Diastereoselective addition of allyl- And crotylstannanes to dicobalt-complexed acetylenic aldehydes

Article abstract of DOI:10.1021/om050019g

In an endeavor to utilize metal carbonyl complexes of acetylenic aldehydes and ketones to control the stereoselectivity of nucleophilic acyl addition, the dicobalt hexacarbonyl and dicobalt pentacarbonyl(triphenylphosphine) complexes of 3-phenylpropynal and 2-hexynal were conveniently prepared. Crotyl transfer from either (E)- or (Z)-crotyltributylstannane to Co₂(CO) ₆-complexed 3-phenylpropynal and 2-hexynal produced 3,4-disubstituted-1,5-enynes with high syn diastereoselectivity. Allyl and 2-methylallyl transfer to Co₂(CO)₅PPh₃- complexed aldehydes was also accomplished with high yields and diastereoselectivities. In all cases, decomplexation of the metal carbonyl moiety was effected, selectively, under very mild oxidative conditions. Exchange of a CO by PPh₃ led to decreased overall reactivity. Two competing kinetic processes were observed: stereoselective allylation was observed at low temperature, but at higher temperatures, the first formed allylic alcohol preferentially underwent elimination leading to dienynes.

Full text of DOI:10.1021/om050019g

Organometallics 2005, 24, 2617-2627
2617
Diastereoselective Addition of Allyl- and
Crotylstannanes to Dicobalt-Complexed Acetylenic
Aldehydes
Sonya Balduzzi,†,‡ Michael A. Brook,*,† and Michael J. McGlinchey*,§
Department of Chemistry, McMaster University, Hamilton, Ontario, Canada L8S 4M1, and
Department of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland
Received January 11, 2005
In an endeavor to utilize metal carbonyl complexes of acetylenic aldehydes and ketones
to control the stereoselectivity of nucleophilic acyl addition, the dicobalt hexacarbonyl and
dicobalt pentacarbonyl(triphenylphosphine) complexes of 3-phenylpropynal and 2-hexynal
were conveniently prepared. Crotyl transfer from either (E)- or (Z)-crotyltributylstannane
to Co2(CO)6-complexed 3-phenylpropynal and 2-hexynal produced 3,4-disubstituted-1,5-
enynes with high syn diastereoselectivity. Allyl and 2-methylallyl transfer to Co2(CO)5PPh3-
complexed aldehydes was also accomplished with high yields and diastereoselectivities. In
all cases, decomplexation of the metal carbonyl moiety was effected, selectively, under very
mild oxidative conditions. Exchange of a CO by PPh3 led to decreased overall reactivity.
Two competing kinetic processes were observed: stereoselective allylation was observed at
low temperature, but at higher temperatures, the first formed allylic alcohol preferentially
underwent elimination leading to dienynes.
Introduction
carbonyl oxygen and delivering the allyl group, the
diastereoselectivity can be attributed to a preferred
orientation of the aldehyde, which minimizes 1,3-diaxial
interactions, in a putative closed, Zimmerman-Traxler
type transition state. Assuming that the dominant steric
interaction is between the alkynyl moiety and the
ligands on boron, the degree of stereoselection reported
is based upon the large difference in steric bulk between
the alkynyl group and the aldehydic proton. The dicobalt
cluster plays a passive role, in that it simply serves to
amplify this intrinsic difference in steric bulk. Conse-
quently, reduced diastereoselectivity would be expected
from the addition of crotylboranes and crotylboronates
to ketones.
Methods for the introduction of nucleophiles at a
propargyl carbon with simultaneous control of stereo-
chemistry are invaluable for the construction of building
blocks that contain multiple asymmetric centers and
sites that are amenable to further transformation. The
1,5-enyne carbon skeleton is an extremely versatile
fragment that continually finds application in total
syntheses.1 One approach to formation of the 1,5-enyne
system, which allows the substituents at C2, C3, and
C4 to be varied with concomitant control of their
stereochemistry, involves allylic transposition from an
allylmetal reagent to an acetylenic aldehyde or ketone.
The allyl transfer reaction is of particular synthetic
value, as the resulting homoallylic alcohol can be
transformed into an aldol derivative upon oxidation of
the double bond, thereby functioning as the synthetic
equivalent of an aldol addition. Some common trans-
formations that allow the 1,5-enyne carbon framework
to be further extended are shown in Scheme 1.2
From our preliminary studies involving allyl transfer
from functionalized allylsilanes onto dicobalt hexacar-
bonyl-complexed acetylenic aldehydes and ketones,6 we
(2) (a) Morgans, D. J., Jr. Tetrahedron Lett. 1981, 22, 3721. (b)
Maruyama, K.; Ishihara, Y.; Yamamoto, Y. Tetrahedron Lett. 1981,
22, 4235. (c) Tomooka, K.; Keong, P.-H.; Nakai, T. Tetrahedron Lett.
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(f) Barrett, A. G. M.; Pilipauskas, D. J. Org. Chem. 1990, 55, 5194. (g)
Zhang, H. X.; Guibe´, F.; Balavoine, G. J. Org. Chem. 1990, 55, 1857.
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R. B. J. Am. Chem. Soc. 1967, 89, 5085. (m) Zweifel, G.; Steele, R. B.
J. Am. Chem. Soc. 1967, 89, 2754. (n) Denmark, S. E.; Jones, T. K. J.
Org. Chem. 1982, 47, 4595. (o) Ohmori, K.; Nishiyama, S.; Yamamura,
S. Tetrahedron Lett. 1995, 36, 6519. (p) Cohen, N.; Lopresti, R. J.;
Neukom, C.; Saucy, G. J. Org. Chem. 1980, 45, 383. (q) Marshall, J.
A.; DeHoff, B. S. J. Org. Chem. 1986, 51, 863. (r) Chemin, D.; Gueugnot,
S.; Linstrumelle, G. Tetrahedron 1992, 48, 4369.
High levels of syn diastereoselectivity3 of the C3-C4
substituents in 3,4-disubstituted-1,5-enynes have been
obtained from the addition of chiral crotylboronates4 and
chiral γ-alkoxyallylboranes5 to dicobalt hexacarbonyl-
complexed acetylenic aldehydes. In both cases, since
boron performs the dual function of coordinating to the
† McMaster University.
‡ Current address: Department of Chemistry, University of Mon-
treal, C.P. 6128, succ. Centre-ville, Montreal, Quebec, Canada H3C
3J7.
§ University College Dublin.
(1) Recent examples include: (a) Nicolaou, K. C.; Murphy, F.;
Barluenga, S.; Ohshima, T.; Wei, H.; Xu, J.; Gray, D. L. F.; Baudoin,
O. J. Am. Chem. Soc. 2000, 122, 3830. (b) Tomooka, K.; Kikuchi, M.;
Igawa, K.; Suzuki, M.; Keong, P.-H.; Nakai, T. Angew. Chem., Int. Ed.
2000, 39, 4502. (c) Smith, A. B., III; Ott, G. R. J. Am. Chem. Soc. 1998,
120, 3935.
(3) Masamune’s stereochemical nomenclature has been adopted.
Masamune, S.; Ali, S. A.; Snitman, D. L.; Garvey, D. S. Angew. Chem.,
Int. Ed. Engl. 1980, 19, 557.
(4) Roush, W. R.; Park, J. C. J. Org. Chem. 1990, 55, 1143.
(5) Ganesh, P.; Nicholas, K. M. J. Org. Chem. 1997, 62, 1737.
(6) Balduzzi, S. Ph.D. Thesis, McMaster University, 2000.
10.1021/om050019g CCC: $30.25 © 2005 American Chemical Society
Publication on Web 04/26/2005

2618 Organometallics, Vol. 24, No. 11, 2005
Balduzzi et al.
Scheme 1
Table 1. Allyl Transfer to Noncomplexed and
Co2(CO)6-Complexed Alkynalsa
recognized that the dicobalt cluster might be made to
assume an active role in controlling the carbonyl facial
selectivity during nucleophilic acyl addition. A general
method to control the stereoselectivity of carbon-carbon
bond formation that could be applied to acetylenic
ketones as well as aldehydes would be synthetically
advantageous. We chose silanes and stannanes as
nucleophilic reactants for an investigation of nucleo-
philic addition to dicobalt-complexed acetylenic alde-
hydes and ketones. These allyl reagents have consid-
erable synthetic utility since substitution at any of the
allylic R, â, or γ positions provides a route to a wealth
of compounds containing the 1,5-enyne system, they can
be readily prepared in large quantities, and they are
configurationally stable at room temperature.
We report herein the diastereoselectivities of 3,4-
disubstituted-1,5-enynes obtained from the addition of
crotyltributylstannanes to dicobalt hexacarbonyl-com-
plexed aliphatic and aromatic acetylenic aldehydes. Also
reported are the diastereoselectivities of allyl transfer
to the corresponding chiral dicobalt pentacarbonyl-
(triphenylphosphine)-complexed propynals. To our knowl-
edge, this is the first report of allyl and crotyl transfer
to dicobalt-complexed aldehydes from reagents based on
group 14 elements.
entry
aldehyde
allylstannane
alcohol
% yieldb
1
2
3
4
5
6
7
8
1
1
6
6
2
2
7
7
3a
3b
3a
3b
3a
3b
3a
3b
4a
4b
8a
8b
5a
5b
9a
9b
70
71
95
96
68
65
94
93
a All reactions were carried out at -78 °C. b Yield after chro-
matography.
of alcohol are the result of subsequent coupling, elimi-
nation, and double allylic transposition, leading, in the
case of alcohol 4a, to the isolated compounds 10 + 11,
12, and 13, respectively. We found that the yields of
homoallylic alcohol could be increased significantly by
employing the corresponding dicobalt hexacarbonyl
complexes of the acetylenic aldehydes. Under identical
experimental conditions, the time required for complete
conversion also increased to approximately 1-2 h at
-78 °C, suggesting that the reactivity of the carbonyl
group had been attenuated by the presence of the
dicobalt cluster, which is well known to stabilize R-cat-
ionic sites.8
Interestingly, double allylic transposition was found
to occur when 2 molar equiv of both allylstannane
reagent and Lewis acid were added to the dicobalt-
complexed aldehydes, whereas an excess of allyl reagent
and Lewis acid did not change the ratio of products
recovered from the corresponding noncomplexed alde-
Results and Discussion
Allyl Transfer to Dicobalt Hexacarbonyl-Com-
plexed Acetylenic Aldehydes. Initially, we examined
BF3-promoted allyl transfer from allyltributylstannane
and (2-methylallyl)tributylstannane to the noncom-
plexed aldehydes 3-phenylpropynal and 2-hexynal. For-
mation of the homoallylic alcohols 4a,b and 5a,b,
reported in Table 1, was complete in all cases within
approximately 30 min at -78 °C.7 The moderate yields
(8) (a) Seyferth, D.; Nestle, M. O.; Wehman, A. T. J. Am. Chem.
