Chemoselective reduction of β-butyltellanyl α,β-unsaturated carbonyl compounds to allylic alcohols

Article abstract of DOI:10.1016/j.tet.2005.06.090

(Z)-β-Butyltellanyl α,β-unsaturated carbonyl compounds were stereoselectively produced by hydrotelluration of alkynones or by an addition/elimination sequence from enol tosylates. The β-butyltellanyl- enones were chemoselectively reduced with NaBH₄

Full text of DOI:10.1016/j.tet.2005.06.090

Tetrahedron 61 (2005) 9173–9179
Chemoselective reduction of b-butyltellanyl a,b-unsaturated
carbonyl compounds to allylic alcohols
*
´
Alcindo A. Dos Santos, Priscila Castelani, Bruno K. Bassora, Jose C. Fogo Junior,
Carlos E. Costa and Joa˜o V. Comasseto
´
Instituto de Quımica, Av. Prof. Lineu Prestes, 748-CEP 05508-900, Sa˜o Paulo-SP, Brazil
Received 25 April 2005; revised 27 June 2005; accepted 27 June 2005
Abstract—(Z)-b-Butyltellanyl a,b-unsaturated carbonyl compounds were stereoselectively produced by hydrotelluration of alkynones or by
an addition/elimination sequence from enol tosylates. The b-butyltellanyl-enones were chemoselectively reduced with NaBH4/MeOH,
NaBH4$CeCl3$7H2O/MeOH and DIBAL-H systems to the corresponding allylic alcohols with retention of the Z stereochemistry.
q 2005 Elsevier Ltd. All rights reserved.
1. Introduction
methods to prepare functionalized vinylic tellurides can be
considered of general character, the hydrotelluration of
activated alkynes 31a,2 and the vinylic substitution of vinyl
halides, triflates, phosphates and acetates4 7 bearing
electron stabilizing groups at the b position (Scheme 1).
Both methods give one single regioisomer of the Z
configuration 6 exclusively.1,2,4 Contrary to the hydro-
telluration of alkynones 3, propargyl alcohols 2 give
mixtures of vinylic tellurides 4 and 5 on hydrotelluration
(Scheme 1).5
The organic chemistry of tellurium experienced a great
development in the last decade.1 One of the most studied
classes of organotellurium compounds are the vinylic
tellurides.1,2 Recently two of such species have been
employed in the total synthesis of two structurally complex
natural products.3 The vinylic telluride 1 used in one of
these synthesis3b presents a hydroxyl group at one end,
which allows the chain elongation by appropriate manipu-
lation of the functionality. At the other end of the molecule,
the vinyltellurium moiety constitutes an equivalent of
vinyl organometallics.1,2 This bifunctional character of
functionalized vinylic tellurides makes them extremely
versatile synthetic building blocks (Fig. 1).
Figure 1. Bifunctional character of functionalized vinylic tellurides.
In view of this fact, in recent years we have dedicated
special attention to the development of general method-
ologies to prepare functionalized tellurides.1a,2 To date, two
Scheme 1. Preparation of functionalized vinylic tellurides.
A good approach to prepare vinylic tellurides 4 in pure form
would be the reduction of 6. However, sodium borohydride
usually promotes the reduction of the carbon–carbon
double bond of a,b-unsaturated ketones.6 The presence of
cerium chloride in the reaction medium avoids this side
Keywords: Vinylic tellurides; Chemoselective reduction; Enones and
allylic alcohols.
*
Corresponding author. Tel./fax: C55 11 3091 2176;
e-mail: alcindo@iq.usp.br
0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2005.06.090

9174
A. A. Dos Santos et al. / Tetrahedron 61 (2005) 9173–9179
reaction.7 Another way to circumvent the 1,4-reduction was
recently described by Zeynizadeh and Yahyaei, where
sodium borohydride in THF under ultrasonic irradiation
performs high selective reduction of enones to the
corresponding allylic alcohols.7c
In this paper, we describe a systematic study on the
reduction of a,b-unsaturated carbonyl compounds bearing a
butyltellanyl group at the b-position, as a route to vinylic
tellurides of the type 4 (Scheme 1).
As a very often mentioned drawback to the use of
organotellurium compounds is their alleged bad smell, it
is important to point out that all the compounds described in
this paper are not bad smelling. Most of them are almost
odourless or present a smell not more unpleasant than most
of the laboratory chemicals normally used in an organic
synthesis laboratory. In the last few years our laboratory
has devoted efforts to avoid the use of bad smelling low
molecular weight alkyl tellurium compounds as starting
materials in the preparation of more complex tellurium
compounds. Elemental tellurium and n-butyllithium have
been used instead in our new synthetic methodologies to
introduce tellurium into organic substrates.1a,4b–d,8 All the
compounds described in this paper, are stable to the ambient
light and can be manipulated in the air. However, long
contact of the compounds with air, especially when in
solution, must be avoided, since alkyltellurides react with
oxygen to give an amorphous white powder, presumably a
telluroxide. After evaporation of the solvents the pure
compounds can be manipulated in the presence of air with
no need of special precautions. Finally, it must be pointed
out that the compounds described here were not tested for
their toxicity. A recent review9 on the pharmacology and
toxicology of organic tellurium compounds mention that the
few studies on this matter indicate that tellurium compounds
are toxic to mammals, in the same way as are many other
widely used compounds of, for example, phosphorous10 and
tin,11 elements routinely used in any organic synthesis
laboratory. In this way, the obvious safety cautions
recommended in the manipulation of laboratory chemicals
must be taken in handling organotellurium compounds.
Scheme 2. Preparation of the b-butyltellanyl enones.
Scheme 3. Large scale preparation of 6d.
The b-butyltellanyl enones 6e and 6f were prepared by a
vinylic substitution reaction using enol tosylates 7e and 7f
and lithium n-butyltellurolate, prepared by addition of
n-butyllithium to elemental tellurium in THF at 0 8C.4b–e
The substitution reaction was completed in few minutes.
