Tandem PtCl2 catalyzed-thermal [3,3] rearrangements of enyne acetates

Article abstract of DOI:10.1016/j.tet.2004.06.151

1,6 Enyne systems flanked with an acetate group at the propargyl position undergo tandem PtCl₂-catalyzed-thermal [3,3] rearrangements leading to trienes. The scope of the transformation has been delineated by varying the nature of the alkynyl substituent R. For R=alkyl or phenyl, a direct 1,3-migration of the acetate group is proposed leading to an allenyl ester intermediate that undergoes a subsequent [3,3] rearrangement. Graphical Abstract.

Full text of DOI:10.1016/j.tet.2004.06.151

Tetrahedron 60 (2004) 9745–9755
Tandem PtCl2 catalyzed–thermal [3,3] rearrangements of
enyne acetates
*
Kevin Cariou, Emily Mainetti, Louis Fensterbank and Max Malacria
*
´
Universite Pierre et Marie Curie, Laboratoire de Chimie Organique, UMR CNRS 7611, Tour 44-54, case 229, 4, place Jussieu,
75252 Paris cedex 05, France
Received 26 May 2004; revised 15 June 2004; accepted 17 June 2004
Available online 24 August 2004
Abstract—1,6 Enyne systems flanked with an acetate group at the propargyl position undergo tandem PtCl2-catalyzed–thermal [3,3]
rearrangements leading to trienes. The scope of the transformation has been delineated by varying the nature of the alkynyl substituent R. For
RZalkyl or phenyl, a direct 1,3-migration of the acetate group is proposed leading to an allenyl ester intermediate that undergoes a
subsequent [3,3] rearrangement.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
intramolecular cyclopropanation via a platinum carbene
complex gives the bicyclic [4.1.0] derivative 3. This
reactivity could be extended to the preparation of cyclooctyl
compounds.
The PtCl2-catalyzed cycloisomerization of enyne systems is
a recent addition to the palette of possible synthetic tools for
the construction of cyclic derivatives.1 The first report by
Murai and Chatani established that this catalyst was ideal
for promoting the formal metathesis of various enyne
systems.2 Applications of this process to the total synthesis
of natural products,3 as well as exploration of new partners4
and mechanism rationalizations5 have then followed
rapidly. Most articles also show that the reactivity of this
catalyst with enynes has largely extended beyond the simple
metathesis process. Cyclopropanated hetero- and carbo-
cycles resulting from carbenoid intermediates have been
generated for instance.5a,b We have recently evidenced an
interesting alteration of the reactivity of dienyne systems of
type 1 by varying the nature of the protecting group of a
hydroxy function at the propargylic position (Scheme 1).6
Thus with a methoxy group, a domino process leads to
diquinane 2 resulting from the formal transformation of the
alkyne partner into a bis-carbene entity. However, with an
acetate group, a 1,2-transposition step followed by an
The 1 to 3 transformation has incited further curiosity from
us. First disclosed by Rautenstrauch on other ynol systems
and catalyzed by PdCl2(MeCN)2 and in a minor extent by
PtCl2(MeCN)2,7 this reactivity has remained dormant for
almost two decades until we initiated its renaissance,6 soon
accompanied by Uemura for the intermolecular version.8
Several parameters have now been examined. Among all of
them, we have notably concentrated on the substitution of
the alkyne partner and, herein, we disclose the elements of
reactivity of enynes of type 4, which could by analogy with
our previous findings give birth to bicyclic derivatives
(Scheme 2).
2. Results and discussions
The general route to precursors is described on Scheme 3.
Scheme 1.
Keywords: Enyne; Cycloisomerization; Flash chromatography.
* Corresponding authors. Tel.: C33-1-44-27-35-85; fax: C33-1-44-27-73-60; e-mail addresses: fensterb@ccr.jussieu.fr; malacria@ccr.jussieu.fr
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.06.151

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K. Cariou et al. / Tetrahedron 60 (2004) 9745–9755
originating from the acetate 1,2-migration and carbene
trapping. Instead, it underwent a smooth transformation in
good yield to allenyl ester 5b (entry 1), which results from a
formal 1,3-migration of the acetate group and also
corresponds to a [3,3] rearrangement of the propargyl
acetate system. Interestingly, when this reaction was run at
80 8C, no allene 5b was observed. A 9:1 mixture of two
polyunsaturated, presumably isomeric products was isolated
and careful spectroscopic analysis suggested trienic struc-
tures of type 6. NOE analysis led to a Z relative
configuration for the minor isomer of 6b (Scheme 5).
Scheme 2.
