Hydrostannation of C-C multiple bonds with Bu3SnH prepared in situ from Bu3SnCl and Et3SiH in the presence of Lewis acid catalysts

Article abstract of DOI:10.1039/a706187k

A number of alkynes 5, allene 11 and alkene 13 smoothly underwent hydrostannation with tributyltin hydride 1, prepared in situ from tributylchlorostannane 6 and triethylsilane 7 in the presence of catalytic amounts of Lewis acids.

Full text of DOI:10.1039/a706187k

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Hydrostannation of C–C multiple bonds with Bu3SnH prepared in situ from
Bu3SnCl and Et3SiH in the presence of Lewis acid catalysts
Vladimir Gevorgyan, Jian-Xiu Liu and Yoshinori Yamamoto*
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-77, Japan
A number of alkynes 5, allene 11 and alkene 13 smoothly
ZrCl4
(3)
+
+
Bu3SnCl
Et3SiH
Bu3SnH
Et3SiCl
underwent hydrostannation with tributyltin hydride 1,
prepared in situ from tributylchlorostannane 6 and triethyl-
silane 7 in the presence of catalytic amounts of Lewis
acids.
6
7
89%
1
11%
9
silyl hydride 7 [reaction (3)], it was presumed that, due to the
fact that ZrCl4 is not a strong enough Lewis acid to the catalyze
hydrosilylation alkynes,12 this reaction would not compete with
the desired hydrostannation process. Motivated by that we
applied this method for the in situ preparation of 1 and
subsequent ZrCl4-catalyzed hydrostannation of phenyl-
acetylene 5d;11 as a result the trans-addition product (Z)-b-
Since the first synthesis of tributyltin hydride 1 by Finholt et al.
in 1947,1 this compound has become one of the most frequently
used organometallic reagents in organic synthesis.2 Along with
wide applicability as a hydrogen source in various kinds of
reductions,2 Bu3SnH is the most popular hydrostannation agent
for the synthesis of vinyl-3 and allyl-stannanes.4 The latter, due
to their great versatility as building blocks, are of increasing
importance in modern synthetic organic chemistry.5 Recently
we reported regio- and stereo-selective methods for the
synthesis of vinyl- and allyl-tributylstannanes via Lewis acid-
catalyzed trans-hydrostannation of acetylenes6 and allenes.7
Although Bu3SnH is commercially available, it gradually
decomposes after storage in a refrigerator for a prolonged
period of time;8 consequently, distillation is needed before use.
It occurred to us that in situ generation of 1 from stable
precursors would be synthetically more convenient for the
hydrostannation reaction. The generation of Bu3SnH in situ
from more stable stannyl precursors and hydride sources could
serve this purpose.9 In general, the preparation of commercially
available tributyltin hydride 1 is carried out by the reduction of
tributyltin oxide 2 with hydrosiloxane 3 [reaction (1)].10
1
(tributylstannyl)styrene 8d was formed in 52% yield (by H
NMR analysis). A brief search for a more efficient Lewis acid
catalyst pointed to B(C6F5)3. We found that 10 mol% of
B(C6F5)3 effectively catalyzed the hydrostannation of various
alkynes 5 with tributylstannane 1, generated in situ from 6 and
7, producing the hydrostannation products 8 and 10 in excellent
