A study of (binap)(enyne)tetracarbonyldicobalt(0) complexes

Article abstract of DOI:10.1002/chem.200700587

Four (binap)(enyne)tetracarbonyldicobalt(0) complexes have been synthesised and their reactivity monitored by variable temperature ³¹P NMR spectroscopy. Formation of (binap)dicarbonylhydridocobalt(-1) 12 occurred at temperatures between 35 and

Full text of DOI:10.1002/chem.200700587

FULL PAPER
DOI: 10.1002/chem.200700587
A Study of (Binap)(enyne)tetracarbonyldicobalt(0) Complexes
G
Susan E. Gibson,*[a] David J. Hardick,[b] PeterR. Haycock, [a] Karina A. C. Kaufmann,[a]
Ayako Miyazaki,[a] Matthew J. Tozer,[b] and Andrew J. P. White[a]
Abstract: Four (binap)(enyne)tetracarbonyldicobalt(0) complexes have been syn-
U
thesised and their reactivity monitored by variable temperature 31P NMR spectros-
copy. Formation of (binap)dicarbonylhydridocobalt(ꢀ1) 12 occurred at tempera-
tures between 35 and 558C, depending on the nature of the alkene and alkyne
components of the enyne. The structure of 12 was determined by X-ray crystallog-
raphy, and its presence under Pauson–Khand reaction conditions was verified by
NMR spectroscopy.
Keywords: alkenes
asymmetric catalysis · cobalt
·
alkynes
·
Introduction
Inspired by Hiroiꢀs successful use of binap in the cobalt-
catalysed PKR,[3] we questioned the nature of the complex
formed between binap and cobalt carbonyl sources.[9] Reac-
tion of binap with a range of
The cobalt-mediated Pauson–Khand reaction (the coupling
of an alkyne, an alkene and carbon monoxide to form a cy-
ꢀ
clopentenone) is an attractive carbon carbon bond-forming
cobalt carbonyl sources typical-
ly used in the PKR revealed
that binap interacts with octa-
carbonyldicobalt(0) to form
reaction[1] that has found many applications in organic syn-
thesis since it was first reported over thirty years ago.[2] Re-
cently there has been much interest in developing asymmet-
ric and catalytic versions of the reaction, often involving
metals other than cobalt,[1d] and significant progress has
been made in each of these areas. Combination of catalysis
and asymmetric induction in the cobalt-catalysed reaction
has been achieved by Hiroi, who employed the bisphos-
phane binap,[3] and Buchwald, who used a binaphthyl-de-
rived phosphite.[4] Experimental evidence for the currently
accepted mechanism of the stoichiometric cobalt Pauson–
Khand reaction (PKR), which was proposed by Magnus in
1985 and involves the step-wise construction of the product
cyclopentenone on a series of di-cobalt complexes,[5] has re-
mained scarce, although computational studies have provid-
ed interesting insights not only into the reaction pathway
itself[6] but also into and the role of additives such as Lewis
bases[7] and the radical promoter TEMPO.[8]
complex 1, in which binap is
Figure 1. (Binap)hexacarbonyl-
chelated to one of the two
dicobalt(0).
cobalt atoms (Figure 1).[9] Com-
plex 1 catalysed the PKR of a
standard substrate, N-(prop-2-
enyl)-N-(prop-2-ynyl)-p-toluene
sulfonamide (3).[9]
G
Given that alkyne coordination is the accepted first event
in the PKR, we subsequently examined the reactivity of 1
towards alkynes. We found that complex 1 reacted with a
range of alkynes to form mixtures of two diastereoisomeric
complexes as exemplified by 2a and 2b (Scheme 1; struc-
tures confirmed by X-ray crystallography).[10] In the case of
2, the two isomers were separable and 31P NMR studies re-
vealed that they interconverted without decomposition at
758C.[10]
One of the proposed pathways for the interconversion of
the diastereoisomers of 2 is illustrated in Scheme 2.[10] The
[a] Prof. S. E. Gibson, P. R. Haycock, K. A. C. Kaufmann, A. Miyazaki,
Dr. A. J. P. White
Department of Chemistry, Imperial College London
South Kensington Campus, London SW7 2AY (UK)
Fax : (+44)207-594-5804
E-mail: s.gibson@imperial.ac.uk
[b] Dr. D. J. Hardick, Dr. M. J. Tozer
Medivir UK Ltd., Chesterford Research Park, Little Chesterford,
Essex C10 1XL (UK)
Scheme 1. Diastereoisomers of complex 2 interconvert.
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isomer and two at d 53.2 and 39.2 ppm corresponding to the
minor isomer. A resonance corresponding to binap at d
ꢀ14.6 ppm was also observed. The 31P NMR spectrum of 4
was consistent with the 31P NMR data obtained for diaste-
reoisomers 2a and 2b, the structures of which had been con-
firmed by X-ray crystallography;[10] this, together with the
X-ray characterisation obtained for complex 6 (see below),
provided the necessary assurance that complex 4 was the de-
sired binap cobalt derivative of enyne 3. The two diastereo-
isomers of 3, formed in a 2:1ratio, could not be separated
by chromatography or recrystallisation.
Scheme 2. A proposed pathway for the interconversion of the diastereo-
isomers of 2.
In a first attempt to discover the fate of complex 4 under
typical Pauson–Khand conditions, it was dissolved in THF
and heated to reflux under nitrogen for 1.3 h. Disappoint-
ingly, the 31P NMR spectrum of the brown product con-
tained only resonances corresponding to the bis- and mono-
oxides of binap. It was thus decided to examine the effect of
heat on complex 4 by variable temperature (VT) 31P NMR
spectroscopy. Complex 4 was dissolved in nitrogen-saturated
1,2-dimethoxyethane (DME) and syringed via a filter needle
into a WILMAD screw cap NMR tube (with a PTFE/sili-
cone septum) under a nitrogen atmosphere. A VT 31P NMR
experiment was performed between 30 and 758C, increasing
the temperature in intervals of 5 or 108C. Although the
quality of the spectra recorded was poor, it was clear that
changes were occurring and that products other than binap
and its oxides were being formed. The experiment was thus
repeated under a carbon monoxide atmosphere.
barrier to alkyne rotation is lowered by locating it on just
one cobalt atom, the binap-free cobalt being selected for
steric reasons.
To relate our studies more closely to the PKR we decided
to synthesise the cobalt alkyne binap complex of the known
PKR substrate 3 (Scheme 3) and study its reactivity. The re-
Scheme 3. Synthesis of complex 4.
sults of this study, together with a discussion of how they
may relate to the PKR are presented below. Some of the re-
sults have been the subject of a preliminary publication.[11]
Complex 4 was dissolved in carbon monoxide saturated
DME and syringed into the NMR tube under a carbon mon-
oxide atmosphere. The 31P NMR spectrum was again record-
ed between 308C and 758C at intervals of 58C and a final
spectrum was recorded at the end of the experiment at
308C. Inspection of the 31P NMR spectrum of complex 4 in
carbon monoxide saturated DME at 308C (Figure 2)
showed resonances associated with the major diastereoiso-
mer (d 59 and 44 ppm) and minor diastereoisomer (d 53 and
40 ppm). The spectrum of complex 4 remained essentially
unchanged up to 458C, but increasing the temperature fur-
ther to 508C resulted in the emergence of two new resonan-
ces at d 54 and 43 ppm. At 608C these new resonances do-
minated the spectrum. On increasing the temperature to
758C and on cooling the NMR experiment to 308C, no fur-
ther changes to the spectra were observed.
