13b:
IR (film): νmax 1972, 1998, 2034 cm-1. 1H NMR (400 MHz, C6D6):
δ 0.52 (s, 9H), 1.88 (s, 3H), 2.63-2.84 (m, 2H), 4.53-4.57 (m, 1H),
5.91 (d, J=7 Hz, 2H), 6.20 (d, J=10 Hz, 1H), 6.61-6.79 (m, 5H),
6.85-7.01 (m, 6H), 7.50-7.54 (m, 2H), 7.77-7.81 (m, 2H), 7.93 (d,
J=8 Hz, 2H) ppm. 13C NMR (75 MHz, C6D6): δ 1.1 (3CH3), 20.9
(CH3), 33.3 (CH2), 81.3 (d, JP=12 Hz, CH), 86.5 (d, JP=10 Hz,
CH), 96.8 (d, JP=10 Hz, C), 126.3 (CH), 127.1 (2CH), 127.9 (2CH),
128.3 (4CH), 128.4 (2CH), 129.4 (CH), 129.5 (2CH), 130.7 (CH),
132.1 (d, JP=12 Hz, 2CH), 133.9 (d, JP=32 Hz, C), 135.9 (d, JP=
13 Hz, 2CH), 137.4 (d, JP=36 Hz, C), 138.5 (C), 142.7 (C),143.2 (d,
JP=7 Hz, C) ppm. 31P NMR (121 MHz, C6D6): δ 56.3 (s) ppm.
HRMS-ESI: m/z calcd for C36H35O5Co2NaPSSi 779.0268, found
779.0277 [Mþ þ Na].
Co2(μ-PhC2H)(CO)4(μ-C23H25OPS) (16b). Following the
general procedure, diphenyl((1R)-(R)-tert-butylsulfinyl(phenyl)-
methyl) phosphine boranecomplex (9-BH3) (200 mg, 0.51 mmol),
DABCO (85 mg, 0.76 mmol), and phenylacetylene dicobalt
complex (216 mg, 0.56 mmol) were reacted. Chromatography
on silica gel (10:1 hexane/EtOAc) afforded 106 mg (30%) of a 1:6
diastereomeric mixture of complexes 16a/16b. The major diaster-
eomer 16b was isolated by crystallization using hexane/toluene:
1
IR (film): νmax 2027, 1999, 1971 cm-1. H NMR (400 MHz,
C6D6): δ 0.95 (s, 9H), 3.92(d, J=9 Hz, 1H), 6.03(d, J=8 Hz, 1H),
6.34 (d, J=9 Hz, 1H), 6.67 (td, J=7 and 1 Hz, 1H), 6.75-6.86 (m,
3H), 6.91-6.96 (m, 2H), 6.99-7.13 (m, 6H), 7.42-7.47 (m, 2H),
7.71 (d, J=7 Hz, 1H), 7.79 (d, J=7 Hz, 2H), 7.95-8.00 (m, 2H)
ppm. 13C NMR (75 MHz, C6D6): δ 24.7 (3CH3), 66.4 (d, JP=
8 Hz, C), 77.7 (d, JP=10 Hz, CH), 81.1 (d, JP=10 Hz, CH), 106.2
(d, JP=18 Hz, C), 127.3 (d, JP=20 Hz, 2CH), 128.1 (d, JP=9 Hz,
2CH), 128.2 (2CH), 128.3 (d, JP=9 Hz, 2CH), 128.8 (2CH), 129.8
(CH), 130.0 (d, JP=4 Hz, 2CH), 130.6 (CH), 131.0 (CH), 131.8
(CH), 133.7 (d, JP=12 Hz, 2CH), 133.9 (d, JP=13 Hz, 2CH),
134.14 (d, JP=25 Hz, C), 141.4 (C) ppm (two carbon signal are
missing due to overlapping). 31P NMR (121 MHz, C6D6): δ 79.2
(s) ppm. HRMS-ESI: m/z calcd for C35H31O5Co2NaPS 735.0186,
found 735.0183 [Mþ þ Na].
Co2(μ-PhC2H)(CO)4(μ-C27H25OPS) (14a/14b). Following the
general procedure, diphenyl((1R)-2-phenyl-1-(S)-(p-tolylsulfinyl)-
ethyl) phosphine borane complex (6-BH3) (300 mg, 0.68 mmol),
DABCO (114 mg, 1.02 mmol), and phenylacetylene dicobalt com-
plex (289 mg, 0.75 mmol) were reacted. Chromatography on silica
gel (10:1 hexane/EtOAc) afforded 172 mg (33%) of a 2:1 diastere-
omeric mixture of complexes 14a/14b. One diastereomer could be
partially separated by silica gel chromatography (50:1 hexane/
General Procedure for the Pauson-Khand Reaction of Opti-
cally Pure Complexes with Norbornadiene. Optically pure
tetracarbonyl complexes (1 equiv), norbornadiene (10 equiv),
and toluene (volume necessary to make to concentration of
the complex 0.1 M) were charged in a Schlenk flask under
nitrogen, and the reaction was stirred at 80 °C for the time
indicated in Table 2. The Pauson-Khand adducts 178b and 188b
were obtained after silica gel chromatography (95:5 hexane/
EtOAc).
1
EtOAc). 14a: IR (film): νmax 1972, 2000, 2060 cm-1. H NMR
(400 MHz, C6D6): δ 1.85 (s, 3H), 2.71-2.90 (m, 2H), 4.88-4.93 (m,
1H), 6.16 (d, J=7 Hz, 2H), 6.23 (d, J=10 Hz, 1H), 6.63-6.87 (m,
10H), 7.02-7.05 (m, 3H), 7.52-7.57 (m, 2H), 7.78-7.85 (m, 5H),
7.97 (d, J=8 Hz, 2H) ppm. 13C NMR (75 MHz, C6D6): δ 20.8
(CH3), 32.4 (d, JP=4 Hz, CH2), 75.9 (d, JP=10 Hz, CH), 80.07 (d,
JP=13 Hz, CH), 105.78 (d, JP=14 Hz, C), 126.1 (CH), 127.4 (2CH),
127.5 (2CH), 128.1-128.4 (m, 7CH), 128.8 (2CH), 129.4 (2CH),
129.7 (CH), 130.1 (CH), 130.2 (CH), 130.4 (CH), 132.5 (d, JP=
12 Hz, 2CH), 132.6 (d, JP=33 Hz, C), 134.4 (d, JP=13 Hz, 2CH),
Acknowledgment. We thank MICINN (CTQ2008-
00763/BQU) and IRB Barcelona for financial support.
Supporting Information Available: NMR spectra of all com-
pounds. X-ray structure of 6-BH3. This material is available free
of charge via the Internet at http://pubs.acs.org.