Tandem intramolecular alkyne silylformylation-allylsilylation: A case of remote 1,5-asymmetric induction

Article abstract of DOI:10.1002/1521-3773(20010803)40:15<2915::AID-ANIE2915>3.0.CO;2-9

Two new C-C bonds as well as a remote stereocenter are formed in the title reaction. With remarkable efficiency, this new reaction provides, through remote 1,5-asymmetric induction, anti-1,5 diols that are useful synthons for polyol synthesis (see scheme;

Full text of DOI:10.1002/1521-3773(20010803)40:15<2915::AID-ANIE2915>3.0.CO;2-9

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ing R ˆ 0.058, Rw ˆ 0.169 and Sw ˆ 1.024 (residual D1 < 1.37 eŠ 3).
Crystallographic data (excluding structure factors) for the structure
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication
no. CCDC-160045. Copies of the data can be obtained free of charge
on application to CCDC, 12 Union Road, Cambridge CB21EZ, UK
(fax: (‡44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk).
ˆ
26.3, 28.9, 31.5, 34.0, 35.4 (CH2), 77.3, 86.3 ( CH), 93.4, 103.8, 128.8, 135.3
1
ˆ
ˆ
ˆ
( C), 140.7 ( CH), 149.3 ( C); IR (nujol): nÄ ˆ 844, 1561, 1630, 3103 cm
;
elemental analysis calcd (%) for C26H36RuClPF6: C 49.57, H 5.76, Cl 5.63;
found: C 49.23, H 5.50, Cl 6.27. Microcrystals of complex 12b were obtained
in a dichloromethane/diethyl ether biphasic system.
Received: March 15, 2001 [Z16777]
[16] P. J. Ridgwell, P. M. Bailey, S. N. Wetherell, E. A. Kelley, P. M. Maitlis,
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Soc. 1992, 114, 8869 ± 8885; Ru: b) A. Mitsudo, K. Kokuryo, Y.
Takegami, J. Chem. Soc. Chem. Commun. 1976, 722 ± 723; c) T.-a.
Mitsudo, K. Kokuryo, T. Shinsugi, Y. Nakagawa, Y. Watanabe, Y.
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595 ± 597; Angew. Chem. Int. Ed. Engl. 1994, 33, 580 ± 581; e) B. N.
Warrener, G. Abbenante, C. H. L. Kennard, J. Am. Chem. Soc. 1994,
116, 3645 ± 3646.
Tandem Intramolecular Alkyne
Silylformylation ± Allylsilylation: A Case of
Remote 1,5-Asymmetric Induction**
Steven J. OꢁMalley and James L. Leighton*
Dedicated to Professor David A. Evans
on the occasion of his 60th birthday
As part of a program dedicated to the development of
stereoselective catalytic methods for the synthesis of polyols,
we have recently reported the tandem intramolecular silyl-
formylation ± allylsilylation of alkenes (Scheme 1a).[1, 2] Al-
kynes are well-known substrates for silylformylation,[3] and it
seemed plausible that tandem allylsilylation of the resultant
unsaturated aldehydes might occur as well (Scheme 1b).
Interestingly, in this system the silicon-substituted carbon
atom is no longer stereogenic. Thus, any diastereoselectivity
[8] K. Kasai, Y. Liu, R. Hara, T. Takahashi, Chem. Commun. 1998, 1989 ±
1990.
[9] L. Trabert, H. Hopf, Liebigs Ann. Chem. 1980, 1786 ± 1800.
[10] E. Piers, E. M. Boehringer, J. G. K. Yee, J. Org. Chem. 1998, 63, 8642 ±
8643.
a)
OH
OH
OH
Â
[11] J. Le Paih, S. Derien, P. H. Dixneuf, Chem. Commun. 1999, 1437 ±
1. [Rh(acac)(CO)2],
CO, PhH, 60 °C
1438.
Si
O
H
R
[12] P. J. Fagan, W. S. Mahoney, J. C. Calabrese, I. D. Williams, Organo-
metallics 1990, 9, 1843 ± 1852.
2. H2O2, NaHCO3,
THF/MeOH, reflux
45-65% yield of major product;
69:31-92:8 ds
R
Â
[13] S. Derien, L. Ropartz, J. Le Paih, P. H. Dixneuf, J. Org. Chem. 1999,
64, 3524 ± 3531.
b)
[14] The NMR spectra with a single resonance (1H) at d ˆ 3.42 and a single
resonance (13C) at d ˆ 69.8 for the alkenyl unit of the cycle show the
symmetry of the complex 11.