Results and Discussion
The standard Pauson–Khand substrate, enyne 3, was pre-
pared by a literature method[12] that involved deprotonation
of N-(prop-2-enyl)-p-toluenesulfonamide[13] and addition of
propargyl bromide. A sample of complex 1 was then pre-
pared by dissolving octacarbonyldicobalt(0) and binap in
THF and stirring the mixture under nitrogen at room tem-
perature for 30 minutes. The reaction mixture was then
heated to 408C for a further 20 minutes before enyne 3 was
added. After stirring at 408C for a further 2 h, purification
by flash column chromatography gave complex 4 as a diffi-
cult to handle, brown air sensitive solid in 45% yield. The
IR spectrum of 4 contained three absorptions at n˜ = 2043,
1980 and 1939 cmꢀ1, values typical of carbonyl ligands in
cobalt(0) complexes. The molecular ion could not be seen in
the mass spectrum of 4 although peaks corresponding to the
molecular ion minus three and four carbon monoxide li-
gands could be seen together with a peak correlating to
binap attached to a single cobalt atom. Characterisation of
Having discovered that the effect of temperature on com-
plex 4 was dramatically different to its effect on complex 2
(Scheme 1), it was decided to probe the role of the pendent
alkene using a complex identical to complex 4 but with the
propenyl substituent replaced by a propyl group.
Deprotonation of N-(propyl)-p-toluenesulfonamide[14] fol-
lowed by addition of propargyl bromide gave the desired
alkyne 5. Complexation of 5 was achieved using the same
procedure described above for complex 4. Purification of
the product mixture by flash column chromatography gave a
brown air-sensitive solid, 6, which was characterised by IR
spectroscopy, mass spectrometry, 31P NMR spectroscopy, el-
emental analysis and X-ray crystallography (Scheme 4).
1
complex 4 by H and 13C NMR spectroscopy was not possi-
ble as the spectra recorded were too broad to interpret. The
31P NMR of 4, however, consisted of five clear resonances,
two at d 58.9 and 44.0 ppm corresponding to the major
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ing and the appearance of the
new resonances at d 43 and
54 ppm at 508C (Figure 2).
In order to probe this process
further, enyne complexes bear-
ing relatively electron-rich and
electron-poor alkenes were con-
structed. A palladium-catalysed
reaction between 3-buten-2-ol
and toluene sulfonyl isocyanate
gave the disubstituted alkene
7.[15] Deprotonation of 7 and re-
action with propargyl bromide
gave enyne 8[16] and complexa-
tion to (binap)hexacarbonyldi-
cobalt(0) 1 gave the required
enyne complex 9 as a 2:1ratio
of diastereoisomers (Scheme 5).
In addition, the known alde-
hyde N-(2-oxoethyl)-N-(prop-2-
ynyl)-p-toluenesulfonamide[17]
was stirred with methyl(triphe-
nylphosphoranylidene) acetate
in benzene at room tempera-
Figure 2. 31P NMR spectra of complex 4 at a) 30, b) 45, c) 50 and d) 608C in DME under carbon monoxide.
Scheme 4. Synthesis of complex 6.
The 31P NMR spectrum of complex 6 contained five reso-
nances, two at d 57.9 and 43.8 ppm corresponding to the
major isomer, two at d 51.6 and 39.9 ppm corresponding to
the minor isomer, and one at d ꢀ14.99 ppm due to a trace
of binap. Although repeated attempts to separate the iso-
mers by chromatography failed, it proved possible on one
occasion to obtain a sample of one of the diastereoisomers
as small brown crystals from CH2Cl2/pentane. X-ray analysis
of these crystals confirmed the structure of 6 (Figure 3).[10]
Complex 6 was dissolved in carbon monoxide saturated
DME, syringed into an NMR tube and subjected to the VT
Figure 3. Molecular structure of 6.
31P NMR sequence described above for complex 4. The ini-
tial spectrum recorded at 308C
contained the four resonances
associated with the two diaste-
reoisomers
of
complex
6
(Figure 4). This situation re-
mained unchanged throughout
the VT sequence up to 758C
and on cooling back to 308C.
It was thus clear at this point
that the pendent alkene is neces-
sary for the chemical transfor-
mation that leads to the con-
sumption of complex 4 on heat- Figure 4. 31P NMR spectra of complex 6 at a) 30 and b) 758C in DME under carbon monoxide.
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S. E. Gibson et al.
alkene binding step to cobalt(0), a process favoured by a
low-lying alkene LUMO.[6e]
Examination of the NMR sequences depicted in Figure 2,
5 and 6, arising from the heating of complexes 4, 9 and 11,
respectively, reveals that they all culminate in spectra con-
taining resonances at d 43 and 54 ppm. As the 31P NMR
spectrum of (binap)hexacarbonyldicobalt(0), 1, in DME
contains a single resonance at d 43 ppm,[9] it was assumed
that this complex is formed on heating complexes 4, 9 and
11. An explanation for the resonance at d 54 ppm was pro-
vided by a combination of X-ray crystallography and a fur-
ther NMR experiment. Brown crystals observed in the
NMR tube after the NMR experiment on complex 4 were
examined by X-ray crystallography, which revealed that
they were the cobalt hydride 12 (Figure 7). Complex 12 is a
trigonal bipyramidal mono cobalt species with an axial hy-
dride, and a binap ligand spanning axial and equatorial posi-
tions.
Scheme 5. Synthesis of complex 9.
Scheme 6. Synthesis of complex 11.
Complex 12 is novel, although similar cobalt hydrides
with achiral bidentate phosphorus ligands such as 13,[19]
14[20,21] and 15[22] have been reported. Comparatively little
detailed data has been collected on these complexes, pre-
sumably because of their sensitivity. Complex 16, which has
been reported in the patent literature as a hydroformylation
catalyst,[23] represents the only previous example of a mono-
cobalt-hydride containing a chiral bidentate phosphorus
ligand (Figure 8).
ture overnight to give enyne 10[18] as a colourless oil. Addi-
tion of 10 to 1 gave a 2:1mixture of the diastereoisomers of
the enyne cobalt complex 11 (Scheme 6).