Soc. 1975, 97, 7417. (b) Seyferth, D.; Williams, G. H.; Eschbach, C. S.;
Nestle, M. O.; Merola, J. S.; Hallgren, J. E. J. Am. Chem. Soc. 1979,
101, 4867. (c) Nicholas, K. M.; Pettit, R. J. Organomet. Chem. 1972,
44, C21. (d) Nicholas, K. M.; Pettit, R. Tetrahedron Lett. 1971, 12, 3475.
(e) Seyferth, D.; Wehman, A. J. Am. Chem. Soc. 1970, 92, 5520.
(7) See Experimental Section for complete details.

Diastereoselective Addition of Allylstannanes
Organometallics, Vol. 24, No. 11, 2005 2619
Table 2. Crotyl Transfer to Noncomplexed and
Co2(CO)6-Complexed Alkynalsa
entry aldehyde allylstannane alcohol % yieldb syn:antic
1
2
3
4
5
6
7
8
1
1
6
6
2
2
7
7
3c
3d
3c
3d
3c
3d
3c
3d
4c
88
100:0
100:0
75:25
86:14
100:0
100:0
73:27
85:15
4c
86
8c + 8d
8c + 8d
5c
5c
9c + 9d
9c + 9d
95d
97d
85
82
96d
94d
a All reactions were carried out at -20 °C. b Yield after chro-
matography. c The diastereomeric ratios of alcohols were deter-
mined by 1H NMR analysis of the mixtures. d Yield of the
diastereomeric mixture of alcohols after chromatography.
hydes. We presumed that the second allyl transfer
proceeded via a dicobalt hexacarbonyl-stabilized second-
ary cation generated upon elimination of a propargyl
alkoxy substituent from the initially formed homoallylic
boron-trifluoride etherate. Indeed, treatment of 8a,
which had been independently synthesized, with 1
molar equiv of allyltributylstannane and BF3‚OEt2
yielded 14 in 87% yield. The structure of 14 was
confirmed by spectroscopic characterization following
oxidative decomplexation using (CH3)3N(O). This reac-
tivity introduces the possibility of incorporating two
different nucleophiles at the propargylic site, possibly
even as a one-pot procedure, giving rise to a trialkyl-
substituted carbon atom from an acetylenic aldehyde,
or a quaternary carbon from an acetylenic ketone.
Crotyl Transfer to Dicobalt Hexacarbonyl-Com-
plexed Acetylenic Aldehydes. With a view toward
constructing the 3,4-disubstituted-1,5-enyne carbon
framework and controlling simple diastereoselectivity,9
crotyl transfer to the dicobalt hexacarbonyl complex of
3-phenylpropynal and 2-hexynal was carried out using
either (E)- or (Z)-crotyltributylstannane. Both crotyltin
reagents led to a diastereomeric mixture in which the
major isomer has C3 methyl and C4 hydroxyl substit-
uents in a syn relationship to each other.3 In contrast,
only the syn diastereomer was obtained from crotyl
transfer to the corresponding noncomplexed acetylenic
aldehydes, irrespective of the stereochemistry of the
crotyltin reagent, as has previously been observed for
the addition of enolsilanes.10 The yields and ratios are
given in Table 2. The relative stereochemistry of 4c was
determined by comparison with a previously reported
1H NMR spectrum.11 LiAlH4 was used to reduce com-
pound 5c to the diene 15 (Scheme 5), whose relative
stereochemistry was assigned by comparison with pre-
oriented at an angle of 180° to each other in the
antiperiplanar model, they are positioned approximately
30° apart in the synclinal model. The various factors
that are believed to influence the preferred orientation
of π-bonds include steric repulsion,16 orbital control,17
metal chelation,18 and Coulombic attraction.19 Both
models predict a preference for formation of the syn
diastereomer from Lewis acid-promoted crotyl transfer
to simple aldehydes, such as 3-phenylpropynal and
2-hexynal. The stereoconvergent syn diastereoselectivity
derives from the π-bond facial selectivity of the crotyl-
metal reagent, which leads to fewer steric interactions
between itself and the aldehyde, which, upon compari-
son of (E)- and (Z)-crotylmetal reagents, is found to be
diametrical. Thus, the exclusive recovery of 4c from 1,
and 5c from 2, is in accord with this postulate.
By virtue of the tetrahedral geometry of the dicobalt
cluster, comprised of two cobalt vertexes and two
acetylene carbon atoms, the aldehydes 6 and 7 possess
a plane of symmetry that bisects the cobalt-cobalt bond.
This makes equivalent the two enantiotopic faces of the
carbonyl group in dicobalt hexacarbonyl-complexed
acetylenic aldehydes, as is the case in the analogous
noncomplexed acetylenic aldehydes. As a result, the
diastereoselectivity of homoallylic alcohol formation
should be determined only by the relative π-bond facial
selectivity of the dicobalt-complexed aldehyde and the
crotyltin reagent during allyl transfer. The predominant
steric interaction that controls this relative facial se-
lectivity is expected to be identical to that which
operates in the case of noncomplexed aldehydes. There-
fore, the dicobalt-complexed aldehydes should give rise
to the same degree of diastereoselectivity as the non-
complexed aldehydes.
1
viously published H NMR12 and 13C NMR13 spectra,
respectively.
Two different open acyclic transition state models,
termed antiperiplanar14 and synclinal,15 have been
advanced for understanding the observed stereoselec-
tivities of addition reactions between trigonal centers.
The two models differ in the relative orientation of the
participating π-bonds. Whereas the reacting π-bonds are
The ability of a Co(CO)3 vertex to interact with and
provide stabilization for positive charge that develops
at a propargyl carbon20 introduces an additional factor,
(16) (a) Heathcock, H. C.; Buse, C. T.; Kleschick, W. A.; Pirrung,
M. C.; Sohn, J. E.; Lampe, J. J. Org. Chem. 1980, 45, 1066. (b) Hayashi,
T.; Konishi, M.; Ito, H.; Kumada, M. J. Am. Chem. Soc. 1982, 104,
4962. (c) Hayashi, T.; Konishi, M.; Kumada, M. J. Am. Chem. Soc.
1982, 104, 4963. (d) Heathcock, H. C.; Flippin, L. A. J. Am. Chem.
Soc. 1983, 105, 1667. (e) Heathcock, C. H.; Kiyooka, S. I.; Blumenkopf,
T. A. J. Org. Chem. 1984, 49, 4214.
(17) (a) Hoffmann, R.; Levin, C. C.; Moss, R. A. J. Am. Chem. Soc.
1973, 95, 629. (b) Paddon-Row, M. N.; Rondan, N. G.; Houk, K. N. J.
Am. Chem. Soc. 1982, 104, 7162.
(18) (a) Meyers, A. I.; Reider, P. J. Am. Chem. Soc. 1979, 101, 2501.
(b) Evans, D. A.; Vogel, E.; Nelson, J. V. J. Am. Chem. Soc. 1979, 101,
6120. (c) Panek, J. S.; Cirillo, P. F. J. Org. Chem. 1993, 58, 999. (d)
Panek, J. S.; Cirillo, P. F. J. Org. Chem. 1994, 59, 5130.
(19) (a) Schlosser, M. Bull. Soc. Chim. Fr. 1971, 453.
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1989, 54, 5426.
(11) Mikami, K.; Azuma, K.; Nakai, T. Tetrahedron 1984, 40, 2303.
(12) Marshall, J. A.; Palovich, M. R. J. Org. Chem. 1998, 63, 4381.
(13) Marton, D.; Vanzan, N. Ann. Chim. 1989, 79, 479.
(14) (a) Yamamoto, Y.; Yatagai, H.; Naruta, Y.; Maruyama, K. J.
Am. Chem. Soc. 1980, 102, 7107. (b) Yamamoto, Y.; Yatagai, H.;
Ishihara, Y.; Maeda, N.; Maruyama, K. Tetrahedron 1984, 40, 2239.
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Denmark, S. E.; Weber, E. J. J. Am. Chem. Soc. 1984, 106, 7970.

2620 Organometallics, Vol. 24, No. 11, 2005
Balduzzi et al.
Scheme 2
Scheme 3
Scheme 4
Scheme 5
with a concomitant inversion of the π-bond facial
selectivity, depicted in the interconversion of 16 and 17.
specific to the complexed aldehydes, that can affect the
stereoselectivity of crotyl transfer. When the two metal
vertexes provide a comparable degree of charge delo-
calization, two different dynamic processes can occur,
as evidenced by variable-temperature NMR studies on
cations generated in solution from dicobalt hexacarbo-
nyl-complexed propargyl alcohols.21 The higher energy
process, termed suprafacial migration, exchanges the
environment of the substituents bonded directly to a
propargyl carbon. A mechanism that is consistent with
the spectroscopic findings involves migration of the
vinylidene group from one cobalt vertex to the other.
This is depicted in the interconversion of structures 16
and 18 in Figure 1. By comparison, the spectroscopic
evidence of a lower energy process, termed antarafacial
migration, is consistent with an exchange of the differ-
ent environments within the propargyl substituents.
This has been rationalized to involve migration of the
vinylidene group from one cobalt vertex to the other
Figure 1.
We have reasoned that the cationic character, which
develops at a carbonyl carbon in a Co2(CO)6-complexed
acetylenic aldehyde upon coordination of a Lewis acid,
could be stabilized through an interaction with the
cobalt vertexes in a similar manner. Furthermore, since
the two cobalt vertexes in Co2(CO)6-complexed alde-
hydes are equivalent, they could both participate in
charge delocalization, giving rise to fluxionality of the
molecule. Antarafacial migration would then expose
both faces of the compound’s π-bond during crotyl
transfer, and it is this process that would lead to a
reduction in the degree of stereoselectivity of nucleo-
philic addition, as compared with noncomplexed alde-
hydes. Antarafacial migration of aldehyde 6 coordinated
to BF3 is illustrated in structures 20 and 22, in Figure
2.