Known aldehyde 19 was alkylated by methyllithium, and
then oxidized to key building block, ketone 2.10
Alkylation of this ketone by a series of lithium acetylides
provided satisfactory yields of the corresponding alcohols
3a–c, which were then acetylated to furnish 4a–c. In the
case of the cyclopropyl precursor, the lithium acetylide was
generated from the cyclopropyldibromoolefin.11 Phenyl
substituted precursor 4e was obtained through Sonagashira
coupling, and precursor 4f after methoxycarboxylation of a
temporary O-silylated enynol substrate (Scheme 3).
Cyclopropyl precursor 4c followed the same reactivity
pattern: at 40 8C, no bicyclic adduct but allenyl ester 5c
(entry 3), and at 80 8C trienic adducts 6 in the same type of
ratio and stereoselectivity (see also Scheme 5).
At that stage, it was interesting to have a better insight in the
reactivity of these systems. Are allenes 5 intermediates
between precursors 4 and trienes 6? Then, would the
transformation of 5 into 6 be platinum-catalyzed? We
answered these questions by heating allenylester 5b in
toluene at 80 8C for a few hours, in the absence of PtCl2.
Very clean and complete conversion of 5b to trienes 6b was
observed, suggesting that trienes 6 would originate from a
These precursors were then exposed to a catalytic amount of
PtCl2 (5 mol%) in toluene (0.025 M) under argon atmo-
sphere at various temperatures (rt, 40 and 80 8C). Results of
these reactions are given in Scheme 4. Thus, hexynyl
substrate 4b at 40 8C did not give any bicyclic adduct
Scheme 3.
OAc
PtCl2, 5 mol %
toluene
AcO
R
R
OAc
R
OAc
R
4
5
(E)- 6
(Z)- 6
Scheme 4.

K. Cariou et al. / Tetrahedron 60 (2004) 9745–9755
9747
Scheme 5.
non metal catalyzed [3,3] (Cope type) rearrangement which
involves an allene component12 (Scheme 5).
(Scheme 7). Corresponding trienic derivatives 6f were
present in a 9:1 ratio with no determination of the relative
stereochemistries. The second component of this mixture
would correspond to another trienic derivative (8), whose
structure is proposed after careful spectroscopic analysis
and relative stereochemistry consistent with the following
mechanism proposal (see below, Scheme 8).
Phenyl-substituted substrate 4d proved more reactive since
at rt a quasi equimolar mixture of allenyl ester 5d and trienes
6d was produced (Scheme 4, entry 5). Gentle heating to
40 8C is sufficient in that case (entry 6) to ensure complete
formation of the trienes 6d.13 In sharp contrast, TMS
precursor 4a furnished very little amount of triene product
6a among a complex mixture after 3 days in refluxing
toluene.14
How to rationalize this new reactivity of the propargylic
system and some of its divergent aspects? Clearly,
substitution at the triple bond brings major alteration in
the platinum-catalyzed step of the sequence, since no
bicyclic adduct is formed. Allenyl esters are to a large extent
the exclusively generated intermediates, which are formed
in good yields and react further in a [3,3] rearrangement.
p-Complexation of the alkyne moiety as in I can give birth
to two s-complexes II and III, whose potential intervention
and relative contribution would be controlled by the nature
of the R group. Thus, the presence of a R group that can
stabilize a positively charged center will favor a species like
III and this would take place through increasing donation
from RZbutyl, then cyclopropyl to phenyl.15 Then, from
III, anchimeric assistance from the best nucleophile, that is,
the acetate group, would trigger the 1,3-migration of this
group giving birth to the formal [3,3] product 5.
It was interesting to complete our study by examining the
behavior of 4d and 4f. In the case of 4d (Scheme 6), no
reaction occurred at 40 8C after 4 h. However, at 80 8C, full
consumption of the starting material was observed. As
anticipated from our previous findings,6 bicyclic adduct 7
was isolated in 55% yield, accompanied also by 13% of an
inseparable mixture of triene derivatives 6d, whose relative
stereochemistries were attributed by NOE.
Reactivity of 4f proved to be relatively sluggish. After
prolonged reaction time (20 h) at 80 8C, starting material
was consumed and an inseperable mixture of 3 products was
isolated after chromatography in moderate overall yield
Scheme 6.
Scheme 7.

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K. Cariou et al. / Tetrahedron 60 (2004) 9745–9755
Scheme 8.
Interestingly, the observed order of reactivity correlates well
with the R group stabilization ability.
and can precede further interesting reactivity. In our case,
the subsequent [3,3] rearrangement gives birth to a variety
of trienes with a high diastereoselectivity that is not yet
rationalized.
Metal catalyzed [3,3] transposition of propargyl acetates
have already been described with Ag(I)16 and further
exploited for an additional step. Thus, starting from a
demethylated analog of 4d and upon catalysis with AgClO4,
Cookson17 observed a clean conversion to the correspond-
ing allenyl ester intermediate, which was then further heated
in boiling xylene to undergo an additional [3,3] rearrange-
ment (Scheme 9).