The VT 31P NMR spectra obtained from complexes 9 and
11 followed a similar pattern to those obtained from com-
plex 4, that is, four resonances associated with the diastereo-
isomers are replaced by resonances at d 54 and 43 ppm as
the temperature increases (Figures 5 and 6). Interestingly
the temperature at which the contribution to the spectrum
from the new resonances becomes significant alters from
508C in the case of complex 4 (Figure 2) to 558C for com-
plex 9 and to 458C in the case of complex 11. Thus the pro-
cess underlying the transformation appears to be favoured
by an electron-poor alkene. This is consistent with an initial
Repetition of the VT 31P NMR experiment performed on
complex 4 (Figure 2) using deuterated [D6]THF in place of
DME, gave identical results and generated a final spectrum
at 308C containing the expected resonances at d 43 and
1
54 ppm. The H NMR spectrum was then recorded and in
addition to the usual broad resonances at d 1–8, another
broad resonance at d ꢀ11.6 ppm, was observed. The newly
observed broad resonance, with
a shift characteristic of a cobalt-
hydride species (Table 1),[24]
thus provided a correlation be-
tween the solid-state structure
and the solution observations.
Earlier in the project, repeat-
ed attempts to recrystallise
complex 4 to obtain a diastereo-
isomerically pure sample had
proved unsuccessful. One re-
crystallisation attempt from
CH2Cl2 and petroleum spirit,
however, produced small brown
crystals after being left for
three weeks at ꢀ108C. X-ray
crystallographic analysis of the
crystals revealed that they were
a s-bonded alkyne complex 17
(Figure 9), not the anticipated
complex 4.
The geometry at the cobalt
Figure 5. 31P NMR spectra of complex 9 at a) 30, b) 50, c) 55 and d) 708C in DME under carbon monoxide. centre is distorted trigonal bi-
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pyramidal with the P(1) and
P(2) phosphorus donors of the
chelating binap ligand occupy-
ing equatorial and axial sites re-
spectively, a situation also seen
in the structure of the hydride
species 12.[11] The metal lies
about 0.11 Š out of the trigonal
plane in the direction of P(2),
and it is noticeable that the
axial Co–P(2) distance of
2.1853(10) Š is about 0.06 Š
shorter than that to its equato-
rial
counterpart
[Co–P(1)
2.2488(10) Š]. In the hydride
species 12 the two distances
differ by only about 0.01Š with
ꢀ
the Co Paxial bond being about
0.01 Š longer [2.1956(11) Š],
ꢀ
and the Co Pequatorial bond
Figure 6. 31P NMR spectra of complex 11 at a) 30, b) 40, c) 45 and d) 608C in DME under carbon monoxide.
about
0.04 Š
shorter
Figure 7. Molecular structure of hydride 12.[11]
Figure 9. Molecular structure of 17.
[2.2091(11) Š], than their counterparts here in 17, respec-
tively. The second axial site is occupied by the s-bound al-
ꢀ
kynyl ligand which is approximately co-linear with the P(2)
Co bond, the P(2)-Co-C(5), Co-C(5)-C(6) and C(5)-C(6)-
C(7) angles being 177.51(11), 177.9(4) and 176.8(5)8, respec-
tively (Table 2). The geometry at the nitrogen centre is
slightly pyramidalised, N(8) lying about 0.15 Š out of the
plane of its substituents.
Figure 8. Cobalt hydrides with bidentate phosphorus ligands.
Table 1. Description of the hydride resonance of complex 12 and litera-
ture cobalt hydrides[24] for comparison.
Our serendipitous observation of complex 17 led us to
speculate that the origin of the hydride in complex 12,
formed on heating complexes 4, 9 and 11, was the terminal
hydrogens of their monosubstituted alkynes. We thus decid-
ed to examine the reactivity of a disubstituted alkyne com-
plex.
Cobalt hydride
[HCo(CO)4]
[HCo(CO)3P
[HCo(CO)2(P
[HCo(CO)2(binap)] (12)
d [ppm]
Multiplicity
Coupling to P [Hz]
R
ꢀ11.4
ꢀ11.2
ꢀ11.9
ꢀ11.6
singlet
doublet
triplet
broad
–
54
12
A
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ACHTREUNG
A
ACHTREUNG
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S. E. Gibson et al.
Table 2. Selected bond lengths [Š] and angles [8] for 17.
with a minor diastereoisomer (together with resonances at d
26–28 ppm associated with binap oxides). The 31P NMR
spectrum of complex 19 in carbon monoxide saturated
DME was recorded at 308C and then the sample was sub-
jected to the standard VT sequence. At 358C two new reso-
nances started to emerge at d 54 and 43 ppm and at 558C
these were the only resonances in the spectrum (Figure 10).
On increasing the temperature to 758C and on cooling of
the NMR experiment to 308C, no further changes to the
spectra were observed.
ꢀ
ꢀ
Co P(1)
2.2488(10)
1.770(4)
1.904(4)
1.468(6)
93.45(3)
Co P(2)
2.1853(10)
1.756(4)
1.194(5)
ꢀ
ꢀ
Co C(1)
Co C(2)
ꢀ
ꢀ
Co C(5)
C(5) C(6)
ꢀ
C(6) C(7)
P(1)-Co-P(2)
P(1)-Co-C(2)
P(2)-Co-C(1)
P(2)-Co-C(5)
C(1)-Co-C(5)
Co-C(5)-C(6)
P(1)-Co-C(1)
P(1)-Co-C(5)
P(2)-Co-C(2)
C(1)-Co-C(2)
C(2)-Co-C(5)
C(5)-C(6)-C(7)
114.43(12)
87.40(11)
95.69(13)
123.37(16)
85.85(17)
176.8(5)
121.11(12)
91.14(11)
177.51(11)
86.38(15)
177.9(4)
Observation of the resonance at d 54 ppm during the VT
31P NMR experiment on complex 19, a derivative of a disub-
stituted alkyne, proved that the hypothesis that the hydro-
gen atom of the cobalt hydride 12 originated from the termi-
nal hydrogen of monosubstituted alkynes was incorrect.
Nevertheless this experiment did reveal that the presence of
the second alkyne substituent resulted in the formation of
the hydride species earlier in the VT experiment (at 358C
for complex 19 vs 508C for complex 4).
Deprotonation
of
N-(prop-2-enyl)-p-toluenesulfona-
mide[13] and addition of 1-bromo-2-butyne generated enyne
18[25] as a crystalline solid in 99% yield. This was then trans-
formed into complex 19 via the standard approach used pre-
viously to synthesise the mono-substituted alkyne complexes
(Scheme 7).
The results described above reveal that pendent alkenes
ꢀ
promote cobalt cobalt bond cleavage in (alkyne)-
(binap)tetracarbonyldicobalt(0) complexes. The process ap-
pears to be facilitated by an electron-poor alkene and a di-
substituted alkyne and disfavoured by an electron-rich
AHCTREUNG
alkene. These observations may be explained by a direct in-
teraction of the alkene in complexes 4, 9, 11 and 19 that
Scheme 7. Synthesis of complex 19.
ꢀ
leads to cobalt cobalt bond cleavage, as postulated below,
The 31P NMR spectrum of complex 19 was examined in
[D8]toluene, since its spectrum in DME gave essentially a
single broad resonance at d 49 ppm (Figure 10). At 308C the
spectrum in [D8]toluene showed two stronger resonances at
d 49 and 48 ppm associated with a major diastereoisomer
and two weaker resonances at d 42 and 40 ppm associated
but an indirect effect resulting from interactions in a down-
stream intermediate en route to cyclopentenone formation
cannot be ruled out.