Si
O
O
Si
O
Si
O
*
?
O
H
[15] Crystal structure analysis: RuClC26H36 ´ PF6, Mr ˆ 630.04, monoclinic,
I2/a, a ˆ 22.704(1), b ˆ 11.221(1), c ˆ 23.530(2) Š, b ˆ 114.57(1), Vˆ
R
H
R
3
3
R
5451.8(7) Š
,
Z ˆ 8, 1 ˆ 1.535 Mgm
,
l(MoKa) ˆ 0.71073 Š, m ˆ
7.86 cm 1, F(000) ˆ 2576, Tˆ 293 K. The crystal, dimensions 0.37 Â
0.27 Â 0.23 mm was studied on a NONIUS Kappa CCD diffractom-
eter with graphite monochromatized MoKa radiation. The cell
parameters are obtained with 10 frames (psi rotation: 18 per frame).
The data collection (Nonius, 1999) (2qmax ˆ 608, 176 frames (117 via
1.68 phi rotation and 16 s per frame, 52 via 1.68 omega rotation) range
hkl: h 25.29, k 0.14, l 25.30) gives 22884 reflections. The data
reduction leads to 6103 independent reflections from which 4681 with
I > 2.0s(I). The absorption correction is made with a faces indexed
crystal. The structure was solved with SIR-97 which reveals the non-
hydrogen atoms of the cation and the anion. One atom (C19) of the
cyclohexene ring appears disordered between two positions. After
anisotropic refinement, many hydrogen atoms may be found with a
Fourier Difference. The whole structure was refined with SHELXL97
by the full-matrix least-square techniques (use of F 2 magnitude; x, y, z,
bij for Ru, Cl, P, C, and Fatoms, x, y, z in riding mode for H atoms ; 316
variables and 4681 observations with I > 2.0s(I); calcd w ˆ 1/
[s2(Fo2† ‡ (0.122P)2 ‡ 10.23P] where P ˆ (Fo2 ‡ 2Fc2†/3 with the result-
Scheme 1. a) Tandem alkene silylformylation ± allylsilylation and b) pro-
posed tandem alkyne silylformylation ± allylsilylation. Hacac ˆ acetylace-
tone.
[*] Prof. J. L. Leighton, S. J. OꢁMalley
Department of Chemistry, Columbia University
New York, NY 10027 (USA)
Fax : (‡ 1)212-932-1289
E-mail: leighton@chem.columbia.edu
[**] Financial support was provided by the National Institutes of Health
(National Institute of General Medical Sciences, GM58133). We are
grateful to Bristol-Myers Squibb for generous financial support in the
form of an Unrestricted Grant in Synthetic Organic Chemistry to
J.L.L. We thank Merck Research Laboratories and DuPont Pharma-
ceuticals for generous financial support.
Supporting information for this article is available on the WWW under
http://www.angewandte.com or from the author.
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in the allylsilylation would have to derive from the original
homopropargylic stereocenter, and would constitute an
example of remote 1,5-stereoinduction.[4]
nature of a syn propargylic methyl group, whereas with an anti
propargylic methyl group (entry 8) useful diastereoselectivity
is still observed.
Our study commenced with diallylsilyl ether 1 [Eq. (1)].
Treatment of this silane with 1.0 mol% of [Rh(acac)(CO)2]
and 6.9 MPa (1000 psi) of CO in benzene at 608C in a
As an alternative to the protodesilylative workup of
Table 1, we have also investigated an oxidative workup to
provide b,b'-dihydroxyketone products. Subjection of silanes
1 and 4 to the standard tandem silylformylation ± allylsilyla-
tion conditions, followed by evaporation of the solvent and
subjection of the residue to the conditions of the Tamao
oxidation[7] (H2O2, NaHCO3, THF/MeOH, reflux) led to
oxodiols 3 and 5 in 71 and 65% yields, respectively, and with
identical diastereoselectivities to entries 4 and 7 in Table 1
[Eq. (2)]. The oxidative workup is noteworthy in the context
of polyol synthesis in that diastereoselective ketone reduc-
tions would allow access to stereochemically diverse triol
arrays.
OAc
OAc
Si
1. [Rh(acac)(CO)2],
CO, PhH, 60 °C
O
H
Me
(1)
Me
2. nBu4NF, THF, ∆
3. Ac2O, py
2
Me
83%; 8:1 ds
Me
1
high-pressure reactor produced a yellow oil upon concen-
tration. The unpurified material was subjected to protodesil-
ylation (nBu4NF, THF, reflux) and peracetylation (Ac2O,
pyridine (py)) to provide an 8:1 mixture of diacetate 2 and
its syn diastereomer in 83% overall yield.[5, 6] Thus, the
allylsilylation proceeded with good 1,5-diastereoselectivity,
providing the 1,5-anti product as the major diastereomer, a
result which is opposite to that observed with alkene
substrates.