In the case of precursors 4d, complex III (Scheme 8) is not
stabilized and for 4f, it is even destabilized. Presumably,
1,2-migration of the acetate takes place via VI (Scheme 10).
A common path would consist of a second 1,2-migration of
the acetate group (via VII) to give the allenyl ester. Then
several paths are open. For RZH, cyclopropanation from
carbenoid VII is the major pathway and provides 7 and for
RZCO2Me, platinum assisted elimination as in IX would
yield to 8.
Very recently, Gevorgyan18 has also used AgClO4 for
catalyzing a [3,3] rearrangement–1,2-migration–cyclo-
isomerization cascade. We have also designed4a a PtCl2-
catalyzed [3,3] rearrangement–cycloisomerization tandem
from a diyne acetate (Scheme 9). Thus, the formation of
allenylesters from propargyl acetates has some precedent
Finally, this reactivity is not restricted to tertiary substrates.
Secondary substrate 9 bearing an activating phenyl group on
the triple bond could undergo the two consecutive [3,3]
Scheme 9.

K. Cariou et al. / Tetrahedron 60 (2004) 9745–9755
9749
Scheme 10.
1
1
transpositions to provide satisfactory yields of the trienic
substrates 10 (Scheme 11), whose relative stereochemistries
were also deduced from NOE analysis.
NMR spectra (1H, 13C, DEPT, COSY H–1H and H–13C,
NOE) were recorded on a 200 MHz ARX 200 or a 400 MHz
1
AVANCE 400 Bruker spectrometers. H NMR spectra are
referenced at 7.26 ppm for CDCl3 and 7.16 ppm for C6D6.
13C NMR spectra are referenced at 77.23 ppm for CDCl3
and 128.62 ppm for C6D6. Chemical shifts are given in ppm.
IR spectra were recorded with a Tensor 27 (ATR diamond)
Bruker spectrometer. IR is reported as characteristic bands
(cmK1) in their maximal intensity.
In conclusion, we have shown that enynes bearing an acetate
group at the propargylic position and substitution on the
triple bond can give birth to versatile transformations such
as two consecutive [3,3] rearrangements, the first one being
catalyzed by PtCl2. The resulting trienes are formed
stereoselectively. The scope of the transformation has
been delineated by varying the nature of the alkynyl
substituent R. For RZalkyl or phenyl, a direct 1,3-
migration of the acetate group is proposed leading to an
allenyl ester intermediate. Further applications of this
valuable set of synthetic processes are underway, notably
for the efficient preparation of relevant polyunsaturated
building blocks.
3.1.1. Synthesis of 2. Synthesis of 4,4-dimethyl-hex-5-en-2-
ol: at K78 8C, MeLi (1.6 M in Et2O, 18.4 mmol, 1.5 equiv)
is added to a solution of aldehyde 19 (1.4 g, 12.5 mmol,
1 equiv) in dry THF (15 mL). The mixture is allowed to heat
up to rt, and then quenched with saturated NH4Cl solution
and extracted with diethylether. The combined organic
layers are washed with brine, dried over MgSO4 and
evaporated to give the crude oil, which is engaged in the
next step without further purification.
3. Experimental
Synthesis of 4,4-dimethyl-hex-5-en-2-one 210: a 100 mL
round bottom flask containing a solution of (COCl)2
(1.4 mL, 16 mmol, 1.3 equiv) in CH2Cl2 (18 mL) is cooled
at K78 8C, under an argon atmosphere. A solution of
DMSO (2.2 mL, 31 mmol, 2.5 equiv) in CH2Cl2 (18 mL), is
transferred, and after 5 min a solution of the crude alcohol
(1.5 g, 12.5 mmol, 1 equiv) in CH2Cl2 (16 mL) is cannu-
lated. After 15 min, Et3N (9.6 mL, 69 mmol, 5.5 equiv) is
added and after 15 min the mixture is allowed to warm up to
rt. The mixture is quenched with saturated NH4Cl solution
and extracted with diethylether. The combined organic
layers are washed with brine, dried over MgSO4 and
3.1. General remarks
Reactions were carried out under an anhydrous atmosphere
of Ar. Glassware was flame-dried under an argon gas flow
prior to use. Anhydrous THF and Et2O were obtained by
distillation over sodium/benzophenone under nitrogen and
used freshly distilled. Et3N was dried then distilled from
KOH; toluene and CH2Cl2 from CaH2. n-Butyllithium was
purchased as 2.5 M solutions in hexanes and titrated before
use. Other reagents were commercially available and used
without further purification unless otherwise indicated.
Scheme 11.

