Siloxy effect on intramolecular cyclization of tungsten-η1-siloxypropargyl complexes: Formation of 2,5-dihydrofurans versus γ-lactones

Article abstract of DOI:10.1021/om970335y

Treatment of tungsten-η¹-4-(triethylsiloxy)propargyl and η¹-4-(tripropylsiloxy)propargyl compounds 8a-d and 9a-d with CF₃CO₂H in cold CH₂Cl₂ yielded a mixture of tungsten η¹-2,5-dihydrofurans 1a-d and η³-syn-γ-lactones 4a-d. The product ratios depend on the types of alkyl and siloxy substituents of the propargyl ligand; η¹-2,5-dihydrofurans 10a-d were formed in significant amount when the substituent is a secondary alkyl group. This cyclization pathway is in sharp contrast to our previous report that the dimethyl-tertbutylsiloxy group yielded only η³-syn-γ-lactones 4a-d. To validate this reaction on a complex system, we prepared the chiral tungsten-η¹-4-(triethylsiloxy)propargyl species 12b, which ultimately gave optically active tungsten η¹-2,5-dihydrofuran 13 in 68percent yields. In connection with our previous report, we elaborated three types of cyclization reactions on chiral tungsten η¹-propargylic triols 12a-c, to afford chiral η¹-2,5-dihydrofurans and unsaturated γ- and δ-lactones in reasonable yields.

Full text of DOI:10.1021/om970335y

Organometallics 1997, 16, 3987-3992
3987
Siloxy Effect on In tr a m olecu la r Cycliza tion of
Tu n gsten -η1-Siloxyp r op a r gyl Com p lexes: F or m a tion of
2,5-Dih yd r ofu r a n s ver su s γ-La cton es
Shwu-J u Shieh, J ang-Shyang Fan, Malapaka Chandrasekharam, Fen-Ling Liao,
Sue-Lein Wang, and Rai-Shung Liu*
Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, ROC
Received April 22, 1997X
Treatment of tungsten-η1-4-(triethylsiloxy)propargyl and η1-4-(tripropylsiloxy)propargyl
compounds 8a -d and 9a -d with CF3CO2H in cold CH2Cl2 yielded a mixture of tungsten
η1-2,5-dihydrofurans 10a -d and η3-syn-γ-lactones 4a -d . The product ratios depend on the
types of alkyl and siloxy substituents of the propargyl ligand; η1-2,5-dihydrofurans 10a -d
were formed in significant amount when the substituent is a secondary alkyl group. This
cyclization pathway is in sharp contrast to our previous report that the dimethyl-tert-
butylsiloxy group yielded only η3-syn-γ-lactones 4a -d . To validate this reaction on a complex
system, we prepared the chiral tungsten-η1-4-(triethylsiloxy)propargyl species 12b, which
ultimately gave optically active tungsten η1-2,5-dihydrofuran 13 in 68% yields. In connection
with our previous report, we elaborated three types of cyclization reactions on chiral tungsten
η1-propargylic triols 12a -c, to afford chiral η1-2,5-dihydrofurans and unsaturated γ- and
δ-lactones in reasonable yields.
In tr od u ction
acidification of tungsten-η1-(dimethyl-tert-butylsiloxy)-
propargyl species 7a -d afforded the syn isomers of
tungsten η3-γ-lactones 4a -d in yields exceeding 80%
(Scheme 2). We now expand this reaction to those
tungsten complexes having different siloxy derivatives.
Scheme 3 shows the results for acidification of 8a and
9a under various conditions. An interesting finding
here is the formation of tungsten η1-2,5-dihydrofuran
10a in addition to the expected syn-η3-γ-lactone 4a .
These two compounds were easily separable on a silica
column; the isolated yields are provided in Scheme 3.
Both triethylsiloxy and tripropylsiloxy derivatives 8a
and 9a gave the products 10a and 4a with close 10a /
4a ratios, i. e. 1.42 and 1.42, respectively (entries 1 and
4). When the reactions were performed with CF3SO3H
or in CH3CN (entries 2 and 3), the resulting ratios 10a /
4b were 1.47 and 1.40, respectively, similar to that
(1.42) in entry 1.
Acid-promoted intramolecular alkoxycarbonylations
of tungsten-η1-propargyl complexes 1-3 led to forma-
tion of η3-γ, η3-δ-, and η3-ꢀ-lactones 4-6 in good yields;1,2
the reaction involved the tungsten-η2-allene cationic
intermediates A.1-5 Among these cyclizations, δ- and
ꢀ-lactones 5 and 6 followed anti and syn stereoselec-
tions1,2 respectively, whereas the η3-γ-lactone 4 was
formed in 1:1 diastereomeric mixtures.1,2 The selectivity
problem of 4 can be circumvented by introduction of a
dimethyl-tert-butylsiloxy group on these η1-propargyl
species such as 7 (Scheme 1, path 2), leading to syn
stereoselection of η3-γ-lactone 4;1,2 the reaction requires
small amounts of H2O and CF3SO3H (optimum condi-
tions: H2O, 0.8-1.0 equiv; CF3SO3H, 0.30 equiv). The
overall reaction is shown in path 2 of Scheme 1; the
proposed formation mechanism of syn η3-γ-lactones 4
is supported by results obtained from isotopic H2O* (O*
)
18O) labeling as well as by isolation of the key η3-2-
We extended the reactions to other tungsten trieth-
ylsiloxy and tripropylsiloxy complexes 8b-d and 9b-
d ; the results were summarized in Scheme 4. Entries
1-3 show the product ratios of 10n /4n (n ) b-d) for
η1-triethylsiloxy derivatives 8b-d having different alkyl
substituents R′. A small ethyl group as in compound
8a gave a low 10b/4b ratio, ca. 0.44 (entry 1) in favor
of the η3-γ-lactone. The 10b/4b ratio increases gradu-
ally with increasing alkyl sizes, i.e. 0.65 for 8b (entry
2, R′ ) MeCdCH2) and 0.90 for 8c (entry 3, R′ )
cyclohexyl). Entries 4-6 show the results for the
tripropylsiloxy derivatives 9b-d ; the 10b/4b ratio was
1.2 for compound 9b (R′ ) Et), significantly larger than
that (10b/4b ) 0.43) for its triethylsiloxy analogue 8b.