(20) (a) Nicholas, K. M. J. Organomet. Chem. 1977, 125, C45. (b)
Schilling, B. E. R.; Hoffmann, R. J. Am. Chem. Soc. 1978, 100, 6274.
(c) Schilling, B. E. R.; Hoffmann, R. J. Am. Chem. Soc. 1979, 101, 3456.
(d) Edidin, R. T.; Norton, J.; Mislow, K. Organometallics 1982, 1, 561.
(e) Padmanabhan, S.; Nicholas, K. M. J. Organomet. Chem. 1983, 268,
23.
The loss of diastereospecificity with complexed, versus
uncomplexed, propynals could also be attributed to an
increased facility for racemization of the product, as has
previously been reported.22 Erosion of diastereoselec-
(21) Schreiber, S. L.; Klimas, M. T.; Sammakia, T. J. Am. Chem.
Soc. 1987, 109, 5749.

Diastereoselective Addition of Allylstannanes
Organometallics, Vol. 24, No. 11, 2005 2621
Figure 2.
tivity, accompanied by elimination reactions, was ob-
served if reaction temperatures were allowed to arise
above 0 °C before quenching. However, in these reac-
tions there was no observed time-dependent change in
diastereoselectivity as would be anticipated from a
racemization process. Thus, we interpret the changeover
in stereoselectivity with complexed materials to arise
from the initial formation of the homoallylic alcohol,
rather than subsequent racemization.
By analogy with the noncomplexed aldehydes, the
dicobalt cluster determines the π-bond facial selectivity
of the crotyltin reagent since, in the putative open
transition state, the two reactants can approach each
other via a pathway that minimizes steric interactions.
An analysis of both the antiperiplanar and synclinal
models reveals that the latter provides a more cogent
rationale for the observed syn diastereoselectivity, as
it allows placement of the smallest substituent of the
crotylstannanesthat being the hydrogen bonded to the
γ-carbonsat the most sterically demanding site in the
transition structuresthat being nearest to a Co(CO)3
vertex. The synclinal orientation and the π-bond facial
selectivity of (Z)-crotyltributylstannane, which is thought
to participate in crotyl transfer, is illustrated in the
Newman projections 21 and 23, in Figure 2.
Allyl Transfer to Chiral Dicobalt Pentacarbonyl-
(triphenylphosphine)-Complexed Acetylenic Al-
dehydes. The dynamic processes described above were
observed in homobimetallic23 cluster compounds, where
the two vertexes provide comparable stabilization of
adjacent positive charge. In contrast, when one metal
vertex can delocalize the charge to a greater extent, as
in heterobimetallic24 or mixed trimetallic25 cluster com-
pounds, the same processes have not been detected on
the NMR time scale. This condition has been applied
to Co2-complexed propargyl alcohols, wherein one of the
cobalt vertexes was made to provide greater charge
stabilization by replacing a weakly σ-donating/strongly
π-accepting CO ligand with the stronger σ-donating/
Figure 3.
weaker π-accepting PPh3 ligand, by Nicholas and co-
workers.22,26 Upon protonation, the resulting Co2(CO)5-
PPh3-complexed propargyl cations were judged to be
more electron-rich than the parent cationic Co2(CO)6
complexes and to have the charge preferentially local-
ized onto the phosphine-bearing cobalt vertexes. Only
one diastereomeric cation was formed from complexes
possessing a bulky substituent at the propargyl carbon,
such as isopropyl or tert-butyl. Its conformation was
determined, by difference NOE NMR experiments, to
have the bulky substituent flanking the less sterically
encumbered cobalt-cobalt bond, rather than the cobalt-
carbon bond. As with bimetallic clusters, fluxionality
was not detected by variable-temperature NMR moni-
toring of the cation.
We anticipated that this phenomenon could be uti-
lized to synthetic advantage if it provides a means by
which the dicobalt-complexed acetylenic aldehyde’s
π-bond facial selectivity could be controlled during allyl
and crotyl transfer. Our observed diastereoselectivities
of crotyl transfer to Co2(CO)6-complexed aldehydes
provide evidence for an interaction between the carbonyl
carbon and both cobalt vertexes of a fluxional cluster.
By inducing preferential delocalization of positive charge
onto one cobalt vertex only, the dynamic process that
exposes both faces of the compound’s π-bond would be
precluded. We predicted that the replacement of a CO
ligand in aldehydes 6 and 7, with PPh3, would produce
a compound in which fluxionality of the cluster was
absent or slow relative to the rate of allyl transfer. Then,
the ratio of diastereomeric homoallylic alcohols formed
would reflect the relative stabilities of the two possible
conformational isomers of the Lewis acid-coordinated
dicobalt-complexed acetylenic aldehydes,27 illustrated in
Figure 3.
(22) Caffyn, A. J. M.; Nicholas, K. M. J. Am. Chem. Soc. 1993, 115,
6438, and references therein.
(23) (a) Meyer, A.; McCabe, D. J.; Curtis, M. D. Organometallics
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Organometallics 1992, 11, 2598. (c) Nicholas, K. M. Acc. Chem. Res.
1987, 20, 207.
(25) (a) Bernhardt, W.; Vahrenkamp, H. Angew. Chem., Int. Ed.
Engl. 1984, 23, 141. (b) Delgado, E.; Jeffery, J. C.; Stone, F. G. A. J.
Chem. Soc., Dalton Trans. 1986, 2105.

2622 Organometallics, Vol. 24, No. 11, 2005
Table 3. Allyl Transfer to Co2(CO)5PPh3-Complexed Propynals
products (mol %)a
Balduzzi et al.
homoallylic alcohols
entry
allyl reagent
aldehyde
reaction temp (°C)
ald.b
alc.c
dien.d
alc.c
ratioe
% yieldf
1
2
3
4
5
6
7
8
9
3a
3a
3a
3a
3a
3a
3a
3b
3b
26
26
26
26
26
26
27
26
27
-78 to 25
-78 to 25
-78 to 25
-10
16
16
0
70
25
14
59
77
10
0
28, 29
28, 29
28, 29
28, 29
28, 29
28, 29
33, 34
31, 32
36, 37
70:30g
60:40
5:95
74:26
90:10
86:14
84:16h
100:0i
85:15j
63
18
15
87
96
98
95
92
93
23
0
90
-20
0
100
100
100
100
100
-30
0
0
-20
0
0
-20
0
0
-20
0
0
a Composition of the crude reaction mixture. b Unreacted aldehyde. c Homoallylic alcohols. d (Z)-Dienyne 30. e The diastereomeric ratios
of alcohols were determined by 1H NMR analysis of alcohol mixtures. The absolute stereochemical assignment of the major diastereomer
has been inferred. f Yield of the diastereomeric mixture of alcohols after chromatography. g Alcohols 28, 29 given as X:Y where X and Y
correspond to the diastereomer having a chemical shift of C4-H at 3.92 and 4.07 ppm, respectively. h Alcohols 33, 34 given as X:Y where
X and Y correspond to the diastereomer having a chemical shift of C4-H at 3.89 and 4.05 ppm, respectively. i Alcohols 31, 32. j Alcohols
36, 37 given as X:Y where X and Y correspond to the diastereomer having a chemical shift of C4-H at 4.14 and 4.30 ppm, respectively.
Scheme 6
The dicobalt pentacarbonyl(triphenylphosphine) com-
plexes of 3-phenylpropynal and 2-hexynal were prepared
by gently refluxing aldehydes 6 and 7 in the presence
of triphenylphosphine. All the reactions described below
were carried out with a racemic mixture of the chiral
compounds 26 and 27. The product mixtures and
diastereoselectivities of the homoallylic alcohols ob-
tained from allyl transfer reactions carried out with
aldehyde 26, while the cooling bath temperature had
been allowed to warm from -78 °C to 25 °C, are given
in entries 1 to 3 in Table 3 and shown in Scheme 6.
The temperature at which allyl transfer was per-
formed proved to be the most critical variable in
determining the yield and product mixture. At cooling
bath temperatures above -10 °C, elimination from the
homoallylic boron-trifluoride etherate took place in
competition with allyl transfer, giving rise to the (Z)-
dienyne 30. These results are noteworthy, as they show
a correlation between large quantities of the (Z)-dienyne
and a seeming “reversal” of diastereoselectivity (com-
pare entries 1 and 3). After having monitored the
in Table 3 are the improved yields and diastereoselec-
tivities obtained at constant cooling bath temperatures
of -30, -20, and -10 °C, in the absence of elimination.
The optimal reaction temperature seems to lie some-
where between -30 and -20 °C; the rate was found to
be sluggish at temperatures below -40 °C.
Whereas allyltrimethylsilane could be used to effect
allyl transfer to Co2(CO)6-complexed aldehydes, the
more nucleophilic allyltributylstannane was required for
Co2(CO)5PPh3-complexed aldehydes; in this case the
reaction time was increased 3-fold under otherwise
identical conditions. The second allylic transposition did
not occur when two or more molar equivalents of
allylstannane and Lewis acid were added to Co2(CO)5-
PPh3-complexed aldehydes, unlike the parent Co2(CO)6-
complexed aldehydes (vide supra). On the basis of the
results reported in Table 3, and allyl transfer studies
carried out with the less sterically encumbered Co2-
(CO)5P(CH3)3-complexed 3-phenylpropynal,28 the at-
tenuated reactivity of the phosphine-bearing compounds
suggests that they are more electron-rich than the
parent compounds and have positive charge delocalized
onto the Co(CO)2PR3 vertex, as shown in Figure 3.
The thermodynamically favorable conformation of
Lewis acid-coordinated Co2(CO)5PPh3-complexed alde-
hydes is expected to be that which places the smallest
propargyl substituentsa hydrogensflanking the more
sterically hindered cobalt-carbon bond, as depicted in
24. Nicholas and co-workers have carried out magne-
tization transfer experiments to probe the existence of
dynamic processes in related Co2(CO)5PPh3-complexed
cations generated in CD2Cl2.26 On the basis of their
report that antarafacial migration was not detected on
the NMR time scale, and our recovery of a single
1
progress of the reaction over time, using TLC and H
NMR, we attribute this “reversal” to the occurrence of
two competing kinetic processes. At lower temperatures,
a diastereoselective allylation of the complexed aldehyde
favors the formation of one isomer, such as 28. However,
as the bath temperature increases, elimination takes
place from 28 preferentially, leaving 29 as the major
homoallylic alcohol product. Judicious manipulation of
the reaction conditions thus allows the reaction to be
directed to either the syn or anti isomer. Also reported
(27) This corresponds to the condition of “kinetic quenching”, derived
from a kinetic treatment of second-order reactions involving two
interconverting substances. Seeman, J. I. Chem. Rev. 1983, 83, 83. This
postulate will only be valid if the π-bond facial selectivity of the
allylstannane is the same for both isomers 24 and 25.