Both methods gave the b-butyltellanyl ketones as yellow or
orange oils in good yields after purification by silica gel
column chromatography. As commented before, 6a–f are
almost odourless compounds.
All compounds were formed as a single Z stereoisomer. The
stereochemistry was assigned by spectroscopic and
chromatography analysis and was in agreement with
previous reports.4b–e
2. Results and discussion
Two routes were used to prepare the b-butyltellanyl
alkenones used in this study. The first one was the
hydrotelluration of alkynones 3.2 The hydrotellurating
agent was prepared by addition of n-butyllithium to a
suspension of elemental tellurium in THF at 0 8C under
nitrogen. A clear yellow solution was formed with the
consumption of the grey tellurium powder. Deoxygenated
water or ethanol was added to this solution and then the
alkynone 3a–d (Scheme 2). The b-butyltellanyl enone 6d
was prepared by an efficient sequential large scale (0.1 mol)
procedure (Scheme 3). To pre-generated monolithium
acetylide in THF at 0 8C was added ZnCl2 and the resulting
solution was stirred for 30 min at 0 8C. Then acetylchloride
in THF was added and after 30 min at room temperature the
mixture was transferred to a pre-formed hydrotelluration
system prepared as described above. The b-butyltellanyl
enone 6d was obtained in 62% overall yield (Scheme 3).
With the b-butyltellanyl enones 6a–f in hands we initiated
the study of their reduction to the vinylic tellurides 4
(Scheme 4). The reducing systems used were sodium
Scheme 4. Reduction of compound 6a by different reducing systems.

A. A. Dos Santos et al. / Tetrahedron 61 (2005) 9173–9179
9175
borohydride in methanol/ethanol, sodium borohydride/
cerium chloride in methanol/ethanol, and diisobutyl-
aluminum hydride (DIBAL-H) in tetrahydrofuran. The
b-butyltellanyl enone 6a was used in this exploratory
study (Scheme 4).
the allylic alcohol 4f as the trimethylsilyl ether 9. In this
case only one peak was observed by GC analysis
(Scheme 5).
It is worth mentioning that DIBAL-H has been used in
highly chemoselective reductions of conjugated aldehydes
and ketones, leading to the corresponding allylic alcohols.12
On the other hand, when conjugated ketones are reduced
with sodium borohydride, a mixture of the allylic and the
corresponding saturated alcohol is formed.6b As mentioned
before, the high selective formation of allylic alcohols is
possible by the addition of cerium chloride to the sodium
borohydride reducing systems.7
Scheme 5. Thermal decomposition of 4f under GC–MS analysis conditions
and its derivatization to TMS ether 9.
In view of these literature reports, the results shown in
Scheme 4 are noteworthy, since the reduction of only the
carbonyl group was observed in the three reducing systems.
More interesting in a practical point of view is the fact that
comparable good yields were obtained when sodium
borohydride only was used as the reducing agent. As the
substituent at the b-position of the conjugated system plays
an important role in the chemoselectivity of the reduction
process,6b we can presume that the high chemoselectivity in
the present case can be attributed to the butyltellanyl group.
In order to test the generality of this behaviour of the
butyltellanyl enones 6, the whole series of compounds 6 was
submitted to the same reaction conditions described in
Scheme 4. The results are summarized in Table 1. Also in
this case, the obtained alcohols are almost odourless yellow
oils.
In one case (alkynone 3a) the hydrotelluration was
performed using the classical conditions employed for this
transformation.1a,2 Dibutylditelluride was reduced with
sodium borohydride in ethanol and then 3a was added to
the hydrotellurating system containing an excess of sodium
borohydride. The alcohol 4a of the Z configuration was
obtained as the only product, indicating that the hydro-
telluration and the carbonyl reduction can be performed in a
one pot operation. In order to avoid the use of the
malodorous dibutylditelluride, the hydrotelluration reaction
was performed using the lithium butyltellurolate/ethanol
method,8 and then sodium borohydride was added to the
reaction mixture. Results similar to the obtained by the
preceding method were obtained (Scheme 6).
Table 1. Reduction of b-butyltellanyl enones 6a–f under the reduction
conditions shown in Scheme 4
Enone
Product
(a) Yield
(%)a,b
(b) Yield
(%)a,b
(c) Yield
(%)a,c
6a
6b
6c
6d
6e
6f
4a
4b
4c
4d
4e
4f
75
98
84
80
60d
86
92
95
70
93
96
70
68
84
76
76
70
78
Scheme 6. Sequential one pot hydrotelluration/reduction of alkynone 3a to
the allylic alcohol 4a.
a Isolated yields after column chromatography on silica gel.
b The reactions were performed at 0 8C.
As an extension of the studies reported above, the
hydrotelluration of ethyl propiolate was performed using
the lithium butyltellurolate/ethanol method.8 The vinylic
telluride 10 of the Z configuration was formed as the only
product in 88% yield (Scheme 7), which was then reduced
with DIBAL-H in THF at K20 8C leading to the alcohol 4g
in 70% yield as the only product. It is worth mentioning that
the preparation of alcohol 4g by hydrotelluration of
propargyl alcohol gives a mixture of regioisomers 4 and 5
(Scheme 1).5
c The reactions were performed at K20 8C.
d The reaction was performed at room temperature.
As can be observed, results very similar to those obtained
for compound 6a (Scheme 4) were obtained for all
b-butyltellanyl enones 6. In all cases it was not observed
any trace of the saturated alcohol. The analytical data of all
compounds showed that only one isomer was formed from
the corresponding Z enone. The NOESY experiments of
compounds 6c and 6e showed that the stereochemistry of
the double bond remains Z.
