Diastereoselective propargylations with planar chiral chromiumcarbonyl arene complex substituted propargyl cations

Article abstract of DOI:10.1021/ja0037116

The ionization of planar chiral ortho-substituted (arene)Cr(CO)₃-substituted α-propargylic acetates 3 with Lewis acids results in the formation of stable (arene)Cr(CO)₃-substituted α-propargyl cations 4. Subsequent additions of sulfur, nitrogen, oxygen, and π-carbon nucleophiles to these organometallic electrophiles give rise to the regio- and highly diastereoselective formation of propargyl derivatives 5 in good yields (44-90%; dr = 70:30 to >99:1). The relative stereochemistry of the propargyl acetates 3 and the trapping products 5 was established by several crystal structure analyses, indicating that the cationic propargylations occurred under retention of configuration at the propargylic center. Most important for the diastereoselectivity of the nucleophilic trapping reaction is the configurational stability of the diastereotopic cation 4 as reflected by substituent effects. In situ ionizations according to an S_Nl-mechanism not only result in a considerable loss but also in an inversion of diastereoselectivity.

Full text of DOI:10.1021/ja0037116

J. Am. Chem. Soc. 2001, 123, 3441-3453
3441
Diastereoselective Propargylations with Planar Chiral
Chromiumcarbonyl Arene Complex Substituted Propargyl Cations
Astrid Netz, Kurt Polborn, and Thomas J. J. Mu1ller*,†
Contribution from the Department Chemie (Organische Chemie) der Ludwig-Maximilians-UniVersita¨t
Mu¨nchen, Butenandtstrasse 5-13 (Haus F), D-81377 Mu¨nchen, Germany
ReceiVed October 17, 2000
Abstract: The ionization of planar chiral ortho-substituted (arene)Cr(CO)3-substituted R-propargylic acetates
3 with Lewis acids results in the formation of stable (arene)Cr(CO)3-substituted R-propargyl cations 4.
Subsequent additions of sulfur, nitrogen, oxygen, and π-carbon nucleophiles to these organometallic electrophiles
give rise to the regio- and highly diastereoselective formation of propargyl derivatives 5 in good yields (44-
90%; dr ) 70:30 to >99:1). The relative stereochemistry of the propargyl acetates 3 and the trapping products
5 was established by several crystal structure analyses, indicating that the cationic propargylations occurred
under retention of configuration at the propargylic center. Most important for the diastereoselectivity of the
nucleophilic trapping reaction is the configurational stability of the diastereotopic cation 4 as reflected by
substituent effects. In situ ionizations according to an SN1-mechanism not only result in a considerable loss
but also in an inversion of diastereoselectivity.
Introduction
Scheme 1. Stabilization of Carbenium Ions by
Representative π-Complex Fragments
Classically, nucleophilic substitutions following an SN1-
mechanism proceed through a trigonal planar carbenium ion
intermediate and inherently cause racemization at the substitu-
tion center. Very few cases of neighboring group participation
give rise to stereocontrolled substitution products.1 However,
the advent of transition metal π-complex stabilization of
R-carbenium ions2 has revolutionized the synthetic application
of these often elusive reactive carbocation intermediates, in
particular, in stereoselective nucleophilic additions with retention
of configuration. Among transition metal π-complex stabilized
carbenium ions2 the most prominent representatives are ferro-
cenyl-, (alkyne)Co2(CO)6-, or (arene)Cr(CO)3-substituted car-
bocations (Scheme 1).
Scheme 2. Alkynyl Cobaltcarbonyl (Nicholas’ Cations) and
Arene Chromiumcarbonyl Complex Substituted Carbenium
Ions
Stereochemically, a pronounced neighboring group effect
arising from an ideal overlap of occupied d-orbitals on the metal
and the vacant p-orbital at the carbenium center in the R-position
also rationalizes a rate-increasing anchimeric assistance in SN1
reactions and the conservation of the stereochemical information
at the previous sp3-center as a consequence of an overall reten-
tion of configuration due to a double inversion mechanism.2c,d,f
In particular, chromiumcarbonyl complexed benzylic cations3
have found applications in asymmetric organic syntheses.2f,4
According to calculations at different levels of theory for
chromiumcarbonyl complexed benzyl cations, the carbenium
center is significantly distorted from coplanarity with the phenyl
ring upon bending toward the metal center.3d,e,5 This distortion
results in a configurational fixation of the side chain in a rigid
conformation at low temperatures.2f
stabilized by the adjacent cobalt(0) fragment under simultaneous
protection of the alkyne can be reacted with a number of
nucleophiles, giving rise to functionalized propargylic deriva-
tives, interesting building blocks in complex natural product
syntheses.7 However, the so-called “Nicholas’ cations” (Scheme
2) can be regarded as cobalt cluster stabilized carbenium ions
rather than propargyl cations, especially since the triple bond
is permanently complexed by the dicobalthexacarbonyl fragment
and even the precursors for ionizations display bond lengths
for the “triple bond” that strongly deviate from those of alkynes.6
Since ionizations of propargyl precursors form ambident
propargyl cations8 that can be interesting intermediates for more
In the extensive work of Nicholas, the activation of the
propargylic position was achieved by attaching a dicobalt-
hexacarbonyl cluster to a triple bond.2e,6 The generated cation
(2) For reviews, see, for example: (a) Haynes, L.; Pettit, R. In Carbonium
Ions; Olah, G. A., Schleyer, P. v. R., Eds.; Wiley: New York, 1975; Vol.
5. (b) Watts, W. E. In ComprehensiVe Organometallic Chemistry; Wilkinson,
G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, 1982; Vol. 8,
Chapter 59, p 1051. (c) Solladie´-Cavallo, A. Polyhedron 1985, 4, 901. (d)
Jaouen, G. Pure Appl. Chem. 1986, 58, 597. (e) Nicholas, K. M. Acc. Chem.
Res. 1987, 20, 207. (f) For stabilization of positive charge in benzylic
positions by chromium carbonyl fragments, see, for example: Davies, S.
G.; Donohoe, T. J. Synlett 1993, 323.
† E-mail: tom@cup.uni-muenchen.de.
(1) (a) AdVanced Organic Chemistry, 3rd ed. Carey, F. A., Sundberg,
R. J., Eds.; Plenum Press: New York, London, 1990; Vol. 1, Chapter 5.10.
(b) Capon, B.; McManus, S. P. Neighboring Group Participation; Plenum
Press: New York, 1976.
10.1021/ja0037116 CCC: $20.00 © 2001 American Chemical Society
Published on Web 03/21/2001

3442 J. Am. Chem. Soc., Vol. 123, No. 15, 2001
Netz et al.
Scheme 3
sophisticated arene side chain functionalizations via aryl pro-
pargyl or allenyl derivatives, we have initiated a program to
investigate (arene)Cr(CO)3 complexes bearing π-substituents,9
particularly propargyl cations.10 In kinetic studies we could
determine the electrophilic reactivity of a (arene)Cr(CO)3
complex substituted propargyl cation, revealing that this system
(Scheme 2, R1 ) H; R2 ) Ph) is 2 orders of magnitude more
reactive than the comparable Nicholas’ cation (Scheme 2, R1,
R3 ) H; R2 ) Ph).11
Recently, we communicated the regio- and diastereoselective
addition of nucleophiles to planar chiral complex substituted
R-propargyl cations.12 Now we wish to disclose our structural
and synthetic investigations on diastereoselective cationic pro-
pargylations with (arene)Cr(CO)3-substituted R-propargyl cat-
ions and several nucleophiles giving rise to complex substituted
propargyl products.
Results and Discussion
Recently, we showed that (arene)Cr(CO)3-stabilized R-pro-
pargylic cations could be easily and quantitatively generated
from a suitable propargylic precursor,10a,c,12 i.e., in our case upon
ionization of dichloromethane solutions of arene complex
substituted propargyl acetates at low temperatures with a
slight excess of a Lewis acid such as boron trifluoride diethyl
etherate, trimethylsilyl triflate (TMSOTf), tin tetrachloride,
or titanium tetrachloride. As shown previously by several
groups, the nucleophilic addition of organolithium or organo-
magnesium reagents to planar chiral ortho-substituted com-
plexed benzaldehyds4d proceeds with excellent diastereoselec-
tivity and allows for high-yield access to diastereomerically pure
racemic mixtures of complex substituted propargyl derivatives.13
Therefore, our strategy to prepare planar chiral (arene)Cr(CO)3-
stabilized R-propargylic cations commences with the nucleo-
philic addition of lithium acetylides 2 to racemic ortho-
substituted η6-(benzaldehyde)Cr(CO)3 complexes 1 at -78 °C
in THF followed by the addition of acetic anhydride, giving
rise to the formation of planar chiral (arene)Cr(CO)3-substituted
propargyl acetates 3 in good yields and with excellent diaste-
reoselectivity (Scheme 3) as deduced from the appearance of
only one set of signals in the proton and carbon NMR spectra.
Characteristically, the resonances of the benzylic proton and
carbon of the compounds 3 appear between δ 6.2 and 6.7 (1H
NMR) and δ 57.7 and 61.9 (13C NMR), respectively. Further-
more, the relative stereochemistry was unambiguously estab-
lished by crystal structure analyses14 of 3b (Figure 1, Table 1)),
3e (Figure 2, Table 1), and 3g (Figure 3, Table 1), indicating
that the observed diastereomer was formed by an exo-attack of
the lithium acetylide in an energetically more favorable transition
state arising from the attack to the anti-conformer (carbonyl
oxygen vs R1) of the ortho-substituted benzaldehyde complexes.4d
The ionization of the propargyl acetates 3 with trimethylsilyl
triflate (TMSOTf), tin tetrachloride, or titanium tetrachloride
is accompanied by a color change from light yellow to deep
(3) (a) Wells, D. K.; Trahanovsky, W. S. J. Am. Chem. Soc. 1969, 91,
5870. (b) Olah, G. A.; Yu, S. H. J. Org. Chem. 1976, 41, 1694. (c) Seyferth,
D.; Merola, S.; Eschbach, C. S. J. Am. Chem. Soc. 1978, 100, 4124. (d)
Clack, D. W.; Kane-Maguire, L. A. P. J. Organomet. Chem. 1978, 145,
201. (e) Downton, P. A.; Sayer, B. G.; McGlinchey, M. J. Organometallics
1992, 11, 3281.
(4) (a) Reetz, M. T.; Sauerwald, M. Tetrahedron Lett. 1983, 24, 2837.
(b) Reetz, M. T.; Sauerwald, M. J. Organomet. Chem. 1990, 382, 121. (c)
Uemura, M.; Kobayashi, T.; Hayashi, Y. Synthesis 1986, 386. (d) For side
chain activation, see, for example: Davies, S. G.; McCarthy, T. D. In
ComprehensiVe Organometallic Chemistry II; Abel, E. W., Stone, F. G.
A., Wilkinson, G., Eds.; Pergamon: 1995; Vol. 12, p 1039. (e) Corey, E.
J.; Helal, C. J. Tetrahedron Lett. 1996, 37, 4837. (f) Tanaka, T.;
Mikamiyama, H.; Maeda, K.; Iwata, C.; In, Y.; Ishida, T. J. Org. Chem.
1998, 63, 9782.
(5) For recent computational studies on the DFT level of theory, see,
for example: (a) Pfletschinger, A.; Dargel, T. K.; Bats, J. W.; Schmalz,
H.-G.; Koch, W. Chem. Eur. J. 1999, 5, 537. (b) Merlic, C. A.; Walsh, J.
C.; Tantillo, D. J.; Houk, K. N. J. Am. Chem. Soc. 1999, 121, 3596.
(6) For excellent reviews, see, for example: (a) Melikyan, G. G.;
Nicholas, K. M. In Modern Acetylene Chemistry; Stang, P. J., Diederich,
F., Eds.; VCH: Weinheim, 1995; p 118. (b) Caffyn, A. J. M.; Nicholas, K.
M. In ComprehensiVe Organometallic Chemistry II; Abel, E. W., Stone, F.
G. A., Wilkinson, G., Eds.; Pergamon: 1995; Vol. 12, p 685.
(7) (a) Nicolaou, K. C.; Dai, W. M. Angew. Chem., Int. Ed. Engl. 1991,
30, 1387. (b) Magnus, P.; Pitterna, T. J. Chem. Soc., Chem. Commun. 1991,
541. (c) Magnus, P. Tetrahedron 1994, 50, 1397.
(8) (a) Murray, M. In Methoden zur Herstellung und Umwandlung Von
Allenen bzw. Kumulenen; Houben-Weyl, Eds.; Georg Thieme Verlag:
Stuttgart, 1977; Vol. 5/2a, p 991. (b) Mayr, H.; Ba¨uml, E.; Tetrahedron
Lett. 1983, 24, 357. (c) Ba¨uml, E.; Mayr, H. Chem. Ber. 1985, 118, 694.
(d) Dau-Schmidt, J.-P.; Mayr, H. Chem. Ber. 1994, 127, 205. (e) Lukyanov,
S. M.; Koblik, A. V.; Muradyan, L. A. Russ. Chem. ReV. 1998, 67, 81.
(9) (a) Mu¨ller, T. J. J.; Lindner, H. J. Chem. Ber. 1996, 129, 607. (b)
Mu¨ller, T. J. J. Tetrahedron Lett. 1997, 38, 1025. (c) Mu¨ller, T. J. J.;
Ansorge, M.; Polborn, K. J. Organomet. Chem. 1999, 578, 252. (d) Ansorge,
M.; Mu¨ller, T. J. J. J. Organomet. Chem. 1999, 585, 174. (e) Mu¨ller, T. J.
J. J. Organomet. Chem. 1999, 578, 95. (f) Mu¨ller, T. J. J.; Netz, A.; Ansorge,
M.; Schma¨lzlin, E.; Bra¨uchle, C.; Meerholz, K. Organometallics 1999, 18,
5066.
(10) (a) Mu¨ller, T. J. J.; Netz, A. Organometallics 1998, 17, 3609. (b)
Mu¨ller, T. J. J.; Ansorge, M.; Polborn, K. Organometallics 1999, 18, 3690.
(c) Netz, A.; Mu¨ller, T. J. J. Organometallics 2000, 19, 1452. (d) Ansorge,
M.; Polborn, K.; Mu¨ller, T. J. J. Eur. J. Inorg. Chem. 2000, 2003.
(11) Netz, A.; Mu¨ller, T. J. J. Tetrahedron 2000, 56, 4149.
(12) Mu¨ller, T. J. J.; Netz, A. Tetrahedron Lett. 1999, 40, 3145.
(13) Baldoli, C.; Del Buttero, P.; Licandro, E.; Maiorana, S.; Papagni,
A.; Torchio, M. Tetrahedron Lett. 1993, 34, 7943.