(28) Balduzzi, S.; Brook, M. A. Unpublished results.

Diastereoselective Addition of Allylstannanes
Organometallics, Vol. 24, No. 11, 2005 2623
Figure 4.
diastereomeric homoallylic alcohol from the addition of
3b to 26, we surmise that isomers 24 and 25 were not
interconverted by a dynamic process under the reaction
conditions used.
We can extend our synclinal transition state model
to BF3-coordinated Co2(CO)5PPh3-complexed aldehydes
in order to illustrate how the conformation of the cluster
itself could be the origin of stereochemical control. The
thermodynamically favorable conformation of BF3-
coordinated complexed aldehydes is believed to have
given rise to 3129 and the major diastereomeric alcohol
in the case of 28/29, 33/34 and 36/37, as depicted in
Figure 4.
Crotyl Transfer to Chiral Dicobalt Pentacarbo-
nyl(triphenylphosphine)-Complexed Acetylenic Al-
dehydes. If the diastereoselectivity of allyl transfer
derives from the conformation of the Lewis acid-
coordinated phosphine-bearing compound, which con-
sequently determines the π-bond facial selectivity of
allylmetal reagents, there exists the potential to effect
crotyl transfer diastereospecifically, under experimental
conditions that favor crotyl addition to one conforma-
tional isomer exclusively. In a parallel set of experi-
ments, we examined crotyl transfer to 26 and 27.
Electrophilic substitution of allylsilanes and their
derivatives has been studied extensively, and the widely
accepted SE2′ mechanism has also been extended to
allylstannanes and allylgermanes.30 On the basis of the
previously reported increased reactivity of (E)- and (Z)-
crotyltrimethylsilane, relative to allyltrimethylsilane,
with cations generated in solution,31 we initially ex-
pected (E)- and (Z)-crotyltributylstannane to be simi-
larly more reactive than allyltributylstannane. From the
addition of each of allyltributylstannane, (E)-crotyl-
tributylstannane and (Z)-crotyltributylstannane, to a
separate solution of 6 and BF3‚OEt2 under identical
conditions, we learned that the crotylstannanes are
actually less reactive than allyltributylstannane and
required twice as much time for complete conversion to
be achieved. Nevertheless, we attempted crotyl transfer
to 26 using (E)- and (Z)-crotyltributylstannane and BF3‚
OEt2, TiCl4, or SnCl4 as Lewis acid at both -20 and 0
°C. In all cases, however, only starting material was
recovered. Thermal decomplexation of the dicobalt
cluster occurred at temperatures above 0 °C.
According to Mayr’s reactivity scales,32 the electro-
philicity of the propargyl cation derived from Co2(CO)6-
complexed propargyl alcohol is reduced by almost an
order of magnitude when the acetylenic proton is
substituted with a phenyl group.33 We speculated that
the electrophilicity of 26 might be increased by replacing
the acetylenic phenyl group with a proton or an aliphatic
group and attempted crotyl transfer to 27 using (E)- and
(Z)-crotyltributylstannane. Disappointingly, only start-
ing material was again recovered.
The electrophilicity of BF3-coordinated Co2(CO)5PPh3-
complexed aldehydes can now be quantified in the
context of Mayr’s reactivity scales. The parameters E
and N in eq 1 correspond to values of electrophilicity
and nucleophilicity, respectively, obtained from numer-
ous “constant selectivity” correlations between cationic
electrophiles and neutral nucleophiles.32 For a given
nucleophile, eq 1 can be used to predict the E value that
an electrophile must possess in order for a reaction to
proceed at 20 °C by setting log k to -5 s (corresponding
to a minimum rate constant of 10-5 L mol-1 s-1). Since
allyltrimethylsilane was found to be unreactive toward
Co2(CO)5PPh3-complexed aldehydes, it sets an approxi-
mate upper limit on the electrophilicity of the phos-
phine-bearing aldehydes. Similarly, since allyltributyl-
stannane and (2-methylallyl)tributylstannane did
undergo allyl transfer, the former sets an approximate
lower limit on their electrophilicity. The N values of 1.62
and 5.72, reported for allyltrimethylsilane and allyl-
tributylstannane, respectively, were used to calculate
E values of -6.62 and -10.72. Therefore, the electro-
philicity of BF3-coordinated aldehydes 26 and 27 falls
within the range of -6.62 and -10.72, as defined by
Mayr. This allows one to predict that a reaction should
occur between BF3-coordinated aldehyde 26 or 27 and
silyl enol ethers, hydride donors, alkoxy-substituted
arenes, amines, and other nucleophiles of comparable
or greater strength.
(29) The absolute configuration at C4 and the dicobalt cluster is
unknown in the absence of X-ray diffraction data and has been inferred.
An R or S configuration can be assigned to a metal cluster according
to the Cahn-Ingold-Prelog selection rules. See ref 21b.
(30) Fleming, I.; Dunogue`s, J.; Smithers, R. Org. React. 1989, 37,
57.
(32) Mayr, H.; Patz, M. Angew. Chem., Int. Ed. Engl. 1994, 33, 938.
(33) Kuhn, O.; Rau, D.; Mayr, H. J. Am. Chem. Soc. 1998, 120, 900.
(31) Hagen, G.; Mayr, H. J. Am. Chem. Soc. 1991, 113, 4954.

2624 Organometallics, Vol. 24, No. 11, 2005
log k ) s(E +N)
Balduzzi et al.
(Z)-2-Butenyltributylstannane (3c). This compound was
prepared in three steps starting from 2-butyn-1-ol. A mixture
of 2-butyn-1-ol (10.0 g, 142.6 mmol) and Lindlar catalyst (1.0
g) in CH3OH (150 mL) was stirred at 25 °C under 1.0 atm of
H2 for approximately 2 h, at which time the alkyne was judged,
using TLC, to have been completely consumed. The mixture
was then filtered through a pad of Celite and concentrated.
Purification by distillation yielded 9.77 g (135.5 mmol, 95%)
of (Z)-2-buten-1-ol (lit.37 bp 123.6 °C). 1H NMR (CDCl3, 200
MHz): δ 5.60 (m, 2H), 4.19 (d, J ) 4.7 Hz, 2H), 1.72 (br s,
1H), 1.66 (d, J ) 5.2 Hz, 3H).
(1)
Summary
The yields and diastereoselectivities of allyl and crotyl
transfer to Co2(CO)6-complexed aldehydes support the
proposal that the development of positive charge at a
carbonyl carbon is stabilized by an interaction with both
cobalt vertexes, which leads to a loss of stereochemical
integrity at that site through dynamic processes. We
have shown that allyl and 2-methylallyl transfer to
Co2(CO)5PPh3-complexed aldehydes can be effected with
high yields and good diastereoselectivities. The reduced
reactivity of the latter complexes suggests they are more
electron-rich than the parent complexes and lends
further support to the proposal of charge stabilization
by a cobalt vertex, particularly Co(CO)2PPh3. We specu-
late that a single diastereomeric homoallylic alcohol 31
was formed from 2-methylallyl transfer to the thermo-
dynamically favored conformational isomer of a static
complex. If the diastereoselection originates from steric
interactions that exist within the dicobalt-complexed
aldehyde itself, it should be possible to control the
stereoselectivity of nucleophilic addition to dicobalt-
complexed acetylenic ketones in a similar manner.
(Z)-2-Buten-1-ol was converted to the chloride by treating
a solution of the alcohol in hexachloroacetone with PPh3.38
Purification by distillation yielded (Z)-1-chloro-2-butene (lit.39
1
bp 84.1 °C (758 mmHg)). H NMR (CDCl3, 200 MHz): δ 5.69
(m, 2H), 4.11 (d, J ) 6.8 Hz, 2H), 1.72 (d, J ) 5.7 Hz, 3H).
The procedure described by Matarasso-Tchiroukhine was
followed for the preparation of the (Z)-crotyltin reagent.40 To
a stirred suspension of finely cut lithium wire (1.26 g, 182.6
mmol) in dry THF (60 mL) under N2 at 25 °C was added Bu3-
SnCl (19.84 g, 60.96 mmol). When the reaction had begun, as
evidenced by the evolution of heat and the formation of a tan
color, an additional 90 mL of THF was added and stirring at
25 °C was continued for 8 h. After allowing the mixture to
stand for 1 h, it was filtered through a plug of glass wool under
N2 into a dry flask, which was then cooled to -40 °C. To this
flask was added a solution of (Z)-1-chloro-2-butene (5.52 g,
60.96 mmol) in THF (6 mL). The mixture was stirred at -40
°C for 30 min, then quenched by adding a saturated aqueous
solution of NH4Cl, which had been cooled to 0 °C. The solution
was brought to room temperature, and the aqueous phase was
extracted twice with ether. The organic phases were combined,
dried over Na2SO4, filtered, and concentrated under reduced
pressure. The residue was purified by distillation to yield 16.42
g (43.28 mmol, 71%) of (Z)-2-butenyltributylstannane, a color-
less oil (lit.41 bp 100-110 °C (1.0 mmHg)). 13C NMR (CDCl3,
50 MHz): δ 129.6, 118.2, 29.3, 27.5, 27.4, 13.8, 12.5, 9.4.
(E)-2-Butenyltributylstannane (3d). This compound was
prepared from (E)-crotyl chloride and Bu3SnCl, using the
Experimental Section
1H NMR spectra were recorded on a Bruker AC-300 spec-
trometer at 300.130 MHz or on a Bruker AC-200 spectrometer
at 200.20 MHz, using CDCl3 as solvent and internal standard.
13C NMR were recorded on the same instrument at 75.467
MHz or at 50.340 MHz, also using CDCl3 as solvent. Infrared
spectra were recorded on a Bio Rad FTS-40 Fourier transform
spectrometer. Liquid samples were used as neat films on NaCl
disks, and solid samples were prepared as KBr pellets.
Chemical ionization (CI), with ammonia as the reagent gas,
and electron impact (EI) mass spectra were recorded at 70 eV
with a source temperature of 200 °C on a VG Analytical ZAB-R
mass spectrometer equipped with a VG 11-250 data system.