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K. Cariou et al. / Tetrahedron 60 (2004) 9745–9755
evaporated to give crude 2. The purification is done by
simple filtration over silica gel and celite to give 1.3 g
(10.4 mmol) of pure 2 (yield: 83% over 2 steps).
3.1.4. Acetic acid 1-cyclopropylethynyl-1,3,3-trimethyl-
pent-4-enyl ester 3c. Synthesis of (2,2-dibromovinyl)-
cyclopropane: to a solution of CBr4 (6.64 g, 20 mmol,
1.4 equiv) in CH2Cl2 (15 mL), a solution of PPh3 (10.48 g,
40 mmol, 2.8 equiv) in CH2Cl2 (15 mL) is added at 0 8C.
After 30 min of stirring a solution of cyclopropylcarbox-
aldehyde (1 g, 14.3 mmol, 1 equiv) in CH2Cl2 (15 mL) is
added. The mixture is allowed to heat up to rt, after 1 h the
reaction is complete. The mixture is poured in 300 mL of
pentane, filtered over celite and concentrated. The residue is
diluted in 200 mL of pentane, filtered over celite and
concentrated to give the crude dibromoalkene, which is
engaged in the next step without further purification.
1H NMR (400 MHz, CDCl3): 5.91 (dd, JZ17.7, 10.3 Hz,
1H, ]CH), 4.95 (m, 2H, ]CH2), 2.43 (s, 2H, CH2), 2.10 (s,
3H, CH3), 1.11 (s, 6H, 2 CH3).
3.1.2. 3,5,5-Trimethyl-1-trimethylsilanyl-hept-6-en-1-
yn-3-ol 3a. A 50 mL round bottom flask, containing
20 mL of dry THF, is cooled at K78 8C, under an argon
atmosphere. First TMSA (1.7 mL, 12 mmol, 1.5 equiv) and
then n-BuLi (2.3 M in hexanes, 4.1 mL, 9.5 mmol,
1.2 equiv), are added. After 40 min the ketone 2 (1.0 g,
8 mmol, 1 equiv), diluted in 20 mL of dry THF, is
transferred. The mixture is kept 30 min at K78 8C and
then is allowed to heat up to rt. The mixture is quenched
with saturated NH4Cl solution and extracted with diethyl-
ether. The combined organic layers are washed with brine,
dried over MgSO4 and evaporated to give 1.75 g (8 mmol)
of crude 3a (yield: 98%), that was engaged in the next step
without further purification.
1H NMR (400 MHz, CDCl3): 5.77 (d, JZ9.3 Hz, 1H,
]CH), 1.55–1.70 (m, 1H, CH), 0.85 (m, 2H, CH2), 0.53 (m,
2H, CH2). Identical to those of the literature.11a
3.1.5. 1-Cyclopropyl-3,5,5-trimethyl-hept-6-en-1-yn-3-ol
3c. To a solution of crude dibromoalkene (1.81 g, 8 mmol,
1.25 equiv) in dry THF (10 mL) 6.8 mL of n-Buli (2.3 M in
hexanes, 15.7 mmol, 2.4 equiv) are added at K78 8C. After
30 min, a solution of ketone 2 (815 mg, 6.5 mmol, 1 equiv)
in dry THF (10 mL) is added. The mixture is then allowed to
heat up to rt. After 45 min the reaction is complete. The
mixture is quenched with saturated NH4Cl solution and
extracted with diethylether. The combined organic layers
are washed with brine, dried over MgSO4 and evaporated to
give crude oil, that is purified by flash chromatography on
silica gel (petroleum ether/Et2O, 95:5) to give 850 mg
(1.8 mmol, 73%) of 3c.
IR (neat): 3550, 3080, 2960, 2930, 2170, 1640 cmK1
.
1H NMR (400 MHz, CDCl3): 6.08 (dd, JZ17.5, 10.7 Hz,
1H, ]CH), 5.08 (dd, JZ17.5, 1.3 Hz, 1H, ]CHH trans),
5.02 (dd, JZ10.7, 1.3 Hz, 1H, ]CHH cis), 1.79 (s, 2H,
CH2), 1.44 (s, 3H, CH3), 1.29 (s, 3H, CH3), 1.08 (s, 3H,
CH3), 0.15 (s, 9H, Si(CH3)3).
13C NMR (100 MHz, CDCl3): 149.1 (]CH), 111.8
(]CH2), 110.7 (C), 88.6 (C), 67.9 (C), 54.8 (C), 37.3 (C),
32.9 (CH3), 30.6 (CH3), 26.6 (CH3), 0.0 (Si(CH3)3).