In entries 5 and 6, attempts to improve the selectivity
of η1-2,5-dihydrofuran were less pronounced for 9c and
9d ; the product ratios 10c/4c ) 0.64 and 10d /4d ) 0.93
were very close to those of their triethylsiloxy analogues
8c and 8d (entries 2 and 3).
carboxyallyl intermediate.1,2 To study thoroughly the
drastic impact of the siloxy group, we report here a new
cyclization of these propargyl complexes with alteration
of their tethered siloxy groups.
Resu lts a n d Discu ssion
As shown in Scheme 2, tungsten-η1-propargyl com-
pounds 1a -d were readily converted to their triethyl-
and tripropylsiloxy derivatives 8a -d and 9a -d in high
yields (>90%). We previously reported1,2 that CF3SO3H
X Abstract published in Advance ACS Abstracts, August 1, 1997.
(1) Chen, C.-C.; Fan J .-S.; Lee, G.-H.; Peng, S.-M.; Wang, S.-L.; Liu,
R.-S. J . Am. Chem. Soc. 1995, 117, 2933.
(2) Chen, C.-C.; Fan J .-S.; Lee, G.-H.; Peng, S.-M.; Wang, S.-L.; Liu,
R.-S. J . Am. Chem. Soc. 1996, 118, 9279.
(3) Charrier, C.; Collin, J .; Merour, J . Y.; Roustan, J . L. J . Orga-
nomet. Chem. 1978, 162, 57.
(4) Cheng, M.-H.; Ho, Y. H.; Chen, C. H.; Lee, G. H.; Peng, S. M.;
Chu, S. Y.; Liu, R. S. Organometallics 1994, 13, 4082.
(5) Lin, S.-H.; Vong, W.-J .; Liu, R.-S. Organometallics 1995, 14,
1619.
The siloxy effect on these cyclization reactions could
be potentially useful for the synthesis of various lactones
S0276-7333(97)00335-X CCC: $14.00 © 1997 American Chemical Society

3988 Organometallics, Vol. 16, No. 18, 1997
Shieh et al.
Sch em e 1
Sch em e 2
F igu r e 1. ORTEP drawing of compound 13. Selected bond
lengths (Å): W(1)-C(10) ) 2.247(4), C(9)-C(10) ) 1.330
(7), C(10)-C(11) ) 1.501(7), C(11)-O(4) ) 1.441(7), C(12)-
O(4) ) 1.410 (7).
Sch em e 3
F igu r e 2. ORTEP drawing of compound 14-a n ti. Selected
bond lengths (Å): W(1)-C(10) ) 2.301(15), W(1)-C(12) )
2.287(16), W(1)-C(10) ) 2.301(15), C(10)-C(12) ) 1.418-
(20), C(11)-C(12) ) 1.416(21), C(13)-O(6) ) 1.190(19).
and dihydrofurans. Toward this direction, we prepared
the chiral chloropropargylic triol6 11a , which was
subsequently transformed into 11b and 11c in 92% and
96% yields, respectively. As shown in Scheme 5, treat-
ment of 11a -c with CpW(CO)3Na7 afforded η1-(trieth-
ylsiloxy)propargyl species 12a -c in good yields (>85%).
In contrast with 8a -d , the triethylsiloxy effect was very
significant in acidification of 12b with CF3CO2H (0.25
equiv), so that chiral 2,5-dihydrofuran 13 was formed
as the major product (68% yield) in addition to a small
amount of the η3-γ-lactone 14-syn (5% yield). If one
equiv of CF3CO2H was used, the yields of 13 and 14
were 61% and 10%, respectively. The X-ray structure8
of 13 is given in Figure 1 to confirm its absolute
configuration. By our previous method given in Scheme
1 (path 1), CF3SO3H-promoted lactonization of 12a
afforded the two diastereomers 14-syn and 14-a n ti that
were separable on a silica column in 33% and 38%
yields, respectively. Figure 2 shows the X-ray structure9
of 14-a n ti to confirm its configuration. Treatment of
(8) Crystal data for compound 13: orthorhombic, space group
P212121, a ) 7.1921(3) Å, b ) 10.1576(5) Å, c ) 23.9737(11) Å, Z ) 4,
V ) 1751.37(23) Å3, final R ) 0.0186, Rw ) 0.0193.
(9) Crystal data for compound 14-a n ti: orthorhombic, space group
P21212, a ) 21.7945(4) Å, b ) 21.8583(2) Å, c ) 7.1876(1) Å, Z ) 8, V
) 3424.1(11) Å3, final R ) 0.0465, Rw ) 0.0434.
(6) Yadav, J . S.; Chander, M. C.; Rao, C. S. Tetrahedron Lett. 1989,
30, 5455.
(7) Fischer, E. O.; Hafner, W.; Stahl, H. O. Z. Anorg. Allg. Chem.
1955, 282, 47.

Siloxy Effect on Cyclization of W Complexes
Organometallics, Vol. 16, No. 18, 1997 3989
Sch em e 4
reactions. As shown in Scheme 7, I2 oxidative demeta-
lation14 of chiral η1-2,5-dihydrofuran 13 in MeOH af-
forded unsaturated ester 17 in 45% yield. Treatment
of a syn and anti diastereomeric mixture of η3-γ-lactone
14 with NOBF4 yielded an allyl cation15-17 that reacted
with Bu4NBH4 to afford chiral furanone 18 in 58% yield.
A similar transformation of chiral η3-δ-lactone 16 into
unsaturated δ-lactone 19 was achieved in 63% yield.