Flash chromatography was performed using Silicycle silica gel
(230-400 mesh). Analytical thin-layer chromatography (TLC)
was performed on aluminum sheets precoated with silica gel
(Merck, Kieselgel 60 F254).
Allyltrimethylsilane, allyltributylstannane, n-butyllithium
in hexanes, tributyltin chloride, 2-butyn-1-ol, trans-crotyl
chloride, 3-chloro-2-methylpropene, N-formyl morpholine,
hexachloroacetone, lithium wire, Lindlar catalyst, phenyl-
acetylene, 1-pentyne, triphenylphosphine, trimethylamine N-
oxide, TiCl4, BF3‚OEt2, and SnCl4 were purchased from Aldrich
and used without purification. Dicobalt octacarbonyl was
purchased from Strem Chemicals and used without further
purification. CH2Cl2 was distilled from CaH2 prior to use; THF
and diethyl ether were distilled from sodium prior to use.
Aldehydes 1 (lit.34 bp 65 °C (0.1 mmHg)) and 2 (lit.35 bp 56-
62 °C (20 mmHg)) were prepared by formylation of the
organolithium derivatives of phenylacetylene and 1-pentyne,
using N-formylpiperidine, as described by Olah.34
procedure described above. 13C NMR (CDCl3, 50 MHz):
130.5, 120.3, 29.3, 27.5, 27.4, 17.9, 13.8, 9.2.
δ
General Procedure for Preparation of Dicobalt Hexa-
carbonyl-Complexed Aldehydes: (3-Phenylpropynal)-
dicobalt Hexacarbonyl Complex (6). To a solution of
dicobalt octacarbonyl (0.31 g, 0.91 mmol) in CH2Cl2 (18 mL)
was added 3-phenylpropynal (0.10 g, 0.76 mmol) in CH2Cl2
(15 mL) at 0 °C under N2. Stirring was continued for 4 h,
followed by concentration of the solvent under reduced pres-
sure and purification by flash chromatography (19:1 pentane/
diethyl ether) to yield 0.31 g (0.74 mmol, 97%) of a red solid:
1H NMR (CDCl3, 200 MHz) δ 10.50 (s, 1H), 7.57 (m, 2H), 7.33
(m, 3H); 13C NMR (CDCl3, 50 MHz) δ 197.6, 190.8, 136.3, 129.7,
129.0, 128.8, 92.1, 85.6. IR (KBr) 2101, 2065, 2032, 1666, 1484,
1442, 1019 cm-1; MS (EI, m/z) 388 (M+ - CO, 21), 360 (M+
-
2 CO, 31), 332 (M+ - 3 CO, 29), 304 (M+ - 4 CO, 53), 276 (M+
- 5 CO, 68), 248 (M+ - 6 CO, 75); MS (CI, NH3, m/z) 417 (M
+ H+, 100), 389 (M + H+ - CO, 56).
(2-Hexynal)dicobalt Hexacarbonyl Complex (7). Puri-
fication by flash chromatography (19:1 pentane/diethyl ether)
yielded 96% of a red solid: 1H NMR (CDCl3, 200 MHz) δ 10.29
(s, 1H), 2.87 (t, J ) 5.9 Hz, 2H), 1.70 (m, 2H), 1.07 (t, J ) 7.3
Hz, 3H); 13C NMR (CDCl3, 50 MHz) δ 198.3, 190.6, 100.7, 87.4,
(2-Methyl-2-propenyl)tributylstannane (3b). This al-
lyltin reagent was prepared by coupling 2-methyl-2-propenyl-
magnesium chloride and Bu3SnCl with external irradiation
of ultrasound, following the procedure of Naruta.36 1H NMR
(CDCl3, 200 MHz): δ 4.66 (br s, 2H), 1.95 (s, 2H), 1.84 (s, 3H),
1.6-1.0 (m, 18H), 0.91 (m, 9H).
(37) Hiskey, C. F.; Slates, H. L.; Wendler, N. L. J. Org. Chem. 1956,
21, 429.
(38) Magid, R. M.; Fruchey, O. S.; Johnson, W. L.; Allen, T. G. J.
Org. Chem. 1979, 44, 359.
(39) Dictionary of Organic Compounds; Chapman & Hall: London
(34) Olah, G. A.; Arvanaghi, M. Angew. Chem., Int. Ed. Engl. 1981,
20, 878.
1996.
(40) Matarasso-Tchiroukhine, E.; Cadiot, P. J. Organomet. Chem.
(35) Kanakam, C. C. J. Chem. Soc., Perkin Trans. 1 1989, 11, 1907.
(36) Naruta, Y.; Nishigaichi, Y.; Maruyama, K. Chem. Lett. 1986,
11, 1857.
1976, 121, 155.
(41) Aoki, S.; Mikami, K.; Terada, M.; Nakai, T. Tetrahedron 1993,
49, 1783.

Diastereoselective Addition of Allylstannanes
Organometallics, Vol. 24, No. 11, 2005 2625
36.4, 25.3, 13.9; IR (KBr) 2968, 2938, 2879, 2809, 2691, 2101,
2059, 2028, 1670, 1580, 1097, 1086 cm-1; MS (EI, m/z) 382
(M+, 10), 354 (M+ - CO, 100), 326 (M+ - 2 CO, 89), 298 (M+
- 3 CO, 54), 270 (M+ - 4 CO, 39), 242 (M+ - 5 CO, 24); MS
(CI, NH3, m/z) 383 (M + H+, 100), 389 (M + H+ - CO, 51);
MS (+ve ES, m/z) 382.3 (8) [M+].
NMR (CDCl3, 50.3 MHz) δ 138.8, 131.7, 128.3, 128.2, 122.6,
117.2, 88.2, 85.9, 66.4, 44.5, 15.7.
1-Nonen-5-yn-4-ol (5a). Purification by flash chromatog-
raphy (7:3 pentane/diethyl ether) yielded 68% of a colorless
oil: 1H NMR (CDCl3, 200 MHz) δ 5.90 (m, 1H), 5.20 (m, 2H),
4.41 (m, 1H), 2.45 (m, 2H), 2.19 (dt, J ) 1.9, 7.0 Hz, 2H), 1.48
(m, 2H), 1.25 (br s, 1H), 0.97 (t, J ) 7.3 Hz, 3H); 13C NMR
(CDCl3, 50.3 MHz) δ 133.3, 117.7, 84.9, 80.6, 61.4, 42.2, 21.7,
20.3, 13.0; IR (neat) 3398, 3079, 2965, 2874, 2230, 1708, 1642,
General Procedure for Preparation of Dicobalt Pen-
tacarbonyl(triarylphosphine)-Complexed Aldehydes: (3-
Phenylpropynal)dicobalt Pentacarbonyl(triphenylphos-
phine) Complex (26). To a solution of (3-phenylpropynal)-
dicobalt hexacarbonyl (0.19 g, 0.45 mmol) in diethyl ether (4.5
mL) and THF (4.5 mL) at 50 °C was added a solution of
triphenylphosphine (0.12 g, 0.45 mmol) in diethyl ether (4.5
mL) and THF (4.5 mL). After gentle reflux for 4 h, the solution
was cooled to room temperature, and the solvent concentrated
under reduced pressure. Purification by flash chromatography
(9:1 pentane/diethyl ether) yielded 0.24 g (0.37 mmol, 81%) of
a red solid: 1H NMR (CDCl3, 200 MHz) δ 9.93 (s, 1H), 7.21
(m, 20H); 13C NMR (CDCl3, 50.3 MHz) δ 204.9, 203.7, 199.5,
190.9, 137.9, 133.7, 133.1, 133.0, 132.9, 132.8, 130.3, 130.1,
128.6, 128.5, 128.3, 127.3, 88.2, 79.6; IR (KBr) 2068, 2022,
2005, 1971, 1652, 1480, 1438, 1098, 753, 699 cm-1; MS (+ve
ES, m/z) 651.0 (7) [M + 1H]+.
1460, 1434, 1032, 916 cm-1
.
2-Methyl-1-nonen-5-yn-4-ol (5b). Purification by flash
chromatography (8:2 pentane/diethyl ether) yielded 65% of a
colorless oil: 1H NMR (CDCl3, 200 MHz) δ 4.89 (br s, 1H), 4.83
(br s, 1H), 4.48 (m, 1H), 2.41 (d, J ) 6.6 Hz, 2H), 2.18 (dt, J )
1.8, 7.0 Hz, 2H), 1.89 (d, J ) 4.4 Hz, 1H), 1.79 (s, 3H), 1.53
(m, 2H), 0.96 (t, J ) 7.3 Hz, 3H); 13C NMR (CDCl3, 50.3 MHz)
δ 141.3, 114.0, 85.4, 80.9, 60.5, 46.5, 22.5, 22.0, 20.6, 13.4; IR
(neat) 3387, 3078, 2965, 2936, 2875, 2232, 1649, 1454, 1378,
1051, 1022, 891 cm-1; MS (EI, m/z) 137 (M+ - CH3, 20), 97
(M+ - CH2C(CH3)dCH2, 100); MS (CI, NH3, m/z) 170 (M +
NH4+, 54), 153 (M + H+, 31), 152 (M+, 35), 135 (M+ - OH,
100); HRMS (m/z) calcd for C9H13O (M+ - CH3) 137.0966,
found 137.0964.
(2-Hexynal)dicobalt Pentacarbonyl(triphenylphos-
phine) Complex (27). Purification by flash chromatography
(9:1 pentane/diethyl ether) yielded 84% of a red solid: 1H NMR
(CDCl3, 200 MHz) δ 9.75 (s, 1H), 7.43 (m, 15 H), 2.06 (m, 2H),
1.30 (m, 2H), 0.75 (t, J ) 7.3 Hz, 3H); 13C NMR (CDCl3, 50.3
MHz) δ 205.2, 203.8, 200.4, 191.1, 134.5, 133.7, 133.2, 133.1,
132.9, 130.5, 128.7, 128.5, 97.4, 81.9, 35.0, 24.9, 13.9; IR (KBr)
3061, 2962, 2932, 2875, 2808, 2067, 2011, 1972, 1653, 1436,
1093, 747, 696 cm-1; MS (+ve ES, m/z) 617.1 (20) [M + 1H]+.