(arene)Cr(CO)-Substituted Propargyl Cations
J. Am. Chem. Soc., Vol. 123, No. 15, 2001 3443
of doublets (C-substitution) in the 1H NMR spectra. Since these
signals are separated by ∆δ 0.01 to 0.61, the integration allows
a reliable assignment of the diastereomers and their ratios. In
most cases the propargyl proton signal appearing at higher field
is that of the major diastereomer. The relative stereochemistry
of the propargyl compounds 5 was unambiguously established
by crystal structure analyses14 of 5c (Figure 4, Table 1)), 5g
(Figure 5, Table 1), and 5t (Figure 6, Table 1), and by
subsequent correlation with the propargyl proton resonances in
1
the H NMR spectra of 5, the dominance of the depicted syn-
diastereomer (alkynyl vs R1) can be readily deduced.
The relative stereochemistry of the products 5 can be
rationalized on the basis of a double inversion mechanism2f that
results in a net retention of the configuration at the epimeric
propargyl center. Assuming a complete and irreversible anti-
periplanar Lewis acid mediated extrusion of the acetate leaving
group by an anchimeric assistance of the chromiumcarbonyl
tripod under kinetic control, the propargyl cation intermediate
6, i.e., the s-syn conformer 7, is formed (Scheme 5). Upon
rotation around the Cipso-CR bond, 7 is converted to the
diastereomeric s-trans conformer 8. These propargyl cations 7
and 8 are not only stabilized by delocalizing the benzylic charge
in the arene substituent but also by a significant contribution
of the chromiumcarbonyl neighboring group participation via
η7-complexation, i.e., an η6-phenyl complexation with a simul-
taneous d-π-overlap at the cationic propargyl center. Finally,
the nucleophilic addition to the diastereomeric propargyl cations
7 and 8 gives rise to the formation of the major diastereomers
5 and the minor compounds 5′.
A crucial point for the diastereoselectivity is the configura-
tional stability of the cation 4 that is reflected by the ease of
the syn-anti-isomerization from 7 and 8. According to semiem-
pirical calculations17 (PM3 level of theory) on the free ligand
systems 9 and 10, the energy difference of both fixed conforma-
tions is only 1.9 kcal/mol; however, the energy barrier of
activation for a syn-anti-isomerization is determined to be 12.0
kcal/mol (Scheme 6).
Therefore, the (arene)chromiumtricarbonyl substituted pro-
pargyl cation can also be considered to be configurationally fixed
in a well-defined conformation. Since an epimerization at the
propargylic center can be deduced from the diastereomeric
cation 8, it is very likely to occur on the stage of the cationic
intermediate through a rotation around the Cipso-CR bond.
Obviously, the configurational stability of the cationic propargyl
side chain is largely preserved due to a hindered rotation around
the Cipso-CR bond. Even in the case of the complex substituted
propargyl cation, the barrier for a syn-anti-isomerization is just
high enough for nucleophilic trapping reactions to proceed at
low temperature with high diastereoselectivity. Thus, the
incoming nucleophile attacks in an exo-fashion anti-periplanar
with respect to the chromiumcarbonyl tripod at the propargylic
position of the ambident electrophile 4 to give preferentially
rise to the formation of 5.
This theoretical consideration can be scrutinized by regarding
the substituent effects on both termini of the propargyl cation
bridge. Upon variation of the ortho substituent in its donor
capacity from the good donor methoxy over methyl to the poorly
electron releasing chlorine for the C-C, C-S, and C-N bond-
forming reaction with silyl ketene acetal, thiols, or amines, a
strong dependence of the stabilization of the propargylic charge
on the diastereomeric excess18 (de) can be easily recognized.
Although thiols are considered to be more nucleophilic than
Figure 1. ORTEP plot of 3b. Selected bond lengths [Å] and dihedral
angles [deg]: C(4)-C(11), 1.521(3); C(11)-C(12), 1.466(3); C(12)-
C(13), 1.191(3); C(13)-C(14), 1.440(3); C(5)-C(4)-C(11)-C(12),
80.24; C(5)-C(4)-C(11)-O(4), 160.95.
purple (4a, 4c, 4d, 4e) or deep blue (4b), indicating the
formation of the (arene)Cr(CO)3-substituted R-propargyl cations
4 (Scheme 4). At low temperatures (<-40 °C) the deep colored
specimens 4 are stable for several hours15 and can be subjected
to C-S, C-N, C-O, and C-C bond-forming reactions with
nucleophiles, such as thiols (2-propanethiol, methyl 3-mercap-
topropionate), secondary amines (diisopropylamine, morpho-
line), allyl alcohol, and π-nucleophiles (phenol, anisol, silyl
ketene acetal, allyl silane) (Table 2). All nucleophilic additions
occur exclusively at the R-position to give the propargylic
derivatives 5 in good yields and with high diastereoselectivities16
ranging from 70:30 to >99: <1. Expectedly, the shift at the
benzylic position in the proton and carbon NMR spectra strongly
depends on the corresponding substituent and can be easily
identified as singlets (S-, N-, and O-substitution) or doublets
(14) Crystallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge Crystal-
lographic Data Centre as supplementary publication nos. CCDC-153794
(3b), CCDC-153797 (3e), CCDC-153796 (3g), CCDC-153795 (5c), CCDC-
153798 (5g), and CCDC-153799 (5s). Copies of the data can be obtained
free of charge on application to CCDC, 12 Union Road, Cambridge CB2
1EZ, U.K (Fax: + 44-1223/336-033. E-mail: deposit@ccdc.cam.ac.uk).
(15) At -70 °C all cations 4 were chemically stable over several hours
according to UV/vis spectroscopy, showing no depression of the molar
decadic extinction coefficient. The configurational stability of cations 4a
and 4c (which will be published elsewhere) has been studied by recording
the 1H, 13C, HETCOR and NOESY spectra at -60 °C with the same NMR
tubes, which takes several hours. Only one set of signals (13C NMR) was
detected at that temperature; however, upon raising the temperature over
-55 °C (4c), the appearance of a second set of signals was observed.
Interestingly, the carbonyl signals still remain split into three signals
indicating that the energy barrier for the tripodal rotation is higher than for
the Cipso-CR rotation.
(16) The diastereomeric ratios were determined by 1H NMR spectroscopy
of the crude product after chromatography.
(17) Quantum CAChe 3.0 Program, Oxford Molecular Group, 1997.
(18) de ) (dr - 1)/(dr + 1) × 100%.

3444 J. Am. Chem. Soc., Vol. 123, No. 15, 2001
Netz et al.
Table 1. Crystal Data and Structure Refinements for 3b, 3e, 3g, 5c, 5g, and 5t
3b
3e
3g
5c
5g
5t
C
emp formula
color, form
formula wt
temp, K
wavelength (Å),
radiation
crystal system
space group
unit cell (Å, deg)
a
C21H16CrO5
yellow plates
400.34
294(0.2)
0.71073
(Mo KR)
triclinic
P1h
C19H20CrO6
yellow plates
396.35
295(0.2)
0.71073
(Mo KR)
triclinic
P1h
C17H16CrO7
yellow blocks
384.30
295(0.2)
0.71073
(Mo KR)
orthorhombic
Pna21
C24H22CrO6
yellow plates
458.42
294(0.2)
0.71073
(Mo KR)
monoclinic
P21/4
C23H21CrNO4
yellow plates
427.41
295(0.2)
0.71073
(Mo KR)
monoclinic
P21/c
23H31CrNO4
yellow blocks
437.49
295(0.2)
0.71073
(Mo KR)
orthorhombic
P212121
9.4639(12)
10.327(2)
10.569(2)
99.741(15)
90.801(12)
113.022(14)
933.3(3)
2
7.7055(13)
11.368(3)
12.699(2)
113.20(2)
90.509(15)
105.57(2)
976.6(3)
2
14.280(2)
8.032(3)
14.868(4)
90.00(3)
90.00(2)
90.00(2)
1705.4(9)
4
11.611(2)
13.932(2)
14.177(2)
90.000(11)
93.734(11)
90.000(11)
2288.4(5)
4
8.0461(10)
33.017 (7)
8.4264(14)
90.000(15)
109.248(0)
90.000(14)
2113.4(6)
4
7.569(2)
15.183(3)
20.575(4)
90.00(2)
90.00(2)
90.00(2)
2364.6(9)
4
b
c
R
â
γ
vol (Å3)
Z
density (calcd),
1.425
1.348
1.497
1.331
1.343
1.229
g/cm3
abs coeff, mm-1
F(000)
0.642
412
0.616
412
0.707
792
0.536
952
0.569
888
0.510
928
crystal size
(mm)
0.43 × 0.47 ×
0.13 × 0.33 ×
0.07 × 0.27 ×
0.17 × 0.47 ×
0.20 × 0.33 ×
0.23 × 0.27 ×
0.60
0.57
0.37
0.57
0.53
0.43
θ range for data
collection
index ranges
2.49-23.97°
2.77-23.97°
2.74-23.97°
2.64-23.97°
2.63-23.96°
2.39-23.97°
-9 e h e 20
-11 e k e 0
-12 e l e 12
3103
-8 e h e 0
-12 e k e 12
-14 e l e 14
3309
0 e h e 16
0 e k e9
-17 e l e 17
2666
0 e h e 13
-15 e k e 0
-16 e l e 16
3766
-9 e h e 8
-37 e k e 0
0 e l e 9
3539
-8 e h e 8
-17 e k e17
-23 e l e 23
4280
reflectns
collected
indep reflectns
obsd (I > 2σ(I))
2923 [R(int)
) 0.0094]
2673
3051 [R(int)
) 0.0186]
2591
2666 [R(int)
) 0.000]
2563
3573 [R(int)
) 0.0202]
2794
3296 [R(int)
) 0.0192]
2293
3706 [R(int)
) 0.0178]
3337
abs correctn
semiempirical
from ψ-scans
0.9138 and
0.9970
full-matrix
least-squares
on F2
semiempirical
from ψ-scans
0.8930 and
0.9991
full-matrix
least-squares
on F2
semiempirical
from ψ-scans
0.9076 and
0.9998
full-matrix
least-squares
on F2
semiempirical
from ψ- scans
0.9497 and
0.9995
full-matrix
least-squares
on F2
semiempirical
from ψ-scans
1.0000 and
0.9515
full-matrix
least-squares
on F2
semiempirical
from ψ-scans
0.9552 and
0.9998
full-matrix
least-squares
on F2
max. and min.
transmission
refinement
method
data/restraints/
parameters
goodness-of-fit
on F2
2673/0/246
2591/0/248
2563/1/229
2794/0/284
2293/0/263
3337/0/269
1.089
1.102
1.016
1.123
1.104
1.065
final R indices
[I>2σ(I)]
R1
0.0282
0.0750
0.0359
0.0924
0.0243
0.0605
0.02424
0.0986
0.0552
0.1169
0.0361
0.0885
wR2
R indices (all data)
R1
wR2
0.0315
0.0779
0.0479
0.1016
0.0258
0.0622
0.0594
0.1100
0.0930
0.1374
0.0430
0.0942
largest diff. peak
0.237 and
-0.226
0.262 and
-0.249
0.145 and
-0.176
0.293 and
-0.216
0.276 and
-0.362
0.265 and
-0.151
and hole (e/Å3)
amines, thioethers are prone to acid-catalyzed ionization and,
thus, an epimerization at a later stage cannot be fully excluded.
Therefore, not only the stability of the cationic intermediate but
also the rate of the kinetically controlled nucleophilic addition
and the stability of the propargyl product toward ionization has
to be taken into account.
Electronically, by leaving the ortho substituent constant even
alkyl substituents are tolerated on the side chain; however, a
resonance stabilization to a certain extent at the γ-position is
more favorable. In agreement with a reduced stability of the
propargyl cation 4, if an aryl substituent is replaced by an alkyl
group its generation (now TiCl4 is necessary as a Lewis acid,
vide infra) is impeded and the diastereomeric excess slightly
drops. This feature is even more important if the complex
stabilization now has to compete with a side chain stabilization
by donor substituents such as an anisyl group at the γ-position.
As a consequence the diminishing of the back-bonding by the
π-complex fragment results in a facilitated rotation around the
Cipso-CR bond and the diastereoselectivity drops.
Another aspect of the cation stabilization of 4 is the ease of
the ionization of the propargyl acetates 3 by various Lewis acids
(Table 3). As reflected by the strength of several Lewis acids,
a high diastereoselectivity only can be achieved if the combina-
tion of the propargyl acetate 3 and the Lewis acid results in a
complete irreversible ionization to the propargyl cation 4.
Incomplete ionizations represent an equilibrium situation be-
tween cation and anion on the product side and propargyl acetate
and Lewis acid on the educt side. In these cases the clear two-
step mechanistic pathway, i.e., complete ionization followed by
nucleophilic addition, is abandoned in favor of a mixed
mechanism consisting of ionization-addition sequences occur-
ring simultaneously, in the sense of an SN1 mechanism or an
SN2 pathway. A lower diastereoselectivity arises in both
mechanistic rationales.