It is documented that octacarbonyldicobalt(0) is readily
transformed at room temperature in THF into the mono-
phosphane derivative 20 or the ionic diphosphane species 21
by the action of one or eight e-
quivalents of triphenylphos-
phane, respectively (Scheme
8).[26] The ionic species 21 is
presumably generated via the
formation of 20, followed by
nucleophilic attack by a second
molecule of triphenylphos-
phane, present in high concen-
tration, and the displacement of
the stable tetracarbonylcobal-
tate anion.
In light of the phosphane re-
activity, it seems reasonable to
postulate that the alkenes pres-
ent in 4, 9, 11 and 19 act as in-
ternal nucleophiles leading to
ꢀ
the cleavage of the cobalt
cobalt bonds and the genera-
tion of cobalt anions. We thus
propose that carbon monoxide
induces the formation of the h2-
Figure 10. 31P NMR spectra of complex 19 at 308C in a) [D8]toluene, and b) 30, c) 35, and d) 558C in DME
under carbon monoxide.
alkyne complex 22 from com-
plex 4 (this is consistent with
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minutes before addition via syringe of one equivalent of
enyne 3 dissolved in carbon monoxide saturated DME. The
NMR tube was then introduced into the NMR probe which
had been preheated to 758C. 31P NMR spectra were record-
ed at 40-minute intervals, but due to the low concentration
of phosphorus species no resonances of interest were ob-
served. Raising the concentration of octacarbonyldicobalt(0)
and binap to 25 mol% led to the observation of resonances
at d 54 and 43 ppm within the first hour of the experiment.
Raising the concentration of octacarbonyldicobalt(0) and
binap still further to give better quality spectra and lowering
the temperature to reduce the rate of the observed changes
in the spectra led to the spectra depicted in Figure 11, which
were recorded using 50 mol% octacarbonyldicobalt(0) and
binap at 658C. After 15 and 30 minutes, resonances associat-
ed with enyne complex 4 were clearly visible together with
resonances associated with binap (d ꢀ13 ppm) and binap
oxides (d 26 ppm). By 60 minutes complex 4 had almost dis-
appeared and the resonances at d 54 and 43 ppm were start-
ing to dominate the spectrum. At 90 minutes complex 4 was
no longer observed and the spectrum was essentially the
same at 120 minutes. Interestingly the binap and binap
oxide resonances are only seen until 30 minutes. (The origin
of the resonance at d 41ppm observed clearly in the final
spectra is unknown but subjecting octacarbonyldicobalt(0)
and binap alone to a VT 31P NMR experiment in carbon
monoxide saturated DME generated a major resonance at d
43 and a minor resonance at 41ppm at 75 8C. Thus the reso-
nance at d 41ppm is not dependent on an enyne substrate
and is probably a higher order binap cobalt cluster.)
Scheme 8. Reactions of octacarbonyldicobalt(0) with triphenylphosphane.
the first step in the proposed mechanism for the interconver-
sion of the diastereoisomers 2a and 2b as depicted in
Scheme 2, and that this is followed by the alkene displacing
the anion of 12 as depicted in Scheme 9. (The activated al-
Scheme 9. Generation of the anion of 12 via displacement by alkene.
lylic/propargylic hydrogens in the resulting undetected
cation 23 may be the source of the proton required to gener-
ate 12, and this will be probed
The constant temperature NMR experiments described
above reveal that the cobalt hydride 12 is generated under
by future labelling studies.)
Finally, in order to relate the
observations described above to
catalytic PKR conditions,
a
series of constant temperature
NMR experiments were per-
formed using substoichiometric
amounts of octacarbonyldico-
balt(0) and binap with the stan-
dard PKR enyne 3. Our estab-
lished method for a catalytic
PKR involves premixing sub-
limed octacarbonyldicobalt(0)
(7.5 mol%)
and
binap
(7.5 mol%) at room tempera-
ture for 15 minutes under
carbon
monoxide,
before
adding the substrate enyne and
heating at 758C for 3–4 h.[9]
Sublimed
octacarbonyldico-
balt(0) (7.5 mol%) and binap
(7.5 mol%) were thus mixed in
carbon monoxide saturated
Figure 11. 31P NMR spectra of octacarbonyldicobalt(0) (50 mol%), binap (50 mol%) and enyne 3 at 658C in
DME in an NMR tube for 15 carbon monoxide saturated DME with time.
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S. E. Gibson et al.
sub-stoichiometric PKR conditions. On the basis of the evi-
dence available to us at present, we postulate that it lies off
the catalytic cycle, and that intermediate 22 is partitioned
between i) hydride formation and ii) continuation of the cat-
alytic cycle (Scheme 10).
Experimental Section
Syntheses were carried out under an atmosphere of nitrogen in oven-
dried glassware using standard Schlenk techniques. THF and DME were
distilled from sodium/benzophenone and dichloromethane was distilled
from calcium hydride. N-(Prop-2-enyl)-p-toluenesulfonamide,[13] N-
propyl-p-toluenesulfonamide,[13,14] and N-(2-oxoethyl)-N-(prop-2-ynyl)-p-
toluenesulfonamide[17] were prepared according to literature procedures.
All other reagents are commercially available and were used as received.
NMR spectra were recorded on Bruker AM 500, Bruker AV 500, Bruker
DRX 400, Bruker AV 400 and Bruker DRX 300 instruments. Some
31P NMR spectra were collected in the inverse gated mode to enable
peak integration. Melting points were recorded in open capillaries on a
Sanyo Gallenkamp melting-point apparatus and are uncorrected. IR
spectra were recorded on a Perkin-Elmer Spectrum RX FT-IR spectrom-
eter. Mass spectra were recorded on Micromass AutoSpec-Q and Micro-
mass Platform II spectrometers. Elemental analyses were performed by
the London Metropolitan University microanalytical service.
[12]
N-(Prop-2-enyl)-N-(prop-2-ynyl)-p-toluenesulfonamide (3):
N-(Prop-
2-enyl)-p-toluenesulfonamide[13] (5.92 g, 28 mmol) was dissolved in anhy-
drous DMF (50 mL) and sodium hydride (1.46 g, 36.4 mmol) was added
with care. The mixture was stirred at room temperature for 30 min. Prop-
argyl bromide (5.15 mL, 46.2 mmol) was added and the reaction was
stirred for 1h. The reaction mixture was then quenched with water
(85 mL) and the product was extracted with diethyl ether (4”40 mL).
The organic layer was dried over magnesium sulfate and concentrated in
vacuo. The brown liquid was then loaded onto a chromatography column
of silica gel and eluted with hexane/diethyl ether 5:1to collect the title
compound 3, which was then recrystallised from diethyl ether/hexane 1:5
(5.95 g, 85%). M.p. 63–658C; 1H NMR (300 MHz, CDCl3): d=2.02 (t,
4J
6 Hz, 2H; NCH2CH=CH2), 4.11 (d, 4J
5.26 (dd, 3J(H,H)=10, 2J
(H,H)=1Hz, 1H; CH =CH2 (E)), 5.31(dd,
A
N
AHCTREUNG
A
ACHTREUNG
2
3
3J
10, 6 Hz, 1H; CH=CH2), 7.32 (d, 3J
(d, 3J(H,H)=8 Hz, 2H; Ar-H); 13C NMR (75 MHz, CDCl3): d=21.6
G
G
ACHTREUNG
AHCTREUNG
Scheme 10. A proposed catalytic cycle for the binap directed PKR indi-
cating a pathway for cobalt loss.