General Procedure for Allyl and Crotyl Transfer to
Noncomplexed and Dicobalt Hexacarbonyl-Complexed
Propynals. To a solution of 3-phenylpropynal (0.2 g, 1.53
mmol) and activated crushed 4 Å molecular sieves (0.04 g) in
CH2Cl2 (30 mL) was added BF3‚OEt2 (0.20 mL, 1.58 mmol) at
-78 °C under N2. After stirring for 20 min, allyltributylstan-
nane (0.48 mL, 1.53 mmol) was added. Stirring was continued
at -78 °C until the starting material was completely con-
sumed, as determined by TLC. The mixture was then quenched
at 0 °C by the addition of a cold aqueous solution of NaHCO3,
and the organic layer was separated, extracted with a satu-
rated aqueous NaCl solution, dried over MgSO4, filtered, and
concentrated under reduced pressure to give a yellow oil.
Separation by flash chromatography (19:1 to 8:2 pentane/
diethyl ether) yielded the products 4a, 10, 11, 12, and 13.
6-Phenyl-1-hexen-5-yn-4-ol (4a).42 Isolated 0.184 g (1.07
mmol) of a colorless oil: 1H NMR (CDCl3, 200 MHz) δ 7.42
(m, 2H), 7.29 (m, 3H), 5.94 (m, 1H), 5.22 (m, 2H), 4.64 (t, J )
6.1 Hz, 1H), 2.56 (m, 2H), 2.11 (br s, 1H); 13C NMR (CDCl3,
50.3 MHz) δ 133.0, 131.5, 128.2, 128.1, 122.4, 118.7, 89.4, 85.0,
61.9, 42.0; IR (neat) 3397, 3080, 2981, 2913, 2232, 1642, 1490,
syn-3-Methyl-1-nonen-5-yn-4-ol (5c). Purification by flash
chromatography (8:2 pentane/diethyl ether) yielded 85% of a
colorless oil: 1H NMR (CDCl3, 200 MHz) δ 5.82 (m, 1H), 5.12
(m, 2H), 4.25 (m, 1H), 2.43 (m, 1H), 2.19 (dt, J ) 1.7, 7.0 Hz,
2H), 1.86 (d, J ) 6.8 Hz, 1H), 1.52 (m, 2H), 1.09 (d, J ) 6.8
Hz, 3H), 0.97 (t, J ) 7.3 Hz, 3H); 13C NMR (CDCl3, 200 MHz)
δ 139.1, 116.7, 86.4, 79.2, 66.1, 44.4, 22.0, 20.6, 15.5, 13.4; IR
(neat) 3411, 3081, 2967, 2935, 2875, 2247, 1641, 1458, 1380,
1015, 913, 734 cm-1; MS (EI, m/z) 137 (M+ - CH3, 4), 97 (M+
+
- CH2C(CH3)dCH2, 100); MS (CI, NH3, m/z) 170 (M + NH4
,
21), 152 (M+, 17), 135 (M+ - OH, 19) 97 (M+ - CH2C(CH3)d
+
CH2, 100); HRMS (m/z) calcd for C10H20NO (M + NH4
170.1545, found 170.1543.
)
(6-Phenyl-1-hexen-5-yn-4-ol)dicobalt Hexacarbonyl
Complex (8a). Purification by flash chromatography (9:1
pentane/diethyl ether) yielded 95% of a red solid: 1H NMR
(CDCl3, 200 MHz) δ 7.55 (m, 2H), 7.35 (m, 3H), 5.99 (m, 1H),
5.26 (m, 2H), 5.08 (m, 1H), 2.68 (m, 1H), 2.46 (m, 1H), 2.22 (d,
J ) 3.8 Hz, 1H); 13C NMR (CDCl3, 50.3 MHz) δ 199.3, 137.6,
134.1, 129.6, 128.8, 127.9, 118.9, 100.2, 90.8, 71.5, 43.9; IR
(KBr) 3467, 3080, 2092, 2053, 2021, 1612, 1483, 1442, 1050,
760, 692 cm-1; MS (EI, m/z) 430 (M+ - CO, 5), 402 (M+ - 2
CO, 35), 374 (M+ - 3 CO, 12), 346 (M+ - 4 CO, 26), 318 (M+
- 5 CO, 48), 290 (M+ - 6 CO, 100); MS (CI, NH3, m/z) 441
(M+ - OH, 100), 413 (M+ - OH - CO, 68), 385 (M+ - OH -
2 CO, 80), 346 (M+ - 4 CO, 63), 290 (M+ - 6 CO, 72); MS
(-ve ES, m/z) 456.9 (100) [M - 1H]-, 457.9 (24) [M].
(2-Methyl-6-phenyl-1-hexen-5-yn-4-ol)dicobalt Hexa-
carbonyl Complex (8b). Purification by flash chromatogra-
phy (9:1 pentane/diethyl ether) yielded 96% of a red solid: 1H
NMR (CDCl3, 200 MHz) δ 7.57 (m, 2H), 7.35 (m, 3H), 5.16 (m,
1H), 5.01 (br s, 1H), 4.97 (br s, 1H), 2.64 (m, 1H), 2.40 (m,
1H), 2.34 (s, 1H) 1.89 (s, 3H); 13C NMR (CDCl3, 50.3 MHz) δ
199.5, 141.8, 137.6, 129.6, 128.8, 127.8, 114.6, 100.2, 90.4, 69.5,
48.2, 22.2; IR (KBr) 3079, 3019, 2925, 2856, 2093, 2055, 2025,
1217, 1067, 759 cm-1; MS (EI, m/z) 416 (M+ - 2 CO, 22), 388
(M+ - 3 CO, 13), 360 (M+ - 4 CO, 20), 332 (M+ - 5 CO, 46),
304 (M+ - 6 CO, 100); MS (CI, NH3, m/z) 455 (M+ - OH, 100),
427 (M+ - OH - CO, 53), 399 (M+ - OH - 2 CO, 79); MS
(-ve ES, m/z) 471.1 (100) [M - 1H]-, 507.1 (22) [M + 35Cl]-,
509.1 (7) [M + 37Cl]-.
1442, 1031, 757, 692 cm-1; MS (EI, m/z) 131 (M+ - CH2CHd
+
CH2, 100), 77 (C6H5+, 36); MS (CI, NH3, m/z) 190 (M + NH4
48), 172 (M+, 62), 155 (M+ - OH, 100).
,
2-Methyl-6-phenyl-1-hexen-5-yn-4-ol (4b).43 Purification
by flash chromatography (9:1 pentane/diethyl ether) yielded
71% of a colorless oil: 1H NMR (CDCl3, 200 MHz) δ 7.43 (m,
2H), 7.28 (m, 3H), 4.94 (br s, 1H), 4.91 (br s, 1H), 4.73 (t, J )
6.6 Hz, 1H), 2.55 (d, J ) 6.6 Hz, 2H), 2.40 (br s, 1H), 1.84 (s,
3H); 13C NMR (CDCl3, 50.3 MHz) δ 140.9, 131.5, 128.2, 128.1,
122.6, 114.2, 60.8, 46.0, 22.6.
syn-3-Methyl-6-phenyl-1-hexen-5-yn-4-ol (4c).11 Purifica-
tion by flash chromatography (9:1 pentane/diethyl ether)
yielded 88% of a colorless oil: 1H NMR (CDCl3, 200 MHz) δ
7.44 (m, 2H), 7.30 (m, 3H), 5.94 (m, 1H), 5.24 (m, 2H), 4.50 (d,
J ) 4.9 Hz, 1H), 2.54 (m, 1H), 1.19 (d, J ) 6.9 Hz, 3H); 13C
(syn-3-Methyl-6-phenyl-1-hexen-5-yn-4-ol)dicobalt Hexa-
carbonyl Complex (8c). Purification by flash chromatogra-
phy (9:1 pentane/diethyl ether) yielded 83% of a red solid: 1H
NMR (CDCl3, 200 MHz) δ 7.51 (m, 2H), 7.31 (m, 3H), 5.90 (m,
1H), 5.12 (m, 2H), 4.98 (m, 1H), 2.56 (m, 1H), 2.13 (d, J ) 4.6
Hz, 1H), 1.17 (d, J ) 6.8 Hz, 3H); 13C NMR (CDCl3, 50.3 MHz)
δ 199.6, 140.4, 137.7, 129.8, 128.8, 127.8, 116.1, 99.4, 92.5, 76.5,
(42) Denmark, S. E.; Wynn, T. J. Am. Chem. Soc. 2001, 123, 6199.
(43) Journet, M.; Malacria, M. J. Org. Chem. 1992, 57, 3085.

2626 Organometallics, Vol. 24, No. 11, 2005
Balduzzi et al.
45.6, 14.9; IR (KBr) 3444, 3081, 2972, 2933, 2091, 2052, 2023,
1596, 1487, 1444, 1029, 920, 758 cm-1; MS (EI, m/z) 416 (M+
- 2 CO, 30), 388 (M+ - 3 CO, 10), 360 (M+ - 4 CO, 28), 332
(M+ - 5 CO, 48), 304 (M+ - 6 CO, 100); MS (CI, NH3, m/z)
455 (M+ - OH, 100), 427 (M+ - OH - CO, 91), 399 (M+ - OH
- 2 CO, 58); MS (-ve ES, m/z) 471.1 (100) [M - 1H]-, 507.1
(16) [M + 35Cl]-, 509.1 (5) [M + 37Cl]-.
(anti-3-Methyl-6-phenyl-1-hexen-5-yn-4-ol)dicobalt Hexa-
carbonyl Complex (8d). 1H NMR (CDCl3, 200 MHz): δ 7.51
(m, 2H), 7.31 (m, 3H), 5.90 (m, 1H), 5.20 (m, 2H), 4.78 (m,
1H), 2.37 (m, 1H), 2.35 (d, J ) 3.7 Hz, 1H), 1.06 (d, J ) 6.8
Hz, 3H).
(neat) 3079, 2980, 2918, 2865, 2231, 1642, 1599, 1490, 1443,
1341, 1070, 917, 756, 691 cm-1; MS (EI, m/z) 285 (M+ - CH2-
CHdCH2, 10), 155 (M+ - C6H5C2CH(O)CH2CHdCH2, 100), 77
(C6H5+, 16); MS (CI, NH3, m/z) 344 (M + NH4+, 33), 285 (M+
- CH2CHdCH2, 16), 172 (M + H+ - C6H5C2CHCH2CHdCH2,
58), 155 (M+ - C6H5C2CH(O)CH2CHdCH2, 100).
