New carbonylation reaction of tungsten-propargyl compounds via protonation at a prolonged period

Article abstract of DOI:10.1021/om980787q

The CpW(CO)₃(η¹-CH₂C=CR) (R = Me 1, Ph 2) complexes were treated with triflic acid (2.0 equiv) in cold dichloromethane (-78°C), and after a long period to the mixture was added water or RNH₂ to give good yields of carbonylation products CpW(CO)₂(η¹,η²-CH ₂-CHCHR-Y-CO-) (R = Me, Ph; Y = RN, O). These products were fully characterized by appropriate physical methods including single-crystal X-ray diffraction. If a chiral amine such as (R)-methylbenzylamine was used in the reaction, two optically active isomers in equal proportions were obtained and further separated on a silica column. In the case of (C₅Me₅)W(CO)₃(η¹-CH ₂C=CPh) (9), its reactions with triflic acid and water in the same reaction sequence produce (C₅Me₅)W(CO)₂(η¹,η ²-CH₂CHCHPh-O-CO-) as two diastereomers which undergo mutual exchange according to variable-temperature ¹H NMR spectroscopy.

Full text of DOI:10.1021/om980787q

748
Organometallics 1999, 18, 748-752
New Ca r bon yla tion Rea ction of Tu n gsten -P r op a r gyl
Com p ou n d s via P r oton a tion a t a P r olon ged P er iod
Reniguntala J . Madhushaw,† Srinivasa Rao Cheruku,† Kesavaram Narkunan,†
Gene-Hsian Lee,‡ Shie-Ming Peng,‡ and Rai-Shung Liu*,†
Department of Chemistry, National Tsing-Hua University, Hsinchu, 30043, Taiwan, ROC, and
Department of Chemistry, National Taiwan University, Taipei, 10764, Taiwan, ROC
Received September 21, 1998
The CpW(CO)3(η1-CH2CtCR) (R ) Me 1, Ph 2) complexes were treated with triflic acid
(2.0 equiv) in cold dichloromethane (-78 °C), and after a long period to the mixture was
added water or RNH2 to give good yields of carbonylation products CpW(CO)2(η1,η2-CH2-
CHCHR-Y-CO-) (R ) Me, Ph; Y ) RN, O). These products were fully characterized by
appropriate physical methods including single-crystal X-ray diffraction. If a chiral amine
such as (R)-methylbenzylamine was used in the reaction, two optically active isomers in
equal proportions were obtained and further separated on a silica column. In the case of
(C5Me5)W(CO)3(η1-CH2CtCPh) (9), its reactions with triflic acid and water in the same
reaction sequence produce (C5Me5)W(CO)2(η1,η2-CH2CHCHPh-O-CO-) as two diastereo-
1
mers which undergo mutual exchange according to variable-temperature H NMR spectros-
copy.
Sch em e 1
In tr od u ction
The action of a metal-η1-unsaturated hydrocarbyl
compound with a strong acid is a general method for
generation of metal-η2-carbocations.1,2 Scheme 1 (eq 1)
shows three representative examples of formation of
metal-η2-alkene3 (A), -η2-allene4 (B), and -η1-
vinylidene5 (C) carbocations via protonation of their
corresponding allyl, propargyl, and alkynyl compounds.
Recently, we discovered6 that protonation of tungsten-
η1-alkynyl complexes in a prolonged reaction period
ultimately led to an oxidative carbonylation reaction to
give tungsten(IV) acyl complexes via a tungsten(II)-
η1-vinylidene intermediate, as shown in Scheme 1 (eq
2). This observation raises an interesting question
regarding the kinetic stabilities of the other two car-
bocations (A and B) in a prolonged reaction period; this
issue has not been studied thoroughly. In this article,
we study the reaction chemistry of tungsten-η1-prop-
argyl complexes CpW(CO)3(η1-CH2CtCR) (R ) Me 1,
Ph 2) after protonation over different periods, and the
effect of reaction time on the chemical reactivity of the
resulting tungsten-η2-allene cation (B) will be reported
in detail.
† National Tsing-Hua University.
‡ National Taiwan University.
(1) Review papers: (a) Norton, J . R. In Inorganic Reactions and
Methods; Verlag Chemie: Weinheim, 1987. (b) Pearson, R. G. Chem.
Rev. 1985, 85, 41.
(2) (a) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Application of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; Chapter 8, p 433.