(CH3), 35.8 (NCH2C=CH), 49.0 (NCH2CH=CH2), 73.7 (NCH2C=CH),
76.5 (NCH2C=CH), 120.0 (NCH2CH=CH2), 127.8 (Cortho), 129.5 (Cmeta),
131.9 (NCH2CH=CH2), 136.0 (Cpara), 143.6 ppm (Cipso); IR (CH2Cl2): n˜ =
3301(s), 3081(w, C =C-H), 2120 (w, C=C), 1644 (m), 992 (m), 934 (s, C=
C), 1347, 1165 cmꢀ1 (s, NSO2); MS (FAB): m/z (%): 250 (100) [M+H]+,
155 (23) [CH3C6H4SO2]+, 91(25) [C H7]+.
Conclusion
7
(Binap)tetracarbonyl[N-(prop-2-enyl)-N-(prop-2-ynyl)-p-toluenesulfona-
mide]dicobalt(0) (4): Octacarbonyldicobalt(0) (75 mg, 0.220 mmol) and
(ꢁ)-2,2’-bis(diphenylphosphino)-1,1’-binaphthalene (140 mg, 0.225 mmol)
were dissolved in THF (15 mL) and stirred at room temperature for
30 min. The mixture was heated to 408C for 230 min. Enyne 3 (56 mg,
0.226 mmol) was added and the reaction was stirred at 408C for 2 h. The
mixture was allowed to cool to room temperature and was then adsorbed
onto neutral alumina (grade II). The brown solid was loaded onto a chro-
matography column of silica gel and eluted under nitrogen, first with
hexane/ethyl acetate 19:1 to remove unreacted octacarbonyldicobalt(0)
and then with hexane/ethyl acetate 7:3 to collect title compound 4 as a
brown solid (109 mg, 45%). 13C NMR (125 MHz, CDCl3): too broad to
interpret; 31P NMR (500 MHz, CDCl3): d=58.9, 53.2, 44.0, 39.2 (CoPPh2-
Ar), ꢀ14.6 ppm (BINAP); IR (CHCl3): n˜ =2043, 1980, 1939 cmꢀ1 (s, C=
Four (binap)
11 and 19, and one (binap)
ACHTREUNG
AHCTREUNG
complex 6 have been synthesised and their reactivity moni-
tored by VT 31P NMR spectroscopy. Formation of (binap)di-
carbonylhydridocobalt(ꢀ1) 12 occurred at temperatures be-
tween 35 and 558C and was facilitated by either an electron-
poor alkene or a disubstituted alkyne. In the absence of a
pendent alkene, complex 6 proved stable up to 758C. These
results reveal that formation of hydride 12 requires a pend-
ent alkene, and a mechanism involving alkene displacement
of a (binap)cobaltate anion may account for the observa-
tions, although formation of 12 at a later stage in the pro-
gression of the enyne through the Pauson–Khand reaction
cannot be discounted. Regardless of its origins, the appear-
ance of hydride 12 in NMR spectra run under Pauson–
Khand conditions suggests that it is of significance in this re-
action and that prevention of its formation may lead to a
more efficient catalytic system. It is anticipated that experi-
ments using phosphorus labelled enynes and binap should
provide further information on how the generation and fate
of 12 relate to cyclopentenone formation.
1
O); H NMR (500 MHz, CDCl3): too broad to interpret; MS (FAB): m/z
(%): 1017 (11) [Mꢀ3CO]+, 989 (40) [Mꢀ4CO]+, 681(010) [Co-
(BINAP)]+, 437 (65) [BINAP-PPh2]+.
General experimental for VT 31P NMR of complexes 4, 6, 9, 11, and 19:
Complex 4, 6, 9, 11 or 19 (about 75 mg) was dissolved in CO saturated
DME (1mL) and syringed via a filter needle into a WILMAD screw cap
(with a PTFE/silicone septum) NMR tube under carbon monoxide. A
variable temperature NMR experiment was then performed (30 to 758C
(in 5/108c intervals) then in one step back to 308C). See Figures 2, 4–6,
and 10 for selected spectra.
N-(Propyl)-N-(prop-2-ynyl)-p-toluenesulfonamide (5): N-Propyl-p-tolu-
ene
sulfonamide (1.77 g, 8 mmol)[13,14] was dissolved in anhydrous DMF
A
7106
www.chemeurj.org
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 7099 – 7109

A
N
FULL PAPER
(15 mL) and sodium hydride (0.43 g, 11 mmol) was added with care. The
mixture was stirred at room temperature for 30 min. Propargyl bromide
(1.5 mL, 14 mmol) was added and the reaction was stirred for 1 h. The re-
action mixture was then quenched with water (50 mL) and the product
was extracted with diethyl ether (4”30 mL). The organic layer was dried
over magnesium sulfate and concentrated in vacuo. The crude mixture
was then loaded onto a chromatography column of silica gel and eluted
with hexane/diethyl ether 5:1to collect the title compound 5, which was
then ground in a mortar and pestle and dried in vacuo (1.39 g, 67%).
12.4 mmol) was added and the reaction was stirred for 1 h. The reaction
mixture was then quenched with water (40 mL) and the product was ex-
tracted with diethyl ether (4”20 mL). The organic layer was dried over
magnesium sulfate and concentrated in vacuo. The brown liquid was then
loaded onto a chromatography column of silica gel and eluted with
hexane/diethyl ether 5:1to collect the title compound 8 (1.68 g, 85%).