It was also observed that the alcohols 4a–f are thermally
unstable under GC analysis conditions producing probably
the corresponding water elimination products 8 (from 4f),
since two peaks of equal mass and similar fragmentation
patterns appeared in the GC–MS spectra of these
compounds. This assumption was confirmed by derivatizing
Scheme 7. Chemoselective reduction of the ester 10 to the alcohol 4g.

9176
A. A. Dos Santos et al. / Tetrahedron 61 (2005) 9173–9179
3. Conclusions
necked round-bottomed flask equipped with magnetic
stirring under nitrogen atmosphere at K70 8C were added
the terminal alkyne (10 mmol) and THF (50 mL). To the
solution was slowly added n-butyllithium (1 equiv,
1.24 mol LK1 solution in hexanes). The solution was
warmed up to 0 8C, stirred at this temperature for 30 min
and then cooled at K70 8C prior to the addition of a solution
of ZnCl2 (1 equiv, 1 mol LK1 solution in THF). The
solution was warmed and stirred at room temperature for
additional 15 min and then recooled at K70 8C. Benzoyl or
acetyl chloride was added in one portion. The reaction
mixture was warmed to room temperature and stirred for
additional 40 min, then diluted with hexane (10 mL) and
washed with brine (3!10 mL). The organic phase was
dried over magnesium sulphate and filtered. The solvents
were evaporated and the residue purified by silica gel
column chromatography eluting with hexane/ethyl ether
70:1 yielding 1.83 g (89%) of (3a), 1,3-diphenylprop-2-yn-
1-one [7338-94-5]; (3b), 4-phenylbut-3-yn-2-one [1817-57-
8]; (3c), oct-3-yn-2-one [1119-58-0].
In conclusion, the chemoselective reduction of b-butyl-
tellanyl enones constitutes a good method to prepare allylic
alcohols containing a butyltellanyl group at the g-position to
the hydroxyl function. Cerium trichloride is a dispensable
additive in the chemoselective reduction of b-butyltellanyl
enones to the corresponding allylic alcohols.
4. Experimental
4.1. Materials
All reagents and solvents used were previously purified and
dried in agreement with the literature.13 THF was distilled
from sodium/benzophenone under nitrogen immediately
before use. n-Butyllithium was titrated using 1,10-phenan-
throline as indicator prior to use.14 Nitrogen gas used in the
reactions was deoxygenated and dried. All operations were
carried out in flame-dried glassware. Column chromato-
graphy separations were performed with Vetec silicagel 60
(0.063–0.200 mm, 70–230 mesh) or Acros Organics
silicagel (0.035–0.075 mm, pore diameter ca. 6 nm).
Tellurium metal of 200 mesh was dried overnight in an
over at 100 8C, sodium borohydride, cerium trichloride
heptahydrate and DIBAL-H (1 mol LK1 in hexanes) were
purchased from Aldrich Chemical Co. The following
reagents were pepared according to literature procedures:
(7e), 4-oxopent-2-en-2-yl 4-methylbenzenesulfonate
[435294-87-4];4e (7f), 5,5-dimethyl-3-oxocyclohex-1-enyl
4-methylbenzenesulfonate [77708-65-7];4c,e (6e), (Z)-4-(n-
butyltellanyl)pent-3-en-one [251991-67-9];4c,e (6f), 3-(n-
butyltellanyl)-5,5-dimethylcycloex-2-enone [849595-89-
7];4c,e (10), (Z)-ethyl 3-butyltellanyl)acrylate [185841-09-
2];15 (4g), (Z)-3-(butyltellanyl)prop-2-1-ol [185841-11-6].15
These last compounds presented analytical data, which agree
with the proposed structures. The remaining chemicals were
obtained from commercial sources.
4.3.2. Preparation of alkenones 6e–f.4c,e To a suspension
of elemental tellurium (1.9 g, 15 mmol) in THF (30 mL)
under nitrogen at 0 8C was slowly added n-butyllithium
(from a 1.4 mol LK1 in hexanes, 10.5 mL, 15 mmol). A
clear yellow solution was formed. Then the appropriated
enol sulfonate (7e or 7f) was added (13 mmol) and the
mixture was stirred at 0 8C until the consumption of the enol
(the reaction was monitored by TLC). After this, the
reaction mixture was diluted with ethyl acetate (100 mL)
and washed with brine (3!50 mL). The organic phase was
dried with magnesium sulfate and the solvents were
evaporated. The residue was purified by silica gel
chromatography eluting with hexane/ethyl acetate 19:1.
All spectral data agree with those of the literate.
4.3.3. Preparation of the b-butyltellanyl enone (6d). A
500 mL, septum capped, round-bottomed flask, equipped
with a magnetic stir bar and purged under N2 was charged
200 mL of dry THF. The apparatus was cooled at 0 8C, and
the solution saturated with acetylene by means of a 10-mm
needle approximately 30 cm in length inserted through the
septum of the flask. n-Butyllithium (50 mmol, 38 mL of a
1.31 mol LK1 solution in hexanes) was introduced dropwise
into the reaction flask over a period of 20 min by means of a
syringe. The inlet end of the needle was pushed below the
surface of the liquid to avoid contact of the organolithium
with the acetylene atmosphere and formation of dilithium
carbide on the needle tip. The contents were resaturated
with acetylene, and zinc chloride (50 mmol, 50 mL of a
1.00 mol LK1 solution in THF) was introduced dropwise via
syringe. The solution was warmed to ambient temperature,
and stirred for 30 min then recooled to 0 8C. A solution of
acetyl chloride (50 mmol, 3.55 mL in 10 mL of THF) was
introduced dropwise via syringe. The resulting solution was
stirred for additional 30 min at 0 8C and then warmed to
room temperature. To a second 1 L-flask containing a
suspension of elemental tellurium (52 mmol, 6.63 g) in THF
(150 mL) at 0 8C n-butyllithium (52 mmol, 39.5 mL of a
1.31 mol LK1) was added. A clear yellow solution was
formed. To this solution was added deoxygenated water
(10 mL). The resulting red solution was stirred for 10 min at
room temperature. The in situ above prepared alkynone was
4.2. Analysis
1H and 13C NMR spectra were obtained on a Bruker AC-200
1
1
(200 MHz, H; 50 MHz, 13C) or DRX-500 (500 MHz, H;
125 MHz, 13C) or on a Varian INOVA 300 (300 MHz, H;
1
75 MHz, 13C) Spectrometers. All spectra were taken in
CDCl3 and the chemical shifts are given in ppm with respect
to tetramethylsilane (TMS) used as internal standard. 125Te
NMR spectra were obtained on a Bruker DRX-500
(157 MHz, 125Te) spectrometer using CDCl3 as solvent.