In conclusion, we have reported the effect of the siloxy
group in the intramolecular cyclization of tungsten
propargylic alcohol. The products may be syn-η3-γ-
lactones and η3-2,5-dihydrofuran. As described before,
utilization of the dimethyl-tert-butylsiloxy group only
yielded an η3-γ-lactone. Formation of η1-2,5-dihydro-
furan was favored by increasing sizes of siloxy groups
and alkyl substituents of the propargyl ligands. Toward
this direction, we prepared the large chiral chloropro-
pargylic alcohol 11, which afforded chiral η1-2,5-dihy-
drofuran in good yield. In connection with our previous
investigation, we also demonstrated that this chiral
chloropropargylic alcohol 11 could ultimately give opti-
cally active unsaturated γ- and ꢀ-lactones in reasonable
yields.
the methyl ether species 12c with CF3SO3H (0.25 equiv)
under similar conditions afforded the η3-δ-lactone 15-
a n ti exclusively in 76% yield. The anti and syn
configurations of 15 refer to the orientation of the
methoxy group relative to CpW(CO)2. Characterization
of the structure of 15-a n ti relies on the X-ray diffraction
study10 of its acetyl derivative 16 that has better crystal
quality; the molecular structure of 16 is shown in Figure
3 to reveal that the methoxy group of 15-a n ti lies away
from the bulky CpW(CO)2 fragment to minimize their
mutual steric interactions. In contrast with 10a -d ,
compound 13 was obtained in high yields (68%); this is
probably due to steric interaction of dioxolane group that
forces triethylsiloxy group tilt toward the tungsten-
allene carbon to induce a cyclization reaction. According
to this conformation effect, we propose that tungsten-
η1-2,5-dihydrofurans are formed more favorably when
the starting propargyl species 8a -d and 9a -d have a
sterically demanding alkyl substituent R′ and siloxy
group OSiR′′3. This model accounts for most of the
product ratios shown in Scheme 4 as R′ and OSiR′′3 were
modified.
The X-ray structure of optically active η1-2,5-dihy-
drofuran 13 enables us to propose its formation mech-
anism as shown in Scheme 6. The Cδ carbon of 13 has
an S configuration, implying retention of stereochem-
istry with respect to the Cδ carbon of 12b. The cycliza-
tion reaction can be envisaged to proceed via protonation
at the tCγ carbon11-13 of 12b, yielding the η2-allene
cationic intermediate A. We believe that the the η2-
allene carbon of A is highly electrophilic,10-12 reacting
with its siloxy oxygen to yield the trioxonium species
B; further cleavage of the Si-O bond of B is achieved
by counterion X. A competitive reaction here is the
formation of the γ-lactone 14-syn that was very difficult
to annihilate because the formation is accelerated by a
catalytic amount of water; elucidation of the mechanism
including the intermediate C has been described in our
previous study.1,2
Exp er im en ta l Section
Unless otherwise noted, all reactions were carried out under
a nitrogen atomsphere 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, CF3CO2H,
CF3SO3H, propargyl chloride, and sodium were obtained
commercially and used without purification. Syntheses of
compounds 1-6 were reported in our previous paper. Elemen-
tal analyses were performed at National Cheng Kung Uni-
versity, Taiwan. The synthetic scheme and characterization
of 11a -c were provided in the Supporting Information of our
previous paper.
(1) Gen er a l P r oced u r e for Syn th eses of Tu n gsten -η1-
(Tr ieth ylsiloxy)p r op a r gyl Com p lexes. Syn th esis of 8a .
To a DMF solution (30 mL) of 1a (1.20 g, 2.70 mmol) and
imidazole (370 mg, 5.40 mmol) was added triethylsilyl chloride
(450 mg, 3.00 mmol); the mixture was stirred for 8 h before
sequential addition of aqueous NaCl (25 mL). The solution
was extracted with diethyl ether (3 × 20 mL) and flash-
chromatographed through a short silica column to yield 8a as
a yellow oil (1.50 g, 2.56 mmol, 95%). IR (neat, cm-1): ν(CO)
2018 (vs), 1921 (vs). 1H NMR (300 MHz; CDCl3): δ 5.48 (s,
5H, Cp), 4.15 (m 1H, OCH), 2.01 (d, J ) 2.1 Hz, 2H, W-CH2),
1.76 (m, 1H, CHMe2), 0.94 (m, 15H, CHMe2 + SiCH2CH3), 0.64
(m, 6H, Si(CH2CH3)3). 13C NMR (75 MHz; CDCl3): δ 229.1,
216.2, 93.8, 92.5, 80.6, 68.1, 18.4, 17.6, 6.8, 4.9, -32.1. MS
(75 eV; m/ e): 530 (M+ - 28).
(2) Syn th esis of 8b. Compound 1b (1.50 g, 3.50 mmol),
imidazole (480 mg, 7.00 mmol), and triethylsilyl chloride (580
mg, 3.80 mmol) afforded 8b as a yellow oil (1.83 g, 3.36 mmol,
96%). IR (neat, cm-1): ν(CO) 2018 (vs), 1921 (vs). 1H NMR
(300 MHz; CDCl3): δ 5.49 (s, 5H, Cp), 4.30 (m, 1H, OCH), 1.99
(d, J ) 2.2 Hz, 2H, W-CH2), 1.63 (m; 2H, CH2), 0.95 (m, 12H,
CH2CH3 + SiCH2CH3), 0.63 (m, 6H, SiCH2CH3). 13C NMR (75
Scheme 5 shows the formation of the three tungsten
η1-heterocycles 13, 14-syn ,a n ti, and 15, derived from
the chiral chloropropargylic triol 11a ; these organome-
tallics ultimately provide optically active 2,5-dihydro-
furans, unsaturated γ- and δ-lactones, and demetalation
(14) Shu, H.-G.; Shiu, L.-H.; Wang, S.-H.; Wang, S.-L.; Lee, G.-H.;
Peng, S.-M.; Liu, R.-S. J . Am. Chem. Soc. 1996, 118, 530.
(15) Faller, J . W.; Rosan, A. M. Ann. N. Y. Acad. Sci. 1977, 295,
186.
(16) Faller, J . W.; Chodosh, D. F.; Katahira, D. J . Organomet. Chem.
1980, 187, 227.
(10) Crystal data for compound 16: monoclinic, space group P21,
a ) 8.0692(2) Å, b ) 9.5150(2) Å, c ) 12.0951(4) Å, z ) 2, V ) 879.6(3)
Å3, final R ) 0.0396, Rw ) 0.0420.
(11) Giulieri, F.; Benaim, J . Nouv. J . Chem. 1985, 9, 335.