OH
O
OH
Si
R
1. [Rh(acac)(CO)2],
CO, PhH, 60 °C
O
H
Me
(2)
Me
2. H2O2, NaHCO3
THF, MeOH, ∆
1 R = H
4 R = Me
Me
R
Me
3 R = H, 71%
5 R = Me, 65%
Optimization of the reaction conditions revealed that the
catalyst loading could be reduced to 0.1 mol% with no
decrease in efficiency. At significantly lower CO pressures,
and/or at significantly lower temperatures there was a small
improvement in the diastereoselectivity, accompanied, how-
ever, by a significant drop in reaction rate. We therefore
settled on 6.9 MPa of CO in benzene at 608C as the standard
reaction conditions.
Based on arguments previously advanced,[1] and in analogy
to the corresponding reactions of alkenes, we propose an
uncatalyzed allylsilylation of the presumed aldehyde inter-
mediates.[8] Binding of the aldehyde by the Lewis acidic silicon
atom[9] is followed by intramolecular allylsilylation as depict-
ed for aldehyde 6 (Scheme 2). In this model, the diastereo-
selectivity is determined by the relative rates at which the
With optimal reaction conditions identified, we set out to
investigate the scope of the reaction with regard to homo-
propargylic and propargylic substituents (Table 1). Entries 1 ±
6 clearly establish a direct correlation between the steric size
of the homopropargylic substituent and the diastereoselec-
tivity of the reaction, as well as a tolerance for alkyne and
silyloxy functional groups. The superior diastereoselectivity
shown in entry 7 indicates the stereochemically reinforcing
a
b
O
O
Si
O
Si
O
H
H
iPr
iPr
H
path b
(minor)
6
path a
(major)
O
Si
O
O
Si
O
Table 1. Tandem alkyne silylformylation ± allylsilylation.
iPr
iPr
1. 0.10 mol%
Scheme 2. Proposed model for remote 1,5-stereoinduction.
Si
[Rh(acac)(CO)2],
O
H
OAc
R2
OAc
CO, PhH, 60 °C
R1
R1
2. nBu4NF,THF, ∆
3. Ac2O, py
diastereotopic allyl groups transfer (path a vs. path b). A
simple working hypothesis for the observed preference for
path a would invoke a destabilizing steric interaction between
the 2-propyl group and the allyl group b. The correlation
between steric size of the homopropargylic substituent and
the selectivity observed in entries 1 ± 6 of Table 1 is consistent
with this hypothesis as is the high selectivity observed in
entry 7. The nearly identical selectivity observed in entries 4
and 8 is less well rationalized by this model and is suggestive
of more subtle stereoelectronic effects.
R3
R3
R2
Entry
R1
nPr
R2
R3
ds[a]
Yield [%][b]
1
2
3[c]
4
5
6
7
8
H
H
H
H
H
H
H
H
Me
4:1
4:1
5:1
8:1
7:1
10:1
23:1
7:1
68
63
63
83
83
66
70
70
ꢀ
HC CCH2
H
TBSOCH2CH2
H
iPr
Ph
tBu
iPr
iPr
H
H
H
Me
H
A key feature of this model is that both of the diastereo-
topic allyl groups can transfer and each leads to a different
product diastereomer. It could therefore be surmised that
selective replacement of either allyl group with a nontrans-
[a] 1,5-anti:1,5-syn; measured by gas chromatography. [b] Yield of the
isolated purified mixture of diastereomers. [c] The tert-butyldimethylsilyl
(TBS) group is cleaved during the protodesilylation step and the triacetate
is isolated.
2916
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Angew. Chem. Int. Ed. 2001, 40, No. 15

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nium fluoride (6.0 mL, 6.0 mmol, 1.0m in THF). The solution is heated at
reflux for 2 h, and then cooled. Saturated aqueous NH4Cl is added, and the
mixture is extracted with Et2O. The combined organic layers are dried
(MgSO4), filtered and concentrated. The resulting diols may be purified by
chromatography on silica gel.
ferable group would lead to a stereospecific reaction. To gain
support for this hypothesis we prepared silane 7 as a 1:1
mixture of diastereomers. Subjection of this mixture to the
standard reaction conditions led, presumably by way of the
illustrated 1:1 mixture of aldehydes, to a 1:1 mixture of diol
diastereomers 8 and 9 (Scheme 3). The clear implication of
this experiment is that either product diastereomer could be
selected for, based only on the availability of the starting
chiral silanes in diastereomerically pure form.