The chemical shifts refer to diphenyl ditelluride (PhTe)2 in
CDCl3 (1 mol LK1) (dZ420 ppm at 25 8C) as external
standard. Low resolution mass spectra were obtained on a
Shimadzu CG-17A/CG/MS-QP5050A instrument. Near IR
spectra were obtained on a Bomen MB-100 spectrometer.
Elemental analyses were performed at the Microanalytical
Laboratory of the Institute of Chemistry, Universidade de
Sa˜o Paulo. The IUPAC names were obtained using the
software ChemDraw, version 8.0.
4.3. Typical procedures
4.3.1. Preparation of alkynones 3a–c.16 To a 100 mL two-

A. A. Dos Santos et al. / Tetrahedron 61 (2005) 9173–9179
9177
transferred via cannula to the second flask containing the
hydrotellurating system. The progress of the reaction was
monitored by TLC. After 5 min the reaction mixture
was diluted with hexane (200 mL) and the organic phase
was washed with brine (3!100 mL) and then dried with
magnesium sulphate. The solvents were evaporated and the
residue was purified by column chromatography on silica
gel eluting with hexane/ethyl acetate 20:1 to give 3.1 g
(62%) of the pure telluride (Z)-4-(butyltellanyl)but-3-en-2-
one (6d): (Found: C, 38.03; H, 5.38. C8H14OTe requires C,
37.86; H, 5.38%); nmax (film) 2957, 2922, 2730, 2376, 2064,
1852, 1750, 1644, 1506, 1360, 1334, 1189, 973, 709, 669.
dH (200 MHz, CDCl3) 0.92 (t, JZ7.5 Hz, 3H); 1.40 (sext.,
JZ7.5 Hz, 2H); 1.80 (quint., JZ7.0 Hz, 2H); 2.24 (s, 3H);
2.51 (t, JZ7.5 Hz, 2H); 7.53 (d, JZ9.2 Hz, 1H); 8.78 (d,
JZ9.2 Hz, 1H); dC (50 MHz, CDCl3) 197.1; 139.8; 129.5;
33.7; 29.9; 24.9; 13.3; 10.5; dTe (157.79 MHz/
300 K/Ph2Te2) 606.7; (m/z (EI, 70 kV) 256 (8, MCC3);
254 (8, MCC1); 252 (5); 251 (2); 200 (2); 199 (46); 196 (45);
195 (25); 193 (10); 192 (7); 190 (3); 57 (10); 55 (11); 43 (100).
(Found: C, 46.61; H, 7.09. C12H22OTe: C, 46.51; H, 7.16%);
nmax (film) 2928, 2867, 1644, 1523, 1461, 1359, 1333, 1249,
1207, 992. dH (500 MHz, CDCl3) 0.91 (t, JZ7.3 Hz, 3H);
0.92 (t, JZ7.3 Hz, 3H); 1.36–1.42 (m, 4H); 1.50–1.54 (m,
2H); 1.60–1.69 (m, 2H); 2.16 (s, 3H), 2.53 (t, JZ7.7 Hz,
2H); 2.61 (t, JZ7.6 Hz, 2H); 7.16 (s, 1H); dC (50 MHz,
CDCl3) 196.2; 159.1; 127.5; 39.4; 33.4; 32.9; 29.8; 25.3;
22.1; 13.8; 13.4; 5.9; dTe (157.79 MHz/295.3 K/Ph2Te2)
451.4; m/z (EI, 70 kV) 312 (MCC2, 2); 310 (MCC1, 25);
255 (100); 254 (10); 253 (91); 251 (53); 250 (21); 249 (13);
211 (8); 95 (21).
4.3.5. Sequential hydrotelluration/reduction procedure
of 3a to 4a by the Bu2Te2/NaBH4 method. To a solution of
dibutyl ditelluride (5 mmol, 1.85 g) in ethanol (7 mL) was
added sodium borohydride (5.2 mmol, 0.19 g) at room
temperature. A solution of ketone 3a (5 mmol, 1.03 g) in
ethanol (2 mL) was then added dropwise. After 30 min, the
reaction mixture was cooled to 0 8C and an ethanolic
solution of sodium borohydride (10 mmol, 0.34 g in 10 mL
of ethanol) was added dropwise. Thirty minutes latter the
reaction mixture was diluted with ethyl ether (100 mL) and
washed with water (2!10 mL) and brine (10 mL). The
residue was purified by column chromatography on silica
gel eluting with hexane/ethyl acetate 5:1, yielding 1.37 g
(70%) of 4a.
4.3.4. Hydrotelluration of 3a–c by the [BuTeLi/EtOH]
method. To a suspension of elemental tellurium (0.96 g,
7.5 mmol) in THF (15 mL) under nitrogen at 0 8C was
slowly added n-butyllithium (7 mmol, 5.25 mL of a
1.4 mol LK1 solution in hexanes). A clear yellow solution
was formed. After 5 min the alkynone (3a, 3b or 3c) was
added in deoxygenated ethanol (2 mL). After 30 min the
reaction mixture was diluted with hexane (30 mL) and
washed with water (2!10 mL) then with brine (2!10 mL),
the phases were separated and the organic phase was dried
with magnesium sulphate. The solvents were evaporated
and the residue was purified by column chromatography on
silica gel eluting with hexane/ethyl acetate 20:1.