(12) Giulieri, F.; Benaim, J . J . Organomet. Chem. 1984, 276, 367.
(13) Rosenblum, M.; Watkins, J . C. J . Am. Chem. Soc. 1990, 112,
6316.
(17) Adams, R. D.; Chodosh, D. F.; Faller, J . W.; Rosan, A. M. J .
Am. Chem. Soc. 1979, 101, 2570.

3990 Organometallics, Vol. 16, No. 18, 1997
Shieh et al.
Sch em e 5
Sch em e 7
F igu r e 3. ORTEP drawing of compound 16. Selected bond
lengths (Å): W(1)-C(8) ) 2.285(11), W(1)-C(1) ) 1.994-
(11), W(1)-C(10) ) 2.267(11), C(9)-C(8) ) 1.416(16), C(9)-
C(10) ) 1.413(17), C(13)-O(5) ) 1.206(14).
0.64 (m, 6H, SiCH2CH3). 13C NMR (75 MHz; CDCl3): δ 229.0,
216.3, 216.2, 146.2, 110.3, 94.3, 92.6, 81.6, 67.1, 17.8 (C7), 6.8,
4.8, -32.3. MS (75 eV; m/ e): 556 (M+).
Sch em e 6
(4) Syn th esis of 8d . Compound 1d (2.00 g, 4.1 mmol),
imidazole (560 mg, 8.2 mmol), and triethylsilyl chloride (680
mg, 4.5 mmol) afforded 8d as a yellow oil (2.32 g, 3.89 mmol,
95%). IR (neat, cm-1): ν(CO) 2018 (s), 1921 (s). 1H NMR (300
MHz; CDCl3): δ 5.48 (s, 5H, Cp), 4.15 (m, 1H, OCH), 2.01 (d,
J ) 2.2 Hz, 2H, W-CH2), 1.83-1.63, 1.23-1.03 (m, 11H,
cyclohexyl), 0.96 (m, 9H, SiCH2CH3), 0.62 (m, 6H, Si(CH2-
CH3)3). 13C NMR (75 MHz; CDCl3): δ 229.1, 216.2, 93.9, 92.6,
81.1, 68.1, 45.7, 29.0, 28.4, 26.6, 26.1, 6.9, 4.9, -32.0. MS (75
eV; m/ e): 570 (M+ - 28).
(5) Syn th esis of 9a . Compound 1a (1.50 g, 3.37 mmol),
imidazole (460 mg, 6.74 mmol), and tripropylsilyl chloride (710
mg, 3.7 mmol) afforded 9a as a yellow oil (1.94 g, 3.24 mmol,
96%). IR (neat, cm-1): ν(CO) 2019 (s), 1931 (s). 1H NMR (300
MHz; CDCl3): δ 5.46 (s, 5H, Cp), 4.15 (m, 1H, OCH), 2.00 (d,
J ) 2.2 Hz, 2H, W-CH2), 1.73 (m, 1H, CHMe2), 1.43-1.33
(m, 6H, (SiCH2CH2CH3), 0.97-0.91 (m, 15H, Si(CH2CH2CH3)
+ 2Me), 0.66-0.59 (m, 6H, SiCH2CH2CH3). 13C NMR (75
MHz; CDCl3): δ 229.1, 216.2, 93.9, 92.6, 80.6, 68.8, 35.9, 18.6,
18.4, 16.7, -32.1. MS (75 eV; m/ e): 600 (M+).
(6) Syn th esis of 9b. Compound 1b (1.50 g, 3.48 mmol),
imidazole (475 mg, 6.96 mmol), and tripropylsilyl chloride (736
mg, 3.83 mmol) afforded 9b as a yellow oil (1.98 g, 3.37 mmol,
97%). IR (neat, cm-1): ν(CO) 2012 (s), 1912 (s). 1H NMR (300
MHz; CDCl3): δ 5.47 (s, 5H, Cp), 4.25 (m, 1H, OCH), 1.98 (d,
J ) 2.2 Hz, 2H, W-CH2), 1.62 (m, 2H, CH2), 1.43-1.33 (m,
6H, SiCH2CH2CH3, 0.94 (m, 12H, SiCH2CH2CH3 + Me), 0.64-
0.58 (m, 6H, SiCH2CH2CH3). 13C NMR (75 MHz; CDCl3): δ
MHz; CDCl3): δ 229.1, 216.3, 93.2, 92.6, 81.8, 64.6, 32.6, 9.7,
6.8, 4.8, -32.3. MS (75 eV; m/ e): 544 (M+).
(3) Syn th esis of 8c. Compound 1c (1.20 g, 2.70 mmol),
imidazole (370 mg, 5.40 mmol), and triethylsilyl chloride (450
mg, 3.00 mmol) afforded 8c as a yellow oil (1.40 g, 2.52 mmol,
93%). IR (neat, cm-1): ν(CO) 2020 (s), 1918 (s). 1H NMR (300
MHz, CDCl3): δ 5.48 (s, 5H, Cp), 5.04 (s, 1H, dCHH′), 4.80 (s,
1H, dCHH′); 4.78 (d, J ) 2.2 Hz, 1H, OCH), 1.98 (d, J ) 2.2
Hz, 2H, WsCH2), 1.82 (s, 3H, Me), 0.95 (m, 9H, SiCH2CH3),

Siloxy Effect on Cyclization of W Complexes
Organometallics, Vol. 16, No. 18, 1997 3991
228.9, 216.1, 93.2, 92.5, 81.8, 64.6, 32.6, 18.5, 18.3, 17.0, 9.6,
-32.3. MS (75 eV; m/ e): 586 (M+).
(75 eV; m/ e): 484 (M+). Anal. Calcd for C18H20WO4: C, 44.65;
H, 4.16. Found: C, 44.80; H, 4.22.