(b) Hegedus, L. S. Transition Metals in the Synthesis of Complex
Organic Molecules; University Science Books: Mill Valley, 1994;
Chapter 2, p 43.
(3) Organic Syntheses via metal-η2-alkene cations, see representa-
tive papers: (a) Welker, M. E. Chem. Rev. 1992, 92, 97. (b) J iang, S.;
Turos, E. Organometallics 1993, 12, 4280. (c) J iang, S.; Turos, E.
Tetrahedron Lett. 1991, 4639. (d) Rosenblum, M.; Watkins, J . C. J .
Am. Chem. Soc. 1990, 112, 6316. (e) Bell, P. B.; Wojcicki, A. Inorg.
Chem. 1981, 20, 1585.
(4) Organic Syntheses via metal-η2-allene cations, see representa-
tive papers: (a) Bell, P. B.; Wojcicki, A. Inorg. Chem. 1981, 20, 1585.
(b) Raghu, S.; Rosenblum, M. J . Am. Chem. Soc. 1973, 95, 3060. (c)
Blosser, P. W.; Shimpff, D. G.; Gallucci, J . C.; Wojcicki, A. Organome-
tallics 1993, 12, 2, 1393. (d) Chen, C.-C.; Fan J .-S.; Shieh, S.-J .; Lee,
G.-H.; Peng, S.-M.; Wang, S.-L.; Liu, R.-S. J . Am. Chem. Soc. 1996,
118, 9279. (e) Benaim, J .; Merour, J .-Y.; Roustan, J . L. C. R. Acad.
Sci. Paris, Ser. C 1971, 272, 789.
Resu lts a n d Discu ssion
It was previously reported7,8 that treatment of tung-
sten-propargyl compounds such as 1 and 2 with triflic
(7) (a) Rosenblum, M.; Raghu, S. J . Am. Chem. Soc. 1973, 95, 3062.
(b) Lichtenberg, D. L.; Wojcicki, A. J . Organomet. Chem. 1975, 94, 311.
(c) Charrier, C.; Collin, J .; Merour, J . Y.; Roustan, J . L. J . Organomet.
Chem. 1978, 162, 57. (d) Giulieri, F.; Benaim, J . Organomet. Chem.
1978, 162, 57.
(8) (a) Lin, S. H.; Vong, W. J .: Liu, R. S. Organometallics 1995, 14,
1619. (b) Chen, C.-H. Fan, J .-S.; Lee, G.-H.; Shieh, S.-J .; Wang, S.-L.;
Peng S.-M.; Liu, R.-S. J . Am. Chem. Soc. 1996, 118, 9279. (c) Shiu, L.
H.; Wang S.-L.; Wu M.-J .; Liu R. S. J . Chem. Soc., Chem. Commun.
1997, 2005. (d) Cheng, M.-H.; Ho, Y.-H.; Lee, G.-H.; Peng, S.-M.; Chu,
S.-Y.; Liu, R.-S. Organometallics 1994, 13, 4082.
(5) Organic Syntheses via metal-η1-vinylidene cations, see repre-
sentative papers: (a) Bruce, M. I. Chem. Rev. 1991, 91, 257. (b) Trost,
B. M.; Dyker, G.; Kulawiec, R. J . J . Am. Chem. Soc. 1990, 112, 7809.
(c) Trost, B. M.; Martinez, J . A.; Indolese, A. F. J . Am. Chem. Soc.
1993, 115, 10402. (d) Trost B. M.; Flygare, J . A. J . Am. Chem. Soc.
1992, 114, 5467. (e) McDonald, F. E.; Bowman, J . L. Tetrahedron Lett.
1996, 4675. (f) McDonald, F. E.; Schultz, C. C. J . Am. Chem. Soc. 1994,
116, 9363.
(6) Liang, K.-W.; Chandrasekharam, M.; Li, C.-L.; Liu, R.-S. Orga-
nometallics 1998, 17, 2683.
10.1021/om980787q CCC: $18.00 © 1999 American Chemical Society
Publication on Web 01/26/1999

Carbonylation Reaction of W-Propargyl Compounds
Organometallics, Vol. 18, No. 4, 1999 749
F igu r e 1. Molecular structure of compound 5 with selected
bond distances (Å) and angles (deg): W-C(3) ) 2.211(6),
W-C(5) ) 2.288(6), W-C(6) ) 2.250(6), C(3)-O(3) ) 1.204-
(7), C(4)-O(4) ) 1.427(7), C(4)-C(5) ) 1.514(9), C(5)-C(6)
) 1.402(8).
