TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 7525–7526
An efficient method for allylation of ketones with
tetra-allylstannane
Rajesh M. Kamble and Vinod K. Singh*
Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India
Received 19 July 2001; accepted 24 August 2001
Abstract—A variety of ketones undergo an allylation reaction with tetra-allyltin in the presence of a catalytic amount of Cu(OTf)2
or Sn(OTf)2. The method was found to be superior to most of the known methods, which are efficient only with aldehydes.
© 2001 Elsevier Science Ltd. All rights reserved.
The allylation of carbonyl compounds using various
allylating reagents is very important in organic synthe-
sis as it gives homoallylic alcohols with the formation
of a new carbonꢀcarbon bond.1 One important applica-
tion of this reaction is the synthesis of d-lactones, for
example via acylation and Grubb’s cyclization.2 The
allylation reaction with tetra-allyltin has been studied
mostly for aldehydes3 but rarely for ketones4 because of
the reactivity difference in these carbonyl groups.
Recently, it was reported that a combination of zinc
triflate and a base such as 2,6-lutidine and pyridine
catalyzed the allylation of ketones.5 However, zinc tri-
flate alone was ineffective as only a 16% yield was
obtained in case of acetophenone. While working on
Cu(OTf)2- and Sn(OTf)2-catalyzed reactions,6 we
observed that allylation of acetophenone using tetra-
allyltin is efficiently catalyzed by these Lewis acids.
Since the reaction did not require any base and it can
be extended to the enantioselective version, we explored
it further and our results are described in this paper.
later found to have been a good choice as other sol-
vents such as MeCN, ether, THF, toluene, and DMSO
were inferior. It was observed that the addition of a
base such as collidine reduced the yield to 5%. The
reaction was extended to several ketones with various
steric and electronic natures, and results are summa-
rized in Table 1. In most of the cases, we obtained a
high yield in the allylation reaction. In the case of
4-t-butylcyclohexanone (entry 21), a mixture of axial
and equatorial alcohols (79:21) was obtained; the ratio
was established by 1H NMR by comparison with a
sample prepared by a different method.7 In the case of
(−)-menthone, the selectivity was reversed due to the
equatorial nature of the isopropyl group. In order to
ascertain how many allyl groups are transferred, 1, 0.5,
and 0.25 equiv. of tetra-allyl tin was used in three
separate experiments by taking an example of a simple
ketone such as cyclododecanone. It was observed that 1
and 0.5 equiv. of the reagent gave the same yield (98%)
of the allylated product (entry 23). However, on use of
0.25 equiv. of the tetra-allyltin, only 60% yield of the
product was obtained even after 24 h at rt. Similar
experiments were carried out with the less reactive
ketone 3-trifluoromethyl benzophenone (entry 17), and
the yield of allylated product dropped from 91 to 74%
when only 0.5 equiv. of the reagent was used in the
reaction. The yield dropped further to 60% when 0.25
equiv. of reagent was used in the reaction. Thus, it was
concluded that two allyl groups are readily transferred
in case of reactive ketones such as cyclododecanone.
But, the transfer of second allyl group is slow in the
case of less reactive ketone.
In a typical procedure, acetophenone (1 mmol) was
treated with tetra-allyltin (1 mmol) in the presence of
Cu(OTf)2 (10 mol%) in dry CH2Cl2 (5 mL) at rt
overnight (10–12 h). The reaction mixture was concen-
trated and the residue was taken up in EtOAc (10 mL).
It was washed with aq NaHCO3, water and brine then
dried. Solvent removal and purification over silica gel
gave the pure product (72% yield). In a similar fashion,
the reaction was attempted in the presence of Sn(OTf)2,
which also gave a clean reaction and similar yield. Since
the former Lewis acid is cheaper than the latter, it was
preferred for other substrates. Dichloromethane was
In conclusion, we have shown that Cu(OTf)2 is an
efficient catalyst for the allylation of ketones. The reac-
* Corresponding author. E-mail: vinodks@iitk.ac.in
0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(01)01606-9
Kamble, Rajesh M