1H NMR (400 MHz, CDCl3): 6.09 (dd, JZ17.6, 10.7 Hz,
1H, ]CH), 5.07 (dd, JZ17.5, 1.3 Hz, 1H, ]CHH trans),
5.03 (dd, JZ10.7, 1.3 Hz, 1H, ]CHH cis), 1.81 (d, JZ
14.4 Hz, 1H, CH2), 1.76 (d, JZ14.4 Hz, 1H, CH2), 1.43 (s,
3H, CH3), 1.28 (s, 3H, CH3), 1.25 (m, 1H, CH), 1.10 (s, 3H,
CH3), 0.75 (m, 2H, CH2), 0.67 (m, 2H, CH2).
3.1.3. 3,3,5-Trimethyl-undec-1-en-6-yn-5-ol 3b. A 50 mL
flask, containing 6 mL of dry THF, is cooled at K78 8C,
under an argon atmosphere. First hex-1-yne (550 mL,
4.8 mmol, 1.5 equiv) and then n-BuLi (2.3 M in hexanes,
1.7 mL, 3.9 mmol, 1.2 equiv), are added. After 40 min the
ketone 2 (400 mg, 3.2 mmol, 1 equiv), diluted in 4 mL of
dry THF, is transferred. The mixture is kept 30 min at
K78 8C and then is allowed to heat up to rt. The mixture is
quenched with saturated NH4Cl solution and extracted with
diethylether. The combined organic layers are washed with
brine, dried over MgSO4 and evaporated to give crude 3b,
that was engaged in the next step without further
purification.
3.1.6. Acetic acid 1-(2,2-dimethyl-but-3-enyl)-1-methyl-
hept-2-ynyl ester 4a. To a solution of crude 3a (255 mg,
1.14 mmol, 1 equiv) in NEt3 (3 mL), DMAP (28 mg,
0.23 mmol, 0.2 equiv) and Ac2O (650 mL, 4.6 mmol,
4 equiv) are added and the mixture is stirred at rt overnight.
The mixture is quenched with saturated NH4Cl solution and
extracted with diethylether. The combined organic layers
are washed with brine, dried over MgSO4 and evaporated to
give the crude oil, which is purified by flash chromato-
graphy on silica gel (pentane/Et2O, 95:5) to give 235 mg
(0.89 mmol, 78%) of pure 4a.
IR (neat): 3500, 3080, 2960, 2870, 2240, 1640 cmK1
.
1H NMR (400 MHz, CDCl3): 6.06 (dd, JZ17.5, 10.7 Hz,
1H, ]CH), 5.03 (dd, JZ17.5, 1.0 Hz, 1H, ]CHH trans),
4.98 (dd, JZ10.7, 1.3 Hz, 1H, ]CHH cis), 2.14 (t, JZ
6.9 Hz, 2H, CH2), 1.78 (d, JZ14.4 Hz, 1H, CH2), 1.75 (d,
JZ14.4 Hz, 1H, CH2), 1.41 (s, 3H, CH3), 1.52–1.28 (m, 4H,
CH2, CH2), 1.25 (s, 3H, CH3), 1.07 (s, 3H, CH3), 0.88 (t, JZ
7.2 Hz, 3H, CH3).
IR (neat): 3080, 2960, 2170, 1750, 840 cmK1
.
1H NMR (400 MHz, CDCl3): 5.95 (dd, JZ17.4, 10.8 Hz,
1H, ]CH), 4.89 (dd, JZ17.4, 1.3 Hz, 1H, ]CHH trans),
4.83 (dd, JZ10.8, 1.3 Hz, 1H, ]CHH cis), 2.13 (d, JZ
14.6 Hz, 1H, CH2), 1.95 (s, 3H, COCH3), 1.88 (d, JZ
14.6 Hz, 1H, CH2), 1.67 (s, 3H, CH3), 1.14 (s, 3H, CH3),
1.13 (s, 3H, CH3), 0.13 (s, 9H, Si(CH3)3).
13C NMR (100 MHz, CDCl3): 149.1 (]CH), 111.1
(]CH2), 84.8, 84.5 (2C), 67.5 (C), 54.8 (C), 37.0 (C),
33.1 (CH3), 30.6 (CH2), 30.1 (CH3), 26.6 (CH3), 22.0 (CH2),
18.4 (C), 13.6 (CH3).
13C NMR (100 MHz, CDCl3): 169.0 (C]O), 148.8 (]CH),
109.5 (]CH2), 106.3 (C), 90.3 (C), 75.2 (C), 51.8 (C), 36.8

K. Cariou et al. / Tetrahedron 60 (2004) 9745–9755
9751
(C), 28.9 (CH3), 28.5 (CH3), 27.9 (CH3), 22.2 (CH2), K0.3
(Si(CH3)3).
are washed with brine, dried over MgSO4 and evaporated to
give 200 mg of 4d (2.6 mmol, 98%), with no need of further
purification.
