Catalytic propargylation of aldehydes with allenyltributylstannane by ytterbium triflate

Article abstract of DOI:10.1016/S0022-328X(99)00339-3

The first ytterbium triflate [Yb(OTf)₃]-catalyzed propargylation of various aldehydes with allenyltributylstannane to afford homopropargyl alcohols in good yields is described. The present result provides a versatile tool for preparation of an array of homopropargyl alcohols from the reaction of aldehydes with allenyltributylstannane; which are known to possess low reactivity.

Full text of DOI:10.1016/S0022-328X(99)00339-3

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Journal of Organometallic Chemistry 588 (1999) 20–21
Catalytic propargylation of aldehydes with allenyltributylstannane
by ytterbium triflate
Jae-Goo Shim
Korea Electric Power Research Institute (KEPRI), Munji-dong, Yusung-ku, Taejon, 305-380 South Korea
Received 12 March 1999
Abstract
The first ytterbium triflate [Yb(OTf)3]-catalyzed propargylation of various aldehydes with allenyltributylstannane to afford
homopropargyl alcohols in good yields is described. The present result provides a versatile tool for preparation of an array of
homopropargyl alcohols from the reaction of aldehydes with allenyltributylstannane; which are known to possess low reactivity.
© 1999 Elsevier Science S.A. All rights reserved.
Keywords: Allenyltributylstannane; Catalytic propargylation; Ytterbium triflate
The carbon–carbon bond-forming reaction has been
considered one of the most challenging subjects in
organic synthesis. A variety of organometals have been
utilized for the above-mentioned purpose. Amongst
these organometals, organotin compounds have been
one of the most frequently used by virtue of their high
reactivity and selectivity. In general, the majority of
examples using organotin compounds reported to date
are based on Lewis acid-promoted reactions of allyl-
stannanes with aldehydes (or their corresponding
imines) affording homoallyl alcohols (or their corre-
sponding homoallyl amines) [1]. However, there are few
examples using allenyltributylstannane compared with
those using allylstannane, presumably due to its low
reactivity. Even the reactions of allenyltributylstan-
nanes with aldehydes employed so far giving homo-
propargyl alcohols required more than stoichiometric
amounts of Lewis acid to accomplish the desired reac-
tion [2,3]. In this paper, the first Yb(OTf)3-catalyzed
reaction of aldehydes with allenyltributylstannane [4] to
afford homopropargyl alcohols in good yields is de-
scribed Eq. (1) [5]1.
Initial studies focused on the development of optimal
conditions for the present reaction. At the outset, the
reaction of benzaldehyde 1a with allenyltributylstan-
nane 2 in THF using 20 mol% Yb(OTf)3 at room
temperature was undertaken. As expected, 1H-NMR
analysis of the reaction mixture revealed that the corre-
sponding homopropargyl alcohol 3a was produced in
82% yield. However, several other solvents such as
CH2Cl2, CH3CN and n-hexane gave the desired
product in lower yield.
Table 1
Yb(OTf)3-catalyzed propargylation of aldehydes a
Entry
Aldehyde
Yield (%)b
1
Benzaldehyde (1a)
p-Nitrobenzaldehyde (1b)
2-Furfural (1c)
82(73) d
91(87) d
71
2 c
3
4
n-Octanal (1d)
66
5
n-Hexanal (1e)
60
6
7
m-Methoxybenzaldehyde (1f)
p-Methoxybenzaldehyde (1g)
60
41
a Unless otherwise noted, all reactions were carried out in the
presence of Yb(OTf)3 (20 mol%) in THF at room temperature for 4
(1)
days.
b 1H-NMR yields.
1 OꢀSn bond which was generated from the reaction of aldehyde
with the tin compound would be hydrolyzed in the work-up stage.
c The reaction was carried out for 2 days.
d Isolated yields.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00339-3

J.-G. Shim / Journal of Organometallic Chemistry 588 (1999) 20–21
21
In summary, the first Yb(OTf)3-catalyzed efficient
propargylation of aldehydes with allenyltributylstan-
nane has been developed. Yb(OTf)3 is a relatively non-
toxic and easily handled catalyst in comparison with
classical Lewis acid. Therefore, the present reaction
provides a versatile tool for the preparation of an array
of homopropargyl alcohols.
The results obtained for various substrates are sum-
marized in Table 1. The aldehydes 1a,b possessing a
phenyl or an electron-deficient aryl substituent reacted
effectively with allenyltributylstannane 2 to afford
homopropargyl alcohols 3a,b, respectively, in high
yields (entries 1 and 2). In addition, 2-furfural (1c)
converted smoothly to the desired alcohol 3c in good
yield (entry 3). Even the aldehydes 1d,e, having an
aliphatic substituted R group, also gave good results
(entries 4 and 5). When the benzophenone was used as
Acknowledgements
a
carbonyl compound, the desired propargylated
The author wishes to thank Professor Yoshinori Ya-
mamoto at Tohoku University, Japan, for valuable
discussions and guidance.
product was produced in lower yield (less than 40%)
even with prolonged reaction time. It is worth noting
that the present reaction of aldehyde with allenyl-
tributylstannane could be used as a useful way afford-
ing propargyl alcohols without transposition giving
allenyl or scrambling products [6,7].
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The ytterbium triflate-catalyzed reaction of benzalde-
hyde (1a) with allenyltributylstannane (2) is representa-
tive. Benzaldehyde (1a) (0.05 ml, 0.5 mmol) was added
to a solution of Yb(OTf)3 (0.061 g, 98 mmol) and
allenyltributylstannane 2 (0.198 g, 0.6 mmol) in THF (2
ml) under an Ar atmosphere. The reaction mixture was
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ane:ethyl acetate (10:1) as eluent in 73% yield (0.054
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g)2,3
.
.
2 When the Sc(OTf)3 was used as a catalyst, the desired product 3a
was produced in 72% 1H-NMR yield. However, in the case of
La(OTf)3, only trace amounts of product was obtained.
3 Selected spectral data for compound 3a: 1H-NMR (270 MHz)
(CDCl3) l 7.41–7.23 (m, 5H), 4.87 (t, 1H, J=6.1 Hz), 2.62 (d, 2H,
J=6.1 Hz), 2.16 (s, 1H), 2.03 (s, 1H). MS (m/z) 146. Anal. Calc.
C,82.160; H, 6.985. Found C, 82.201; H, 6.888.