F igu r e 2. Molecular structure of compound 8b with
selected bond distances (Å) and angles (deg): W-C(3) )
2.240(5), W-C(5) ) 2.299(5), W-C(4) ) 2.240(4), C(3)-
O(3) ) 1.235(6), C(3)-N(1) ) 1.376(6), C(6)-N(1) ) 1.458-
(6), C(5)-C(6) ) 1.518(6), C(4)-C(5) ) 1.400(7).
acid (CF3SO3H) in cold CH2Cl2 (-78 °C) followed by
immediate addition of water, alcohol, and amine led to
alkoxycarbonylation reaction to yield syn-π-2-carboxy-
lated allyl complexes 3. According to the chemistry of
related CpFe(CO)2(η1-CH2CtCR) complexes,7 formation
of 3 can be envisaged to originate from the cis-η2-allene
intermediate (D), of which the CO group is initially
attacked by YXH (YX ) HO, RO, R2N) to form species
E; further insertion of the W-COXY bond of E into its
central allene carbon generates the syn-isomer of 3. To
study the effect of reaction time on the chemical
reactivity of tungsten-η2-allene cation D, the solution
was warmed to 23 °C in a period of 10 h before
treatment of water or R′NH2 (R′ ) Bui, PhCH2). After
workup of the solution, the new organometallic products
4-7 show NMR spectral data distinct from those
expected for tungsten-syn-π-allyl complexes 3, although
compounds of these two types have the same formula
according to mass and elemental analyses. In addition
to an ν(CO) absorption band in the 1650-1600 cm-1
region, there are two terminal W-CO stretching fre-
quencies (ν(CO) ca. 2000 and 1930 cm-1) for compounds
4-7, and these values are much larger than those (ν-
(CO) 1940 and 1870 cm-1) of compound 3.7,8 This
information suggests that a new carbonylation reaction
occurs in the reaction of water or amine with the aged
solution of D′. In contrast, the reaction of MeOH with
the same aged solution D′ did not produce any neutral
organometallic product. It is very difficult to deduce the
structures of 4-7 based on their spectral data alone.
Characterization of the structures relies on an X-ray
diffraction study of compound 5.9 Figure 1 shows the
ORTEP drawing for its molecular structure, which
reveals that CpW(CO)2 fragment is bound to an R-hy-
droxycarbonyl alkene moiety in a η1,η2 fashion. The C(4)
carbon of 5 becomes an sp3-hydridized carbon, whereas
the C(5)-C(6) carbon resembles a coordinated olefin, as
shown by the C(4)-C(5) (1.514 Å) and C(5)-C(6) (1.402
Å) bond lengths. The arrangement of the C(4)-C(5)-
C(6)-N atoms of 5 is close to a U-shaped conformation,
with the W-C(5) bond trans to the C(6)-Ph bond to
minimize its steric hindrance. Only one single diaste-
reomer was observed for compounds 4-7, and the lack
of the other diastereomer is probably due to its sterically
congested structure because it is shown later that
analogous diastereomers can undergo mutual exchange
at room temperature (vide infra). We also investigated
this reaction with chiral (R)-methylbenzylamine with
an aged acidification solution of compound 2, and two
optically pure diastereomers 8a and 8b were produced
and further separated on a silica column to give 28%
and 29% yields, respectively. Both 8a and 8b presumbly
have the same configuration (2S*, 3S*) at the two C2H-
C3HPh carbons because the magnitudes of the coupling
constant (J 23 ) 2.9-3.0 Hz) are very close to those (J 23
) 2.8-3.3 Hz) of compounds 4-7. The X-ray structure10
of chiral compound 8b is shown in Figure 2, which
confirms the proposed configurations at the C(5) and
C(6) carbons as that of compound 5. Similarly, the
W-C(5) bond of 8b is trans to the C(6)-Ph group to
minimize steric interactions.
We attempted to characterize the proposed tungsten-
η2-cis-allene cation (D) generated from 2 as well as the
species in its aged solution D′. Protonation of CpM(CO)3-
(η1-CH2CtCR) (M ) Mo, W)7,8 with strong acid is
believed to yield η2-cis-allene species initially, but its
NMR characterization is not yet reported. Addition of
excess anhydrous diethyl ether to the two solution gave
two dark black solids D and D′, respectively, which were
virtually insoluble in polar solvents such as CH2Cl2,
CHCl3, and CH3CN. We therefore prepared Cp*W(CO)3-
(η1-CH2CtCPh)11 (Cp* ) C5Me5) (9) because penta-
methylcyclopentadienylmetal complexes are usually
more soluble12 than their cyclopentadienylmetal ana-
logues. Scheme 3 shows the outcome for the same
reaction sequence.