(arene)Cr(CO)-Substituted Propargyl Cations
J. Am. Chem. Soc., Vol. 123, No. 15, 2001 3445
the pure SN1 mechanism as reflected by the formation of the
dominant product 5′. This diastereomer is rather formed by an
inversion of the configuration at the propargylic center by SN2
attack of the nucleophile under simultaneous activation by TiCl4
(Scheme 8) than by a syn-anti-isomerization from 7 and 8.
Most interestingly, in situ ionization conditions require fairly
strong Lewis acids to achieve a sufficient activation of the
acetate leaving group. Although titanium tetrachloride is suitable
for complete cation formation, the reaction pathway is not
necessarily shifted in the direction of a pure SN1 reaction (Table
4, entry 3). Furthermore, a deactivation of silyl ketene acetal
by coordination and/or side reactions with titanium tetrachloride
cannot be fully excluded and, thus, a rapid kinetically controlled
substitution is hampered. As a consequence, in situ ionization
conditions rather lead to the formation of equilibrium products.
Therefore, conducting these cationic propargylations in a
stepwise process, i.e., complete ionization of 3 to give 4
followed by nucleophilic addition, is not only more convenient
but also gives rise to highly diastereoselective formation of the
propargylation products 5.
Figure 2. ORTEP plot of 3e. Selected bond lengths [Å] and bond
angles [deg]: C(4)-C(10), 1.516(3); C(10)-C(11), 1.471(4); C(11)-
C(12), 1.182(4); C(12)-C(13), 1.475(4); C(5)-C(4)-C(10)-C(11),
80.27; C(5)-C(4)-C(10)-O(5), 159.88.
Conclusion
Cationic propargylations with stable (arene)Cr(CO)3-substi-
tuted R-propargyl cations 4 and carbon, nitrogen, oxygen, and
sulfur nucleophiles give rise to complex-substituted propargy-
lation products 5 with good to excellent diastereoselectivity.
This stereoselective propargylation is complementary to the
well-established nucleophilic trapping Nicholas’ cations;2e,6
however, the triple bond remains uncomplexed and the complex-
substituted propargyl cations 4 are even more electrophilic.11
Further studies investigating the structure and the configurational
stability of the intermediates 4 and the development of enan-
tioselective and double diastereoselective propargylations di-
rected toward sophisticated side chain functionalizations and
natural product syntheses are currently underway.
Experimental Section
All reactions involving tricarbonylchromium complexes were carried
out in flame-dried Schlenk flasks under nitrogen by using septum and
syringe techniques. Solvents were dried and distilled according to
standard procedures.19 Column chromatography: silica gel 60 (Merck,
Darmstadt), mesh 70-230 . TLC: silica gel plates (60 F254 Merck,
Darmstadt). Melting points (uncorrected values): Reichert-Jung Ther-
movar and Bu¨chi Melting Point B-540. Phenylacetylene, 1-hexyne, and
the trapping nucleophiles were purchased from Aldrich, Fluka, or Merck
and used without further purification. 3-Methoxypropyne was synthe-
sized according to the literature,20 and p-methoxyphenylacetylene was
prepared by Sonogashira coupling of p-iodoanisol followed by subse-
quent alkaline desilylation in excellent yield.21 The Cr(CO)3-complexed
benzaldehydes were prepared in analogy to published procedures via
the complexation of the dimethylacetals.10a,22 All crystalline chromium
arene complexes can be handled in air. 1H and 13C NMR spectra:
Bruker ARX 300, Varian VXR 400S, [D6]DMSO and CDCl3. The
assignments of quaternary C, CH, CH2, and CH3 has been made by
using DEPT spectra. IR: Perkin-Elmer Models Lambda 16. MS:
Finnigan MAT 90 and MAT 95 Q. Elemental analyses were carried
out in the Microanalytical Laboratory of the Department Chemie,
Ludwig-Maximilians-Universita¨t Mu¨nchen.
Figure 3. ORTEP plot of 3g. Selected bond lengths [Å] and bond
angles [deg]: C(4)-C(10), 1.514(3); C(10)-C(11), 1.470(3); C(11)-
C(12), 1.182(3); C(12)-C(13), 1.469(3); C(5)-C(4)-C(10)-C(11),
86.08; C(5)-C(4)-C(10)-O(6), 32.17.
In the next set of experiments we investigated the possibility
of conducting the stepwise ionization-nucleophilic addition
sequence in an SN1 fashion, i.e., the in situ generation of the
propargyl cation intermediate 4 in the presence of the trapping
nucleophile. In particular, if the applied Lewis acid is strong
enough to ensure complete ionization, these SN1 reactions should
proceed with high diastereoselectivity. However, the in situ
ionization experiments (Table 4, entries 1 and 2) reveal that
not only does the diastereoselectivity drop considerably to a
34:66 or 43:57 ratio but also the selectivity of the propargylation
is reversed from 5 to 5′. It is noteworthy mentioning that
according to MM2 force field calculations17 the diastereomers,
e.g., 5c and 5c′ (∆E ) 0.3 kcal/mol), are almost equal in energy
(Scheme 7). Obviously, the in situ ionization conditions infringe
(19) Various editors, Organikum, 19th ed.; VEB Deutscher Verlag der
Wissenschaften: Berlin, 1993.
(20) Brandsma, L. In PreparatiVe Acetylenic Chemistry, 2nd ed.;
Elsevier: Amsterdam, Oxford, New York, Tokyo, 1988; p 259.
(21) (a) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N.
Synthesis 1980, 627. (b) Sonogashira, K. In Metal catalyzed Cross-coupling
Reactions; Diederich, F., Stang, P. J., Eds.; Wiley-VCH: Weinheim, 1998;
p 203.
(22) Mahaffy, C. A. L.; Pauson, P. L. Inorg. Synth. 1990, 28, 136.

3446 J. Am. Chem. Soc., Vol. 123, No. 15, 2001
Netz et al.
Scheme 4
Table 2. Substituent Keys of 4 and 5, Yields, and Diastereomeric Ratios of the Nucleophilic Trapping Reactions
X-ray Structure Determination of Compounds 3b, 3e, 3g, 5c, 5g,
and 5t. Suitable Crystals were mounted on a capillary and transferred
to an Enraf-Nonius CAD4 diffractometer. The structures were solved
by direct methods and refined anisotropically on F2 (program SHELXS-
86, SHELXL-93, G. M. Sheldrick, University of Go¨ttingen). Hydrogen
atoms were found from differential Fourier synthesis and refined. The
data of the X-ray structure analyses of 3b, 3e, 3g, 5c, 5g, and 5t are
summarized in Table 1.
acetic anhydride in 2.5 mL of THF was added and stirring was
continued for 100 min. After the external cooling had been removed,
50 mL of water was added to the mixture which was then allowed to
come to room temperature. After extraction of the aqueous phase with
diethyl ether (3 × 50 mL), the combined organic layers were washed
with an aqueous saturated sodium bicarbonate solution (2 × 50 mL).
The organic phase was dried with magnesium sulfate and filtered, and
the solvents were evaporated in vacuo. Most of the residual oils
crystallized either neat at -20 °C or from diethyl ether/pentane as
yellow crystalline solids.
Cr(CO)3(o-OCH3-η6-C6H4)CH[OC(O)CH3]CdCPh (3a). Yellow
crystals, mp 96 °C. 1H NMR ([D6]DMSO, 400 MHz): δ 2.16 (s, 3 H),
3.82 (s, 3 H), 5.24 (t, J ) 6.4 Hz, 1 H), 5.68 (d, J ) 6.9 Hz, 1 H), 6.05
(dt, J ) 7.1 Hz, J ) 1.2 Hz, 1 H), 6.28 (dd, J ) 6.4 Hz, J ) 1.2 Hz,
1 H), 6.61 (s, 1 H), 7.36-7.47 (m, 5 H). 13C NMR ([D6]DMSO, 100
MHz): δ 20.33 (CH3), 56.83 (CH3), 58.42 (CH), 75.63 (CH), 85.18
Ortho-Substituted Acetates 3. To a degassed solution of the alkyne
2 in dry THF (1 M) was added 1.1 equiv of a 1.6 M solution of
n-butyllithium in hexanes dropwise at -78 °C (for experimental details,
see Table 5). After stirring at that temperature for 15 min, the solution
was allowed to come to room temperature for 1 h. After recooling to
-78 °C, a solution of the complexed benzaldehyde 1 in 15 mL of THF
was added dropwise over a period of 10 min. This reaction mixture
was then stirred at -78 °C for the time indicated before a solution of

(arene)Cr(CO)-Substituted Propargyl Cations
J. Am. Chem. Soc., Vol. 123, No. 15, 2001 3447
Figure 6. ORTEP plot of 5t (view from the top). Selected bond lengths
[Å] and dihedral angles [deg]: C(4)-C(11), 1.528(4); C(11)-C(12),
1.485(5); C(12)-C(13), 1.176(5); C(13)-C(14), 1.487(5); C(5)-C(4)-
C(11)-C(12), 73.21; C(5)-C(4)-C(11)-N(1), 159.09.
Figure 4. ORTEP plot of 5c. Selected bond lengths [Å] and dihedral
angles [deg]: C(4)-C(11), 1.527(4); C(11)-C(12), 1.468(4); C(12)-
C(13), 1.183(4); C(13)-C(14), 1.446(4); C(5)-C(4)-C(11)-C(12),
39.91; C(5)-C(4)-C(11)-C(20), 88.31.
(CH), 85.11 (Cquat.), 86.82 (Cquat.), 90.07 (CH), 94.11 (CH), 96.82 (CH),
97.31 (CH), 106.46 (Cquat.), 111.25 (Cquat.), 120.92 (Cquat.), 128.86 (CH),
129.59 (CH), 131.73 (CH), 168.78 (Cquat.), 233.43 (Cquat., CO). EI MS
(70 eV, m/z (%)): 400 (M+, 7), 344 (M+ - 2 CO, 4), 316 (M+ - 3
CO, 100), 258 (25), 205 (M+ - Cr(CO)3, - C2H3O2, 20), 190 (M+
-
Cr(CO)3, - C2H3O2, - CH3, 3), 111 (10), 52 (Cr+, 21). IR (KBr): ν˜
2227, 1965, 1891, 1757, 1629, 1214, 1021 cm-1. UV/vis (DMSO):
λmax (ꢀ) 318 nm (9800). Anal. Calcd for C21H16CrO5 (400.35): C, 63.00;
H, 4.03. Found: C, 63.25; H, 4.13.
Cr(CO)3(o-CH3-η6-C6H4)CH[OC(O)CH3]CdC-p-C6H4OCH3 (3c).
Yellow brownish crystals, mp 75 °C. 1H NMR ([D6]DMSO, 300
MHz): δ 2.15 (s, 3 H), 2.37 (s, 3 H), 3.76 (s, 3 H), 5.50 (t, J ) 6.5
Hz, 1 H), 5.54 (d, J ) 6.5 Hz, 1 H), 5.87 (t, J ) 6.3 Hz, 1 H), 6.17 (d,
J ) 6.5 Hz, 1 H), 6.45 (s, 1 H), 6.93 (d, J ) 8.7 Hz, 2 H), 7.40 (d, J
) 8.6 Hz, 2 H). 13C NMR ([D6]DMSO, 75 MHz): δ 18.10 (CH3),
20.48 (CH3), 55.43 (CH3), 61.86 (CH), 83.76 (Cquat.), 87.02 (Cquat.),
90.11 (CH), 94.11 (CH), 96.69 (CH), 97.26 (CH), 106.80 (Cquat.), 111.17
(Cquat.), 112.79 (Cquat.), 114.51 (CH), 133.42 (CH), 160.17 (Cquat.), 168.81
(Cquat.), 233.49 (Cquat., CO). EI MS (70 eV, m/z (%)): 430 (M+, 8),
374 (M+ - 2 CO, 6), 346 (M+ - 3 CO, 85), 288 (C17H16CrO+, 100),
235 (M+ - Cr(CO)3, - C2H3O2, 29), 121 (25), 52 (Cr+, 40). IR
(KBr): ν˜ 2228, 1965, 1925, 1893, 1880, 1743, 1606, 1510, 1251, 1225,
1033, 835 cm-1. UV/vis (DMSO): λmax (ꢀ) 318 nm (10600), 294 (6800).
Anal. Calcd for C22H18CrO6 (430.38): C, 61.40; H, 4.22. Found: C,
61.76; H, 4.16.
Figure 5. ORTEP plot of 5g. Selected bond lengths [Å] and dihedral
angles [deg]: C(4)-C(11), 1.530(5); C(11)-C(12), 1.476(6); C(12)-
C(13), 1.183(6); C(13)-C(14), 1.448(6); C(5)-C(4)-C(11)-C(12),
66.32; C(5)-C(4)-C(11)-N(1), 57.54.
Cr(CO)3(o-Cl-η6-C6H4)CH[OC(O)CH3]CtCPh (3d). Yellow pow-
1
der, mp 115-119 °C. H NMR (CDCl3, 300 MHz): δ 2.22 (s, 3 H),
5.03 (t, J ) 6.1 Hz, 1 H), 5.38 (d, J ) 6.3 Hz, 1 H), 5.47 (t, J ) 6.0
Hz, 1 H), 5.95 (d, J ) 6.3 Hz, 1 H), 6.64 (s, 1 H), 7.29-7.31 (m, 3 H),
7.33-7.45 (m, 2 H). 13C NMR (CDCl3, 75 MHz): δ 20.48 (CH3), 61.07
(CH), 83.87 (Cquat.), 86.37 (CH), 87.34 (Cquat.), 89.55 (CH), 92.54 (CH),
93.30 (CH), 103.73 (Cquat.), 113.24 (Cquat.), 121.31 (Cquat.), 128.28 (CH),
129.16 (CH), 131.93 (CH), 168.74 (Cquat.), 230.76 (Cquat., CO). EI MS
(70 eV, m/z (%)): 422/420 (M+, 0.08/0.36), 366/364 (M+ - 2 CO,
1/3), 338/336 (M+ - 3 CO, 5/15), 280/278 (6/17), 258 (32), 190 (M+
- Cr(CO)3, - C2H3O2, - Cl, 19), 83 (100), 52 (Cr+, 17). IR (KBr):
ν˜ 2233, 1984, 1914, 1883, 1734, 1638, 1222, 662, 620 cm-1. UV/vis
(DMSO): λmax (ꢀ) 322 nm (10300). Anal. Calcd for C20H13CrO5Cl
(420.77): C, 57.09; H, 3.11; Cl, 8.43. Found: C, 56.62; H, 3.21; Cl,
8.34.
(Cquat.), 85.80 (CH), 85.92 (Cquat.), 96.77 (Cquat.), 96.86 (CH), 97.52 (CH),
120.94 (Cquat.), 128.88 (CH), 129.62 (CH), 131.87 (CH), 142.86 (Cquat.),
168.63 (Cquat.), 233.44 (Cquat., CO). EI MS (70 eV, m/z (%)): 416 (M+,
3), 361 (M+ - 2 CO, 3), 332 (M+ - 3 CO, 93), 317 (M+ - 3 CO -
CH3, 100), 280 (M+ - Cr(CO)3, 1), 274 (66), 222 (M+ - Cr(CO)3, -
C2H3O2, 30), 207 (90), 190 (M+ - Cr(CO)3, - C2H3O2, - OCH3, 6),
52 (Cr+, 19). IR (KBr): ν˜ 2229, 1964, 1886, 1740, 1630, 1224, 1018
cm-1. UV/vis (DMSO): λmax (ꢀ) 316 nm (8500). Anal. Calcd for C21H16-
CrO6 (416.35): C, 60.58; H, 3.87. Found: C, 60.79; H, 3.94.
Cr(CO)3(o-CH3-η6-C6H4)CH[OC(O)CH3]CdCPh (3b). Yellow
crystals, mp 80 °C. 1H NMR ([D6]DMSO, 400 MHz): δ 2.16 (s, 3 H),
2.38 (s, 3 H), 5.50 (dt, J ) 6.3 Hz, J ) 0.7 Hz, 1 H), 5.56 (d, J ) 6.4
Hz, 1 H), 5.88 (dt, J ) 6.4 Hz, J ) 0.7 Hz, 1 H), 6.18 (d, J ) 6.1 Hz,
1 H), 6.47 (s, 1 H), 7.36-7.41 (m, 3 H), 7.43-7.48 (m, 2 H). 13C
NMR ([D6]DMSO, 100 MHz): δ 18.09 (CH3), 20.44 (CH3), 61.85
Cr(CO)3(o-OCH3-η6-C6H4)CH[OC(O)CH3]CtC(CH2)3CH3 (3e).
1
Yellow crystals, mp 62-64 °C. H NMR ([D6]DMSO, 300 MHz): δ
0.83 (t, J ) 7.2 Hz, 3 H), 1.24-1.44 (m, 4 H), 2.11 (s, 3 H), 2.22 (dt,