4.3.6. Sequential hydrotelluration/reduction procedure
of 3a to 4a by the [BuTeLi/EtOH] method. To a
suspension of elemental tellurium (0.19 g, 1.5 mmol) in
THF (5 mL) under nitrogen at 0 8C, was slowly added
n-butyllithium (from a 1.4 mol LK1 solution in hexanes,
1.2 mL, 1.5 mmol). A clear yellow solution was formed.
Then an ethanolic solution of alkynone 3a was added (2 mL,
0.31 g, 1.5 mmol) and the mixture was stirred at room
temperature for 30 min. After 30 min, the reaction mixture
was cooled to 0 8C and an ethanolic solution of sodium
borohydride (10 mmol, 0.34 g in 10 mL of ethanol) was
added dropwise. Thirty minutes latter the reaction mixture
was diluted with ethyl ether (100 mL) and washed with
water (2!10 mL) and brine (10 mL). The organic phase
was dried with magnesium sulphate and the solvents were
evaporated. The residue was purified by silica gel column
chromatography eluting with hexane/ethyl acetate 5:1,
yielding 0.42 g (70%) of 4a.
(Z)-3-(Butyltellanyl)-1,3-diphenylprop-2-en-1-one (6a)
(92%)
(Found: C, 58.39; H, 5.21. C19H20OTe requires C, 58.16; H,
5.10%); nmax (film) 2957, 2864, 2864, 1958, 1899, 1813,
1615, 1573, 1513, 1480, 1337, 1238, 1045. dH (300 MHz,
CDCl3) 0.75 (t, JZ7.5 Hz, 3H); 1.17 (sext., JZ7.5 Hz, 2H);
1.47 (quint., JZ7.8 Hz, 2H); 2.1 (t, JZ7.2 Hz, 2H); 7.29–
7.60 (m, 8H); 8.02 (s, 1H); 8.04–8.10 (2H); dC (75 MHz,
CDCl3) 188.1; 160.4; 142.8; 138.1; 132.3; 128.6; 128.1;
127.9; 127.3; 126.4; 32.9; 25.1; 13.2; 10.5; dTe
(157.79 MHz/295.3 K/Ph2Te2) 686.0; m/z (EI, 70 kV) 390
(1); 337 (31); 333 (17); 207 (17); 205 (10); 180 (10); 105
(10); 77 (100); 51 (22).
4.3.7. General procedure for reduction of enones to the
corresponding allylic alcohol by NaBH4. To a solution of
the appropriate enone (1 mmol) in methanol (5 mL) at 0 8C,
a solution of NaBH4 in ethanol was added by means of a
dropping funnel (usually 2 equiv was needed; 2 mL from a
1 mol LK1, 2 mmol, 2 equiv). The reaction was monitored
by thin layer chromatography. After total consumption of
the starting material, the reaction mixture was diluted with a
mixture of hexane/diethyl ether (1:1, 15 mL) and washed
with water (3!10 mL) and brine (2!10 mL). The solvents
were evaporated and the residue was purified by column
chromatography on silica gel eluting with hexane/ethyl
acetate 5:1.
(Z)-4-(Butyltellanyl)-4-phenylbut-3-en-2-one (6b) (62%)
(Found: C, 51.13; H, 5.35. C14H18OTe requires C, 50.97; H,
5.50%); nmax (film) 3058, 2957, 2923, 1614, 1575, 1518,
1238, 1059, 774, 699. dH (200 MHz, CDCl3) 0.70 (t, JZ
7.5 Hz, 3H); 1.10 (sext., JZ7.0 Hz, 2H); 1.38 (quint., JZ
7.5 Hz, 2H); 2.00 (t, JZ7.5 Hz, 2H); 2.27 (s, 3H); 7.18–7.42
(m, 5H); dC (75 MHz, CDCl3) 196.1; 156.3; 142.2; 130.0;
128.0; 127.9; 127.3; 33.0; 30.1; 25.0; 13.2; 9.8; dTe
(157.79 MHz/295.3 K/Ph2Te2) 578.0; m/z (EI, 70 kV) 275
(100); 145 (20); 105 (70); 77 (85).
(Z)-3-(Butyltellanyl)-1,3-diphenylprop-2-en-1-ol (4a)
(92%)
(Z)-4-(Butyltellanyl)oct-3-en-2-one (6c) (79%)

9178
A. A. Dos Santos et al. / Tetrahedron 61 (2005) 9173–9179
(Found: C, 58.02; H, 5.71. C19H20OTe requires C, 57.92; H,
5.59%); nmax (film) 3361, 3057, 2957, 2926, 1949, 1882,
1806, 1755, 1677, 1599, 1488, 1447, 1013, 759. dH
(200 MHz, CDCl3) 0.74 (t, JZ7.0 Hz, 3H); 1.20 (sext.,
JZ7.0 Hz, 2H); 1.52 (quint., JZ7.5 Hz, 2H); 2.02 (sl, 1H);
1.30–1.36 (m, 2H); 5.61 (d, JZ7.5 Hz, 1H), 6.16 (d, JZ
7.9 Hz, 1H); 7.22–7.48 (m, 10H); 7.16 (s, 1H); dC (50 MHz,
CDCl3) 143.0; 142.9; 140.8; 128.8; 128.6; 128.1; 127.6;
127.5; 126.3; 124.3; 77.6; 33.8; 24.8; 13.2; 8.3; dTe
(157.79 MHz/295.3 K/Ph2Te2) 361.7.