Similar to its cyclopentadienyl analogue 1 and 2,
compounds 10 and 11a ,b are obtained in 85% and 56%
yields, respectively, via water treatment of the fresh (D)
and the aged (D′) solution of 9 after acidification with
triflic acid. The diastereoisomeric ratio of 11a and 11b
was ca. 3:1; these two isomers could undergo mutual
exchange (vide infra) at elevated temperatures. Addition
of benzylamine to the aged solution D′ of 9 also gave
the new carbonylation product 12 as a single diastere-
omer in 49% yield. The stereochemistry of 12 is assigned
(9) Crystal data for 5: monoclinic space group, P21/n, a ) 6.4197-
(20) Å, b ) 11.2660(14) Å, c ) 20.658(3) Å, â ) 95.27(3)°, V ) 1487.7-
(5) Å3, Z ) 4. Of the 2621 unique reflections, 2181 were considered
observed having I > 2σ(I). Final R ) 0.020, Rw ) 0.020.
(10) Crystal data for 8b: monoclinic space group, P212121, a
)
12.1514(2) Å, b ) 13.2603(2) Å, c ) 13.5770(3) Å, V ) 2187.68(7) Å3,
Z ) 4. Of the 13 374 unique reflections, 5021 were considered observed
having I > 2σ(I). Final R ) 0.028, Rw ) 0.048.
(11) Bell, P. B.; Wojcicki, A. Inorg. Chem. 1981, 20, 1585.
(12) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.
Principles and Application of Organotransition Metal Chemistry;
University Science Books: Mill Valley, CA, 1987; Chapter 3, p 165.

750 Organometallics, Vol. 18, No. 4, 1999
Madhushaw et al.
Sch em e 2
Sch em e 3
to have the (2R*, 3R*) configuration as inferred from
the coupling constant J 23 ) 3.4 Hz. Attempts to obtain
the NMR spectral data of the solid forms precipitated
from the solutions D and D′ were still unsuccessful due
to their poor solubility in common solvents. We are
aware that solid samples D and D′ have different
chemical properties compared to the solution species in
mother CH2Cl2. For instance, treatment of the two solid
samples with water gave compounds 10 and 11a in 38%
and 12% yields, respectively; the yield was very low,
particularly for D′. It is likely that the species in these
two phases are not the same.
proton signal (δ 3.12 ppm) of 11b showed a complete
disappearance of the C2H proton signal (δ 4.12 ppm) of
11a . Scheme 3 (eq 2) shows the mechanism for mutual
exchange of these two species. We propose the mecha-
nism in Scheme 3, which involves dissociation of the Cd
C double bond of 11a from the tungsten center to form
the 16e species F ′. Subsequent rotation of the C2-C3
single bond of F ′ gives another conformer F ′′, and finally
compound 11b.
One unanswered issue is the alternation of chemose-
lectivity for the fresh and aged solution of tungsten-
η1-propargyl complexes after acidification with triflic
acid. We did not have experimental data to elucidate
the formation mechanism of the new carbonylation
products 4-7, 8a ,b, and 11a ,b because NMR charac-
terization of the two solution species was unsuccessful.