Tamao oxidation: To
a solution of the residue from the tandem
silylformylation ± allylsilylation in THF (3.0 mL) and MeOH (3.0 mL) is
added NaHCO3 (0.15 g, 1.8 mmol) and H2O2 (1.5 mL, 35% in H2O). The
solution is heated at reflux for 3 h, and then cooled. Saturated aqueous
NaCl is added, followed by saturated aqueous Na2S2O3, and the mixture is
extracted with Et2O. The combined organic layers are dried (MgSO4),
filtered and concentrated. The resulting oxodiols may be purified by
chromatography on silica gel.
Ph
Si
Received: April 5, 2001 [Z16904]
O
H
(1:1 mixture of
diastereomers)
7
iPr
1. [Rh(acac)(CO)2],
CO, PhH, 60 °C
2. nBu4NF, THF, ∆
[1] M. J. Zacuto, J. L. Leighton, J. Am. Chem. Soc. 2000, 122, 8587 ± 8588.
[2] A conceptually similar tandem hydroformylation ± allylboration reac-
tion was earlier reported by Hoffmann et al., see: a) R. W. Hoffmann,
D. Brückner, V. J. Gerusz, Heterocycles 2000, 52, 121 ± 124; b) R. W.
Hoffmann, J. Krüger, D. Brückner, New J. Chem. 2001, 25, 102 ± 107;
c) R. W. Hoffmann, D. Brückner, New J. Chem. 2001, 25, 369 ± 373.
[3] a) I. Matsuda, A. Ogiso, S. Sato, Y. Izumi, J. Am. Chem. Soc. 1989, 111,
2332 ± 2333; b) I. Ojima, P. Ingallina, R. J. Donovan, N. Clos, Organo-
metallics 1991, 10, 38 ± 41; c) I. Ojima, R. J. Donovan, W. R. Shay, J.
Am. Chem. Soc. 1992, 114, 6580 ± 6582; d) I. Ojima, M. Tzamarioudaki,
C.-Y. Tsai, J. Am. Chem. Soc. 1994, 116, 3643 ± 3644; e) F. Monteil, I.
Matsuda, H. Alper, J. Am. Chem. Soc. 1995, 117, 4419 ± 4420; f) I.
Ojima, E. Vidal, M. Tzamarioudaki, I. Matsuda, J. Am. Chem. Soc.
1995, 117, 6797 ± 6798; g) I. Ojima, J. V. McCullagh, W. R. Shay, J.
Organomet. Chem. 1996, 521, 421 ± 423.
Ph
Ph
O
O
Si
O
Si
O
+
iPr
H
iPr
H
1:1
OH
OH
OH
OH
+
iPr
iPr
1:1
9
8
Scheme 3. Evidence for the stereochemical model.
[4] For examples of 1,5-stereoiduction in C C bond forming reactions, see:
a) J. Fujiwara, Y. Fukutani, M. Hasegawa, K. Maruoka, H. Yamamoto,
J. Am. Chem. Soc. 1984, 106, 5004 ± 5005; b) T. Harada, T. Hayashi, I.
Wada, N. Iwaake, A. Oku, J. Am. Chem. Soc. 1987, 109, 527 ± 532; c) K.
Tomooka, T. Okinaga, K. Suzuki, G.-I. Tsuchihashi, Tetrahedron Lett.
1987, 28, 6335 ± 6338; d) A. H. McNeill, E. J. Thomas, Tetrahedron Lett.
1990, 31, 6239 ± 6242; e) G. Erker, F. Sosna, P. Betz, S. Werner, C.
Krüger, J. Am. Chem. Soc. 1991, 113, 564 ± 573; f) M. Nishida, E.
Ueyama, H. Hayashi, Y. Ohtake, Y. Yamaura, E. Yanaginuma, O.
Yonemitsu, A. Nishida, N. Kawahara, J. Am. Chem. Soc. 1994, 116,
6455 ± 6456; g) M. P. Sibi, J. Ji, J. B. Sausker, C. P. Jasperse, J. Am.
Chem. Soc. 1999, 121, 7517 ± 7526; h) L. F. Tietze, C. Schünke, Eur. J.
Org. Chem. 1998, 2089 ± 2099; i) D. Badone, J.-M. Bernassau, R.
Cardamone, U. Guzzi, Angew. Chem. 1996, 108, 575 ± 578; Angew.