chemical yields [reaction (4), Table 1]. The hydrostannation of
+
Et3SiH
R
R1
+ Bu3SnCl
5a–h
6
7
B(C6F5)3 (10 mol%)
R
toluene
R1
SnBu3
R1
R
+
(4)
SnBu3
heat
8
10
+
2 (MeSiO1.5)n (1)
+
n (Bu3Sn)2O 2 (MeSiHO)n
2n Bu3SnH
2
3
1
4
all the monosubstituted alkynes tested (5a–f) proceeded in a
regiospecific manner affording the b-hydrostannation products
(8a–f, 10) exclusively (entries 1–6, Table 1). Except for the
reactions with 5b and 5g in which small amounts of the cis-
addition products were formed (entries 2,7), the reaction was
also trans-stereoselective (entries 1,3–6,8, Table 1) as was
reported for the conventional method for the Lewis acid-
catalyzed hydrostannation of alkynes.6 The preparation of 8a
from 5a is representative. Tributylstannyl chloride 6 (1.5
mmol), triethylsilane 7 (1.0 mmol) and 5a (1 mmol) were
consecutively added at 0 °C to a solution of B(C6F5)3 (0.1
mmol) in dry toluene (0.25 ml) under an argon atmosphere.
After being stirred for 40 min at 0 °C the reaction temperature
was allowed to warm to 25 °C and the mixture was stirred for
another 3 h. The reaction was quenched by adding Et3N (0.5
mmol) at ambient temperature. Hexane was added and the
resulting mixture was filtered through Celite and concentrated
under reduced pressure. Purification by column chromato-
graphy (aluminium oxide, 90 mesh, n-hexane as eluent) gave
220 mg (78%) of 8a.
Accordingly, we attempted to employ this method for the in situ
preparation of 1 under the conditions of the Lewis acid-
catalyzed hydrostannation reaction.6,7 However, no hydro-
stannation products were detected, instead the starting alkynes
were recovered quantitatively. It is probable that, due to the
strong affinity of the Lewis acid for the oxygen of either the
reactants (2 and/or 3) or of the byproduct 4, it is deactivated and
thus not effective as a catalyst in the hydrostannation reaction.
Hence, a non-oxygen containing precursor should be employed
for the in situ preparation of 1.
Herein we report the first example of the Lewis acid-
catalyzed hydrostannation reaction of alkynes with tributyltin
hydride 1, prepared in situ from Bu3SnCl 6 and Et3SiH 7
[reactions (2) and (4)].
ZrCl4 (20 mol%)
Ph
SnBu3
(2)
+
+
Et3SiH
Ph
Bu3SnCl
5d
6
7
8d
In our initial experiments we found that simple mixing of 6
and 7 in toluene at room temperature did not produce any
detectable amount of tin hydride 1. In contrast, a redistribution
Finally, we disclose our initial experiments on the application
of this method for the hydrostannation of an allene and alkene.
We reported recently that tributyltin hydride 1 in the presence of
Lewis acids reacted with a number of allenes affording the
corresponding vinylstannanes in good chemical yields.7 We
found that 1, prepared in situ from 6 and 7 in the presence of 10
mol% of B(C6F5)3, smoothly reacted with phenylallene 11
11
took place by the addition of 20 mol% ZrCl4 to the same
reaction mixture and noticeable amounts of 1 were detected by
1H NMR analysis of the reaction mixture after one hour
[reaction (3)]. Although the mixture contained a large amount of
Chem. Commun., 1998
37