Neverthelss, a speculative mechanism is helpful to
understand the nature of whole reaction sequence. It
is reported earlier that protonation of CpFe(CO)2(η1-
Figure 3 shows variable-temperature 1H NMR spectra
for the two diastereomers 11a and 11b in CDCl3. The
major diastereomer 11a is assigned to have the (2R*,
3R*) configuration based on the proton coupling con-
stant J 23 ) 2.9 Hz and the chemical shift of C2H (δ 4.12
ppm), which are close to those (J 23 ) 3.0 Hz and C2H δ
4.00 ppm) of compound 5. The minor isomer 11b is
assigned to have the (2R*, 3S*) configuration, and its
proton parameters (J 23 ) 0. Hz and C2H δ 3.12 ppm)
are quite distinct from compounds 11a and 5. As the
temperatures were raised from -10 °C, the resonances
become broad in the 40-50 °C range. Recooling the
temperatures to -10 °C regenerates the well-defined
spectra of the two species. Attempts to raise the tem-
peratures above 60 °C led to rapid decomposition of the
compound. A proton spin transfer experiment also
supported the exchange process. Irradiation of the C2H
7a
CH2CtCPh) with HPF6 in acetic anhydride gave cis-
η2-allene as the kinetic product, which was then isomer-
ized to the more stable trans-η2-allene species such as
D′ in Scheme 4 as the temperatures was raised. In
Scheme 4, the fresh acidification solution of compounds
1 and 2 consisted exclusively of cis-η2-allene species D,
which reacted with water to give syn-π-allyl complexes
3. In a prolonged reaction period, species D undergoes
isomerization to give trans-η2-allene D′ species via
intermediate D′′.13 The C2-C3 bond of D′′ can be

Carbonylation Reaction of W-Propargyl Compounds
Organometallics, Vol. 18, No. 4, 1999 751
Sch em e 4
In summary, we demonstrate two types of carbony-
lation reactions in the acidification solution of tungsten-
propargyl compounds 1 and 2 via treatment with water
and amines. The alternation of chemoselectivities is
probably due to the presence of different tungsten-η2-
allene cations, which respectively yield syn-π-allyl and
η1,η2-carboxylated olefin species such as 4-7, 8a , b, and
11a ,b. We have characterized new carbonylation prod-
ucts 4-7, 8a ,b, and 11a ,b with appropriate physical
methods including X-ray diffraction studies of the
representative compounds 5 and 8b. Variable-temper-
ature 1H NMR spectra show that the two diastereomers
11a and 11b can undergo mutual exchange at elevated
temperatures; the mechanism of exchange is proposed
to precede via dissociation of the coordinated olefin to
form a 16e species.
Exp er im en ta l Section
Unless otherwise noted, all reactions were carried out under
nitrogen atmosphere in oven-dried glassware using standard
syringe, cannula, and septa apparatus. Benzene, diethyl ether,
tetrahydrofuran, and hexane were dried with sodium ben-
zophenone and distilled before use. Dichloromethane was dried
over CaH2 and distilled before use. W(CO)6, dicyclopentadiene,
propargyl alcohol, and sodium were obtained commercially and
used without purification. Tungsten propargyl compounds 1,
2, and 9 were prepared according to the procedures in the
literature.7a,11
Syn th esis of Com p ou n d 4. To a CH2Cl2 solution (15 mL)
of compound 1 (200 mg, 0.52 mmol) was added CF3SO3H (160
mg, 1.05 mmol) at - 78 °C, and the mixture was stirred for 1
h before the reaction mixture was slowly warmed to room
temperature over 12 h. The solution was recooled to - 78 °C
and treated with saturated NaHCO3 (5.0 mL) solution. The
mixture was warmed to 23 °C and the organic layer was
extracted with diethyl ether twice (15 mL). The combined
organic extract was dried in vacuo and chromatographed on a
silica column to yield compound 4 as a yellow solid (120 mg,
0.29 mmol, 57%). IR (CH2Cl2, cm-1): ν(W-CO) 2003(s); 1930-
(s); 1639(br s). 1H NMR (CDCl3, 300 MHz): δ 5.45 (5H, s, Cp),
4.54 (1H, m, C3H), 3.82 (1H, m, C2H), 2.32 (1H, d, J ) 6.3 Hz,
C1H), 2.18 (1H, d, J ) 7.2 Hz, C1H), 1.46 (3H, d, J ) 6.1 Hz,
Me). 13C NMR (CDCl3, 100 MHz): δ 220.4, 214.0, 209.1, 90.9,
73.4, 73.2, 22.5, 16.0. MS (EI; 75 eV/m): 404 (M+). Anal. Calcd
for C12H12WO4: C, 35.67; H, 2.99. Found: C, 35.34; H, 3.13.
Syth esis of Com p ou n d 5. To a CH2Cl2 (15 mL) solution
of compound 2 (200 mg, 0.45 mmol) at - 78 °C was added CF3-
SO3H (134 mg, 0.89 mmol), and the mixture was stirred for 1
h before it was slowly warmed to 23 °C over 12 h. The reaction
mixture was recooled to - 78 °C and treated with NaHCO3
(3.0 mL), and the mixture was warmed to 23 °C over 6 h. The
organic layer was extracted with diethyl ether (15 mL) and
evaporated under reduced pressure. The crude product was
chromatographed on a silica column to yield compound 5 as a
F igu r e 3. NMR spectra of compounds 11a and 11b in
CDCl3 at various temperatures: (a) -10 °C, (b) 10 °C, (c)
25 °C, (d) 35 °C, (e) 45 °C.
attacked by water because it is coordinated to a tung-
sten fragment. We envisage that formation of new
carbonylation products such as 4 and 5 likely arises
from addition of water at the C3 carbon of D′′ to yield
the species G, and this process is proposed to be
reversible. Further cleavage of the W-vinyl bond of G
yields species H, which undergoes subsequent intramo-
lecular alkoxycarbonylation to give the observed prod-
ucts 4 and 5.