(7) Syn th esis of 9c. Compound 1c (1.40 g, 3.16 mmol),
imidazole (430 mg, 6.32 mmol), and tripropylsilyl chloride (670
mg, 3.47 mmol) afforded 9c as a yellow oil (1.8 g, 3.0 mmol,
95%). IR (neat, cm-1): ν(CO) 2021 (s), 1923 (s). 1H NMR (300
MHz; CDCl3): δ 5.46 (s, 5H, Cp), 5.45 (s, 1H, dCHH′), 5.02 (s,
1H, CHH′), 4.78 (s, 1H, OCH), 1.98 (d, J ) 2.2 Hz, 2H,
WsCH2), 1.82 (s, 3H, C5H), 1.44-1.28 (m, 6H, SiCH2CH2CH3),
0.97-0.91 (m, 9H, SiCH2CH2CH3), 0.65-0.60 (m, 6H, SiCH2-
CH2CH3). 13C NMR (75 MHz; CDCl3): δ 228.9, 216.1, 146.2,
110.2, 94.2, 92.5, 80.4, 67.1, 18.6, 18.3, 17.7, 16.7, -32.3. MS
(75 eV; m/ e): 598 (M+).
(8) Syn th esis of 9d . Compound 1d (1.6 g, 3.3 mmol),
imidazole (450 mg, 6.6 mmol), and tripropylsilyl chloride (700
mg, 3.63 mmol) afforded 9d as a yellow oil (2.05 g, 3.2 mmol,
97%). IR (neat, cm-1): ν(CO) 2023 (s), 1927 (s). 1H NMR (300
MHz; CDCl3): δ 5.46 (s, 5H, Cp), 4.12 (m, 1H, C4H), 2.00 (d,
J 14 ) 2.0 Hz, 2H, C1H), 1.75-1.65, 1.42-1.27, 1.25-1.01, 0.96-
0.90, 0.65-0.58 (m, 32H, cyclohexyl + OTPS). 13C NMR (75
MHz; CDCl3): δ 229.1, 216.2 (3W-CO), 93.9 (C3), 92.6 (Cp),
81.0 (C2), 68.1 (C4), 45.7 (C5), 28.9, 28.2, 26.6, 26.1, 25.9
(cyclohexyl), 18.6 (Si(CH2CH2CH3)3), 18.5 (Si(CH2CH2CH3)3),
16.8 (Si(CH2CH2CH3)3), -32.0 (C1). MS (75 eV; m/ e): 640
(M+).
(13) Syn th esis of Ch ir a l Tu n gsten -η1-P r op a r gyl Com -
p lex 12a . To a THF solution (50 mL) of CpW(CO)3Na (5.25
g, 14.7 mmol) was slowly added the chloropropargylic triol6
11a (3.00 g, 14.7 mmol) in THF (5.0 mL); the mixture was
stirred for 5 h at 23 °C. The solution was evaporated to
dryness, and the residue was chromatographed on a silica
column to yield 12a as a yellow solid (6.50 mg, 13.1 mmol).
[R] ) 7.20° (c ) 0.50, CH2Cl2). IR (Nujol, cm-1): 3445 (vs),
ν(CO) 2015 (s), 1920 (s). 1H NMR (400 MHz, CDCl3): δ 5.48
(s, 5H, Cp), 4.39 (dt, J ) 4.7, 2.3 Hz, 1H, OCH), 4.08 (ddd, J
) 11.2, 6.1, 4.7 Hz, 1H, OCH), 4.02-3.92 (m, 2H, OCH2), 1.91
(d, J ) 2.3 Hz, 2H, W-CH2). 13C NMR (100 MHz, CDCl3): δ
228.6, 216.5, 109.6, 95.9, 91.2, 78.9, 77.9, 65.5, 62.8, 26.5, 26.2,
-33.2. MS (EI, 12 eV; m/ e): 502 (M+).
(14) Syn th esis of 12b. Optically active chloropropargylic
triol 11b (2.00 g, 6.30 mmol) and CpW(CO)3Na (2.30 g, 6.30
mmol) afforded 12b (3.56 g, 5.78 mol) as a yellow solid. [R] )
33.5° (c ) 0.33, CH2Cl2). IR (Nujol, cm-1): ν(CO) 2013 (s), 1918
(s). 1H NMR (400 MHz, C6D6): δ 4.78 (s, 5H, Cp), 4.52 (dt, J
) 5.3, 2.1 Hz, 1H, SiOCH), 4.10-4.06 (m, 3H, OCH + OCH2),
1.93 (d, J ) 2.1 Hz, 2H, W-CH2), 1.45 (s, 3H, CH3), 1.30 (s,
3H, CH3), 1.07 (t, J ) 8.0 Hz, 9H, SiCH2CH3), 0.74 (q, J ) 8.0
Hz, 6H, SiCH2CH3). 13C NMR (100 MHz, C6D6): δ 229.4,
216.6, 100.6, 92.5, 95.3, 79.9, 80.3, 66.6, 64.9, 27.0, 25.7, 6.9,
5.5, -32.5. MS (EI, 12 eV; m/ e): 616 (M+), 588 (M+ - CO),
560 (M+ - 2CO).
(15) Syn th esis of 12c. Optically active chloropropargylic
triol 11c (2.00 g, 6.30 mmol) and CpW(CO)3Na (4.00 g, 11.23
mmol) afforded 12c (4.38 g, 9.21 mmol) as a yellow solid. [R]
) 29.5° (c ) 0.25, CH2Cl2). IR (Nujol, cm-1): ν(OH) 3444 (vs),
ν(CO) 2016 (s), 1915 (s). 1H NMR (400 MHz, CDCl3): δ 5.47
(s, 5H, Cp), 4.13 (dt, J ) 5.5, 2.3 Hz, 1H, OCH), 3.83 (q, J )
6.0 Hz, 1H, OCH), 3.75-3.69 (m, 2H, OCH2), 3.39 (s, 3H,
OCH3), 1.97(d, J ) 2.3 Hz, 2H, W-CH2). 13C NMR (100 MHz,
CDCl3): δ 228.1, 216.7, 92.4, 92.0, 74.9, 74.6, 73.3, 63.4, 56.6.
-32.1. MS (EI, 12 eV; m/ e): 476 (M+).