M.p. 64–668C; 1H NMR (500 MHz, CDCl3): d=1.67–1.69 (m, 3H; CH3),
2.00 (t, 4J
3J(H,H)=7 Hz, 2H; NCH2CH=CHCH3), 4.10 (d, 4J
NCH2C=CH), 5.38–5.31(m, 1H; NCH 2CH=CHCH3), 5.73–5.66 (m, 1H;
NCH2CH=CHCH3), 7.28 (d, 3J
(H,H)=8 Hz, 2H; Ar-H), 7.71ppm (d,
3J(H,H)=8 Hz, 2H; Ar-H); 13C NMR (125 MHz, CDCl3): d=17.6 (CH3),
ACHTREUNG
A
ACHTREUNG
M.p. 47–498C; 1H NMR (500 MHz, CDCl3): d=0.91(t, 3J
3H; CH3), 1.58 (tq, 3J
(H,H)=7, 7 Hz, 2H; NCH2CH2CH3), 2.00 (t,
4J(H,H)=2 Hz, 1H; NCH2C=CH), 2.40 (s, 3H; CH3), 3.14 (t, 3J
(H,H)=
(H,H)=2 Hz, 2H; NCH2C=CH),
(H,H)=8 Hz, 2H; Ar-H), 7.71ppm (d, 3J
(H,H)=8 Hz, 2H;
13C NMR
(125 MHz, CDCl3): d=11.0 (CH3), 20.8
A
E
ACHTREUNG
A
N
ACHTREUNG
7 Hz, 2H; NCH2CH2CH3), 4.11 (d, 4J
N
21.5 (CH3), 35.4 (NCH2C=CH), 48.2 (NCH2CH=CHCH3), 73.5 (NCH2C=
CH), 76.7 (NCH2C=CH), 124.4 (NCH2CH=CHCH3), 127.7 (Cortho), 129.4
(Cmeta), 131.6 (NCH2CH=CHCH3), 136.1 (Cpara), 143.4 ppm (Cipso); IR
(CHCl3): n˜ =3308 (s, C=C-H), 3038 (m, C=C-H), 1673 (w, C=C), 1348,
1160 cmꢀ1 (s, NSO2); MS (FAB): m/z (%): 264 (100) [M+H]+, 262 (28)
7.27 (d, 3J
A
ACHTREUNG
Ar-H);
(NCH2CH2CH3), 21.4 (CH3), 36.1(N CH2C=CH), 48.0 (NCH2CH2CH3),
73.5 (NCH2C=CH), 76.6 (NCH2C=CH), 127.6 (Cortho), 129.4 (Cmeta), 136.0
(Cpara), 143.3 ppm (Cipso); IR (CHCl3): n˜
=
3308 (m, C=C-H), 1348,
[MꢀH]+,
222
(36)
[MꢀCH=CHCH3]+,
210
(72)
1159 cmꢀ1 (s, NSO2); MS (FAB): m/z (%): 252 (100) [M+H]+, 155 (18)
[CH3C6H4SO2NHCH2CH=CH]+, 155 (41) [CH3C6H4SO2]+, 108 (32)
[CH3C6H4SO2]+, 91(24) [C H7]+.
[HC=CCH2NCH2CH=CHCH3]+, 91(39) [C H7]+.
7
7
A
G
ACHTREUNG
dicobalt(0) (6): Octacarbonyldicobalt(0) (75 mg, 0.220 mmol) and (ꢁ)-
2,2’-bis(diphenylphosphino)-1,1’-binaphthalene (140 mg, 0.225 mmol)
were dissolved in THF (15 mL) and stirred at room temperature for
30 min. The mixture was heated to 408C for 30 min. Enyne 5 (57 mg,
0.226 mmol) was added and the reaction was stirred at 408C for 2 h. The
mixture was allowed to cool to room temperature and was then absorbed
onto neutral alumina (grade II). The brown solid was loaded onto a chro-
matography column of silica gel and eluted under nitrogen, first with
hexane/ethyl acetate 19:1 to remove unreacted octacarbonyldicobalt(0)
and then with hexane/ethyl acetate 7:3 to collect compound 6 as a brown
ACHTREUNG
(ꢁ)-2,2’-bis(diphenylphosphino)-1,1’-binaphthalene (140 mg, 0.225 mmol)
were dissolved in THF (15 mL) and stirred at room temperature for
30 min. The mixture was heated to 408C for 30 min. Enyne 8 (59 mg,
0.224 mmol) was added and the reaction was stirred at 408C for 2 h. The
mixture was allowed to cool to room temperature and was then adsorbed
onto neutral alumina (grade II). The brown solid was loaded onto a chro-
matography column of silica gel and eluted under nitrogen, first with
hexane/ethyl acetate 19:1 to remove unreacted octacarbonyldicobalt and
then with hexane/ethyl acetate 7:3 to collect the title compound 9 as a
brown solid (152 mg, 62%). 1H NMR (500 MHz, CDCl3): too broad to
interpret; 13C NMR (125 MHz, CDCl3): too broad to interpret; 31P NMR
(202 MHz, CDCl3): d=58.7, 53.0, 43.7, 39.0 (CoPPh2-Ar), ꢀ14.7 ppm
(BINAP); IR (CHCl3): n˜ =2041, 1977, 1935 cmꢀ1 (s, C=O); MS (FAB):
m/z (%): 1031 (20) [Mꢀ3CO]+, 1003 (58) [Mꢀ4CO]+, 681(100) [Co-
1
solid (159 mg, 66%). H NMR (500 MHz, CDCl3): too broad to interpret;
13C NMR (125 MHz, CDCl3): too broad to interpret; 31P NMR
(202 MHz, CDCl3): d=57.9, 51.6, 43.8, 39.9 (CoPPh2-Ar), ꢀ14.9 ppm
(BINAP); IR (CHCl3): n˜ =2044 (m), 1980 (s), 1940 cmꢀ1 (w, C=O); MS
(FAB): m/z (%): 1019 (18) [Mꢀ3CO]+, 991(54) [ Mꢀ4CO]+, 681(16)
[Co(BINAP)]+, 437 (24) [BINAP-PPh2]+, 71(100) [CH 2NCH2CH2CH3]+;
recrystallisation from CH2Cl2/pentane gave a pure sample; elemental
analysis calcd (%) for C61H49Co2NO6P2S (1103.92): C 66.37, H 4.47, N
1.27; found: C 66.32, H 4.41, N 1.17.
(BINAP)]+, 437 (56) [BINAP-PPh2]+.
N-(3-Carbomethoxyprop-2-enyl)-N-(prop-2-ynyl)-p-toluenesulfonamide
(10):[18] N-(2-oxoethyl)-N-(prop-2-ynyl)-p-toluenesulfonamide[17] (1.49 g,
6 mmol) and methyl(triphenylphosphoranylidene) acetate (3.96 g,
12 mmol) were dissolved in benzene (30 mL). The solution was stirred
overnight at room temperature under nitrogen. The mixture was then
concentrated in vacuo and loaded onto a chromatography column of
silica gel and eluted with hexane/ethyl acetate 5:1. The title compound
10 was collected as a colourless oil (1.42 g, 78%). 1H NMR (500 MHz,
N-(But-2-enyl)-p-toluenesulfonamide (7):[15] p-Toluene sulfonyl isocya-
nate (0.34 mL, 2.2 mmol) and 3-buten-2-ol (0.17 mL, 2 mmol) were dis-
solved in THF (10 mL) and stirred at room temperature for 10 min. The
reaction mixture was then concentrated in vacuo and redissolved in
DMF (10 mL). Palladium (ii) acetate (22 mg, 0.1mmol) and lithium bro-
mide (0.69 g, 8 mmol) were added and the reaction was stirred at 1008C
for 22.5 h. The reaction mixture was allowed to cool before extraction
with diethyl ether (200 mL) and the organic layer was washed with water
(3”40 mL) and brine (3”40 mL). The crude product was dried over
magnesium sulfate and concentrated in vacuo before being loaded onto a
chromatography column of silica gel and eluted with hexane/ethyl acetate
7:3. The title compound 7 was collected as a white solid (288 mg, 64%).