(13) Ben-Shoshan, R.; Petit, R. J . Am. Chem. Soc. 1967, 89, 2231.

752 Organometallics, Vol. 18, No. 4, 1999
Madhushaw et al.
yellow solid (130 mg, 0.27 mmol, 65%). IR (CH2Cl2, cm-1): ν-
Sp ectr a l Da ta for 8b: IR (CH2Cl2, cm-1): 1995(s), 1926-
(s), 1642(br). 1H NMR (CDCl3, 400 MHz): δ 7.44-7.27 (m, 9H,
Ph), 7.12 (1H, d, J ) 2.8 Hz, Ph), 5.66 (5H, s, Cp), 5.09 (1H,
m, NCH), 5.02 (1H, d, J ) 2.9 Hz, C3H), 3.87 (1H, m, C2H),
2.71 (1H, d, J ) 10.0 Hz), 2.49 (1H, d, J ) 8.4 Hz, CHH′), 1.64
(3H, d, J ) 7.2 Hz, CHH′). 13C NMR (CDCl3, 75 MHz): δ 224.0,
1
(W-CO) 2012(s), 1946(s), 1648. H NMR (CDCl3, 400 MHz):
δ 7.43-7.23 (5H, m, Ph), 5.51 (5H, s, Cp), 5.45 (1H, d, J ) 2.8
Hz, C3H), 4.00 (1H, m, C2H), 2.32 (1H, d, J ) 7.8 Hz, C1HH′),
2.30 (1H, d, J ) 7.8 Hz, C1HH′). 13C NMR (CDCl3, 100 MHz):
δ 219.9, 214.0, 207.8, 141.7, 128.4, 127.8, 126.2, 91.1, 79.0, 72.2,
15.9; MS (EI; 75 eV/m): 466 (M+). Anal. Calcd for C17H14
WO4: C, 43.80; H, 3.03. Found: C, 43.70; H, 3.02
-
216.3, 206.5, 143.6, 143.2, 128.7, 127.6, 127.5, 127.4, 91.7, 67.5,
25
66.4, 51.4, 17.3, 16.6. MS (EI+, 75 eV/m): 569 (M+). [R]D
)
98.6 (c ) 1.0, CH2Cl2). Anal. Calcd for C25H23WNO3: C, 52.74;
Syn th esis of Com p ou n d 6. To a CH2Cl2 solution (15 mL)
of compound 1 (200 mg, 0.52 mmol) at - 78 °C was added CF3-
SO3H (160 mg, 1.05 mmol), and the mixture was stirred for 1
h and then slowly warmed to 23 °C over 12 h. The reaction
mixture was recooled to - 78 °C and treated with isobuty-
lamine (73.6 mg, 1 mmol). The solution was warmed to 23 °C
with rapid stirring for 6 h. The organic material was extracted
with diethyl ether (15 mL) and evaporated to dryness under
reduced pressure. The crude product was then purified on a
silica column to yield compound 6 as a yellow solid (130 mg,
0.28 mmol, 55%). IR (CH2Cl2, cm-1): ν(CO) 1992(s), 1925(s),
1620(br s). 1H NMR (CDCl3, 400 MHz): δ 5.38 (5H, s, Cp),
3.76 (1H, m, C3H), 3.66 (1H, m, C2H), 3.46 (1H, m), 2.37 (1H,
m), 2.32 (1H, d, J ) 8.0 Hz, CHH′), 2.02 (1H, d, J ) 7.1 Hz,
CHH′), 1.70 (1H, m, CHMe2), 1.37 (3H, d, J ) 6.3 Hz, Me),
0.80 (3H, d, J ) 3.2 Hz, Me), 0.74 (3H, d, J ) 3.2 Hz, Me). 13C
NMR (CDCl3, 300 MHz: δ 225.2, 217.1, 205.7, 91.5, 68.7, 58.2,
48.8, 26.5, 24.2, 19.9, 18.1. MS (EI, 75 eV/m): 458(M+). Anal.