(9) Gen er a l P r oced u r e for Syn th eses of Cp W(CO)3(η1-
2,5-d ih yd r ofu r a n ) Com p ou n d s. Syn th esis of 10a . In a
typical reaction, to a cold CH2Cl2 (-40 °C) solution (20 mL) of
8a (480 mg, 0.86 mmol) was added CF3CO2H (98 mg, 0.86
mmol), and the mixture was stirred for 4 h before the
temperature was raised to 0 °C. To this solution was added a
saturated NaHCO3 solution, followed by evaporation to half
its volume. The organic layer was extracted with diethyl ether
(2 × 20 mL), concentrated, and eluted through a silica column
(diethyl ether/hexane, 1/1) to give 10a (Rf 0.4, 141 mg, 0.32
mmol, 37%) and 4a (Rf 0.60, 99 mg, 0.22 mmol, 26%). Spectral
data for 10a : IR (Nujol, cm-1) ν(CO) 2023 (s), 1930 (s); 1H NMR
(300 MHz; C6D6) δ 5.70 (br s, 1H, dCH), 4.7 (m, 1H, OCH),
4.63 (m, 2H, OCH2), 4.50 (s, 5H, Cp), 1.85 (m, 1H, CHMe2),
(16) In tr a m olecu la r Cycliza tion of 12a . Compound 12a
(2.50 g, 4.98 mmol) and CF3CO2H (1.25 mmol) in cold CH2Cl2
(-40 °C) afforded 14-a n ti (825 mg, 1.64 mmol, 33%) and 14-
syn (950 mg, 1.89 mol, 38%) after chromatographic separation.
Spectral data for 14-syn : [R] ) -47.5° (c ) 0.10, CH2Cl2);
1.02 (t, J ) 6.8 Hz, 3H, Me), 1.00 (t, J ) 6.8 Hz, 3H, Me); 13
C
NMR (75 MHz; C6D6) δ 228.4, 216.9, 216.8, 141.6, 118.7, 92.7,
90.9, 89.2, 34.6, 18.6, 18.1; MS (EI, 12 eV; m/ e) 472 (M+). Anal.
Calcd for C15H16WO4: C, 40.57; H, 3.67. Found: C, 40.68; H,
3.70.
1
IR (neat, cm-1) ν(CO) 2018 (s), 1917 (s); H NMR (400 MHz,
(10) Syn th esis of 10b. Compound 8b (510 mg, 0.94 mmol)
and CF3CO2H (107 mg, 0.94 mmol) in cold CH2Cl2 (-40 °C)
afforded 10b (86 mg, 0.20 mmol, 21%) and 4b (194 mg, 0.45
mmol, 48%). IR (neat, cm-1): ν(CO) 2012 (s), 1912 (s). 1H
NMR (300 MHz; CDCl3): δ 5.65 (br s, 1H, dCH), 5.48 (s, 5H,
Cp), 4.65 (m, 1H, OCH), 4.50 (m, 2H, OCH2), 1.48 (m, 2H, CH2),
0.85 (t, J ) 7.4 Hz, 3H, CH3). 13C NMR (75 MHz; CDCl3) δ
227.1, 216, 142.7, 117.5, 91.2, 88.6, 88.3, 29.1, 9.1. MS (EI,
12 eV; m/ e): 430 (M+). Anal. Calcd for C14H14WO4: C, 39.10;
H, 3.28. Found: C, 39.28; H, 3.17.
(11) Syn th esis of 10c. Compound 8c (500 mg, 0.90 mmol),
and CF3CO2H (103 mg, 0.90 mmol) in cold CH2Cl2 (-40 °C)
afforded 10c (104 mg, 0.23 mmol, 26%) and 4c (160 mg, 0.36
mol, 40%). IR (neat, cm-1): ν(CO) 2013 (s), 1912 (s). 1H NMR
(300 MHz; CDCl3): δ 5.54 (br s, 1H, dCH), 5.49 (s, 5H, Cp),
4.87 (s, 1H, dCHH′), 4.74 (s, 1H, dCHH′), 4.57 (m, 2H, C1H),
1.59 (s, 3H, C7H). 13C NMR (75 MHz; CDCl3): δ 226.8, 216.0,
147.1, 141.1, 118.7, 110.8, 93.9, 91.0, 89.5, 17.0. MS (EI, 12
eV; m/ e): 442 (M+). Anal. Calcd for C15H14WO4: C, 40.75;
H, 3.19. Found: C, 40.45; H, 3.11.
CDCl3) δ 5.32 (s, 5H, Cp), 4.86 (dd, J ) 9.2, 3.9 Hz, 1H, OCH),
4.11-4.00 (m, 2H, OCH2), 3.76 (d, J ) 3.9 Hz, 1H, η3-CH),
3.48 (dt, J ) 9.2, 5.0 Hz, 1H, OCH), 3.05 (d, J ) 4.0 Hz, 1H,
η3-CHH′), 1.49 (d, J ) 4.0 Hz, 1H, η3-CHH′), 1.45 (s, 3H, CH3),
1.36 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3) δ 221.9, 220.5,
176.1, 110.0, 93.5, 81.0, 79.5, 68.8, 67.4, 65.4, 27.0, 25.3, 20.0;
MS (75 eV; m/ e) 502 (M+), 474 (M+ - CO). Anal. Calcd for
C
17H18WO6: C, 40.66; H, 3.61. Found: C, 40.65; H, 3.77.
Spectral data for 14-a n ti: [R] ) 66.9° (c ) 0.25, CH2Cl2);
IR (neat, cm-1): ν(CO) 1956 (vs), 1887 (vs); 1H NMR (400 MHz,
CDCl3) δ 5.33 (s, 5H, Cp), 4.42 (d, J ) 6.8 Hz, 1H, OCH), 4.16-
4.02 (m, 3H, OCH + OCH2), 3.65 (s, 1H, η3-CH), 3.05 (d, J )
4.0 Hz, 1H, η3-CHH′), 1.47 (d, J ) 4.0 Hz, 1H, η3-CHH′), 1.41
(s, 3H, CH3), 1.33 (s, 3H, CH3); 13C NMR (100 MHz, CDCl3) δ
224.7, 218.8, 176.0, 110.4, 93.8, 83.0, 82.8, 78.1, 68.1, 62.9, 26.7,
24.9, 20.9; MS (75 eV; m/ e) 502 (M+), 474 (M+ - CO). Anal.
Calcd for C17H18WO6: C, 40.66; H, 3.61. Found: C, 40.55; H,
3.76.