M.p. 62–648C; 1H NMR (500 MHz, CDCl3): d=1.59–1.61 (m, 3H; CH3),
CDCl3): d=2.05 (t, 4J
ACHTREUNG
3.71(s, 3H; OCH 3), 3.96 (dd, 4J
U
ACHTREUNG
NCH2CH=CH), 4.07 (d, 4J
ACHTREUNG
4J
C
N
(H,H)=16,
3
3
ACHTREUNG
6 Hz, 1H; NCH2CH=CH), 7.29 (d, 3J
(d, 3J
ACHTREUNG
(CH3), 36.7 (NCH2C=CH), 47.1(N CH2CH=CH), 51.7 (OCH3), 74.5
(NCH2C=CH), 76.0 (NCH2C=CH), 124.3 (NCH2HC=CH), 127.7 (Cortho),
129.7 (Cmeta), 135.6 (Cpara), 141.6 (NCH2CH=CH), 144.0 (Cipso), 166.0 ppm
(C=O); IR (CH2Cl2): n˜ = 3300 (m, C=C-H), 1722 (s, C=O), 1664, 983
2.42 (s, 3H; CH3), 3.50 (tt, 3J
N
3
4.46 (t, J
ACHTREUNG
5.60–5.52 (m, 1H; NCH2CH=CHCH3), 7.30 (d, 3J
H), 7.74 ppm (d, 3J
(m, C=C), 1351, 1163 (s, NSO2), 1197, 1096 cmꢀ1 (m, C O); MS (FAB):
ꢀ
A
m/z (%): 308 (100) [M+H]+, 276 (34) [MꢀOCH3]+, 155 (46)
CDCl3): d=17.5 (CH3), 21.5 (CH3), 45.3 (NCH2CH=CHCH3), 125.6
(NCH2CH=CHCH3), 127.1 (Cortho), 129.6 (Cmeta), 129.7 (NCH2CH=
CHCH3), 137.0 (Cpara), 143.2 ppm (Cipso); IR (CHCl3): n˜ =3380, 1496 (m,
N-H), 1673 (w, C=C), 1329, 1159 cmꢀ1 (s, NSO2); MS (FAB): m/z (%):
226 (67) [M+H]+, 224 (34) [MꢀH]+, 172 (100) [CH3C6H4SO2NH3]+, 1 55
(50) [CH3C6H4SO2]+, 91(55) [C 7H7]+, 69 (59) [CH3CH=CHCH2N]+, 55
(85) [CH3CH=CHCH2]+.
N-(But-2-enyl)-N-(prop-2-ynyl)-p-toluenesulfonamide (8):[16] Sulfonamide
7 (1.70 g, 7.5 mmol) was dissolved in anhydrous DMF (15 mL) and
sodium hydride (0.39 g, 9.8 mmol) was added with care. The mixture was
stirred at room temperature for 30 min. Propargyl bromide (2.4 mL,
[CH3C6H4SO2]+, 91(46) [C H7]+.
7
AHCTREUNG
0.225 mmol) were dissolved in THF (15 mL) and stirred at room temper-
ature for 30 min. The mixture was heated to 408C for 30 min. Enyne 10
(67.7 mg, 0.220 mmol) was added and the reaction was stirred at 408C for
2 h. The mixture was allowed to cool and was then adsorbed onto neutral
alumina (grade II). The brown solid was loaded onto a chromatography
column of silica gel and eluted under nitrogen, first with hexane/ethyl
acetate 19:1 to remove unreacted octacarbonyldicobalt and then with
Chem. Eur. J. 2007, 13, 7099 – 7109
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
7107

S. E. Gibson et al.
hexane/ethyl acetate 7:3 to collect the title compound 11 as a brown solid
(114 mg, 45%). 1H NMR (500 MHz, CDCl3): too broad to interpret;
13C NMR (125 MHz, CDCl3): too broad to interpret; 31P NMR
(202 MHz, CDCl3): d=58.7, 51.7, 44.0, 40.1 (CoPPh2-Ar), ꢀ14.3 ppm
(BINAP); IR (CHCl3): n˜ =2044, 1981, 1941 (s, C=O), 1720 cmꢀ1 (m, O-
C=O); MS (FAB): m/z (%): 1075 (16) [Mꢀ3CO]+, 1 047 (30) [Mꢀ4CO]+,
(grade II). The brown solid was loaded onto a chromatography column
of silica gel and eluted under nitrogen, first with hexane then with
hexane/ethyl acetate 19:1 to remove unreacted octacarbonyldicobalt and
then with hexane/ethyl acetate 7:3 to collect title compound 19 as a
brown solid (75 mg, 31%).1H NMR (500 MHz, CDCl3): Too broad to in-
terpret; 13C NMR (125 MHz, CDCl3): Too broad to interpret; 31P NMR
(500 MHz, [D8]toluene): d = 49.0, 47.9, 41.4, 39.4 (CoPPh2-Ar), ꢀ14.6
(BINAP); IR (CHCl3): n˜ =2040, 1977 (s), 1928 cmꢀ1 (m, C=O); MS
(FAB): m/z (%): 1031 (10) [Mꢀ3CO]+, 1003 (47) [Mꢀ4CO]+, 681(100)
681(100) [Co
(BINAP)]+, 437 (68) [BINAP-PPh2]+.
G
(Binap)dicarbonylhydridocobalt(I): Enyne complex 4 (35 mg) was dis-
solved in CO-saturated DME (0.8 mL) and syringed via a filter needle
into a WILMAD screw cap (with a PTFE/silicon septum) NMR tube
filled with carbon monoxide; 31P NMR spectra were recorded between
308C and 758C. The NMR tube was then allowed to cool to 308C and
the 31P NMR spectrum was recorded at this temperature, 31P NMR
(160 MHz, DME): d = 53.4, 43.2, (CoPPh2-Ar), ꢀ14.2 (binap; <5%).
On storing the NMR tube in the freezer, small brown crystals appeared
in the NMR tube and these were identified as hydride 12 by X-ray crys-
tallography[11] and mass spectrometry MS (FAB): m/z (%): 710 (63)
[MꢀCO]+, 437 (100) [BINAP-PPh2]+. The early stages of the experiment
were subsequently repeated in [D8]THF. On cooling to 308C, the 31P and
[Co
(BINAP)]+, 437 (90) [BINAP-PPh2]+.
U
Examination of the PKR by 31P NMR spectroscopy at 658C: Octacarbo-
nyldicobalt(0) (19.3 mg, 0.06 mmol), (S)-BINAP (37.4 mg, 0.06 mmol)
and enyne 3 (29.4 mg, 0.12 mmol) were dissolved in CO saturated DME
(3 mL) and syringed via a filter needle into a WILMAD screw cap (with
a PTFE/silicone septum) NMR tube under CO and the NMR tube was
left at room temperature for 15 min. The NMR tube was introduced into
the NMR probe which had been preheated to 658C and a 31P NMR ex-
periment was performed collecting a spectrum at set time intervals.
1H NMR spectra were recorded, 31P NMR (160 MHz, [D8]THF): d
=
1
52.9, 42.6; H NMR (400 MHz, [D8]THF): d = ꢀ11.6 (broad, Co-H).
[1] For recent reviews on various aspects of the PKR, see a) S. E.