Di-4-(6-phenyl-1-hexen-5-yn)Ether(enantiomers(4R,4′R
and 4S,4′S) or meso compound) (11). Isolated 0.029 g (0.18
mmol) of a colorless oil: 1H NMR (CDCl3, 200 MHz) δ 7.43
(m, 4H), 7.28 (m, 6H), 5.99 (m, 2H), 5.20 (m, 4H), 4.63 (t, J )
6.5 Hz, 2H), 2.63 (m, 4H); 13C NMR (CDCl3, 50.3 MHz) δ 133.5,
131.7, 128.3, 128.2, 122.7, 117.9, 88.0, 86.2, 68.6, 40.1; MS (EI,
m/z) 285 (M+ - CH2CHdCH2, 8), 155 (M+ - C6H5C2CH(O)-
CH2CHdCH2, 100), 77 (C6H5+, 63); MS (CI, NH3, m/z) 344 (M
(1-Nonen-5-yn-4-ol)dicobalt Hexacarbonyl Complex
(9a). Purification by flash chromatography (9:1 pentane/
diethyl ether) yielded 94% of a red solid: 1H NMR (CDCl3,
200 MHz) δ 5.93 (m, 1H), 5.24 (m, 2H), 4.82 (m, 1H), 2.80 (m,
2H), 2.46 (m, 2H), 2.01 (d, J ) 4.3 Hz, 1H), 1.65 (m, 2H), 1.07
(t, J ) 7.3 Hz, 3H); 13C NMR (CDCl3, 50.3 MHz) δ 199.8, 134.0,
118.7, 100.3, 98.6, 71.5, 43.8, 35.9, 25.2, 14.1; IR (KBr) 3468,
3083, 2966, 2937, 2878, 2090, 2045, 2019, 1642, 1611, 1434,
1380, 1046, 997, 920 cm-1; MS (EI, m/z) 396 (M+ - CO, 7),
368 (M+ - 2 CO, 65), 340 (M+ - 3 CO, 54), 312 (M+ - 4 CO,
84), 284 (M+ - 5 CO, 90), 256 (M+ - 6 CO, 100); MS (CI, NH3,
m/z) 424 (M+, 6), 407 (M+ - OH, 100), 379 (M+ - OH - CO,
30), 351 (M+ - OH - 2 CO, 18); MS (-ve ES, m/z) 423.2 (100)
[M - 1H]-, 459.1 (15) [M + 35Cl]-, 461.1 (5) [M + 37Cl]-.
(2-Methyl-1-nonen-5-yn-4-ol)dicobalt Hexacarbonyl
Complex (9b). Purification by flash chromatography (9:1
pentane/diethyl ether) yielded 93% of a red solid: 1H NMR
(CDCl3, 200 MHz) δ 4.93 (m, 2H), 4.89 (m, 1H), 2.81 (m, 2H),
2.49 (m, 1H), 2.30 (m, 1H), 2.07 (d, J ) 3.5 Hz, 1H), 1.85 (s,
3H), 1.68 (m, 2H), 1.07 (t, J ) 7.3 Hz, 3H); 13C NMR (CDCl3,
50.3 MHz) δ 200.0, 141.7, 114.3, 100.4, 98.5, 69.4, 48.0, 35.8,
25.2, 22.2, 14.1; IR (KBr) 3478, 3081, 2966, 2937, 2878, 2090,
2047, 2018, 1649, 1611, 1456, 1378, 1059, 898 cm-1; MS (EI,
m/z) 410 (M+ - CO, 8), 382 (M+ - 2 CO, 71), 354 (M+ - 3 CO,
65), 326 (M+ - 4 CO, 84), 298 (M+ - 5 CO, 100), 270 (M+ - 6
+ NH4+, 69), 285 (M+ - CH2CHdCH2, 21), 172 (M + H+
-
C6H5C2CHCH2CHdCH2, 65), 155 (M+ - C6H5C2CH(O)CH2-
CHdCH2, 100).
(Z)-6-Phenyl-1,3-hexadien-5-yne (12).44 Isolated 0.013 g
(0.07 mmol) of a colorless oil: 1H NMR (CDCl3, 200 MHz) δ
7.44 (m, 2H), 7.30 (m, 3H), 6.97 (ddd, J ) 16.6, 10.6, 10.0 Hz,
1H), 6.43 (dd, J ) 10.8, 10.6 Hz, 1H), 5.68 (d, J ) 10.8 Hz,
1H), 5.40 (dd, J ) 16.6, 1.4 Hz, 1H), 5.31 (dd, J ) 10.0, 1.4
Hz, 1H).
4-(Phenylacetylene)-1,6-heptadiene (13). Isolated 0.004
g (0.02 mmol) of a colorless oil: 1H NMR (CDCl3, 200 MHz) δ
7.37 (m, 2H), 7.26 (m, 3H), 5.94 (m, 2H), 5.10 (m, 4H), 2.69
(quintet, J ) 4.5 Hz, 1H), 2.31 (dd, J ) 4.5, 4.5 Hz, 4H); 13C
NMR (CDCl3, 50.3 MHz) δ 135.8, 131.6, 128.1, 127.5, 123.8,
116.7, 92.2, 82.4, 38.6, 32.0; IR (neat) 3079, 2962, 2928, 1724,
1642, 1599, 1490, 1442, 1262, 1070, 1030, 997, 916, 756 cm-1
;
MS (EI, m/z) 196 (M+, 7), 168 (M+ - CH2dCH2, 26), 155 (M+
- CH2CHdCH2, 79), 129 (M+ - HCtCH - CH2CHdCH2, 45),
77 (C6H5+, 44), 43 (C3H7, 100); MS (CI, NH3, m/z) 197 (M +
H+, 40), 155 (M+ - CH2CHdCH2, 25), 76 (C6H4+, 100).
(4-(Phenylacetylene)-1,6-heptadiene)dicobalt Hexa-
carbonyl Complex (14). To a solution of (3-phenylpropynal)-
dicobalt hexacarbonyl (0.22 g, 0.52 mmol) and BF3‚OEt2 (0.15
mL, 1.19 mmol) in CH2Cl2 (11 mL) at -78 °C under N2 was
added allyltributylstannane (0.37 mL, 1.19 mmol). Stirring at
-78 °C was continued until the starting material could no
longer be detected by TLC. After quenching the reaction
mixture at 0 °C by adding a cold aqueous solution of NaHCO3,
the organic layer was separated, extracted with aqueous NaCl,
dried over MgSO4, filtered, and concentrated under reduced
pressure. The mixture was purified by flash chromatography
(9:1 pentane/diethyl ether) to yield 0.21 g (0.45 mmol, 87%) of
a brown solid: 1H NMR (CDCl3, 200 MHz) δ 7.39 (m, 2H), 7.27
(m, 3H), 5.84 (m, 2H), 5.05 (m, 4H), 3.23 (quintet, J ) 6.6 Hz,
1H), 2.44 (dd, J ) 6.6, 6.1 Hz, 4H).
CO, 83); MS (CI, NH3, m/z) 421 (M+ - OH, 100), 393 (M+
-
OH - CO, 26), 365 (M+ - OH - 2 CO, 24); MS (-ve ES, m/z)
437.2 (100) [M - 1H]-, 473.2 (26) [M + 35Cl]-, 475.2 (9) [M +
37Cl]-.
(syn-3-Methyl-1-nonen-5-yn-4-ol)dicobalt Hexacarbo-
nyl Complex (9c). Purification by flash chromatography (9:1
pentane/diethyl ether) yielded 80% of a red solid: 1H NMR
(CDCl3, 200 MHz) δ 5.85 (m, 1H), 5.15 (m, 2H), 4.57 (dd, J )
5.5, 7.2 Hz, 1H), 2.79 (m, 2H), 2.42 (m, 1H), 1.86 (d, J ) 5.4
Hz, 1H), 1.62 (m, 2H), 1.23 (d, J ) 6.8 Hz, 3H), 1.06 (t, J )
7.3 Hz, 3H); 13C NMR (CDCl3, 200 MHz) δ 199.9, 139.9, 116.2,
100.2, 99.2, 76.1, 46.2, 36.3, 25.2, 17.1, 14.1; IR (KBr) 3479,
3081, 3021, 2962, 2930, 2875, 2089, 2032, 2010, 1460, 1217,
1024, 924, 773 cm-1; MS (EI, m/z) 410 (M+ - CO, 16), 382
(M+ - 2 CO, 100), 354 (M+ - 3 CO, 34), 326 (M+ - 4 CO, 44),
298 (M+ - 5 CO, 32), 270 (M+ - 6 CO, 47); MS (CI, NH3, m/z)
421 (M+ - OH, 100), 393 (M+ - OH - CO, 66), 365 (M+ - OH
- 2 CO, 55), 337 (M+ - OH - 3 CO, 22); MS (-ve ES, m/z)
437.2 (74) [M - 1H]-, 517.1 (42) [M + 79Br]-, 519.1 (40) [M +
81Br]-.
(anti-3-Methyl-1-nonen-5-yn-4-ol)dicobalt Hexacarbo-
nyl Complex (9d). Purification by flash chromatography (9:1
pentane/diethyl ether) yielded 14% of a red solid: 1H NMR
(CDCl3, 200 MHz) δ 5.91 (m, 1H), 5.24 (m, 2H), 4.46 (dd, J )
3.9, 7.5 Hz, 1H), 2.79 (m, 2H), 2.33 (m, 1H), 2.15 (d, J ) 3.9
Hz, 1H), 1.65 (m, 2H), 1.14 (d, J ) 6.8 Hz, 3H), 1.07 (t, J )
7.4 Hz, 3H); 13C NMR (CDCl3, 200 MHz) δ 200.2, 139.8, 117.5,
99.7, 98.6, 75.1, 47.2, 36.3, 25.2, 17.0, 14.2.