2.67–2.80 (m, 2H), 4.45 (q, JZ6.3 Hz, 1H); 1.80–1.82 (dq,
JZ7.8, 1.2 Hz, 1H); dC (50 MHz, CDCl3) 140.2; 114.4;
71.4; 34.4; 29.1; 25.0; 22.9; 13.4; 4.8; dTe (157.79 MHz/
295.3 K/Ph2Te2) 326.5; m/z (EI, 70 kV) 272 (5); 270 (5);
268 (2); 215 (9); 213 (11); 85 (36); 69 (19); 67 (58); 57 (43);
55 (14); 45 (35); 43 (100).
3-(Butyltellanyl)-5,5-dimethylcyclohex-2-enol (4f) (96%)
(Found: C, 46.30; H, 6.97. C12H22OTe requires C, 46.60; H,
7.11%); nmax (film) 3340, 2952, 2924, 1618, 1461, 1161,
1098, 1038, 1001, 940, 803. dH (500 MHz, CDCl3) 0.92 (t,
JZ7.4 Hz, 3H); 0.94 (s, 3H); 0.99 (s, 3H); 1.06 (sl, 1H);
1.31 (dd, JZ12.5, 3.2 Hz, 1H); 1.39 (sext., JZ7.4 Hz, 2H),
1.77 (quint. a, JZ7.6 Hz, 2H); 1.80–1.82 (m, 1H); 2.05 (dd,
JZ17.4, 1.3 Hz, 1H); 2.19 (dt, JZ17.4, 2.6 Hz, 1H); 2.72–
2.78 (m, 2H); 4.28 (m, 1H); 6.14 (s, 1H); dC (125 MHz,
CDCl3) 137.6; 113.9; 67.9; 49.2; 44.7; 33.9; 32.9; 31.5;
30.9; 25.9; 2.1; 24.7; 13.7; 13.4; 5.8; dTe (157.79 MHz/
295.3 K/Ph2Te2) 452.8; m/z (EI, 70 kV) 312 (7); 310 (7);
308 (4); 125 (94); 107 (36); 91 (29); 83 (12); 81 (15); 79
(27); 69 (43); 67 (12); 57 (56); 55 (52); 43 (100).
(Z)-4-(Butyltellanyl)-4-phenylbut-3-en-2-ol (4b) (95%)
(Found: C, 51.09; H, 6.16. C14H22OTe requires C, 50.75; H,
6.04%); nmax (film) 3326, 3019, 2866, 1947, 1883, 1805,
1754, 1676, 1598, 1445, 1247, 1136, 1089, 1059, 759, 698.
dH (200 MHz, CDCl3) 0.74 (t, JZ7.0 Hz, 3H); 1.07–1.30
(m, 2H); 1.34 (d, JZ6.6 Hz, 3H); 1.50 (quint., JZ7.9 Hz,
2H); 2.30 (ta, JZ9.2 Hz, 2H); 4.65 (quint., JZ6.6 Hz, 1H),
5.96 (d, JZ7.5 Hz, 1H); 7.10–7.50 (m, 5H); dC (50 MHz,
CDCl3) 142.9; 142.7; 128.6; 128.0; 127.3; 121.9; 71.5; 33.7;
24.7; 23.0; 13.1; 7.8; dTe (157.79 MHz/295.3 K/Ph2Te2)
355.3; m/z (EI, 70 kV) 334 (MCC3, 24); 332 (MCC2, 23);
330 (13); 277 (14); 275 (14); 147 (45); 145 (16); 131 (19);
130 (17); 129 (64); 128 (34); 127 (12); 103 (100); 102 (29);
77 (45); 76 (11); 69 (45); 57 (51); 55 (18); 51 (15).
4.3.8. General procedure for reduction of the enones to
the corresponding allylic alcohol by NaBH4$CeCl3. To a
solution of cerium trichloride heptahydrate (1 mmol,
0.372 g) in methanol was added the appropriated enone
(1 mmol) at 0 8C. To the resulting mixture, a solution of
NaBH4 in ethanol was added by means of a dropping funnel
(Z)-4-(Butyltellanyl)oct-3-en-2-ol (4c)17 (70%)
nmax (film) 3339, 2959, 2926, 2866, 1618, 1459, 1370, 1057,
865. dH (200 MHz, CDCl3) 0.92 (ta, JZ7.0 Hz, 6H); 1.20–
1.50 (m, 8H); 1.65–1.80 (m, 2H); 2.01 (sl, 1H); 2.32 (ta, JZ
7.9 Hz, 2H); 2.68 (td, JZ7.9, 2.2 Hz, 2H), 4.56 (quint. a,
JZ6.2 Hz, 1H); 5.70 (d, JZ7.9 Hz, 1H); dC (50 MHz,
CDCl3) 140.5; 121.4; 71.7; 41.5; 34.2; 32.0; 31.9; 25.0;
23.0; 21.8; 13.9; 13.3; 5.2; dTe (157.79 MHz/
295.3 K/Ph2Te2) 265.6; m/z (EI, 70 kV) 314 (25); 312
(24); 311 (2); 310 (15); 257 (39); 255 (40); 253 (26); 188
(4); 127 (42); 126 (92); 111 (11); 110 (21); 109 (45); 98 (4);
97 (54); 93 (12); 84 (11); 83 (23); 81 (50); 79 (21); 71 (58);
69 (35); 68 (47); 67 (80); 65 (11); 57 (94); 55 (100).
(usually 2 equiv was needed; 2 mL from a 1 mol LK1
,
2 mmol, 2 equiv). The reaction was monitored by TLC.
