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].
References
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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
then stirred at room temperature. When the starting
aldehyde was completely consumed, the reaction mix-
ture was quenched with water and then extracted with
diethyl ether. After the evaporation of diethyl ether, the
resulting crude oil was treated with ethyl acetate (2 ml)
and a saturated KF solution (3 ml). The mixture was
stirred for 5 h and then extracted with diethyl ether.
After the usual work-up, the product 3a was isolated by
column chromatography on silica gel using n-hex-
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.