3448 J. Am. Chem. Soc., Vol. 123, No. 15, 2001
Netz et al.
Scheme 5
Table 3. Influence of the Ionizing Lewis Acid on the de (de ) (dr
-1)/(dr + 1))
Scheme 6
propargyl acetate 3
Lewis acid
3aa
3bb
3ac
3ed
BF3‚OEt2
TMSOTf
SnCl4
2
98
44
86
38
90
24
40
36
72
TiCl4
a 2-Propanethiol as trapping nucleophile (reaction product 5a). b 2-
Propanethiol as trapping nucleophile (reaction product 5f). c 1-Methoxy-
2-methyl-1-trimethylsiloxypropene as trapping nucleophile (reaction
product 5c). d 1-Methoxy-2-methyl-1-trimethylsiloxypropene as trapping
nucleophile (reaction product 5u).
Scheme 7
Table 4. Diastereomeric Ratios (dr) of Stepwise vs in Situ
Ionizations of the Propargyl Acetates 3a, 3b, and 3e in the Presence
of 1-Methoxy-2-methyl-1-trimethylsiloxypropene as Trapping
Nucleophile To Give the Propargyl Derivatives 5c, 5h, and 5u,
Respectively
propargyl
acetate 3
stepwise ionization and
nucleophilic addition
in situ ionization
Scheme 8. SN2 Attack of the Nucleophile under
Simultaneous Activation of the Acetate by TiCl4
entry 1
entry 2
entry 3
3a
3e
3b
>95:5a
86:14b
93:7a
43:57b
34:66b
no reactiona,c
a Ionization with TMSOTf. b Ionization with TiCl4. c Only 3b was
recovered.
315 nm (8600). Anal. Calcd for C19H20CrO6 (396.36): C, 57.58; H,
5.09. Found: C, 57.86; H, 5.16.
Cr(CO)3(o-CH3-η6-C6H4)CH[OC(O)CH3]CtC(CH2)3CH3 (3f). Yel-
low oil. H NMR ([D6]DMSO, 300 MHz): δ 0.83 (t, J ) 7.0 Hz, 3
1
J ) 6.8 Hz, J ) 1.7 Hz, 2 H), 3.77 (s, 3 H), 5.21 (t, J ) 6.2 Hz, 1 H),
5.64 (d, J ) 6.9 Hz, 1 H), 6.01 (t, J ) 6.5 Hz, 1 H), 6.15 (d, J ) 6.3
Hz, 1 H), 6.35 (s, 1 H). 13C NMR ([D6]DMSO, 75 MHz): δ 13.50
(CH3), 17.69 (CH2), 20.31 (CH3), 21.42 (CH2), 29.93 (CH2), 56.72
(CH3), 57.95 (CH), 75.58 (CH), 76.45 (Cquat.), 85.79 (CH), 87.72 (Cquat.),
96.37 (CH), 97.34 (Cquat.), 97.67 (CH), 142.58 (Cquat.), 168.52 (Cquat.),
233.50 (Cquat., CO). EI MS (70 eV, m/z (%)): 396 (M+, 3), 340 (M+
- 2 CO, 13), 312 (M+ - 3 CO, 100), 297 (M+ - 3 CO, - CH3, 58),
253 (M+ - 3CO, - C2H3O2, 20), 201 (M+ - Cr(CO)3, - C2H3O2,
30), 52 (Cr+, 38). IR (KBr): ν˜ 2938, 2228, 1966, 1896, 1878, 1742,
1637, 1468, 1226, 1017, 666, 628 cm-1. UV/vis (DMSO): λmax (ꢀ)
H), 1.22-1.45 (m, J ) 7.1 Hz, 4 H), 2.11 (s, 3 H), 2.23 (t, J ) 6.9 Hz,
2 H), 2.28 (s, 3 H), 5.48 (t, J ) 6.5 Hz, 1 H), 5.54 (d, J ) 6.2 Hz, 1
H), 5.85 (t, J ) 6.3 Hz, 1 H), 6.06 (d, J ) 6.7 Hz, 1 H), 6.18 (s, 1 H).
13C NMR ([D6]DMSO, 75 MHz): δ 13.58 (CH3), 17.76 (CH2), 17.98
(CH3), 20.51 (CH3), 21.51 (CH2), 29.91 (CH2), 61.28 (CH), 76.35
(Cquat.), 88.67 (Cquat.), 90.36 (CH), 94.31 (CH), 96.06 (CH), 97.13 (CH),
107.36 (Cquat.), 110.82 (Cquat.), 168.78 (Cquat.), 233.60 (Cquat., CO). pos.
FAB MS (Ar, 5-6 kV, mNBA, m/z (%)): 381 ([M + H]+, 1), 380
(M+, 3), 321 (15), 296 (M+ - 3 CO, 100), 272 (24), 237 (M+ - 3
CO, - C2H3O2, 55), 185 (M+ - Cr(CO)3, - C2H3O2, 15), 105 (25),

(arene)Cr(CO)-Substituted Propargyl Cations
J. Am. Chem. Soc., Vol. 123, No. 15, 2001 3449
Table 5. Experimental Details on the Synthesis of the Complex Substituted Propargyl Acetates 3
alkyne 2
(mmol)
n-BuLi
mL (mmol)
aldehyde 1
g (mmol)
reaction time,
min.
acetic anhydride
mL (mmol)
acetate 3
yield g (%)
1.15 mL (10.5) of 2a
1.15 mL (10.5) of 2a
1.64 g (12.4) of 2c
0.50 mL (4.6) of 2a
1.10 mL (8.8) of 2b
1.23 mL (10.8) of 2b
0.68 g (9.73) of 2d
6.6 (10.5)
6.5 (10.4)
7.8 (12.5)
2.7 (4.3)
2.72 (10.0) of 1a
2.51 (9.8) of 1b
2.92 (11.4) of 1b
1.14 (4.12) of 1c
2.00 (7.38) of 1a
2.51 (9.8) of 1b
2.50 (9.19) of 1a
190
70
150
270
120
150
145
2.17 (23.0)
2.2 (23.3)
(23.3)
1.0 (10.6)
1.70 (15.4)
2.5 (21.7)
1.80 (19.0)
4.33 (100) of 3a
3.66 (94) of 3b
4.31 (88) of 3c
1.53 (88) of 3d
2.14 (73) of 3e
2.86 (77) of 3f
2.50 (71) of 3g
5.0 (8.0)
10.7 (17.1)
6.4 (10.2)
Table 6. Experimental Details on the Cationic Propargylations with Cations 4
acetate 3
mg (mmol)
TMSOTf
µL (mmol)
ionization
time [min.]
reaction
time [min.]
propargyl product 5
nucleophile (mmol)
yield, mg (%)
202 (0.49) of 3a
204 (0.49) of 3a
202 (0.49) of 3a
120 (0.66)
105 (0.58)
96 (0.53)
60
38
55
0.10 mL (1.06) of 2-propanethiol
0.15 mL (1.07) of diisopropylamine
0.20 mL (0.99) of methoxy-2-methyl-
1-trimethylsiloxypropene
0.10 mL (0.63) of allyl trimethylsilane
0.06 mL (0.55) of anisole in 0.5 mL of
dichloromethane
100
60
173 (82) of 5a dr ) >99:1
200 (89) of 5b dr ) 95:5
184 (83) of 5c dr ) >95:5
60
103 (0.25) of 3a
100 (0.24) of 3a
45 (0.36)a
49 (0.39)a
15
50
50
120
64 (65) of 5d dr ) 71:29
39 (35) of 5e dr ) 92:8
109 (0.27) of 3b
102 (0.26) of 3b
202 (0.51) of 3b
55 (0.3)
80 (0.44)
120 (0.66)
55
45
85
0.10 mL (1.06) of 2-propanethiol
0.10 mL (1.15) of morpholine
0.21 mL (1.04) of methoxy-2-methyl-1-
trimethylsiloxypropene
0.10 mL (1.46) of allyl alcohol
0.24 g (2.55 mmol) of phenol in 3 mL of
dichloromethane
60
75
90 (79) of 5f dr ) 93:7
77 (71) of 5g dr ) >99:1
150 (67) of 5h dr ) 93:7
120
202 (0.51) of 3b
210 (0.53) of 3b
100 (0.55)
120 (0.66)
65
30
40
110
143 (70) of 5i dr ) 91:9
100 (44) of 5j dr ) 96:4
103 (0.24) of 3c
202 (0.47) of 3c
206 (0.48) of 3c
50 (0.28)
93 (0.52)
96 (0.53)
60
65
45
0.10 mL (1.06) of 2-propanethiol
0.10 mL (0.71) of diisopropylamine
0.15 mL (0.74) of methoxy-2-methyl-1-
trimethylsiloxypropene
0.70 mL (4.39) of allyl trimethylsilane in
1.3 mL of dichloromethane
60
25
83 (78) of 5k dr ) 91:9
118 (53) of 5l dr ) 94:6
160 (71) of 5m dr ) 87:13
120
750 (1.74) of 3c
38 (2.10)
60
120
621 (86) of 5n dr ) 91:9
200 (0.48) of 3d
201 (0.48) of 3d
100 (0.24) of 3d
200 (0.48) of 3d
130 (0.72)
112 (0.62)
50 (0.43)b
110 (0.94)b
60
40
50
60
0.10 mL (1.07) of 2-propanethiol
0.15 mL (1.20) of methyl 3-mercaptopropionate
0.20 mL (2.30) of morpholine
0.40 mL (1.97) of methoxy-2-methyl-1-
trimethylsiloxypropene
0.15 mL (1.20) of methyl 3-mercaptopropionate
0.16 mL (1.14) of diisopropylamine
0.22 mL (1.09) of methoxy-2-methyl-1-
trimethylsiloxypropene
105
120
180
120
145 (70) of 5o dr ) 78:22
188 (82) of 5p dr ) 86:14
96 (90) of 5q dr ) 97:3
177 (81) of 5r dr ) 80:20
202 (0.51) of 3e
202 (0.51) of 3e
205 (0.52) of 3e
100 (0.53)c
70 (0.64)c
70 (0.64)c
30
25
12
105
110
60
155 (67) of 5s dr ) 83:17
180 (81) of 5t dr ) 93:7
168 (74) of 5u dr ) 86:14
a Ionization with BF3‚OEt2. b Ionization with SnCl4. c Ionization with TiCl4.
52 (Cr+, 12). IR (KBr): ν˜ 2960, 2935, 2289, 2213, 1966, 1886, 1745,
1674, 1460, 1370, 1225, 1020, 665, 628 cm-1. UV/vis (DMSO): λmax
(ꢀ) 317 nm (9500). Anal. Calcd for C19H20CrO5 (380.36): C, 60.00;
H, 5.30. Found: C, 60.21; H, 5.78.
deep colored to yellow. After the reaction time, 20 mL of diethyl ether
and 20 mL of water were added and the external cooling was removed.
After extraction of the aqueous phase with diethyl ether (2 × 25 mL),
the combined organic layers were dried with magnesium sulfate and
filtered and the solvents were evaporated in vacuo. The residues were
dried in vacuo and, if not crystalline, then subjected to flash chroma-
tography. The diastereoselectivities were determined from the combined
collected yellow fractions by integration (1H NMR spectra) of the
significant propargyl proton signals and/or in some cases by integration
of the signals of ortho substituents on the complexed ring.
Cr(CO)3(o-OCH3-η6-C6H4)CH[OC(O)CH3]CtCCH2OCH3 (3g).
1
Yellow crystals, mp 107-108 °C. H NMR ([D6]DMSO, 300 MHz):
δ 2.14 (s, 3 H), 3.22 (s, 3 H), 3.79 (s, 3 H), 4.13 (s, 2 H), 5.22 (t, J )
6.3 Hz, 1 H), 5.65 (d, J ) 7.0 Hz, 1 H), 6.03 (t, J ) 6.5 Hz, 1 H), 6.17
(d, J ) 6.4 Hz, 1 H), 6.42 (s, 1 H). 13C NMR ([D6]DMSO, 75 MHz):
δ 20.27 (CH3), 56.81 (CH3), 57.14 (CH3), 57.70 (CH), 59.01 (CH2),
75.59 (CH), 82.06 (Cquat.), 83.13 (Cquat.), 85.83 (CH), 96.29 (CH), 96.70
(Cquat.), 97.43 (CH), 142.64 (Cquat.), 168.53 (Cquat.), 233.40 (Cquat., CO).
EI MS (70 eV, m/z (%)): 384 (M+, 14), 328 (M+ - 2 CO, 17), 300
(M+ - 3 CO, 28), 268 (M+ - 3 CO, - OCH3, - H, 100), 255 (28),
241 (M+ - 3 CO, - C2H3O2, 7), 212 (50), 158 (70), 115 (C10H7+, 41),
52 (Cr+, 75). IR (KBr): ν˜ 1966, 1957, 1874, 1748, 1629, 1220, 1094,
1019, 669, 632 cm-1. UV/vis (DMSO): λmax (ꢀ) 316 nm (19600). Anal.
Calcd for C17H16CrO7 (384.31): C, 53.13; H, 4.20. Found: C, 53.28;
H, 4.23.
Cr(CO)3(o-OCH3-η6-C6H4)CH[SCH(CH3)2]CtCPh (5a). Yellow
1
crystals, mp 140 °C (dichloromethane/diethyl ether). H NMR ([D6]-
DMSO, 400 MHz): δ 1.26-1.30 (m, 6 H), 3.25-3.37 (m, J ) 6.8
Hz, 1 H), 3.79 (s, 3 H), 5.10 (s, 1 H), 5.30 (t, J ) 6.3 Hz, 1 H), 5.60
(d, J ) 7.1 Hz, 1 H), 5.96 (t, J ) 6.6 Hz, 1 H), 6.25 (d, J ) 6.4 Hz,
1 H), 7.35-7.52 (m, 5 H). 13C NMR ([D6]DMSO, 75 MHz): δ 22.96
(CH3), 23.32 (CH3), 32.26 (CH), 36.71 (CH), 56.69 (CH3), 75.47 (CH),
84.07 (Cquat.), 85.67 (CH), 88.14 (Cquat.), 97.08 (CH), 98.66 (CH), 100.21
(Cquat.), 122.26 (Cquat.), 128.78 (2 signals, CH), 131.55 (CH), 142.59
(Cquat.), 233.69 (Cquat., CO). EI MS (70 eV, m/z (%)): 432 (M+, 17),
376 (M+ - 2 CO, 22), 348 (M+ - 3 CO, 100), 290 (21), 274 (66),
259 (46), 221 (M+ - Cr(CO)3, - SC3H7, 27), 52 (Cr+, 22). IR (KBr):
Diastereoselective Propargylations. Generation of the Propargyl
Cations and Nucleophilic Trapping (General Procedure). To a
solution of the acetate 3 in 5-10 mL of dry dichloromethane was added
dropwise 1.1-1.7 equiv of the corresponding Lewis acid at -78 °C
(for experimental details, see Table 6). Immediately a deep red to blue
solution of the propargyl cation was formed that was stirred at that
temperature for 15-50 min. To this reaction mixture was then added
at -78 °C the corresponding nucleophile, neat or as a solution in
dichloromethane. The reaction can be followed by a color change from
ν˜ 2926, 1958, 1884, 1876, 1858, 1636, 1470, 1260, 757, 667, 631 cm-1
.
UV/vis (DMSO): λmax (ꢀ) ) 318 nm (8800). Anal. Calcd for C22H20-
CrO4S (432.46): C, 61.10; H, 4.66; S, 7.41. Found: C, 60.71; H, 4.82;
S, 7.36.
Cr(CO)3(o-OCH3-η6-C6H4)CH[N(iPr)2]CtCPh (5b). Yellow crys-
tals, mp 124-134 °C (diethyl ether). 1H NMR ([D6]DMSO, 300