After total consumption of the starting material, the reaction
mixture was diluted with a mixture of hexane/diethyl ether
(1:1, 15 mL) and washed with water (3!10 mL) and brine
(2!10 mL). The solvents were evaporated and the residue
was purified by column chromatography on silica gel
eluting with hexane/ethyl acetate 5:1. (Z)-(Butyltellanyl)-1,
3-diphenylprop-2-en-1-ol (4a), 92%. (Z)-4-(Butyltellanyl)-
4-phenylbut-3-en-2-ol (4b), 98%. (Z)-4-(Butyltellanyl)oct-
3-en-2-ol (4c), 84%. (Z)-4-(Butyltellanyl)but-3-en-2-ol
(4d), 80%. 3-(Butyltellanyl)-5,5-dimethylcyclohex-2-enol
(4f), 60%. (Z)-4-(Butyltellanyl)pent-3-en-2-ol (4e), 86%.
The spectral data are identical to those described in Section
4.3.7 for the same compounds.
(Z)-4-(Butyltellanyl)but-3-en-2-ol (4d) (93%)
(Found: C, 37.16; H, 5.80. C8H16OTe requires C, 37.54; H,
6.20%); nmax (film) 3349, 2960, 2925, 2868, 1597, 1457,
1282, 1108, 1046, 706. dH (300 MHz, CDCl3) 0.92 (t, JZ
7.2 Hz, 3H); 1.27 (d, JZ6.3 Hz, 3H); 1.39 (sext., JZ7.8 Hz,
2H); 1.78 (q, JZ7.8 Hz, 2H); 1.94 (sl, 1H); 2.65 (td, JZ
7.5 Hz, 2H), 4.34 (quint. a, JZ6.3 Hz, 1H); 6.28 (dd, JZ
6.6, 9.9 Hz, 1H); 6.70 (dd, JZ1.2, 9.9 Hz, 1H); dC (50 MHz,
CDCl3) 141.8; 103.4; 70.5; 34.0; 24.9; 22.4; 13.3; 7.2; dTe
(157.79 MHz/295.3 K/Ph2Te2) 280.9; m/z (EI, 70 kV) 258
(13); 256 (12); 201 (15); 199 (15); 71 (100); 57 (60); 55
(40); 53 (35); 45 (22); 43 (81); 41 (55).
4.3.9. General procedure for reduction of the enones to
the corresponding allylic alcohol by DIBAL-H. To a
solution of the appropriate enone (1 mmol) in dry THF
(5 mL) at K20 8C, was slowly added a solution of DIBAL-H
(1.1 equiv from a 1 mol LK1 in hexane). The reaction was
monitored by TLC. After total consumption of the starting
material, to the cooled solution was added 0.5 mL of
methanol, 0.5 mL of water, 0.7 g of magnesium sulphate
and 0.7 g of Celitew. The reaction mixture was stirred at
0 8C for additional 30 min. The solid was separated by
filtration and the solid residue washed with ethyl acetate.
The organic layer was washed with brine (2!5 mL) and
dried with magnesium sulphate. The solvents were
evaporated and the residue was purified by column
chromatography on silica gel eluting with hexane/ethyl
acetate 5:1. (Z)-(Butyltellanyl)-1,3-diphenylprop-2-en-1-ol
(4a), 68%. (Z)-4-(butyltellanyl)-4-phenylbut-3-en-2-ol
(4b), 84%. (Z)-4-(butyltellanyl)oct-3-en-2-ol (4c), 76%.
(Z)-4-(Butyltellanyl)pent-3-en-2-ol (4e) (70%)
(Found: C, 40.00; H, 6.30. C9H18OTe requires C, 40.06; H,
6.67%); nmax (film) 3350, 2959, 2933, 2348, 1443, 1264,
1109, 1058, 939. dH (300 MHz, CDCl3) 0.92 (t, JZ7.5 Hz,
3H); 1.26 (d, JZ6.3 Hz, 3H); 1.39 (sext, JZ7.5 Hz, 2H);
1.75 (quint a, JZ7.2 Hz, 2H); 2.26 (d, JZ1.8 Hz, 3H);

A. A. Dos Santos et al. / Tetrahedron 61 (2005) 9173–9179
9179
(Z)-4-(Butyltellanyl)but-3-en-2-ol (4d), 76%. 3-(butyl-
References and notes
tellanyl)-5,5-dimethylcyclohex-2-enol (4f), 70%. (Z)-4-
(Butyltellanyl)pent-3-en-2-ol (4e), 78%. The spectral data
are identical to those described in Section 4.3.7 for the same
compounds.
1. For recent reviews see: (a) Comasseto, J. V.; Barrientos-
Astigarraga, R. E. Aldrichim. Acta 2000, 33, 66–78. (b)
Petragnani, N.; Stefani, H. A. Tetrahedron 2005, 61,
1613–1679.
2. Vieira, M. L.; Zinn, F. K.; Comasseto, J. V. J. Braz. Chem.
Soc. 2001, 12, 586–596 and references therein.
4.3.10. Reduction of (Z)-ethyl 3-(butyltellanyl)acrylate
(10) to (Z)-3-(butyltellanyl)prop-2-en-1-ol with DIBAL-H.
To a solution of ester 10 (1 mmol, 0.283 g) in dry THF
(5 mL) at K20 8C, was slowly added a solution of DIBAL-H
(2 mmol, 2 mL, 1 mol LK1 solution in hexane). The
reaction was monitored by TLC. After total consumption
of the starting material, to the cooled solution was added
0.5 mL of methanol, 0.5 mL of water, 0.7 g of magnesium
sulphate and 0.7 g of Celitew. The reaction mixture was
stirred at 0 8C for additional 30 min. The solid was separated
by filtration and washed with ethyl acetate. The organic
layer was washed with brine (2!5 mL) and dried with
magnesium sulphate. The solvents were evaporated and the
residue was purified by column chromatography on silica
gel eluting with hexane/ethyl acetate 5:1, affording 0.169 g
(70%).
3. (a) Yang, J.; Cohn, S. T.; Romo, D. Org. Lett. 2000, 2,
763–766. (b) Marino, J. P.; McClure, M. S.; Holub, D. P.;
Comasseto, J. V.; Tucci, F. C. J. Am. Chem. Soc. 2002, 124,
1664–1688.