3.1.7. Acetic acid 1-(2,2-dimethyl-but-3-enyl)-1-methyl-
hept-2-ynyl ester 4b. Compound 3b (132 mg, 0.63 mmol,
1 equiv) is acylated using the same procedure as for alcohol
3a, with 25 mg (0.2 mmol, 0.3 equiv) of DMAP, 250 mL of
Ac2O (2.6 mmol, 4.2 equiv) in 3 mL of NEt3. After
purification by flash chromatography on silica gel (pentane/
Et2O, 95:5), 112 mg (0.45 mmol, 71%) of pure 4b were
isolated.
IR (neat): 3290, 2970, 2880, 2140, 1750, 1650 cmK1
.
1H NMR (400 MHz, CDCl3): 5.95 (dd, JZ17.5, 10.7 Hz,
1H, ]CH), 4.93 (dd, JZ17.5, 1.3 Hz, 1H, ]CHH trans),
4.88 (dd, JZ10.7, 1.3 Hz, 1H, ]CHH cis), 2.58 (s, 1H,
CH), 2.11 (d, JZ14.7 Hz, 1H, CH2), 1.99 (s, 3H, COCH3),
1.95 (d, JZ14.7 Hz, 1H, CH2), 1.70 (s, 3H, CH3), 1.16 (s,
3H, CH3), 1.14 (s, 3H, CH3).
IR (neat): 3080, 2960, 2930, 2250, 1740, 1640 cmK1
.
13C NMR (100 MHz, CDCl3): 169 (C]O), 149.1 (]CH),
110.1 (]CH2), 85.2 (C), 74.9 (C), 74.7 (C), 52.3 (C), 37.3
(C), 29.1 (2CH3), 28.2 (CH3), 22.6 (CH3).
1H NMR (400 MHz, CDCl3): 5.95 (dd, JZ17.6, 10.7 Hz,
1H, ]CH), 4.88 (dd, JZ17.6, 1.2 Hz, 1H, ]CHH trans),
4.83 (dd, JZ10.7, 1.2 Hz, 1H, ]CHH cis), 2.16 (t, JZ
7.1 Hz, 2H, CH2), 2.08 (d, JZ14.5 Hz, 1H, CH2), 1.94 (s,
3H, COCH3), 1.86 (d, JZ14.5 Hz, 1H, CH2), 1.64 (s, 3H,
CH3), 1.53–1.30 (m, 4H, 2CH2), 1.12 (s, 3H, CH3), 1.11 (s,
3H, CH3), 0.87 (t, JZ7.2 Hz, 3H, CH3).
3.1.10. Acetic acid 1,3,3-trimethyl-1-phenylethynyl-pent-
4-enyl ester 4e. Compound 4d (200 mg, 1.05 mmol,
1 equiv) is introduced under an argon atmosphere with
PhI (120 mL, 1.08 mmol, 1.02 equiv). Dry NEt3 (4 mL) is
added and the solution is degassed with argon during
15 min. CuI (20 mg, 0.105 mmol, 0.1 equiv) and PdPPh3Cl2
(15 mg, 0.02 mmol, 0.02 equiv) are added, the mixture is
heated at 70 8C. After 1 h the reaction is complete. The
mixture is quenched with saturated NH4Cl solution and
extracted with diethylether. The combined organic layers
are washed with brine, dried over MgSO4 and evaporated to
give the crude, which is purified by flash chromatography on
silica gel (pentane/Et2O, 95:5) to give 154 mg (0.57 mmol,
60%) of pure 4e.
13C NMR (100 MHz, CDCl3): 169.3 (C]O), 149.0 (]CH),
109.2 (]CH2), 86.6 (C), 81.2 (C), 75.5 (C), 52.3 (C), 36.8
(C), 30.4 (CH2), 29.4 (CH3), 28.4 (CH3), 28.0 (CH3), 22.0
(CH2), 18.5 (C), 13.6 (CH3).
Anal. Calcd for C16H26O2: C, 76.75; H, 10.47. Found: C,
76.26; H, 10.93.
3.1.8. Acetic acid 1-cyclopropylethynyl-1,3,3-trimethyl-
pent-4-enyl ester 4c. Compound 3c (350 mg, 1.8 mmol,
1 equiv) is acylated using the same procedure as for alcohol
3a, with 67 mg (0.55 mmol, 0.3 equiv) of DMAP, 0.5 mL of
Ac2O (5.25 mmol, 3 equiv) in 3 mL of NEt3. After
purification by flash chromatography on silica gel (pentane/
Et2O, 95:5), 321 mg (1.37 mmol, 76%) of pure 4c were
isolated.
IR (neat): 3080, 2960, 2870, 2240, 1745, 1640 cmK1
.