(17) In tr a m olecu la r Cycliza tion of 12b. Compound 12b
(3.00 g, 4.87 mmol) and CF3CO2H (0.10 mL, 1.22 mmol) in cold
CH2Cl2 (-40 °C) afforded 13 (1.66 g, 3.31 mmol, 68%) and 14-
syn (0.12, 0.24 mmol, 5%) after chromatographic separation.
[R] ) -9.5° (c ) 0.44, CHCl3). IR (neat, cm-1): ν(CO) 2025
(s), 1919 (s), 1457, 1371. 1H NMR (400 MHz, CDCl3): δ 5.71
(t, J ) 1.5 Hz, 1H, dCH), 5.45 (s, 5H, Cp), 4.64 (dd, J ) 6.0,
1.5 Hz, 1H, OCH), 4.50 (dd, J ) 4.4, 2.2 Hz, 2H, OCH2), 3.98
(dd, J ) 7.7, 6.4 Hz, 1H, OCH), 3.88 (q, J ) 6.2 Hz, 1H,
OCHH′), 3.78 (dd, J ) 7.7, 5.8 Hz, 1H, OCHH′), 1.40 (s, 3H,
(12) Syn th esis of 10d . Compound 8d (600 mg, 1.00 mmol)
and CF3CO2H (114.0 mg, 1.00 mmol) in cold CH2Cl2 (-40 °C)
afforded 10d (145.6 mg, 0.30 mmol, 30%) and 4d (131 mg, 0.27
mmol, 27%). IR (neat, cm-1): ν(CO) 2012 (s), 1912 (s). 1H
NMR (300 MHz; CDCl3): δ 5.64 (d, J ) 2.0 Hz, 1H, dCH),
5.46 (s, 5H, Cp), 4.45 (m, 3H, OCH + OCH2), 1.69-0.91 (m,
11H, cyclohexyl). 13C NMR (75 MHz; CDCl3): δ 227.1, 216.1,
141.3, 117.3, 91.7, 91.1, 88.6, 44.1, 28.7, 28.3, 26.6, 26.2. MS

3992 Organometallics, Vol. 16, No. 18, 1997
Shieh et al.
CH3), 1.33 (s, 3H, CH3). 13C NMR (100 MHz, CDCl3): δ 226.6,
216.0, 138.9, 120.9, 109.8, 91.2, 89.4, 87.7, 78.7, 66.5, 26.6, 25.3.
MS (75 eV; m/ e): 502 (M+). Anal. Calcd for C17H18WO6: C,
40.66; H, 3.61. Found: C, 40.75; H, 3.77.
(21) Syn th esis of Un sa tu r a ted γ-La cton e 18. To a
mixture of 14-syn and 14-a n ti (500 mg, 0.996 mmol) in CH3-
CN (5.0 mL, 0 °C) was added NOBF4 (115 mg, 0.996 mmol),
and the mixture was stirred for 20 min. To the resulting
solution was added Bu4NBH4 (320 mg, 1.25 mmol) at 23 °C,
and after 1 h Ce(NH4)2(NO3)6 (1.10 g, 1.99 mmol) was added
to the mixture. The solution was concentrated and chromato-
graphed by a preparative silica TLC to yield 18 as an oil (158
mg, 0.80 mmol, 58%). [R] ) -45.4° (c ) 1.0, CHCl3). IR (neat,
cm-1): ν(CO) 1765 (s), ν(CdC) 1644 (m). 1H NMR (400 MHz,
CDCl3): δ 7.10 (t, J ) 1.7 Hz, 1H, dCH), 4.69 (dd, J ) 8.5, 1.7
Hz, 1H, OCH), 4.13-4.03 (dd, J ) 9.4, 6.0 Hz, 2H, OCH2), 3.83
(m, 1H, OCH), 1.91 (t, J ) 1.6 Hz, 3H, dCCH3), 1.43 (s, 3H,
CH3), 1.32 (s, 3H, CH3). 13C NMR (100 MHz, CDCl3): δ 175.3,
146.8, 131.2, 110.3, 80.9, 76.6, 67.2, 26.7, 25.0, 10.5. MS (75
eV; m/ e): 198 (M+). HRMS: calcd for C10H14O4 198.0892,
found 198.0890.
(18) In tr a m olecu la r Cycliza tion of 12c. Compound 12c
(1.00 g, 2.10 mmol) and CF3CO2H (40 µL, 0.53 mmol) in cold
CH2Cl2 (-40 °C) afforded 15-a n ti (0.81 g, 1.60 mmol, 76%).
[R] ) -103.7° (c ) 0.4, CDCl3). IR (neat, cm-1): ν(CO) 3423
(vs), 1970 (vs), 1898 (vs). 1H NMR (400 MHz, CDCl3): endo
form, δ 5.35 (s, 5H, Cp), 4.54 (dd, J ) 10.4, 1.5 Hz, 1H,
CHOCH3), 4.28 (dt, J ) 10, 3.5 Hz, 1H, OCH), 3.89-3.74 (dd,
J ) 12.5, 3.5 Hz, 2H, CH2OH), 3.42 (s, 3H, OCH3), 3.17 (d, J
) 1.5 Hz, 1H, η3-CH), 2.93 (s, 1H, η3-CHH′), 1.62 (s, 1H, η3-
CHH′); exo form, 5.44 (s, 5H, Cp), 4.35 (dt, J ) 10.2, 3.2 Hz,
1H, OCH), 3.99 (dd, J ) 10.2, 1.5 Hz, 1H, CHOCH3), 3.89-
3.74 (dd, J ) 12.5, 3.5 Hz, 2H, OCH2), 3.54 (s, 3H, OCH3),
3.17 (d, J ) 1.5 Hz, 1H, η3-CH), 2.32 (d, J ) 2.2 Hz, 1H, η3-
CHH′), 1.06 (d, J ) 2.2 Hz, 1H, η3-CHH′). 13C NMR (100 MHz,
CDCl3): endo form, δ 223.6, 219.2, 169.7, 88.7, 83.3, 74.5, 72.5,
61.3, 57.6, 46.0, 23.6; exo-form, 244.0, 216.6, 172.6, 94.7, 83.5,
73.5, 73.6, 60.6, 58.2, 57.9, 55.6, 29.5. MS (75 eV; m/ e): 502
(M+). Anal. Calcd for C17H18WO6: C, 40.66; H, 3.61. Found:
C, 40.88; H, 3.77.