General Procedure for Oxidative Decomplexation of
the Dicobalt Cluster. To a solution of 14 (0.21 g, 0.45 mmol)
in CH3OH (4 mL) at 25 °C was added trimethylamine N-oxide
(0.30 g, 3.99 mmol). The reaction mixture was stirred at 25
°C until the starting material could no longer be detected by
TLC. It was then filtered through glass wool and brought to a
volume of approximately 20 mL by the addition of diethyl
ether. The organic layer was extracted with a saturated
aqueous solution of NaCl, dried over MgSO4, filtered, and
concentrated under reduced pressure to yield 0.075 g (0.38
mmol, 85%) of a yellow oil. The product was confirmed to be
1
4-(phenylacetylene)-1,6-heptadiene (13) by comparing its H
NMR spectrum with that previously obtained.
syn-(5E)-3-Methyl-1,5-nonadien-4-ol (15).12,13 To a solu-
tion of syn-3-methyl-1-nonen-5-yn-4-ol (5c) (0.050 g, 0.32
mmol) in THF (3.5 mL) was added LiAlH4 (0.018 g, 0.47 mmol)
at 25 °C. The reaction mixture was refluxed for 12 h, then
cooled to 0 °C and quenched by the dropwise addition of 10
mL of a cold aqueous solution of 2 N H2SO4. Diethyl ether (5
Di-4-(6-phenyl-1-hexen-5-yn)Ether(enantiomers(4R,4′R
and 4S,4′S) or meso compound) (10). Isolated 0.027 g (0.17
mmol) of a colorless oil: 1H NMR (CDCl3, 200 MHz) δ 7.47
(m, 4H), 7.33 (m, 6H), 6.00 (m, 2H), 5.20 (m, 4H), 4.79 (t, J )
6.5 Hz, 2H), 2.63 (m, 4H); 13C NMR (CDCl3, 50.3 MHz) δ 133.6,
131.7, 128.2, 128.1, 122.7, 117.6, 87.5.0, 86.2, 67.4, 40.1; IR
(44) Wang, Y.; Koreeda, M.; Chatterji, T.; Gates, K. S. J. Org. Chem.
1998, 63, 8544.

Diastereoselective Addition of Allylstannanes
Organometallics, Vol. 24, No. 11, 2005 2627
mL) was added to the flask, and the organic layer was
separated, extracted with a saturated aqueous solution of
NaCl, dried over MgSO4, filtered, and concentrated under
reduced pressure to yield 0.045 g of a mixture of 5c and 15.
Compound 15: 1H NMR (CDCl3, 200 MHz) δ 5.82 (m, 1H),
5.70-5.39 (m, 2H), 5.11 (br s, 1H), 5.05 (br s, 1H), 3.97 (m,
1H), 2.41 (m, 1H), 2.02 (m, 2H), 1.40 (m, 2H), 1.03 (d, J ) 6.8
Hz, 3H), 0.89 (t, J ) 7.3 Hz, 3H).
General Procedure for Allyl Transfer to Dicobalt
Pentacarbonyl(triarylphosphine)-Complexed Propy-
nals. Entries 1 to 3 of Table 3 correspond to reactions in which
the reagents were all added to a flask immersed in a cooling
bath at a temperature of -78 °C, as described for the
preparation of 6-phenyl-1-hexen-5-yn-4-ol (4a). The tempera-
ture of the cooling bath was allowed to warm to 25 °C over a
period of approximately 4, 6, and 12 h, for entries 1, 2, and 3,
respectively. Entries 4 to 9 correspond to reactions in which
the reagents were added, and the cooling bath was maintained,
at the temperature specified for the duration of the reaction.
The reaction mixtures were all quenched at 0 °C by the
addition of a cold aqueous solution of NaHCO3 and worked
up as described for 4a.
(6-Phenyl-1-hexen-5-yn-4-ol)dicobalt Pentacarbonyl-
(triphenylphosphine) Complex (28, 29). Major Diastereo-
mer. Purification by flash chromatography (8:2 pentane/
diethyl ether) yielded 87% of a red solid: 1H NMR (CDCl3,
200 MHz) δ 7.27 (m, 20H), 5.74 (m, 1H), 5.09 (m, 2H), 3.92
(m, 1H), 2.29 (m, 1H), 2.10 (m, 1H), 1.97 (d, J ) 4.7 Hz, 1H);
13C NMR (CDCl3, 200 MHz) δ 205.0, 205.1, 201.4, 139.3, 135.3,
134.4, 133.6, 133.1, 133.0, 130.3, 130.1, 128.4, 128.4, 128.2,
128.2, 126.5, 117.1, 96.1, 83.9, 70.0, 44.1; IR (KBr) 3311, 3078,
3059, 2908, 2858, 2058, 2008, 1961, 1642, 1593, 1488, 1438,
1182, 1120, 1069, 997, 916, 756, 723, 694 cm-1; MS (-ve ES,
m/z) 726.8 (62) [M + 35Cl]-, 728.8 (27) [M + 37Cl]-.
(6-Phenyl-1-hexen-5-yn-4-ol)dicobalt Pentacarbonyl-
(triphenylphosphine) Complex (28,29). Minor Diastereo-
mer. Purification by flash chromatography (8:2 pentane/
diethyl ether) yielded 13% of a red solid: 1H NMR (CDCl3, 500
MHz) δ 7.27 (m, 20H), 5.74 (m, 1H), 5.14 (m, 2H), 4.06 (m,
1H), 2.65 (m, 1H), 2.29 (m, 1H), 1.64 (d, J ) 4.7 Hz, 1H); 13C
NMR (CDCl3, 500 MHz) δ 205.5, 205.4, 201.3, 139.3, 135.1,
134.1, 133.8, 132.9, 132.8, 130.3, 130.0, 128.4, 128.4, 128.3,
128.3, 126.5, 117.8, 93.9, 86.8, 70.1, 44.0.
(2-Methyl-6-phenyl-1-hexen-5-yn-4-ol)dicobalt Penta-
carbonyl(triphenylphosphine) Complex (31, 32). Purifica-
tion by flash chromatography (8:2 pentane/diethyl ether)
yielded 92% of a red solid: 1H NMR (CDCl3, 200 MHz) δ 7.25
(m, 20H), 4.80 (br s, 1H), 4.72 (br s, 1H), 4.0 (m, 1H), 2.25 (m,
1H), 2.03 (m, 1H), 1.71 (d, J ) 3.5 Hz, 1H) 1.58 (s, 3H); 13C
NMR (CDCl3, 50.3 MHz) δ 206.8, 206.7, 201.8, 142.5, 139.4,
134.3, 133.5, 133.2, 133.0, 130.1, 130.1, 128.3, 128.3, 128.1,
128.1, 126.5, 113.2, 96.3, 83.1, 67.7, 48.3, 22.3; IR (KBr) 3380,
3077, 3062, 2968, 2917, 2857, 2059, 2007, 1963, 1647, 1489,
1438, 1179, 1120, 1059, 1027, 849, 757, 723, 693 cm-1; MS (-ve
ES, m/z) 705.3 (4) [M - 1H]-, 741.2 (7) [M + 35Cl]-, 743.2 (3)
[M + 37Cl]-.
(1-Nonen-5-yn-4-ol)dicobalt Pentacarbonyl(triphenyl-
phosphine) Complex (33, 34). Major Diastereomer. Pu-
rification by flash chromatography (7:3 pentane/diethyl ether)
yielded 80% of a red solid: 1H NMR (CDCl3, 200 MHz) δ 7.56
(6H), 7.42 (m, 9H), 5.64 (m, 1H), 5.00 (m, 2H), 3.91 (m, 1H),
2.15 (m, 2H), 1.61 (m, 2H), 1.46 (m, 2H), 0.79 (t, J ) 7.1 Hz,
3H); 13C NMR (CDCl3, 50.3 MHz) δ 205.8, 205.7, 202.0, 135.2,
135.1, 134.2, 133.0, 132.8, 130.3, 130.3, 128.6, 128.4, 117.2,
95.1, 94.4, 70.5, 43.6, 33.7, 25.1, 13.9; IR (KBr) 3583, 3062,
3011, 2961, 2934, 2875, 2057, 1996, 1959, 1482, 1436, 1092,
918, 758, 697 cm-1; MS (-ve ES, m/z) 656.9 (100) [M - 1H]-.
(1-Nonen-5-yn-4-ol)dicobalt Pentacarbonyl(triphenyl-
phosphine) Complex (33, 34). Minor Diastereomer. 13C
NMR (CDCl3, 50.3 MHz): δ 205.8, 205.7, 202.0, 135.3, 135.2,
134.5, 133.0, 132.8, 130.3, 130.3, 128.6, 128.4, 117.6, 96.3, 94.6,
71.2, 44.1, 34.6, 25.2, 14.0.
(2-Methyl-1-nonen-5-yn-4-ol)dicobalt Pentacarbonyl-
(triphenylphosphine) Complex (36, 37). Major Diastereo-
mer. Purification by flash chromatography (7:3 pentane/
diethyl ether) yielded 79% of a red solid: 1H NMR (CDCl3,
200 MHz) δ 7.55 (m, 6H), 7.42 (m, 9H), 4.78 (br s, 1H), 4.68
(br s, 1H), 4.14 (m, 1H), 2.09 (m, 2H), 1.65 (m, 2H), 1.57 (m,
2H), 1.55 (s, 3H), 0.82 (t, J ) 7.3 Hz, 3H); 13C NMR (CDCl3,
50.3 MHz) δ 205.7, 205.5, 201.4, 142.3, 135.1, 134.3, 133.1,
132.9, 130.3, 130.3, 128.6, 128.4, 113.1, 95.2, 94.2, 68.5, 47.7,
33.6, 25.0, 22.3, 13.9; IR (KBr) 3344, 3062, 2961, 2931, 2873,
2055, 1998, 1959, 1437, 1185, 1120, 1092, 746, 723, 696 cm-1
;
MS (-ve ES, m/z) 671.3 (100) [M - 1H]-, 707.3 (50) [M +
35Cl]-, 709.3 (22) [M + 37Cl]-.
(Z)-6-Phenyl-1,3-hexadien-5-yne)dicobalt Pentacarbo-
nyl(triphenylphosphine) Complex (30). Isolated by flash
chromatography (8:2 pentane/diethyl ether) from the reactions
described in entries 1 to 3 in Table 3. After oxidative decom-
plexation using trimethylamine N-oxide, the compound was
confirmed to be (Z)-6-phenyl-1,3-hexadien-5-yne by comparison
(2-Methyl-1-nonen-5-yn-4-ol)dicobalt Pentacarbonyl-
(triphenylphosphine) Complex (36,37). Minor Diastereo-
mer. 13C NMR (CDCl3, 50.3 MHz): δ 205.7, 205.5, 201.4, 142.7,
135.3, 134.5, 133.1, 132.9, 130.3, 130.3, 128.6, 128.4, 113.3,
96.6, 94.3, 69.5, 48.3, 34.7, 25.2, 22.6, 14.1.
1
of its H NMR spectrum with that previously obtained.
OM050019G