1H NMR (400 MHz, CDCl3): 7.42 (m, 2H, HAr), 7.28 (m,
3H, HAr), 6.02 (dd, JZ17.5, 10.7 Hz, 1H, ]CH), 4.96 (dd,
JZ17.5, 1.1 Hz, 1H, ]CHH trans), 4.91 (dd, JZ10.7,
1.1 Hz, 1H, ]CHH cis), 2.23 (d, JZ14.7 Hz, 1H, CH2),
2.01 (s, 3H, COCH3), 2.00 (d, JZ14.7 Hz, 1H, CH2), 1.79
(s, 3H, CH3), 1.21 (s, 3H, CH3), 1.20 (s, 3H, CH3).
IR (neat): 3290, 2970, 2880, 2120, 1750, 1650 cmK1
.
13C NMR (100 MHz, CDCl3): 169.3 (C]O), 148.9 (]CH),
131.6 (2 CH, Ar), 128.3 (CH, Ar), 128.0 (2 CH, Ar), 109.6
(]CH2), 90.3 (C), 85.6 (C), 75.3 (C), 52.3 (C), 36.9 (C),
29.0 (CH3), 28.4 (CH3), 28.2 (CH3), 22.3 (CH3).
1H NMR (400 MHz, CDCl3): 5.98 (dd, JZ17.4, 10.6 Hz,
1H, ]CH), 4.90 (dd, JZ17.4, 1.3 Hz, 1H, ]CHH trans),
4.85 (dd, JZ10.6, 1.3 Hz, 1H, ]CHH cis), 2.08 (d, JZ
14.7 Hz, 1H, CH2), 1.96 (s, 3H, COCH3), 1.84 (d, JZ
14.4 Hz, 1H, CH2), 1.63 (s, 3H, CH3), 1.24 (m, 1H, CH),
1.12 (s, 3H, CH3), 1.10 (s, 3H, CH3), 0.73 (m, 2H, CH2),
0.67 (m, 2H, CH2).
Anal. Calcd for C18H22O2: C, 79.96; H, 8.20. Found: C,
79.46; H, 8.46.
13C NMR (100 MHz, CDCl3): 169.5 (C]O), 149.1 (]CH),
109.5 (]CH2), 89.5 (C), 76.5 (C), 75.6 (C), 52.5 (C), 37.0
(C), 29.3 (CH3), 28.5 (CH3), 28.3 (CH3), 22.8 (CH3), 8.3
(2CH2), 0.0 (CH).
3.1.11. 4-Acetoxy-4,6,6-trimethyl-oct-7-en-2-ynoic acid
methyl ester 4f. Synthesis of 3,5,5-trimethyl-hept-6-en-1-
yn-3-ol: crude alcohol 3a (3.2 g, 14.3 mmol, 1 equiv) is
diluted with 45 mL of DMSO. KF (1.34 g, 23 mmol,
1.6 equiv) and a few drops of water are added. After
45 min the reaction is complete. The mixture is quenched
with saturated NH4Cl solution and extracted with diethyl-
ether. The combined organic layers are washed with brine,
dried over MgSO4 and evaporated to give the crude, which
is engaged in the next step without further purification.
Anal. Calcd for C15H22O2: C, 76.88; H, 9.46. Found: C,
76.70; H, 9.63.
3.1.9. Acetic acid 1-ethynyl-1,3,3-trimethyl-pent-4-enyl
ester 4d. Compound 4a (280 mg, 1.05 mmol, 1 equiv) is
diluted with 8 mL of DMSO. KF (100 mg, 1.7 mmol,
1.6 equiv) and a few drops of water are added. After 45 min
the mixture is quenched with saturated NH4Cl solution and
extracted with diethylether. The combined organic layers
1H NMR (400 MHz, CDCl3): 6.08 (dd, JZ17.5, 10.7 Hz,
1H, ]CH), 5.10 (dd, JZ17.5, 1.3 Hz, 1H, ]CHH trans),
5.02 (dd, JZ10.7, 1.3 Hz, 1H, ]CHH cis), 2.47 (s, 1H,

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K. Cariou et al. / Tetrahedron 60 (2004) 9745–9755
CH), 1.81 (s, 2H, CH2), 1.48 (s, 3H, CH3), 1.31 (s, 3H,
CH3), 1.09 (s, 3H, CH3).
3d, with 29 mL of Ac2O (305 mmol, 30 equiv) in 45 mL of
pyridine. After purification by flash chromatography on
silica gel (PE/Et2O 9:1) 800 mg (3.1 mmol, 30%, 5 steps) of
pure 3f were isolated.