Gibson, N. Mainolfi, Angew. Chem. 2005, 117, 3082–3097; Angew.
Chem. Int. Ed. 2005, 44, 3022–3037; S. Laschat, A. Becheanu, T.
Bell, A. Baro, Synlett 2005, 2547–2570; b) L.V. R. Bonaga, M. E.
Krafft, Tetrahedron 2004, 60, 9795–9833; c) J. Blanco-Urgoiti, L.
Anorbe, L. Perez-Serrano, G. Dominguez, J. Perez-Castells, Chem.
Soc. Rev. 2004, 33, 32–42; d) S. E. Gibson, A. Stevenazzi, Angew.
Chem. 2003, 115, 1844–1854; Angew. Chem. Int. Ed. 2003, 42, 1800–
1810; K. M. Brummond, J. L. Kent, Tetrahedron 2000, 56, 3263–
3283.
X-ray crystallography of complex 17: Enyne complex
4 (48 mg,
0.04 mmol) was dissolved in degassed CH2Cl2 (4 mL) and syringed care-
fully into a sealed test tube under nitrogen. Degassed petroleum spirit
(15 mL) was then carefully syringed on top of the CH2Cl2 layer, avoiding
the mixing of the two solvents. The test tube was then placed in the
freezer for three weeks after which brown crystals could be observed.
¯
Crystal data: [C59H46CoNO4P2S].0.5CH2Cl2, M=1028.36, triclinic, P1 (no.
2), a=11.1811(8), b=13.3311(8), c=18.3365(12) Š, a=75.184(5), b=
84.931(5) g=80.246(5)8, V=2601(3) Š3, Z=2, 1calcd =1.313 gcmꢀ3
, m-
A
bur PX Ultra diffractometer; 9650 independent measured reflections, F2
refinement, R1 =0.0664, wR2 =0.1773, 8223 independent observed absorp-
[2] I. U. Khand, G. R. Knox, P. L. Pauson, W. E. Watts, J. Chem. Soc. D
1971, 36.
[3] a) K. Hiroi, T. Watanabe, R. Kawagishi, I. Abe, Tetrahedron Lett.
2000, 41, 891–895; b) K. Hiroi, T. Watanabe, R. Kawagishi, I. Abe,
Tetrahedron: Asymmetry 2000, 11, 797–808.
tion corrected reflections [jFo j>4s(jFoj), 2qmax =1428], 654 parameters.
U
[4] S. J. Sturla, S. L. Buchwald, J. Org. Chem. 2002, 67, 3398–3403.
[5] P. Magnus, L. M. Principe, Tetrahedron Lett. 1985, 26, 4851–4854.
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1708; b) T. J. M. de Bruin, A. Milet, F. Robert, Y. Gimbert, A. E.
Greene, J. Am. Chem. Soc. 2001, 123, 7184–7185; c) M. A. Pericas,
J. Balsells, J. Castro, I. Marchueta, A. Moyano, A. Riera, J. Vazquez,
X. Verdaguer, Pure Appl. Chem. 2002, 74, 167–174; d) Y. Gimbert,
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Greene, Y. Gimbert, J. Org. Chem. 2004, 69, 1075–1080..
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[8] A. Lagunas, A. Mairata, I Payeras, C. Jimeno, M. A. Pericas, Org.
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Acta 1997, 80, 623–639.
N-(Prop-2-enyl)-N-(but-2-ynyl)-p-toluenesulfonamide (18):[25] N-(Prop-2-
enyl)-p-toluenesulfonamide (4.0 g, 18.9 mmol) was dissolved in anhy-
drous DMF (40 mL) and sodium hydride (0.99 g, 24.6 mmol) was added
with care. The mixture was stirred at room temperature for 30 min. 1-
Bromo-but-2-yne (2.75 mL, 31.4 mmol) was added and the reaction was
stirred for 1h. The reaction mixture was then quenched with water
(100 mL) and the product was extracted with diethyl ether (3”50 mL).
The organic washings were dried over magnesium sulfate and concentrat-
ed in vacuo. The brown liquid was then loaded onto a chromatography
column of silica gel and eluted with hexane/diethyl ether 5:1to collect
the title compound 18 as a crystalline solid (4.95 g, 99%). M.p. 35–368C;
1H NMR (400 MHz, CDCl3): d=1.53 (t, 4J
2.42 (s, 3H; CH3), 3.79 (d, 3J
(H,H)=6 Hz, 2H; NCH2CH=CH2), 4.01(q,
4J(H,H)=2 Hz, 2H; NCH2C=CCH3), 5.21(dd, 3J(H,H)=10, 2J
(H,H)=
1Hz, 1H; CH =CH2 (E)), 5.26 (dd, 3J(H,H)=17, 2J
(H,H)=1Hz, 1H;
CH=CH2 (Z)), 5.73 (ddt, 3J
(H,H)=17, 10, 6 Hz, 1H; CH=CH2), 7.29 (d,
3J(H,H)=8 Hz, 2H, Ar-H), 7.73 ppm (d, 3J
(H,H)=8 Hz, 2H; Ar-H);
A
AHCTREUNG
A
N
ACHTREUNG
A
ACHTREUNG
AHCTREUNG
A
ACHTREUNG
13C NMR (100 MHz, CDCl3): d=3.2 (C=CCH3), 21.5 (CH3), 36.3
(NCH2C=CCH3), 48.9 (NCH2CH=CH2), 71.7 (NCH2C=CCH3), 81.5
(NCH2C=CCH3), 119.4 (NCH2CH=CH2), 127.9 (Cortho), 129.2 (Cmeta),
132.3 (NCH2CH=CH2), 136.3 (Cpara), 143.2 ppm (Cipso); IR (CHCl3): n˜ =
2225 (w, C=C), 1645, 992, 936 (m, C=C), 1348, 1160 cmꢀ1 (s, NSO2); MS
(CI): m/z (%): 281(100) [ M+NH4]+, 264 (88) [M+H]+, 110 (52) [H3CC=
CCH2H2NCH2CHCH2]+.
[13] F. E. Scully, K. Bowdring, J. Org. Chem. 1981, 46, 5077–5081.
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Chem. 2002, 67, 1233–1246.
ACHTREUNG
ACHTREUNG
(ꢁ)-2,2’-bis(diphenylphosphino)-1,1’-binaphthalene (138 mg, 0.222 mmol)
were dissolved in THF (15 mL) and stirred at room temperature for
30 min. The mixture was heated to 408C for 30 min. Enyne 18 (57 mg,
0.216 mmol) was added and the reaction was stirred at 408C for 2 h. The
mixture was allowed to cool and was then adsorbed onto neutral alumina
[17] M. Ishizaki, O. Hoshino, Tetrahedron 2000, 56, 8813–8819.
[18] S. Watanuki, M. Mori, Organometallics 1995, 14, 5054–5061.
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Parker, Inorg. Chem. 1985, 24, 3956–3962.
7108
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ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2007, 13, 7099 – 7109

A
N
FULL PAPER
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Received: April 16, 2007
Published online: June 26, 2007
Chem. Eur. J. 2007, 13, 7099 – 7109
ꢁ 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
7109