4. (a) Minkin, V. J.; Sadekov, I. D.; Rivkin, B. B.; Zakharov,
A. V.; Nivorozhkin, V. L.; Kompan, O. E.; Struchkov, Y. T.
J. Organomet. Chem. 1997, 536, 233–248. (b)
Barrientos-Astigarraga, R. E.; Castelani, P.; Sumida, C. Y.;
Comasseto, J. V. Tetrahedron Lett. 1999, 40, 7717–7720. (c)
Barrientos-Astigarraga, R. E.; Castelani, P.; Sumida, C. Y.;
Zuckerman-Schpector, J.; Comasseto, J. V. Tetrahedron 2002,
58, 1051–1059. (d) Castelani, P.; Comasseto, J. V. J. Braz.
Chem. Soc. 2004, 15, 461–463. (e) Castelani, P.; Comasseto,
J. V. Tetrahedron 2005, 61, 2319–2326.
5. (a) Barrientos-Astigarraga, R. E.; Castelani, P.; Comasseto,
J. V.; Formiga, H. B.; Silva, N. C.; Sumida, C. Y.; Vieira,
M. L. J. Organomet. Chem. 2001, 623, 43–47. (b) Raminelli,
C.; Silva, N. C.; Dos Santos, A. A.; Porto, A. L. M.; Andrade,
L. H.; Comasseto, J. V. Tetrahedron 2005, 61, 409–415.
6. (a) Wheeler, J. W.; Chung, R. H. J. Org. Chem. 1969, 34,
1149–1151. (b) Johnson, M. R.; Rickborn, B. J. Org. Chem.
1970, 35, 1041–1045.
4.3.11. Derivatization of the allylic alcohol 3e with
chlorotrimethylsilane. To a 2.5 mL round-bottomed
flask, was added imidazol (0.25 mmol, 17 mg) in dichloro-
methane (1 mL). The resulting solution was cooled to 0 8C,
and then chlorotrimethylsilane (0.25 mmol, 0.03 mL) was
slowly added. The resulting mixture was stirred for 10 min
and the alcohol (4e) (0.03 mmol, 10 mg) was introduced via
syringe. The mixture was diluted in hexane and analyzed by
gas chromatography.
7. (a) Gemal, A. L.; Luche, J.-L. J. Am. Chem. Soc. 1981, 103,
5454–5459. (b) Luche, J.-L. J. Am. Chem. Soc. 1979, 101,
5848–5849. (c) Zeynizadeh, B.; Yahyaei, S. Z. Naturforsch. B
2005, 59, 699–703.
4.3.12. Derivatization of alcohol 4c to the corresponding
acetate 4c0. To a solution of 4c (0.560 g, 1.8 mmol) in
pyridine (3 mL) under nitrogen at room temperature, was
added acetic anhydride (0.36 g, 0.34 mL, 3.6 mmol,
2 equiv). The resulting solution was warmed at 45 8C for
2 h and then cooled to room temperature, diluted with
hexane (10 mL) and washed with a 10% solution of cooper
sulfate (5!5 mL). The organic phase was dried with
magnesium suphate and the solvents were evaporated. The
residue was purified by silica gel column chromatography
eluting with hexane/ethyl acetate 19:1, yielding 0.54 g
(85%) of (Z)-4-(butyltellanyl)oct-3-en-2-yl acetate (4c0) as a
clear yellow oil. (Found: C, 47.71; H, 6.90. C14H26O2Te
requires C, 47.51; H, 7.35%); nmax (film) 2958, 2928, 2871,
1739, 1460, 1370, 1239, 1044. dH (200 MHz, CDCl3) 0.90
(t, JZ7.2 Hz, 6H); 1.28 (d, JZ6.6 Hz, 3H); 1.32–1.8 (m,
10); 2.02 (s, 3H); 2.33 (t, JZ7.0 Hz, 2H); 2.68 (t, 7.5 Hz,
2H); 5.55 (quint., JZ6.2 Hz, 1H), 5.68 (d., JZ7.9 Hz, 1H);
dC (50 MHz, CDCl3) 170.1; 136.3; 123.6; 75.2; 41.5; 34.11;
31.8; 25.0; 21.8; 21.1; 20.5; 13.9; 13.3; 5.3.
8. Zeni, G.; Formiga, H. B.; Comasseto, J. V. Tetrahedron Lett.
2000, 41, 1311–1313.
9. Nogueira, C. W.; Zeni, G.; Rocha, J. B. T. Chem. Rev. 2004,
104, 6255–6286.
10. Gralewicz, S.; Lutz, P.; Kur, B. Neurotoxicology 2005, 26,
159–171 and references therein.
11. Pereyre, M.; Quintard, J.-P.; Rahm, A. Tin in Organic
Synthesis; Butterworth: London, 1987.
12. Yoon, N. M.; Gyoung, Y. S. J. Org. Chem. 1985, 50,
2443–2450.
13. Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals; Pergamon: Oxford, 1980.
14. Watson, S. C.; Eastham, J. F. J. Organomet. Chem. 1976, 9,
165–168.
15. Rahmeier, L. H. S.; Comasseto, J. V. Organometallics 1997,
16, 651–656.
16. (a) Toussaint, D.; Suffert, J. Organic Synthesis; Collect. Vol.
10, 627; Vol. 76, 214. (b) Mortier, J.; Vaultier, M.; Correaux,
F.; Douin, J.-M. J. Org. Chem. 1998, 63, 3515–3516.
17. Compound 4c was very unstable under GC and GS–MS
analysis conditions. No acceptable elemental analysis was
obtained for this compound. In this way it was converted into
1
Acknowledgements
the corresponding acetate 4c0, which presented H NMR, 13C
NMR, elemental analysis and IR in agreement with the
proposed structure.
The authors acknowledge CNPq and FAPESP for support.