Calcd for C16H21WO3N: C, 41.85; H, 4.61; N, 3.05. Found: C,
41.88; H, 4.82; N, 3.01.
Syn th esis of Com p ou n d 7. To a CH2Cl2 solution (15 mL)
of compound 2 (200 mg, 0.45 mmol) at - 78 °C was added CF3-
SO3H (134 mg, 0.89 mmol), and the mixture was stirred for 1
h before it was slowly warmed to 23 °C over 12 h. The reaction
mixture was recooled to - 78 °C and treated with benzylamine
(982 mg, 9.16 mmol). The mixture was kept stirring for 8 h.
The solution was then quenched with water and washed with
saturated NH4Cl solution. The organic material was extracted
with diethyl ether (15 mL). The combined organic extract was
dried and evaporated under reduced pressure.The crude
product was then purified using preparative TLC (diethyl
ether/hexane, 1:1) to yield compound 7 as a yellow solid (100
mg, 0.18 mmol, 42%), IR (CH2Cl2, cm-1): 1992(s), 1925(s),
1638(br). 1H NMR (CDCl3, 300 MHz): δ 7.32-7.26 (2H, m,
Ph), 7.12-7.08 (6H, m, Ph), 6.78 (2H, m, Ph), 5.47 (5H, s, Cp),
5.23 (1H, d, J ) 13.0 Hz, NCHH,), 4.39 (1H, d, J ) 3.2 Hz,
C3H), 3.71 (1H, m, C2H), 3.10 (1H, d, J ) 13.0 Hz, NCHH′),
2.45 (1H, d, J ) 6.9 Hz, C1HH′), 2.27 (1H, d, J ) 6.6 Hz,
C1HH′). 13C NMR (CDCl3, 100 MHz): δ 223.4, 216.0, 207.0,
143.2, 132.6, 128.7, 128.4, 128.2, 127.2, 127.8, 127.7, 127.6,
126.6, 91.4, 68.1, 64.8, 45.2, 17.7. MS (EI, 75 eV/m): 550 (M+).
Anal. Calcd for C24H21WNO3: C, 51.91; H, 3.81; N, 2.52.
Found: C, 52.49; H, 3.97; N, 2.50.
H, 4.07; N, 2.46. Found: C, 52.55; H, 4.18; N, 2.51.
Syn th esis of Com p ou n d s 11a a n d 11b. To a CH2Cl2
solution (15.0 mL) of compound 9 (200 mg, 0.38 mmol) at -
78 °C was added CF3SO3H (115.8 mg, 0.77 mmol), and the
mixture was stirred for 1 h before it was warmed to room
temperature over 12 h. The reaction mixture was recooled to
-78 °C and treated with saturated NaHCO3 solution. This cold
solution was warmed to 23 °C over 24 h with rapid stirring.
The organic layer was separated, concentrated, and purified
on a silica column to yield compounds 11a and 11b as yellow
solids (116 mg, 0.21 mmol, 56%, 11a /11b ) 3:1). IR (CH2Cl2,
cm-1): 1995(s), 1928(s), 1637 (br). 1H NMR (CDCl3, 400
MHz): for 11a , δ 7.45-7.30 (10H, m), 5.36 (1H, d, J ) 2.9 Hz,
C3H), 4.12 (1H, m, C2H), 2.10 (15H, Me), 2.00 (1H, d, J ) 6.0
Hz, C1HH′), 1.60 (1H, 1H, d, J ) 6.0 Hz, C1HH′), for 11b, δ
7.45-7.30 (10H, m), 4.95 (1H, s, C3H), 3.12 (1H, m, C2H), 2.14
(15H, Me), the two C1H2 proton resonances were masked by
those of pentamethyl groups. 13C NMR (CDCl3, 100 MHz):
11a , 227.2, 218.0, 211.5, 142.0, 128.2, 127.6, 126.2, 103.1, 78.4,
75.7, 25.5, 10.6; 11b, 222.0, 211.5, 208.8, 142,5, 128.5, 127,4,
125.7, 101.5, 79.8, 50.7, 33.4, 10.6. Anal. Calcd for C22H24WO4:
C, 49.27; H, 4.51. Found: C, 49.68; H, 4.56.
Syn th esis of Com p ou n d 12. To a CH2Cl2 solution (15.0
mL) of compound 9 (200 mg, 0.38 mmol) at - 78 °C was added
CF3SO3H (116 mg, 0.77 mmol), and the mixture was stirred
for 1 h before it was warmed to room temperature over 12 h.