(19) Syn th esis of Com p ou n d 16. To 15-a n ti (1,00 g, 1.99
mL) in CH2Cl2 (10 mL) was added Ac2O (0.28 mL, 2.99 mmol)
and DMAP (0.48 g, 3.98 mL) at 23 °C; the mixture was stirred
for 1 h. The solution was concentrated and eluted through a
silica column to afford 16 (0.96 mg, 1.77 mmol, 89%) as a
yellow solid. [R] ) -172.5° (c ) 1.0, CDCl3). IR (neat, cm-1):
ν(CO) 1969 (vs), 1804 (vs), 1742 (s), 1708 (s). 1H NMR (400
MHz, CDCl3): endo form, δ 5.34 (s, 5H, Cp), 4.36-4.25 (m,
3H, OCH + OCH2), 3.78 (d, J ) 8.5 Hz, 1H, CHOMe), 3.40 (s,
3H, OCH3), 3.17 (1H, s, η3-CHH′), 2.65 (s, 1H, η3-CHH′), 2.03
(s, 3H, OAc), 1.62 (s, 1H, η3-CHH′); exo form, 5.39 (s, 5H, Cp),
4.54 (d, J ) 6.2 Hz, 1H, CHOCH3), 4.37-4.22 (3H, m), 3.46 (s,
3H, OCH3), 3.17 (1H, s, η3-CHH′), 2.38 (1H, s, η3-CH), 2.07 (s,
3H, OAc), 1.11 (1H, s, η3-CHH′). 13C NMR (100 MHz, CDCl3):
endo form, δ 223.4, 220.7, 170.7, 169.8, 88.8, 80.5, 75.7, 72.9,
62.5, 57.6, 45.6, 23.9, 20.6; endo form, 223.7, 216.5, 171.5,
168.0, 94.3, 80.7, 75.0, 62.6, 59.1, 58.6, 55.2, 29.6, 20.6. MS
(75 eV; m/ e): 518 (M+). Anal. Calcd for C17H18O7W: C, 39.41;
H, 3.5. Found: C, 39.46; H, 3.5.
(20) I2 Oxid a tion of Com p ou n d 13. To compound 13 (200
mg, 0.44 mmol) in MeOH (3.0 mL) was added I2 (120 mg, 0.48
mmol) at -40 °C, and the mixture was stirred for 4 h before
an aqueous NaHSO3 (2.00 M) solution (5.00 mL) was added.
The solution was reduced to ca. 5 mL, and the remaining
solution was extracted with diethyl ether (2 × 10 mL). The
solution was concentrated and chromatographed by a prepara-
tive silica TLC to yield 17 (37.2 mg, 0.20 mmol, 45%) as an
oil. [R] ) -15.5° (c ) 0.5, CHCl3). IR (neat, cm-1): ν(OH)
3450 (vs), ν(CO) 1700 (s), ν(CdC) 1624 (m). 1H NMR (400
MHz, CDCl3): δ 6.84 (s, 1H, dCHH′), 4.96(dd, 1H, J ) 9.6,
4.4 Hz, OCH), 4.78-4.85 (m, 2H, OCH2), 3.76 (s, 3H, OMe),
3.67-3.78 (m, 3H, OCH+OCH2). 13C NMR (100 MHz,
CDCl3): δ 163.9, 155.1, 121.3, 89.4, 87.3, 78.6, 66.5, 51.2. MS
(75 eV; m/ e): 186 (M+). HRMS: calcd for C8H10O5 186.0528,
found 186.0497.
(22) Syn th esis of Un sa tu r a ted δ-La cton e 19. Compound
16 (0.50 g, 0.92 mmol), NOBF4 (107 mg, 0.92 mmol), and Bu4-
NBH4 (237 mg, 0.92 mmol) afforded 19 as an oil (123 mg, 0.58
mmol, 63%). [R] ) 30.5° (c ) 1, CHCl3). IR (neat, cm-1): ν-
(CO) 1745 (s), ν(CdC) 1634 (m). 1H NMR (400 MHz, CDCl3):
δ 6.61 (d, J ) 1.5 Hz, 1H, dCH), 4.43 (ddd, J ) 8.7, 4.7, 3.2
Hz, 1H, OCH), 4.36-4.26 (dd, J ) 12.3, 4.7, 3.2 Hz, 2H, CH2-
OAc), 3.42 (s, 3H, OCH3), 2.07 (s, 3H, OAc), 1.93 (t, J ) 1.6
Hz, dCMe, 3H). 13C NMR (100 MHz, CDCl3): δ 170.2, 163.3,
138.5, 129.1, 78.2, 71.9, 62.8, 57.0, 20.5, 16.8; MS (75 eV
m/ e): 214 (M+). HRMS: calcd for C10H14O5 214.0814, found
214.0812.
X-r a y Diffr a ction Stu d ies of 13, 14-a n ti, a n d 16. Single
crystals of 13, 14-a n ti, and 16 were sealed in glass capillaries
under an inert atmosphere. Data for 13, 14-a n ti, and 16 were
collected on a Siemens SMART CCD diffractometer using
graphite monochromated Mo KR radiation. The structures of
13, 14-a n ti, and 16 were solved by direct methods; all data
reduction and structural refinements were performed with the
Siemens SHELXTL-PLUS package. Crystal data, details of
data collection and structural analysis of these three com-
pounds are provided in the Supporting Information. For all
structures, all non-hydrogen atoms were refined with aniso-
tropic parameters, and all hydrogen atoms included in the
structure factors were placed in idealized positions.
Ack n ow led gm en t. We wish to thank the National
Science Council and National Institute of Health,
Taiwan, ROC, for financial support of this work.
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, atomic coordinates, bond distances and angles, and
thermal parameters for compounds 13, 14-a n ti, and 16 and
an additional ORTEP drawing for 14-syn (23 pages). Ordering
information is given on any current masthead page.
OM970335Y