3450 J. Am. Chem. Soc., Vol. 123, No. 15, 2001
Netz et al.
MHz): δ 1.17 (d, J ) 6.2 Hz, 6 H), 1.23 (d, J ) 6.0 Hz, 6 H), 3.35
(m, 2 H), 3.80 (s, 3 H), 4.87 (s, 1 H), 5.23 (t, J ) 5.7 Hz, 1 H), 5.60
(d, J ) 6.5 Hz, 1 H), 5.94 (t, J ) 6.1 Hz, 1 H), 6.00 (d, J ) 5.8 Hz,
1 H), 7.33-7.62 (m, 5 H). Additional signals for the minor diastere-
omer: δ 0.93 (d, J ) 6.7 Hz, 6 H), 3.73 (s, 3 H), 4.99 (s, 1 H), 6.28
(d, J ) 6.0 Hz, 1 H). 13C NMR ([D6]DMSO, 75 MHz): δ 20.23 (CH3),
23.86 (CH3), 45.85 (CH), 47.45 (CH), 56.46 (CH3), 75.94 (CH), 83.50
(Cquat.), 85.74 (CH), 90.49 (Cquat.), 96.97 (CH), 97.48 (CH), 105.49
(Cquat.), 122.76 (Cquat.), 128.49 (CH), 128.79 (CH), 131.15 (CH), 142.64
(Cquat.), 234.29 (Cquat., CO). Additional signals for the minor diastere-
omer: δ 87.69 (Cquat.), 129.21 (CH). EI MS (70 eV, m/z (%)): 457
signals for the minor diastereomer: δ 128.87 (CH), 131.51 (CH). EI
MS (70 eV, m/z (%)): 464 (M+, 15), 394 (M+ - 2 CO, 8), 380 (M+
- 3 CO, 100), 328 (M+ - Cr(CO)3, 7), 313 (M+ - Cr(CO)3, - CH3,
8), 297 (M+ - Cr(CO)3, - OCH3, 1), 52 (Cr+, 4). IR (KBr): ν˜ 1960,
1879, 1630, 1509, 1254, 1031, 811, 759, 632 cm-1. UV/vis (DMSO):
λmax (ꢀ) ) 316 nm (8200). Anal. Calcd for C26H20CrO5 (464.44): C,
67.24; H, 4.34. Found: C, 67.00; H, 4.21.
Cr(CO)3(o-CH3-η6-C6H4)CH[SCH(CH3)2]CtCPh (5f). Yellow
crystals, mp 51-52 °C (diethyl ether/pentane). 1H NMR ([D6]DMSO,
400 MHz): δ 1.29 (d, J ) 6.6 Hz, 3 H), 1.33 (d, J ) 6.8 Hz, 3 H),
2.47 (s, 3 H), 3.22 (sept, J ) 6.8 Hz, 1 H), 5.14 (s, 1 H), 5.45 (t, J )
6.5 Hz, 1 H), 5.50 (d, J ) 6.3 Hz, 1 H), 5.84 (t, J ) 6.4 Hz, 1 H), 6.19
(d, J ) 6.4 Hz, 1 H), 7.38-7.45 (m, 5 H). Additional signals for the
minor diastereomer: δ 1.24 (d, J ) 6.6 Hz, 3 H), 1.26 (d, J ) 6.8 Hz,
3 H), 2.32 (s, 3 H), 3.02-3.05 (m, 1 H), 5.19 (s, 1 H), 6.10 (d, J ) 6.8
Hz, 1 H). 13C NMR ([D6]DMSO, 75 MHz): δ 18.33 (CH3), 23.14
(CH3), 23.42 (CH3), 36.11 (CH), 36.97 (CH), 85.54 (Cquat.), 87.68
(Cquat.), 89.81 (CH), 94.11 (CH), 97.17 (CH), 98.88 (CH), 109.27 (Cquat.),
111.79 (Cquat.), 122.14 (Cquat.), 128.79 (CH), 128.89 (CH), 131.39 (CH),
233.74 (Cquat., CO). Additional signals for the minor diastereomer: δ
17.82 (CH3), 36.69 (CH), 91.52 (CH), 94.65 (CH), 95.52 (CH), 96.44
(CH), 110.63 (Cquat.). EI MS (70 eV), m/z (%): 416 (M+, 9), 360 (M+
- 2 CO, 6), 332 (M+ - 3 CO, 52), 258 (M+ - 3 CO, - SdCMe2,
100), 257 (M+ - 3 CO, - SC3H7, 11), 205 (M+ - Cr(CO)3, - SC3H7,
18), 190 (C15H10+, 3), 52 (Cr+, 20). IR (KBr): ν˜ 1963, 1887, 1636,
758, 666, 628 cm-1. UV/vis (DMSO): λmax (ꢀ) ) 320 nm (9400). Anal.
Calcd for C22H20CrO3S (416.46): C, 63.45; H, 4.84; S, 7.70. Found:
C, 63.42; H, 4.93; S, 7.54.
(M+, 32), 401 (M+ - 2 CO, 2), 373 (M+ - 3 CO, 50), 321 (M+
-
Cr(CO)3, 6), 290 (M+ - Cr(CO)3, - OCH3, 1), 274 (M+ - 3 CO, -
iPrNdCMe2, 75), 259 (64), 221 (100), 190 (C15H10+, 4), 151 (71), 115
(H3CN(iPr)2+, 61), 52 (Cr+, 50). IR (KBr): ν˜ 2966, 1953, 1876, 1629,
1598, 1461, 1265 cm-1. UV/vis (DMSO): λmax (ꢀ) 315 nm (8700).
Anal. Calcd for C25H27CrO4N (457.49): C, 65.64; H, 5.95; N, 3.06.
Found: C, 65.25; H, 5.92; N, 3.01.
Cr(CO)3(o-OCH3-η6-C6H4)CH[C(CH3)2COOCH3]CtCPh (5c).
Yellow crystals, mp 138-139 °C (diethyl ether/pentane). 1H NMR ([D6]-
DMSO, 400 MHz): δ 1.26 (s, 3 H), 1.27 (s, 3 H), 3.62 (s, 3 H), 3.73
(s, 3 H), 3.88 (s, 1 H), 5.14 (t, J ) 6.2 Hz, 1 H), 5.64 (d, J ) 7.1 Hz,
1 H), 5.96 (t, J ) 6.5 Hz, 1 H), 6.04 (d, J ) 6.4 Hz, 1 H), 7.32-7.39
(m, 5 H). Additional signals for the minor diastereomer: δ 1.15 (s, 3
H), 3.63 (s, 3 H), 4.46 (s, 1 H), 5.32 (t, J ) 6.1 Hz, 1 H), 5.60 (d, J
) 6.9 Hz, 1 H), 6.11 (d, J ) 6.3 Hz, 1 H). 13C NMR ([D6]DMSO, 100
MHz): δ 23.47 (CH3), 23.51 (CH3), 44.52 (CH), 48.24 (Cquat.), 52.06
(CH3), 56.14 (CH3), 76.58 (CH), 83.98 (Cquat.), 85.66 (CH), 87.51
(Cquat.), 97.51 (CH), 97.80 (Cquat.), 101.54 (CH), 123.47 (Cquat.), 128.05
(CH), 128.56 (CH), 131.27 (CH), 143.83 (Cquat.), 175.12 (Cquat.), 233.84
(Cquat., CO). pos. FAB MS (Ar, 5-6 kV, mNBA, m/z (%)): 459 ([M
Cr(CO)3(o-CH3-η6-C6H4)CH[N(CH2)4O]CtCPh (5g). Yellow crys-
tals, mp 117-118 °C (diethyl ether). 1H NMR ([D6]DMSO, 400
MHz): δ 2.43 (s, 3 H), 2.54-2.57 (m, 2 H), 2.79 (m, 2 H), 3.64 (m,
4 H), 4.60 (s, 1 H), 5.46 (t, J ) 6.1 Hz, 1 H), 5.51 (d, J ) 5.9 Hz, 1
H), 5.84 (t, J ) 6.0 Hz, 1 H), 6.10 (d, J ) 6.3 Hz, 1 H), 7.39-7.48
(m, 5 H). 13C NMR ([D6]DMSO, 100 MHz): δ 18.56 (CH3), 51.00
(CH2), 59.09 (CH), 66.29 (CH2), 85.27 (Cquat.), 88.18 (Cquat.), 89.95
(CH), 94.47 (CH), 97.45 (CH), 99.62 (CH), 109.65 (Cquat.), 112.44
(Cquat.), 122.04 (Cquat.), 128.80 (CH), 128.92 (CH), 131.53 (CH), 234.03
(Cquat., CO). EI MS (70 eV, m/z (%)): 427 (M+, 2), 371 (M+ - 2 CO,
12), 343 (M+ - 3 CO, 33), 258 (M+ - 3 CO, - NC4H7O, 100), 190
(M+ - Cr(CO)3, - CH3, - NC4H8O, 55), 52 (Cr+, 25). IR (KBr): ν˜
+ H]+, 1), 402 (M+ - 2 CO, 17), 374 (M+ - 3 CO, 100), 274 (M+
-
3 CO, - C(CH3)2CO2CH3, 12), 259 (10), 221 (M+ - Cr(CO)3, -
C(CH3)2CO2CH3, 11), 115 (12), 52 (Cr+, 17). IR (KBr): ν˜ 1966, 1887,
1873, 1729, 1628, 1474, 1269, 755, 670, 630 cm-1. UV/vis (DMSO):
λmax (ꢀ) ) 315 nm (8300). Anal. Calcd for C24H22CrO6 (458.43): C,
62.88; H, 4.84. Found: C, 63.24; H, 4.99.
Cr(CO)3(o-OCH3-η6-C6H4)CH[CH2CHdCH2]CtCPh (5d). Yel-
1
low oil. H NMR ([D6]DMSO, 400 MHz): δ 2.52-2.64 (m, 2 H),
3.79 (s, 3 H), 3.91 (dd, J ) 10.0 Hz, J ) 5.1 Hz, 1 H), 5.06-5.23 (m,
2 H), 5.22 (t, J ) 6.6 Hz, 1 H), 5.65 (d, J ) 6.6 Hz, 1 H), 5.84-6.02
(m, 1 H), 5.98 (t, J ) 6.9 Hz, 1 H), 6.25 (dd, J ) 6.6 Hz, J ) 0.9 Hz,
1 H), 7.33-7.48 (m, 5 H). Additional signals for the minor diastere-
omer: δ 2.38-2.43 (m, 2 H), 3.77 (s, 3 H), 4.12 (dd, J ) 7.9 Hz, J )
5.0 Hz, 1 H), 5.29 (t, J ) 6.3 Hz, 1 H), 5.63 (d, J ) 6.3 Hz, 1 H), 6.02
(t, J ) 7.0 Hz, 1 H), 6.13 (dd, J ) 6.4 Hz, J ) 1.0 Hz, 1 H). 13C NMR
([D6]DMSO, 100 MHz): δ 30.90 (CH), 40.43 (CH2), 56.64 (CH3),
76.19 (CH), 83.22 (Cquat.), 86.23 (CH), 90.25 (Cquat.), 97.15 (CH), 98.33
(CH), 102.94 (Cquat.), 117.66 (CH2), 122.67 (Cquat.), 128.48 (CH), 128.68
(CH), 131.51 (CH), 135.65 (CH), 142.58 (Cquat.), 234.15 (Cquat., CO).
Additional signals for the minor diastereomer: δ 31.83 (CH), 40.39
(CH2), 56.60 (CH3), 76.28 (CH), 84.18 (Cquat.), 87.06 (CH), 88.67
(Cquat.), 96.54 (CH), 96.83 (CH), 101.01 (Cquat.), 118.20 (CH2), 122.71
(Cquat.), 128.51 (CH), 128.65 (CH), 131.57 (CH), 134.61 (CH), 142.32
(Cquat.). EI MS (70 eV, m/z (%)): 398 (M+, 16), 342 (M+ - 2 CO, 1),
314 (M+ - 3 CO, 100), 299 (M+ - 3 CO, - CH3, 12), 273 (M+ - 3
CO, - CH2CHdCH2, 18), 262 (M+ - Cr(CO)3, 1), 52 (Cr+, 22). IR
(KBr): ν˜ 2924, 1960, 1875, 1642, 1469, 1261, 1017, 758, 667, 630
cm-1. UV/vis (DMSO): λmax (ꢀ) ) 315 nm (8200). Anal. Calcd for
C22H18CrO4 (398.38): C, 66.33; H, 4.55. Found: C, 66.89; H, 4.66.
Cr(CO)3(o-OCH3-η6-C6H4)CH[p-C6H4OCH3]CtCPh (5e). Yellow
orange solid, mp 132-136 °C (dichloromethane/diethyl ether). 1H NMR
([D6]DMSO, 400 MHz): δ 3.71 (s, 3 H), 3.74 (s, 3 H), 5.29 (s, 1 H),
5.32 (m, 1 H), 5.60 (d, J ) 6.4 Hz, 1 H), 5.91 (m, 1 H), 6.39 (d, J )
5.5 Hz, 1 H), 6.89 (d, J ) 7.9 Hz, 2 H), 7.24-7.39 (m, 5 H), 7.50 (m,
2 H). Additional signals for the minor diastereomer: δ 3.86 (s, 3 H),
3.90 (s, 3 H). 13C NMR ([D6]DMSO, 100 MHz): δ 36.00 (CH), 55.27
(CH3), 56.64 (CH3), 76.24 (CH), 84.12 (Cquat.), 87.29 (CH), 89.10
(Cquat.), 96.37 (CH), 96.55 (CH), 102.55 (Cquat.), 114.27 (CH), 122.60
(Cquat.), 128.64 (CH), 128.66 (CH), 128.74 (CH), 131.62 (CH), 132.56
(Cquat.), 142.06 (Cquat.), 158.64 (Cquat.), 234.11 (Cquat., CO). Additional
2965, 1951, 1881, 1639, 1491, 1446, 1116, 871, 760, 666, 630 cm-1
.
UV/vis (DMSO): λmax (ꢀ) 318 nm (9400). Anal. Calcd for C23H21-
CrO4N (427.42): C, 64.63; H, 4.95; N, 3.28. Found: C, 64.36; H, 5.14;
N, 3.26.
Cr(CO)3(o-CH3-η6-C6H4)CH[C(CH3)2COOCH3]CtCPh (5h). Yel-
1
low blocks, mp 101-103 °C (diethyl ether/pentane). H NMR ([D6]-
DMSO, 300 MHz): δ 1.30 (s, 3 H), 1.31 (s, 3 H), 2.46 (s, 3 H), 3.65
(s, 3 H), 4.05 (s, 1 H), 5.43-5.48 (m, J ) 6.4 Hz, 2 H), 5.79-5.84
(m, J ) 6.4 Hz, 2 H), 7.33-7.40 (m, 5 H). Additional signals for the
minor diastereomer: δ 1.22 (s, 3 H), 1.23 (s, 3 H), 2.35 (s, 3 H), 3.62
(s, 3 H), 4.52 (s, 1 H), 5.61 (t, J ) 6.4 Hz, 1 H), 5.95 (d, J ) 5.8 Hz,
1 H). 13C NMR ([D6]DMSO, 75 MHz): δ 19.62 (CH3), 23.43 (CH3),
23.64 (CH3), 46.17 (CH), 48.70 (CH3), 52.37 (Cquat.), 86.14 (Cquat.),
87.41 (Cquat.), 90.61 (CH), 95.63 (CH), 97.14 (CH), 100.68 (CH), 107.57
(Cquat.), 111.93 (Cquat.), 122.55 (Cquat.), 128.69 (CH), 128.83 (CH), 131.18
(CH), 175.15 (Cquat.), 233.83 (Cquat., CO). Additional signal for the minor
diastereomer: δ 131.41 (CH). EI MS (70 eV, m/z (%)): 442 (M+, 5),
386 (M+ - 2 CO, 3), 358 (M+ - 3 CO, 67), 306 (M+ - Cr(CO)3, 1),
288 (36), 260 (M+ - Cr(CO)3, - CH3, - OCH3, 6), 258 (M+ - 3 CO,
- CH2dC(CH3)CO2CH3, 100), 205 (78), 190 (C15H10+, 3), 52 (Cr+,
35). IR (KBr): ν˜ 2950, 1966, 1890, 1872, 1730, 1597, 1434, 1246,
1131, 756, 667, 628 cm-1. UV/vis (DMSO): λmax (ꢀ) 317 nm (8900).
Anal. Calcd for C24H22CrO5 (442.43): C, 65.15; H, 5.01. Found: C,
65.40; H, 5.14.
Cr(CO)3(o-CH3-η6-C6H4)CH[OCH2CHdCH2]CtCPh (5i). Yel-
1
low crystals, mp 90-93 °C (diethyl ether/pentane). H NMR ([D6]-
DMSO, 400 MHz): δ 2.34 (s, 3 H), 4.18 (dd, J ) 13.0 Hz, J ) 5.3
Hz, 1 H), 4.37 (dd, J ) 13.0 Hz, J ) 5.1 Hz, 1 H), 5.22 (dd, J ) 10.5
Hz, J ) 1.2 Hz, 1 H), 5.35 (s, 1 H), 5.40 (dd, J ) 17.3 Hz, J ) 1.5
Hz, 1 H), 5.53 (t, J ) 6.5 Hz, 1 H), 5.57 (d, J ) 6.4 Hz, 1 H), 5.80 (t,
J ) 6.3 Hz, 1 H), 5.91-6.03 (m, 1 H), 6.06 (d, J ) 6.6 Hz, 1 H),