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Table 1 B(C6F5)3-catalyzed hydrostannation of alkynes with Bu3SnH generated in situ from Bu3SnCl and Et3SiH
Yield of
Entry
1
R
R1
H
Conditions
8 + 10a (%)
Ratio 8:10b
C6H13
5a
40 min/0 °C
3 h/rtc
2 h/0 °C
78
85
85
77
89
70
> 95:5
86:14
> 95:5
> 95:5
> 95:5
> 95:5
2
3
4
5
6
7
Cyclohexenyl
PhCH2
Ph
p-MeC6H4
p-MeOC6H4
Pentyl
H
H
H
H
H
Pentyl
5b
5c
5d
5e
5f
4 h/0 °C
2.5 h/0 °C
2.5 h/0 °C
1.5 h/235 °C
40 min/0 °C
3 h/rt
5g
90
71
80:20
> 95:5
8
Ph
Ph
5h
40 min/0 °C
3 h/rt
a Isolated yield. b Determined by 1H NMR analysis of crude reaction mixtures. c rt = room temp.
1987, 60, 3468; K. Kikuhawa, F. Umekawa, G. Wada and T. Matsuda,
Chem. Lett., 1988, 881; H. Miyake and K. Yamamura, Chem. Lett.,
1989, 981.
4 H. G. Kuivila, W. Rahman and R. H. Fish, J. Am. Chem. Soc., 1965, 87,
2835; M. Koreeda and Y. Tanaka, Tetrahedron Lett., 1987, 28, 143;
Y. Ichinose, K. Oshima and K. Utimoto, Bull. Chem. Soc. Jpn., 1988,
61, 2693; T. N. Mitchell and U. Schneider, J. Organomet. Chem., 1991,
405, 195; K. Koerber, J. Gore and J.-M. Vatele, Tetrahedron Lett., 1991,
32, 1187.
5 (a) M. Pereyre, J.-P. Quintard and A. Rahm, Tin in Organic Synthesis,
Butterworths, London, 1987; (b) A. J. Leusink, H. A. Budding and
W. Drenth, J. Organomet. Chem., 1967, 9, 285; 1967, 9, 295; (c)
Y. Yamamoto and N. Asao, Chem. Rev., 1993, 93, 2207; (d) J. K. Stille,
Angew. Chem., Int. Ed. Engl., 1986, 25, 508; (e) R. F. Heck, Palladium
Reagents in Organic Synthesis, Academic Press, New York, 1985.
6 N. Asao, J.-X. Liu, T. Sudoh and Y. Yamamoto, J. Org. Chem., 1996,
61, 4568; N. Asao, J.-X. Liu, T. Sudoh and Y. Yamamoto, J. Chem.
Soc., Chem. Commun., 1995, 2405.
Ph
B(C6F5)3 (10 mol%)
toluene
•
+
Bu3SnCl + Et3SiH
(5)
Ph
Bu3Sn
11
6
7
12
affording the vinylstannane 12 in 51% yield [reaction (5)]. In
addition, the same method could be employed for the hydro-
stannation of alkenes: styrene 13 was converted into the
corresponding alkylstannane 14 in 70% isolated yield [reaction
(6)]. To the best of our knowledge, reaction (6) is the first
B(C6F5)3 (10 mol%)
SnBu3
+
+ Bu3SnCl
(6)
Et3SiH
Ph
Ph
toluene
13
6
7
14
7 V. Gevorgyan, J.-X. Liu and Y. Yamamoto, J. Org. Chem., 1997, 62,
2963.
8 G. Ba¨hr and S. Pawlenko, in Methoden der Organischen Chemie, ed. E.
Mu¨ller and O. Bayer, Thieme Verlag, Stuttgart, 1978, vol. 13/6, p. 181;
A. G. Davies and P. J. Smith, in Comprehensive Organometallic
Chemistry, ed. G. Wilkinson, Pergamon Press, Oxford, 1982, vol. 2,
Tin, see also refs. 2, 5(a).
9 The reduction of various organic halides with 1 prepared in situ from
tributyltin chloride and LiAlH4 or NaBH4 has been reported: E. J. Corey
and J. W. Suggs, J. Org. Chem., 1975, 40, 2554; H. G. Kuivila and
L. W. Menapace, J. Org. Chem., 1963, 28, 2165. However, due to the
presence of reactive metal hydrides in the reaction mixture, this method
could not be applied to the Lewis acid-catalyzed hydrostannation
reaction.
example of the Lewis acid-catalyzed hydrostannation of
alkenes.
In conclusion, a synthetically useful and convenient method
for the Lewis acid-catalyzed hydrostannation of carbon–carbon
multiple bonds with tributyltin hydride 1, prepared in situ from
easily handled and cheap chlorostannane 6 and hydrosilane 7,
has been developed. The first example of the Lewis acid-
catalyzed hydrostannation of an alkene has been demon-
strated.
Footnote and References
10 K. Hayashi, J. Iyoda and I. Shiihara, J. Organomet. Chem., 1967, 10,
81.
* E-mail: yoshi@yamamoto1.chem.tohoku.ac.jp
11 Since ZrCl4 was reported to be the best Lewis acid catalyst for trans-
hydrostannation of alkynes with Bu3SnH6 it was chosen for our initial
experiments for the in situ hydrostannation of alkynes.
1 A. E. Finholt, A. C. Bond, K. E. Wilzbach and H. I. Schlesinger, J. Am.
Chem. Soc., 1947, 69, 2693.
2 For a leading review, see W. P. Neumann, Synthesis, 1987, 665.
3 H. X. Zhang, F. Guibe´ and G. Balavoine, J. Org. Chem., 1990, 55, 1857;
Y. Ichinose, H. Oda, K. Oshima and K. Utimoto, Bull. Chem. Soc. Jpn.,
12 N. Asao, T. Sudoh and Y. Yamamoto, J. Org. Chem., 1996, 61, 7654.
Received in Cambridge, UK, 26th August 1997; 7/06187K
38
Chem. Commun., 1998