Chem. Int. Ed. Engl. 1996, 35, 535 ± 538. j) I. Paterson, K. R. Gibson,
R. M. Oballa, Tetrahedron Lett. 1996, 37, 8585 ± 8588; k) D. A. Evans,
The reactions reported here should find broad application
in organic synthesis. The entire sequence (homopropargylic
alcohol to 1,5-diol or oxodiol) can be carried out in a day and
requires only readily available reagents (HSiCl3, AllylMgBr,
CO, nBu4NF or H2O2). In the tandem silylformylation ± al-
lylsilylation reaction two new C C bonds are formed as well
as a remote stereocenter. Further studies to extend the
synthetic utility of this process are in progress.
Experimental Section
Preparation of the diallylsilyl ethers: To a solution of the homopropargylic
alcohol (10.0 mmol) in Et2O (20 mL) is added trichlorosilane (20.0 mmol).
The solution is heated at reflux for 2 h, and then concentrated (Caution!
HCl evolution). The residue is redissolved in Et2O (20 mL) and the solution
is cooled to 08C. Allylmagnesium bromide (20.0 mL, 20.0 mmol, 1.0m in
Et2O) is then added with vigorous stirring. The reaction mixture is warmed
to room temperature and diluted with pentane. The mixture is filtered
through a pad of Celite and the filtrate is concentrated. The residue is
treated with pentane, and the mixture is filtered through a pad of Celite.
The filtrate is concentrated and the residue is typically purified by
distillation under vacuum (<1.0 Torr).
à Â
P. J. Coleman, B. Cote, J. Org. Chem. 1997, 62, 788 ± 789; l) L. N.
Pridgen, K. Huang, S. Shilcrat, A. Tickner-Eldridge, C. DeBrosse, R. C.
Â
Haltiwanger, Synlett 1999, 1612 ± 1614; m) E. Nicolas, K. C. Russell,
V. J. Hruby, J. Org. Chem. 1993, 58, 766 ± 770 .
[5] Although the diols can be cleanly isolated, a quantitative assay of the
diastereoselectivity (by gas chromatography) was best performed with
the derived diacetates.
[6] See the Supporting Information for a description of the stereochemical
proofs.
[7] For a review on the Tamao and Fleming oxidations, see: G. R. Jones, Y.
Landais, Tetrahedron 1996, 52, 7599 ± 7662.
Tandem Silylformylation ± Allylsilylation: A glass liner for a stainless steel
45 mL Parr high-pressure reactor equipped with a stir bar and septum is
charged with a solution of the diallylsilyl ether substrate (2.0 mmol) in
benzene (6.0 mL). The solution is cooled to 788C and [Rh(acac)(CO)2]
(0.5 mg, 0.002 mmol) is added. The liner is inserted into the Parr reactor,
and the pressure gauge and gas inlet assembly is attached. The reactor is
charged to 3.4 MPa (500 psi) with CO, and vented. The reactor is then
charged to 6.9 MPa (1000 psi) with CO and immersed (ꢁ2.5 cm) in an oil
bath at 608C. After 2 ± 3 h, the reactor is cooled to 08C and then vented.
The solution is concentrated and the residue is immediately subjected to
either workup procedure without further purification.
[8] We are aware of only one other example of an uncatalyzed/unpromoted
allylsilylation of aldehydes using a tetracoordinate allylsilane, see: K.
Matsumoto, K. Oshima, K. Utimoto, J. Org. Chem. 1994, 59, 7152± 7155.
[9] This is believed to be an example of ring strain-induced Lewis acidity.
See ref. [1] and: a) E. F. Perozzi, R. S. Michalak, G. D. Figuly, W. H.
Stevenson III, D. B. Dess, M. R. Ross, J. C. Martin, J. Org. Chem. 1981,
46, 1049 ± 1053; b) S. E. Denmark, R. T. Jacobs, G. Dai-Ho, S. Wilson,
Organometallics 1990, 9, 3015 ± 3019; c) A. G. Myers, S. E. Kephart, H.
Chen, J. Am. Chem. Soc. 1992, 114, 7922 ± 7923; d) S. E. Denmark,
B. D. Griedel, D. M. Coe, M. E. Schnute, J. Am. Chem. Soc. 1994, 116,
7026 ± 7043; e) K. Omoto, Y. Sawada, H. Fujimoto, J. Am. Chem. Soc.
1996, 118, 1750 ± 1755.
Protodesilylation: To a solution of the residue from the tandem silylfor-
mylation ± allylsilylation in THF (10.0 mL) is added tetra-n-butylammo-
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