(arene)Cr(CO)-Substituted Propargyl Cations
J. Am. Chem. Soc., Vol. 123, No. 15, 2001 3451
7.35-7.59 (m, 5 H). Additional signals for the minor diastereomer: δ
2.27 (s, 3 H), 4.09 (dd, J ) 12.5 Hz, J ) 5.6 Hz, 1 H), 4.28 (dd, J )
12.5 Hz, J ) 5.4 Hz, 1 H), 5.17-5.19 (m, 1 H), 5.28-5.33 (m, 1 H),
for the minor diastereomer: δ 19.02 (CH3), 20.73 (CH3), 23.87 (CH3),
46.74 (CH), 49.58 (CH), 86.58 (Cquat.), 87.99 (Cquat.), 90.82 (CH), 95.07
(CH), 96.96 (CH), 98.06 (CH), 109.54 (Cquat.), 111.88 (Cquat.), 114.45
(CH), 114.76 (Cquat.), 132.47 (CH), 159.49 (Cquat.), 234.15 (Cquat., CO).
EI MS (70 eV, m/z (%)): 471 (M+, 11), 415 (M+ - 2 CO, 3), 387
5.47 (s, 1 H), 5.88 (t, J ) 6.5 Hz, 1 H), 6.22 (d, J ) 6.4 Hz, 1 H). 13
C
NMR ([D6]DMSO, 100 MHz): δ 18.08 (CH3), 67.37 (CH), 69.87
(CH2), 86.39 (Cquat.), 87.15 (Cquat.), 90.91 (CH), 94.99 (CH), 95.30 (CH),
96.40 (CH), 109.19 (Cquat.), 110.23 (Cquat.), 117.31 (CH2), 121.43 (Cquat.),
(M+ - 3 CO, 26), 288 (M+ - 3 CO, - iPrNdCMe2, 28), 235 (M+
-
Cr(CO)3, - N(iPr)2, 15), 204 (M+ - Cr(CO)3, - N(iPr)2, - OCH3,
100), 151 (43), 52 (Cr+, 16). IR (KBr): ν˜ 2967, 2231, 1960, 1899,
1866, 1607, 1509, 1463, 1249, 1175, 1033, 834, 669, 631 cm-1. UV/
vis (DMSO): λmax (ꢀ) 316 nm (11100). Anal. Calcd for C26H29CrO4N
(471.52): C, 66.23; H, 6.20; N, 2.97. Found: C, 66.25; H, 5.92; N,
2.81.
128.83 (CH), 129.28 (CH), 131.62 (CH), 134.26 (CH), 233.88 (Cquat.
,
CO). Additional signals for the minor diastereomer: δ 17.75 (CH3),
67.79 (CH), 69.55 (CH2), 84.77 (Cquat.), 88.38 (Cquat.), 90.86 (CH), 94.41
(CH), 96.73 (CH), 97.24 (CH), 105.89 (Cquat.), 112.20 (Cquat.), 117.81
(CH2), 121.54 (Cquat.), 130.74 (CH), 131.58 (CH), 131.72 (CH), 134.35
(CH), 233.62 (Cquat., CO). EI MS (70 eV), m/z (%): 398 (M+, 12),
342 (M+ - 2 CO, 4), 314 (M+ - 3 CO, 19), 258 (M+ - 3 CO, -
OdCHCHdCH2, 100), 205 (M+ - Cr(CO)3, - OCH2CHdCH2, 5),
52 (Cr+, 18). R (KBr): ν˜ ) 1959, 1893, 1873, 1636, 1491, 1293, 1071,
764, 664, 630 cm-1. UV/vis (DMSO): λmax. (ꢀ) ) 318 nm (10600).
Anal. Calcd for C22H18CrO4 (398.38): C, 66.33; H, 4.55. Found: C,
66.00; H, 4.41.
Cr(CO)3(o-CH3-η6-C6H4)CH[p-C6H4OH]CdCPh (5j). Orange foam.
1H NMR ([D6]DMSO, 300 MHz): δ 2.37 (s, 3 H), 5.21 (s, 1 H), 5.40-
5.56 (m, J ) 6.4 Hz, 3 H), 5.77 (t, J ) 6.2 Hz, 1 H), 6.82 (d, J ) 8.5
Hz, 2 H), 7.32-7.37 (m, 5 H), 7.44-7.48 (m, 2 H), 9.51 (s, 1 H).
Additional signals for the minor diastereomer: δ 2.27 (s, 3 H), 5.28
(s, 1 H), 5.62 (t, J ) 6.4 Hz, 1 H), 6.15 (t, J ) 6.4 Hz, 1 H), 9.84 (s,
1 H). 13C NMR ([D6]DMSO, 75 MHz): δ 18.53 (CH3), 38.79 (CH),
84.75 (Cquat.), 89.39 (Cquat.), 90.95 (CH), 94.58 (CH), 96.90 (CH), 97.53
(CH), 111.63 (Cquat.), 113.69 (Cquat.), 115.42 (CH), 122.48 (Cquat.), 127.42
(Cquat.), 128.72 (CH), 128.79 (CH), 129.63 (CH), 131.51 (CH), 156.97
(Cquat.), 234.00 (Cquat., CO). Additional signals for the minor diastere-
omer: δ 17.73 (CH3), 90.68 (CH), 98.61 (CH), 116.03 (CH), 128.92
(CH). EI MS (70 eV, m/z (%)): 434 (M+, 8), 350 (M+ - 3 CO, 100),
298 (M+ - Cr(CO)3, 62), 283 (M+ - Cr(CO)3, - CH3, 22), 206 (M+
- Cr(CO)3, - CH3, - C6H5, 6), 91 (C6H4CH3+, 20), 77 (C6H5+, 11),
52 (Cr+, 35). IR (KBr): ν˜ 2925, 1961, 1883, 1614, 1512, 1442, 1264,
846, 757, 666, 630 cm-1. UV/vis (DMSO): λmax (ꢀ) 318 nm (9100).
Anal. Calcd for C25H18CrO4 (434.42): C, 69.12; H, 4.18. Found: C,
69.60; H, 4.84.
Cr(CO)3(o-CH3-η6-C6H4)CH[SCH(CH3)2]CtC-p-C6H4OCH3 (5k).
Yellow needles, mp 88 °C (diethyl ether/pentane). 1H NMR ([D6]-
DMSO, 300 MHz): δ 1.28 (d, J ) 6.6 Hz, 3 H), 1.32 (d, J ) 6.7 Hz,
3 H), 2.46 (s, 3 H), 3.14-3.25 (m, J ) 6.7 Hz, 1 H), 3.76 (s, 3 H),
5.09 (s, 1 H), 5.42-5.49 (m, J ) 6.5 Hz, 2 H), 5.83 (t, J ) 6.3 Hz, 1
H), 6.18 (d, J ) 6.5 Hz, 1 H), 6.93 (d, J ) 8.7 Hz, 2 H), 7.37 (d, J )
8.7 Hz, 2 H). Additional signals for the minor diastereomer: δ 1.36
(d, J ) 6.7 Hz, 3 H), 2.31 (s, 3 H), 5.14 (s, 1 H), 5.55 (m, 2 H), 6.13
(d, J ) 6.9 Hz, 1 H), 7.43 (d, J ) 8.8 Hz, 2 H). 13C NMR ([D6]DMSO,
75 MHz): δ 18.32 (CH3), 23.16 (CH3), 23.46 (CH3), 36.20 (CH), 36.90
(CH), 55.44 (CH3), 85.59 (Cquat.), 86.10 (Cquat.), 89.88 (CH), 94.17 (CH),
97.25 (CH), 98.92 (CH), 109.66 (Cquat.), 111.88 (Cquat.), 114.08 (Cquat.),
114.49 (CH), 132.94 (CH), 159.69 (Cquat.), 233.81 (Cquat., CO). EI MS
(70 eV, m/z (%)): 446 (M+, 4), 390 (M+ - 2 CO, 10), 362 (M+ - 3
CO, 81), 288 (M+ - 3 CO, - SdCMe2, 100), 235 (M+ - Cr(CO)3, -
SC3H7, 66), 52 (Cr+, 21). IR (KBr): ν˜ 2960, 2221, 1956, 1909, 1873,
1604, 1510, 1460, 838, 666, 629 cm-1. UV/vis (DMSO): λmax (ꢀ) 320
nm (9840). Anal. Calcd for C23H22CrO4S (446.49): C, 61.87; H, 4.97;
S, 7.18. Found: C, 62.05; H, 5.25; S, 7.26.
Cr(CO)3(o-CH3-η6-C6H4)CH[N(iPr)2]CtC-p-C6H4OCH3 (5l). Yel-
low crystals, mp 111-112 °C (diethyl ether/pentane). 1H NMR ([D6]-
DMSO, 300 MHz): δ 1.15 (d, J ) 6.6 Hz, 6 H), 1.23 (d, J ) 6.3 Hz,
6 H), 2.40 (s, 3 H), 3.21-3.30 (m, J ) 6.6 Hz, 2 H), 3.73 (s, 3 H),
4.76 (s, 1 H), 5.47 (d, J ) 6.2 Hz, 1 H), 5.52 (t, J ) 6.3 Hz, 1 H), 5.81
(t, J ) 6.3 Hz, 1 H), 5.95 (d, J ) 6.4 Hz, 1 H), 6.90 (d, J ) 8.8 Hz,
2 H), 7.30 (d, J ) 8.8 Hz, 2 H). Additional signals for the minor
diastereomer: δ 1.00 (d, J ) 6.5 Hz, 6 H), 2.29 (s, 3 H), 3.75 (s, 3 H),
4.89 (s, 1 H), 6.26 (d, J ) 6.6 Hz, 1 H), 6.93 (d, J ) 9.0 Hz, 2 H),
7.36 (d, J ) 8.7 Hz, 2 H). 13C NMR ([D6]DMSO, 75 MHz): δ 19.67
(CH3), 20.36 (CH3), 23.34 (CH3), 47.36 (CH), 48.49 (CH), 55.37 (CH3),
84.93 (Cquat.), 88.28 (Cquat.), 90.27 (CH), 94.07 (CH), 96.08 (CH), 97.91
(CH), 110.96 (Cquat.), 114.32 (Cquat.), 114.48 (2 signals, CH, Cquat.),
132.57 (CH), 159.55 (Cquat.), 234.34 (Cquat., CO). Additional signals
Cr(CO)3(o-CH3-η6-C6H4)CH[C(CH3)2COOCH3]CtC-p-
C6H4OCH3 (5m). Yellow crystals, mp 108 °C (diethyl ether). 1H NMR
([D6]DMSO, 300 MHz): δ 1.29 (s, 3 H), 1.30 (s, 3 H), 2.46 (s, 3 H),
3.64 (s, 3 H), 3.75 (s, 3 H), 4.01 (s, 1 H), 5.42-5.48 (m, J ) 6.2 Hz,
2 H), 5.79-5.82 (m, J ) 6.2 Hz, 2 H), 6.93 (d, J ) 8.6 Hz, 2 H), 7.32
(d, J ) 8.5 Hz, 2 H). Additional signals for the minor diastereomer:
δ 1.22 (s, 3 H), 2.23 (s, 3 H), 3.62 (s, 3 H), 4.25 (s, 1 H), 5.50-5.61
(m, J ) 6.5 Hz, 2 H), 5.93-6.05 (m, J ) 6.4 Hz, 2 H). 13C NMR
([D6]DMSO, 75 MHz): δ 19.65 (CH3), 23.33 (CH3), 23.69 (CH3), 46.23
(CH), 48.73 (Cquat.), 52.32 (CH3), 55.42 (CH3), 85.71 (Cquat.), 86.10
(Cquat.), 90.58 (CH), 95.63 (CH), 97.15 (CH), 100.65 (CH), 107.91
(Cquat.), 111.98 (Cquat.), 114.48 (CH), 114.56 (Cquat.), 132.65 (CH), 159.50
(Cquat.), 175.22 (Cquat.), 233.86 (Cquat., CO). Additional signal for the
minor diastereomer: δ 133.03 (CH). EI MS (70 eV, m/z (%)): 472
(M+, 3), 444 (M+ - CO, 2), 416 (M+ - 2 CO, 8), 388 (M+ - 3 CO,
73), 319 (14), 318 (M+ - 3 CO, - C4H6O, 48), 288 (M+ - 3 CO, -
CH2dC(CH3)CO2CH3, 100), 235 (M+ - Cr(CO)3, - C(CH3)2CO2CH3,
12), 52 (Cr+, 17). IR (KBr): ν˜ 2954, 2230, 1961, 1886, 1729, 1607,
1512, 1469, 1252, 1032, 835, 669, 630 cm-1. UV/vis (DMSO): λmax
(ꢀ) 317 nm (9300). Anal. Calcd for C25H24CrO6 (472.46): C, 63.56;
H, 5.12. Found: C, 63.72; H, 5.11.
Cr(CO)3(o-CH3-η6-C6H4)CH[CH2CHdCH2]CtC-p-C6H4OCH3
(5n). Yellow crystals, mp 65 °C (diethyl ether/pentane). 1H NMR ([D6]-
DMSO, 300 MHz): δ 2.36 (s, 3 H), 2.41-2.53 (m, 1 H), 2.61-2.72
(m, 1 H), 3.74 (s, 3 H), 3.82 (dd, J ) 9.8 Hz, J ) 5.3 Hz, 1 H), 5.13
(d, J ) 10.2 Hz, 1 H), 5.20 (dd, J ) 17.1 Hz, J ) 1.4 Hz, 1 H), 5.50
(t, J ) 6.4 Hz, 1 H), 5.56 (d, J ) 6.2 Hz, 1 H), 5.79 (t, J ) 6.3 Hz,
1 H), 5.90-6.03 (m, 1 H), 5.98 (d, J ) 6.4 Hz, 1 H), 6.89 (d, J ) 8.8
Hz, 2 H), 7.30 (d, J ) 8.7 Hz, 2 H). Additional signals for the minor
diastereomer: δ 2.24 (s, 3 H), 3.75 (s, 3 H), 4.03 (dd, J ) 7.9 Hz, J
) 5.0 Hz, 1 H), 5.06 (d, J ) 9.9 Hz, 1 H), 5.74 (d, J ) 6.3 Hz, 1 H),
7.39 (d, J ) 8.7 Hz, 2 H). 13C NMR ([D6]DMSO, 75 MHz): δ 18.40
(CH3), 34.14 (CH), 38.86 (CH2), 55.38 (CH3), 83.68 (Cquat.), 88.45
(Cquat.), 91.54 (CH), 95.29 (CH), 96.43 (CH), 96.80 (CH), 111.16 (Cquat.),
112.53 (Cquat.), 114.37 (CH), 114.53 (Cquat.), 117.80 (CH2), 132.94 (CH),
135.50 (CH), 159.42 (Cquat.), 234.23 (Cquat., CO). Additional signals
for the minor diastereomer: δ 18.13 (CH3), 34.00 (CH), 41.25 (CH2),
84.25 (Cquat.), 87.46 (Cquat.), 94.94 (CH), 95.62 (CH), 96.06 (CH), 110.41
(Cquat.), 111.77 (Cquat.), 114.33 (CH), 114.77 (Cquat.), 118.30 (CH2),
133.00 (CH), 134.63 (CH), 234.26 (Cquat., CO). EI MS (70 eV, m/z
(%)): 412 (M+, 23), 328 (M+ - 3 CO, 100), 287 (M+ - 3 CO, -
CH2CHdCH2, 12), 276 (M+ - Cr(CO)3, 4), 235 (M+ - Cr(CO)3, -
CH2CHdCH2, 50), 52 (Cr+, 16). IR (KBr): ν˜ 1959, 1890, 1643, 1606,
1509, 1291, 1249, 1031, 834, 664, 631 cm-1. UV/vis (DMSO): λmax
(ꢀ) 316 nm (10000). Anal. Calcd for C23H20CrO4 (412.41): C, 66.99;
H, 4.89. Found: C, 67.29; H, 5.00.
Cr(CO)3(o-Cl-η6-C6H4)CH[SCH(CH3)2]CdCPh (5o). Yellow oil.
1H NMR (CDCl3, 300 MHz): δ 1.42 (m, 6 H), 3.39 (m, 1 H), 5.02-
5.09 (m, 2 H), 5.34-5.46 (m, 2 H), 6.02 (m, 1 H), 7.30-7.51 (m, 5
H). 13C NMR (CDCl3, 75 MHz): δ 22.76 (CH3), 23.12 (CH3), 35.06
(CH), 37.26 (CH), 85.81 (Cquat.), 86.16 (CH), 86.57 (Cquat.), 88.95 (CH),
93.68 (CH), 94.58 (CH), 106.47 (Cquat.), 114.46 (Cquat.), 122.35 (Cquat.),
128.28 (CH), 128.59 (CH), 131.72 (CH), 231.09 (Cquat., CO). Additional
signals for the minor diastereomer: δ 23.20 (CH3), 36.15 (CH), 37.42
(CH), 84.93 (Cquat.), 87.82 (CH), 90.37 (CH), 92.41 (CH), 92.85 (CH),
128.33 (CH), 128.71 (CH), 131.84 (CH). EI MS (70 eV, m/z (%)):
436 (M+, 3), 382/380 (M+ - 2 CO, 11/26), 354/352 (M+ - 3 CO,
31/77), 311/309 (M+ - 3 CO, - C3H7, 9/15), 280/278 (M+ - 3 CO,
- SdCMe2, 33/95), 274 (100), 242 (M+ - 3 CO, - SC3H7, - Cl,