The reaction mixture was recooled to - 78 °C and treated with
benzylamine (2.0 mL). This cold solution was stirred and
warmed to 23 °C over 24 h. The organic layer was separated,
concentrated, and purified on a silica column to yield com-
pound 12 as yellow solid (118 mg, 0.18 mmol, 49%). IR (CH2-
Cl2, cm-1): 1993(s), 1927(s), 1608 (br). 1H NMR (CDCl3, 400
MHz): δ 7.35-7.10 (8H, m), 6.75-6.80 (2H, br s, Ph), 5.28
(1H, d, J ) 13.2 Hz, NCHH′), 4.20 (1H, d, J ) 3.4 Hz C1HH′),
3.88 (1H, m, C2H), 3.13 (1H, d, J ) 13.2 Hz, NCHH′), 2.10
(1H, s, Me), 1.56 (1H, d, J ) 5.2 Hz, C1HH′). 13C NMR (CDCl3,
100 Hz): 231.0, 220.3, 210.5, 143.6, 138.1, 128.8, 128.3, 127.8,
127.4, 126.4, 102.8, 71.7, 64.8, 45.0, 28.1, 10.5. MS (EI, 75 eV/
m): 625 (M+). Anal. Calcd for C29H31WNO3: C, 55.69; H, 4.02.
Found: C, 55.76; H, 4.14.
X-r a y Diffr a ction Stu d ies of 5 a n d 8b. Single crystals of
5 and 8b were sealed in glass capillaries under an inert
atmosphere. Data for 5 and 8b were collected on a Nonius CAD
4 using graphite-monochromated Mo KR radiation. The struc-
tures of 5 and 8b were solved by the heavy-atom method,
respectively; all data reduction and structural refinements
were performed with the NRCCSDP package. Crystal data,
details of data collection, and structural analysis of these three
compounds are presented in the Supporting Information. For
all structures, all nonhydrogen atoms were refined with
anisotropic parameters, and all hydrogen atoms included in
the structure factors were placed in idealized positions.
Syn th esis of Com p ou n d s 8a a n d 8b. To a CH2Cl2 solution
(15.0 mL) of compound 2 (200 mg, 0.45 mmol) at - 78 °C was
added CF3SO3H (134 mg, 0.89 mmol), and the mixture was
stirred for 1 h before it was warmed to room temperature over
12 h. The reaction mixture was recooled to -78 °C and treated
with (R-(+)-R-methylbenzylamine (752 mg, 6.2 mmol). The
solution was warmed to 23 °C over 24 h before treatment with
saturated NH4Cl solution (3.0 mL). The organic layer was
separated, concentrated, and purified on a silica column to
yield compounds 8a (71 mg, 0.12 mmol, 27%) and 8b (71 mg,
0.25 mmol, 28%), respectively.
Sp ectr a l Da ta for 8a : IR (CH2Cl2, cm-1): 1995(s), 1928-
(s), 1641(br). 1H NMR (CDCl3, 400 MHz): δ 7.14-7.04 (8H,
m, Ph), 6.81 (2H, d, J ) 5.8 Hz, Ph), 5.45 (5H, s, Cp), 5.12
(1H, m, NCH), 4.37 (1H, d, J ) 3.0 Hz, C3H), 3.73 (1H, m,
C2H), 2.55 (1H, d, J ) 8.0 Hz, C1HH′), 2.29 (1H, d, J ) 8.4 Hz,
C1HH), 1.05 (3H, d, J ) 7.2 Hz, Me). 13C NMR (CDCl3, 75
MHz): δ 224.1, 216.7, 206.0 144.1, 140.6, 128.6, 127.8, 127.7,
126.2, 91.6 (Cp), 68.1, 65.6, 51.0, 17.9, 17.3. MS (EI+, 75 eV/
Ack n ow led gm en t. We gratefully acknowledge fi-
nancial support of this work from the National Science
Council, Republic of China.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, atomic coordinates, and bond distances and angles of 5
and 8b. This material is available free of charge via the
Internet at http://pubs.acs.org.
m): 569 (M+). [R]D ) -6.3 (c ) 1.0, CH2Cl2). Anal. Calcd for
25
C
25H23WNO3: C, 52.74; H, 4.07; N, 2.46. Found: C, 52.63; H,
4.28; N, 2.53.
OM980787Q