3452 J. Am. Chem. Soc., Vol. 123, No. 15, 2001
Netz et al.
10), 223 (82), 190 (C15H10+, 18), 52 (Cr+, 28). IR (KBr): ν˜ 2964, 2926,
J ) 1.9 Hz, 2 H), 3.58 (s, 3 H), 3.74 (s, 3 H), 4.85 (s, 1 H), 5.29 (t, J
) 6.3 Hz, 1 H), 5.61 (d, J ) 7.0 Hz, 1 H), 6.07 (d, J ) 5.9 Hz, 1 H).
13C NMR ([D6]DMSO, 75 MHz): δ 13.55 (CH3), 17.92 (CH2), 21.46
(CH2), 27.96 (CH2), 30.29 (CH2), 32.31 (CH), 34.09 (CH2), 51.59 (CH3),
56.54 (CH3), 75.22 (CH), 78.01 (Cquat.), 85.42 (CH), 85.86 (Cquat.), 96.99
(CH), 98.51 (CH), 100.47 (Cquat.), 142.50 (Cquat.), 171.92 (Cquat.), 233.62
(Cquat., CO). Additional signals for the minor diastereomer: δ 18.02
(CH2), 21.59 (CH2), 26.23 (CH2), 30.19 (CH2), 32.44 (CH), 34.05 (CH2),
56.65 (CH3), 78.52 (Cquat.), 86.80 (Cquat.), 99.60 (Cquat.), 141.79 (Cquat.),
171.80 (Cquat.), 233.72 (Cquat., CO). EI MS (70 eV, m/z (%)): 456 (M+,
5), 372 (M+ - 3 CO, 2), 254 (M+ - 3 CO, - SdCHCH2CO2CH3,
17), 220 (25), 201 (81), 52 (Cr+, 100). IR (KBr): ν˜ 2956, 2934, 2229,
1963, 1881, 1737, 1599, 1529, 1468, 1436, 1359, 1266, 1246, 1015,
666, 629 cm-1. UV/vis (DMSO): λmax (ꢀ) 316 nm (7600). Anal. Calcd
for C21H24CrO6S (456.48): C, 55.26; H, 5.30; S: 7.02. Found: C, 55.78;
H, 5.64; S: 7.62.
1974, 1902, 1598, 1491, 1243, 1053, 820, 757, 692, 656, 619 cm-1
.
UV/vis (CHCl3): λmax (ꢀ) 247 nm (38600), 326 (13400). Anal. Calcd
for C21H17ClCrO3S (436.88): C, 57.74; H, 3.92; Cl, 8.12; S, 7.34.
Found: C, 56.56; H, 4.01; Cl, 8.55; S, 7.65.
Cr(CO)3(o-Cl-η6-C6H4)CH[S(CH2)2COOCH3]CdCPh (5p). Yel-
1
low oil. H NMR (CDCl3, 400 MHz): δ 2.64-2.79 (m, 2 H), 3.12-
3.20 (m, 2 H), 3.69 (s, 3 H), 4.97 (m, 1 H), 5.09 (s, 1 H), 5.28-5.33
(m, 1 H), 5.41-5.47 (m, 1 H), 5.97-6.03 (m, 1 H), 7.31-7.52 (m, 5
H). 13C NMR (CDCl3, 100 MHz): 28.69 (CH2), 34.41 (CH2), 36.04
(CH), 51.87 (CH3), 85.61 (Cquat.), 85.95 (CH), 86.69 (Cquat.), 88.79 (CH),
93.78 (CH), 94.64 (CH), 105.73 (Cquat.), 114.52 (Cquat.), 122.04 (Cquat.),
128.32 (CH), 128.77 (CH), 131.75 (CH), 172.05 (Cquat.), 230.90 (Cquat.
,
CO). Additional signals for the minor diastereomer: δ 36.51 (CH),
87.66 (CH), 90.38 (CH), 92.85 (CH), 91.94 (CH), 131.87 (CH). neg.
FAB MS (Cs+, 20 kV, mNBA, m/z): 479.5 ([M-H]-). EI MS (70
eV, m/z (%)): 398/396 (M+ - 3 CO, 23/51), 280/278 (M+ - 3 CO, -
SdCHCH2CO2CH3, 9/23), 227/225 (M+ - Cr(CO)3, - S(CH2)2CO2-
CH3, 33/100), 190 (C15H10+, 18), 52 (Cr+, 14). IR (KBr): ν˜ 3084, 2953,
2926, 2222, 1973, 1901, 1738, 1598, 1491, 1437, 1361, 1247, 1051,
823, 759, 692, 657, 621 cm-1. UV/vis (CH2Cl2): λmax (ꢀ) 245 (25700),
326 nm (9500). Anal. Calcd for C22H17ClCrO5S (480.89): C, 54.95;
H, 3.56; Cl, 7.37; S, 6.67. Found: C, 55.48; H, 3.99; Cl, 7.07; S, 7.08.
Cr(CO)3(o-Cl-η6-C6H4)CH[N(CH2)4O]CtCPh (5q). Yellow crys-
tals, mp 145 °C (diethyl ether/pentane). 1H NMR (CDCl3, 300 MHz):
δ 2.69 (m, 4 H), 3.69-3.72 (m, J ) 4.8 Hz, 4 H), 4.91 (s, 1 H), 5.04
(m, 1 H), 5.42-5.45 (m, 2 H), 5.90 (d, J ) 6.2 Hz, 1 H), 7.32-7.54
(m, 5 H). Additional signals for the minor diastereomer: δ 3.82 (m, 4
H), 5.11 (m, 1 H), 6.23 (d, J ) 6.0 Hz, 1 H). 13C NMR (CDCl3, 75
MHz): δ 49.42 (CH2), 59.04 (CH), 66.96 (CH2), 81.11 (Cquat.), 86.97
(CH), 90.03 (Cquat.), 90.96 (CH), 93.20 (CH), 93.65 (CH), 103.39 (Cquat.),
114.56 (Cquat.), 122.14 (Cquat.), 128.37 (CH), 128.69 (CH), 131.93 (CH),
231.09 (Cquat., CO). EI MS (70 eV, m/z (%)): 447 (M+, 4), 393/391
(M+ - 2 CO, 2/6), 365/363 (M+ - 3 CO, 12/32), 276 (M+ - Cr(CO)3,
- Cl, 76), 248 (32), 227/225 (M+ - Cr(CO)3, - NC4H8O, 9/27) 191
((M+ - Cr(CO)3, - NC4H7O, - Cl, 100), 190 (C15H10+, 10), 189 (42),
52 (Cr+, 14). IR (KBr): ν˜ 2924, 2855 1977, 1901, 1630, 1490, 1115,
1070, 760, 621 cm-1. UV/vis (CHCl3): λmax (ꢀ) 323 nm (10800). Anal.
Calcd for C22H18ClCrNO4 (447.84): C, 59.00; H, 4.05; Cl, 7.92; N,
3.13. Found: C, 59.18; H, 3.98; Cl, 7.92; N, 2.87.
Cr(CO)3(o-OCH3-η6-C6H4)CH[N(iPr)2]CtC(CH2)3CH3 (5t). Yel-
1
low powder, mp 79-81 °C (diethyl ether/pentane). H NMR ([D6]-
DMSO, 300 MHz): δ 0.80-0.88 (m, J ) 6.8 Hz, 3 H), 1.13 (d, J )
6.7 Hz, 6 H), 1.17 (d, J ) 6.4 Hz, 6 H), 1.24-1.38 (m, 4 H), 2.10-
2.14 (m, 2 H), 3.13-3.27 (m, J ) 6.3 Hz, 2 H), 3.74 (s, 3 H), 4.63 (s,
1 H), 5.18 (t, J ) 6.3 Hz, 1 H), 5.54 (d, J ) 6.9 Hz, 1 H), 5.88-5.92
(m, 2 H). Additional signals for the minor diastereomer: δ 2.19-2.23
(m, 2 H), 3.68 (s, 3 H), 4.73 (s, 1 H), 5.26 (t, J ) 6.6 Hz, 1 H), 6.15
(d, J ) 6.8 Hz, 1 H). 13C NMR ([D6]DMSO, 75 MHz): δ 13.52 (CH3),
17.94 (CH2), 20.13 (CH3), 21.39 (CH2), 23.84 (CH3), 30.24 (CH2), 45.10
(CH), 47.36 (CH), 56.27 (CH3), 75.66 (CH), 80.59 (Cquat.), 83.86 (Cquat.),
85.53 (CH), 96.61 (CH), 97.38 (CH), 107.01 (Cquat.), 142.42 (Cquat.),
234.39 (Cquat., CO). Additional signals for the minor diastereomer: δ
18.07 (CH2), 20.23 (CH3), 21.61 (CH2), 23.99 (CH3), 30.29 (CH2), 45.66
(CH), 45.73 (CH). EI MS (70 eV, m/z (%)): 437 (M+, 13), 353 (M+
i
- 3 CO, 23), 254 (M+ - 3 CO, - PrNdCMe2, 11), 220 (24), 151
(100), 52 (Cr+, 15). IR (KBr): ν˜ 2965, 2934, 1957, 1880, 1631, 1530,
1462, 1262, 644, 630 cm-1. UV/vis (DMSO): λmax (ꢀ) 314 nm (8800).
Anal. Calcd for C23H31CrO4N (437.50): C, 63.14; H, 7.14; N, 3.20.
Found: C, 63.47; H, 7.08; N, 3.20.
Cr(CO)3(o-OCH3-η6-C6H4)CH[C(CH3)2COOCH3]CtC-
(CH2)3CH3 (5u). Yellow oil. 1H NMR ([D6]DMSO, 300 MHz): δ 0.86
(t, J ) 6.9 Hz, 3 H), 1.18 (s, 3 H), 1.20 (s, 3 H), 1.39-1.42 (m, J )
3.3 Hz, 4 H), 2.16-2.22 (m, 2 H), 3.55-3.59 (m, J ) 2.0 Hz, 1 H),
3.57 (s, 3 H), 3.69 (s, 3 H), 5.07 (t, J ) 6.2 Hz, 1 H), 5.58 (d, J ) 7.1
Hz, 1 H), 5.89-5.93 (m, J ) 6.3 Hz, 2 H). Additional signals for the
minor diastereomer: δ 1.06 (s, 3 H), 4.18 (m, J ) 2.1 Hz, 1 H), 5.28
(t, J ) 6.2 Hz, 1 H), 5.53 (d, J ) 6.9 Hz, 1 H), 5.96 (d, J ) 6.5 Hz,
1 H). 13C NMR ([D6]DMSO, 75 MHz): δ 13.57 (CH3), 17.98 (CH2),
21.31 (CH2), 23.19 (CH3), 23.71 (CH3), 30.51 (CH2), 44.00 (CH), 48.02
(Cquat.), 51.93 (CH3), 55.91 (CH3), 76.38 (CH), 77.45 (Cquat.), 84.08
(Cquat.), 85.39 (CH), 97.41 (CH), 98.99 (Cquat.), 101.70 (CH), 143.88
(Cquat.), 175.36 (Cquat.), 233.93 (Cquat., CO). Additional signals for the
minor diastereomer: δ 17.86 (CH2), 21.45 (CH2), 22.01 (CH3), 22.54
(CH3), 30.36 (CH2), 38.01 (CH), 47.30 (Cquat.), 52.00 (CH3), 56.30
(CH3), 75.11 (CH), 77.80 (Cquat.), 84.59 (Cquat.), 86.37 (CH), 96.98 (CH),
98.09 (CH), 99.46 (Cquat.), 143.17 (Cquat.), 175.31 (Cquat.). MS (70 eV,
Cr(CO)3(o-Cl-η6-C6H4)CH[C(CH3)2COOCH3]CtCPh (5r). Yel-
1
low oil. H NMR (CDCl3, 300 MHz): δ 1.40 (s, 3 H), 1.49 (s, 3 H),
3.70 (s, 3 H), 4.15 (s, 1 H), 4.91 (dt, J ) 6.1 Hz, J ) 1.2 Hz, 1 H),
5.34-5.43 (m, 2), 5.45 (d, J ) 6.4 Hz, 1 H), 7.26-7.30 (m, 3 H),
7.44-7.49 (m, 2 H). Additional signals for the minor diastereomer: δ
1.31 (s, 3 H), 3.71 (s, 3 H), 4.62 (s, 1 H), 5.06 (dt, J ) 6.2 Hz, J ) 1.0
Hz, 1 H), 5.86 (dd, J ) 6.4 Hz, J ) 1.0 Hz, 1 H). 13C NMR (CDCl3,
75 MHz): δ 22.51 (CH3), 25.19 (CH3), 46.46 (CH), 49.58 (Cquat.), 52.28
(CH3), 85.32 (Cquat.), 86.47 (CH), 87.28 (Cquat.), 91.56 (CH), 93.43 (CH),
96.87 (CH), 104.77 (Cquat.), 114.02 (Cquat.), 123.17 (Cquat.), 128.09 (CH),
128.18 (CH), 131.48 (CH), 175.79 (Cquat.), 231.06 (Cquat., CO).
Additional signals for the minor diastereomer: δ 22.11 (CH3), 23.24
(CH3), 41.84 (CH), 48.78 (Cquat.), 85.46 (Cquat.), 86.60 (Cquat.), 87.00
(CH), 89.36 (CH), 93.64 (CH), 93.80 (CH), 105.73 (Cquat.), 114.33
(Cquat.), 122.61 (Cquat.), 128.19 (CH), 128.31 (CH), 131.78 (CH), 175.44
(Cquat.), 231.09 (Cquat., CO). EI MS (70 eV, m/z (%)): 462 (M+, < 1),
406 (M+ - 2 CO, 2), 380/378 (M+ - 3 CO, 7/19), 276 (M+ - Cr-
(CO)3, - Cl, - CH3, 2), 227/225 (M+ - Cr(CO)3, - C(CH3)2CO2-
CH3, 30/100), 191 (M+ - Cr(CO)3, - CH2dC(CH3)CO2CH3, - Cl,
12), 52 (Cr+, 4). IR (KBr): ν˜ 2982, 2951, 1973, 1902, 1731, 1598,
1491, 1469, 1443, 1250, 1128, 1057, 758, 692, 659, 621 cm-1. UV/vis
(CHCl3): λmax (ꢀ) 324 nm (7600). Anal. Calcd for C23H19ClCrO5
(462.85): C, 59.69; H, 4.14; Cl: 7.66. Found: C, 60.03; H, 4.31; Cl,
7.48.
m/z (%)): 438 (M+, 2), 382 (M+ - 2 CO, 5), 354 (M+ - 3 CO, 41),
212 (11), 201 (M+ - Cr(CO)3 - C(CH3)2CO2CH3, 100), 170 (C13H14
,
+
2), 52 (Cr+, 14). IR (KBr): ν˜ 2955, 2936, 1963, 1882, 1732, 1528,
1470, 1264, 1128, 1017, 669, 628 cm-1. UV/vis (DMSO): λmax (ꢀ)
315 nm (8000). Anal. Calcd for C22H26CrO6 (438.44): C, 60.27; H,
5.98. Found: C, 60.86; H, 6.41.
Influence of the Lewis Acid on the Diastereomeric Ratio. (a) BF3‚
OEt2. According to the General Procedure, 107 mg (0.27 mmol) of 3e
was ionized with 50 µL (0.35 mmol) of BF3‚OEt2 for 75 min and then
reacted with 0.11 mL (0.54 mmol) of 1-methoxy-2-methyl-1-trimeth-
ylsiloxypropene for 120 min. After flash chromatography on silica gel,
83 mg (70%) of 5u was isolated as a yellow oil and the diastereomeric
ratio was determined by integration of the significant triplet signals (δ
Cr(CO)3(o-OCH3-η6-C6H4)CH[S(CH2)2COOCH3]CtC-
(CH2)3CH3 (5s). Yellow oil. 1H NMR ([D6]DMSO, 300 MHz): δ
0.83-0.90 (t, J ) 7.1 Hz, 3 H), 1.29-1.52 (m, 4 H), 2.22 (dt, J ) 6.5
Hz, J ) 1.9 Hz, 2 H), 2.56-2.75 (m, 2 H), 2.84-3.02 (m, 2 H), 3.60
(s, 3 H), 3.75 (s, 3 H), 4.86 (s, 1 H), 5.16 (t, J ) 6.3 Hz, 1 H), 5.56 (d,
J ) 7.0 Hz, 1 H), 5.94 (t, J ) 6.2 Hz, 1 H), 6.16 (d, J ) 6.0 Hz, 1 H).
Additional signals for the minor diastereomer: δ 2.29 (dt, J ) 6.7 Hz,
1
5.07 and 5.28, respectively) on the complexed arene ring in the H
NMR spectrum to give dr ) 62:38.
(b) TMSOTf. According to the General Procedure, 106 mg (0.27
mmol) of 3e was ionized with 60 µL (0.33 mmol) of TMSOTf for 75
min and then reacted with 0.11 mL (0.54 mmol) of 1-methoxy-2-

(arene)Cr(CO)-Substituted Propargyl Cations
J. Am. Chem. Soc., Vol. 123, No. 15, 2001 3453
methyl-1-trimethylsiloxypropene for 45 min. After flash chromatog-
raphy on silica gel, 69 mg (59%) of 5u was isolated as a yellow oil
and the diastereomeric ratio was determined by integration of the
significant triplet signals (δ 5.07 and 5.28, respectively) on the
(CH), 47.29 (Cquat.), 51.97 (CH3), 56.26 (CH3), 75.04 (CH), 77.78
(Cquat.), 84.57 (Cquat.), 86.30 (CH), 96.93 (CH), 98.04 (CH), 99.43 (Cquat.),
143.13 (Cquat.), 175.31 (Cquat.), 233.87 (Cquat., CO). Additional signals
for the minor diastereomer: δ 13.55 (CH3), 17.98 (CH2), 21.31 (CH2),
23.14 (CH3), 23.72 (CH3), 30.51 (CH2), 44.01 (CH), 48.03 (Cquat.), 51.90
(CH3), 55.87 (CH3), 76.32 (CH), 77.43 (Cquat.), 84.08 (Cquat.), 85.33
(CH), 97.35 (CH), 98.96 (Cquat.), 101.65 (CH), 143.86 (Cquat.), 175.35
(Cquat.), 233.89 (Cquat., CO).
1
complexed arene ring in the H NMR spectrum to give dr ) 70:30.
(c) SnCl4. According to the General Procedure, 100 mg (0.25 mmol)
of 3e was ionized with 40 µL (0.34 mmol) of SnCl4 for 40 min and
then reacted with 0.12 mL (0.59 mmol) of 1-methoxy-2-methyl-1-
trimethylsiloxypropene for 20 min. After flash chromatography on silica
gel, 59 mg (53%) of 5u was isolated as a yellow oil and the
diastereomeric ratio was determined by integration of the significant
triplet signals (δ 5.07 and 5.28, respectively) on the complexed arene
5c. A solution of 105 mg (0.25 mmol) of 3a in 8 mL of
dichloromethane was cooled to -78 °C, and 0.11 mL (0.54 mmol) of
1-methoxy-2-methyl-1-trimethylsiloxypropene was added. To this mix-
turewas added 55 µL (0.50 mmol) of TiCl4 dropwise. After 35 min of
stirring at that temperature, the reaction mixture was worked up
according to the General Procedure. After flash chromatography on
silica gel, 60 mg (54%) of 5c was isolated as a yellow oil and the
diastereomeric ratio was determined by integration of the significant
propargyl proton signals in the 1H NMR spectrum to give dr ) 43:57.
1H NMR ([D6]DMSO, 300 MHz): δ 1.15 (s, 3 H), 1.30 (s, 3 H),
3.63 (s, 3 H), 3.73 (s, 3 H), 4.47 (s, 1 H), 5.31 (t, J ) 6.2 Hz, 1 H),
5.58 (d, J ) 6.9 Hz, 1 H), 5.90-5.97 (m, J ) 6.3 Hz, 1 H), 6.10 (d,
J ) 6.3 Hz, 1 H), 7.32-7.45 (m, 5 H). Additional signals for the minor
diastereomer: δ 1.27 (s, 6 H), 3.62 (s, 3 H), 3.89 (s, 1 H), 5.13 (t, J )
6.2 Hz, 1 H), 5.62 (d, J ) 6.9 Hz, 1 H), 6.03 (d, J ) 6.1 Hz, 1 H). -
13C NMR ([D6]DMSO, 75 MHz): δ 22.01 (CH3), 22.74 (CH3), 38.63
(CH), 47.69 (Cquat.), 52.19 (CH3), 56.39 (CH3), 75.34 (CH), 84.24
(Cquat.), 86.62 (CH), 87.53 (Cquat.), 97.03 (CH), 97.98 (CH), 98.41 (Cquat.),
122.54 (Cquat.), 128.06 (CH), 128.61 (CH), 131.59 (CH), 143.00 (Cquat.),
175.23 (Cquat.), 233.82 (Cquat., CO). Additional signals for the minor
diastereomer: δ 23.47 (CH3), 23.53 (CH3), 44.57 (CH), 48.28 (Cquat.),
52.08 (CH3), 56.13 (CH3), 76.52 (CH), 84.01 (Cquat.), 85.63 (CH), 87.52
(Cquat.), 97.51 (CH), 97.76 (Cquat.), 101.55 (CH), 123.51 (Cquat.), 128.57
(CH), 131.30 (CH), 143.85 (Cquat.), 175.15 (Cquat.), 233.85 (Cquat., CO).
1
ring in the H NMR spectrum to give dr ) 68:32.
1H NMR ([D6]DMSO, 300 MHz): δ 0.86 (t, J ) 6.8 Hz, 3 H), 1.19
(s, 3 H), 1.20 (s, 3 H), 1.35-1.44 (m, 4 H), 2.16-2.22 (m, 2 H), 3.57
(s, 3 H), 3.57-3.59 (m, J ) 2.2 Hz, 1 H), 3.69 (s, 3 H), 5.07 (t, J )
6.3 Hz, 1 H), 5.58 (d, J ) 7.0 Hz, 1 H), 5.89-5.93 (m, J ) 6.0 Hz, 2
H). Additional signals for the minor diastereomer: δ 1.06 (s, 3 H),
4.18 (m, J ) 2.2 Hz, 1 H), 5.28 (m, J ) 6.3 Hz, 1 H), 5.53 (d, J ) 6.7
Hz, 1 H), 5.95 (dd, J ) 6.4 Hz, J ) 1.0 Hz, 1 H). 13C NMR ([D6]-
DMSO, 75 MHz): δ 13.55 (CH3), 17.98 (CH2), 21.31 (CH2), 23.16
(CH3), 23.71 (CH3), 30.51 (CH2), 44.01 (CH), 48.02 (Cquat.), 51.91
(CH3), 55.89 (CH3), 76.34 (CH), 77.43 (Cquat.), 84.08 (Cquat.), 85.35
(CH), 97.38 (CH), 98.97 (Cquat.), 101.67 (CH), 143.86 (Cquat.), 175.35
(Cquat.), 233.91 (Cquat., CO). Additional signals for the minor diastere-
omer: δ 17.86 (CH2), 21.45 (CH2), 22.00 (CH3), 22.52 (CH3), 30.36
(CH2), 38.01 (CH), 47.29 (Cquat.), 51.98 (CH3), 56.27 (CH3), 75.07 (CH),
77.79 (Cquat.), 84.58 (Cquat.), 86.33 (CH), 96.95 (CH), 98.06 (CH), 99.44
(Cquat.), 143.15 (Cquat.), 175.31 (Cquat.), 233.89 (Cquat., CO).
(d) TiCl4. Vide Supra Compound 5u. In Situ Ionization with
TiCl4 in the Presence of Nucleophile. 5u. A solution of 101 mg (0.26
mmol) of 3e in 8 mL of dichloromethane was cooled to -78 °C, and
0.11 mL (0.54 mmol) of 1-methoxy-2-methyl-1-trimethylsiloxypropene
was added. To this mixture was added 50 µL (0.46 mmol) of TiCl4
dropwise. After 25 min of stirring at that temperature, the reaction
mixture was worked up according to the General Procedure. After flash
chromatography on silica gel, 60 mg (54%) of 5u was isolated as a
yellow oil and the diastereomeric ratio was determined by integration
of the significant triplet signals (δ 5.07 and 5.27, respectively) on the
Acknowledgment. Dedicated to Prof. Dr. Barry M. Trost
on the occasion of his 60th birthday. The financial support of
the Fonds der Chemischen Industrie, Deutsche Forschungsge-
meinschaft, and Dr.-Otto-Ro¨hm Geda¨chtnisstiftung is gratefully
acknowledged. We cordially thank Mr. Tuan-Huy La for
experimental assistance and wish to express our appreciation
to Prof. H. Mayr for his generous support.
1
complexed arene ring in the H NMR spectrum to give dr ) 34:66.
1H NMR ([D6]DMSO, 300 MHz): δ 0.87 (t, J ) 6.8 Hz, 3 H), 1.06
(s, 3 H), 1.21 (s, 3 H), 1.33-1.49 (m, 4 H), 2.16-2.22 (m, 2 H), 3.58
(s, 3 H), 3.69 (s, 3 H), 4.18 (m, J ) 2.1 Hz, 1 H), 5.27 (t, J ) 6.3 Hz,
1 H), 5.53 (d, J ) 6.9 Hz, 1 H), 5.87-5.92 (m, J ) 6.0 Hz, 1 H), 5.96
(d, J ) 6.2 Hz, 1 H). Additional signals for the minor diastereomer:
δ 1.19 (s, 3 H), 3.57-3.59 (m, 1 H), 5.07 (t, J ) 6.2 Hz, 1 H), 5.57
(d, J ) 7.2 Hz, 1 H). 13C NMR ([D6]DMSO, 75 MHz): δ 13.53 (CH3),
17.86 (CH2), 21.45 (CH2), 22.00 (CH3), 22.51 (CH3), 30.36 (CH2), 38.01
Supporting Information Available: Tables of data collec-
tion parameters, bond lengths and angles, positional and thermal
parameter, and least-squares planes for compounds 3b, 3e, 3g,
5c, 5g, and 5t. This material is available free of charge via the
Internet at http://pubs.acs.org.
JA0037116