Synthesis of (1-ethynyl-1,3,3-trimethyl-pent-4-enyloxy)-
trimethyl-silane: to a solution of the resulting alcohol
(1.6 g, 10.5 mmol, 1 equiv) in CH2Cl2 (50 mL), 8.6 mL of
NEt3 (62 mmol, 6 equiv) and 380 mg of DMAP (3.1 mmol,
0.3 equiv) are added. The solution is cooled at 0 8C and the
TMSCl (4 mL, 31.5 mmol, 3 equiv) is slowly added. The
mixture is allowed to heat up to rt, the reaction is complete.
The mixture is quenched with saturated NH4Cl solution and
extracted with diethylether. The combined organic layers
are washed with brine, dried on MgSO4 and evaporated to
give crude silylether, which is engaged in the next step
without further purification.
IR (neat): 3080, 2960, 2870, 2240, 1750, 1715 cmK1
.
1H NMR (400 MHz, CDCl3): 5.91 (dd, JZ17.4, 10.6 Hz,
1H, ]CH), 4.95 (dd, JZ17.4, 1.4 Hz, 1H, ]CHH trans),
4.89 (dd, JZ10.6, 1.4 Hz, 1H, ]CHH cis), 3.76 (s, 3H,
OCH3), 2.12 (d, JZ14.7 Hz, 1H, CH2), 2.01 (s, 3H,
COCH3), 1.97 (d, JZ14.7 Hz, 1H, CH2), 1.72 (s, 3H,
CH3), 1.13 (s, 3H, CH3), 1.15 (s, 6H, CH3).
13C NMR (100 MHz, CDCl3): 169 (C]O), 149.1 (]CH),
110.1 (]CH2), 85.2 (C), 74.9 (C), 74.7 (C), 52.3 (C), 37.3
(C), 29.1 (2CH3), 28.2 (CH3), 22.6 (CH3).
1H NMR (400 MHz, CDCl3): 6.02 (dd, JZ17.4, 10.6 Hz,
1H, ]CH), 4.90 (dd, JZ17.4, 1.2 Hz, 1H, ]CHH trans),
4.84 (dd, JZ10.6, 1.2 Hz, 1H, ]CHH cis), 2.45 (s, 1H,
CH), 1.80 (d, JZ14.7 Hz, 1H, CH2), 1.76 (d, JZ14.5 Hz,
1H, CH2), 1.48 (s, 3H, CH3), 1.15 (s, 3H, CH3), 1.13 (s, 3H,
CH3), 0.02 (s, 9H, Si(CH3)3).
3.2. Products from the PtCl2-catalyzed reactions.
General procedure for reactions involving PtCl2
Reactions are carried out in anhydrous toluene. The enyne is
introduced under an argon atmosphere. The solvent is then
added and the solution (cZ0.025 M) is submitted to argon
bubbling during 15 min. The catalyst is then added, still
under an argon atmosphere. The reaction requires stirring
and heating. The reaction is monitored by TLC. When the
reaction is complete, the solvent is evaporated and the crude
4,6,6-Trimethyl-4-trimethylsilanyloxy-oct-7-en-2-ynoic
acid methyl ester: to a solution of the crude resulting
silylether (2.3 g, 10.5 mmol, 1 equiv) in dry THF (50 mL)
5 mL of a 2.3 M solution of n-BuLi (11.3 mmol, 1.1 equiv)
is added at K78 8C. The ClCO2Me (2.4 mL, 31 mmol,
3 equiv) is added and the mixture is allowed to heat up to rt,
the reaction is complete The mixture is quenched with
saturated NH4Cl solution and extracted with diethylether.
The combined organic layers are washed with brine, dried
over MgSO4 and evaporated to give the crude methyl
ethynate, which is engaged in the next step without further
purification.
1
is analyzed by H NMR analysis before purification.
3.2.1. Acetic acid 1-trimethylsilyl-2-isopropenyl-5-
methyl-hexa-1,4-dienyl esters E-6a. General procedure is
applied to 4a (146 mg, 0.55 mmol, 1 equiv), with 8.5 mg of
PtCl2 (0.032 mmol, 0.05 equiv), in 20 mL of toluene. The
mixture is heated at reflux for 3d. After purification by flash
chromatography on silica gel (pentane/CH2Cl2, 8:2), 11 mg
(8%) of 6a are isolated.
1H NMR (400 MHz, CDCl3): 6.00 (dd, JZ17.4, 10.6 Hz,
1H, ]CH), 4.92 (dd, JZ17.4, 1.4 Hz, 1H, ]CHH trans),
4.84 (dd, JZ10.6, 1.4 Hz, 1H, ]CHH cis), 3.77 (s, 3H,
OCH3), 1.80 (d, JZ14.7 Hz, 1H, CH2), 1.75 (d, JZ14.7 Hz,
1H, CH2), 1.50 (s, 3H, CH3), 1.13 (s, 3H, CH3), 1.12 (s, 3H,
CH3), 0.02 (s, 9H, Si(CH3)3).
IR (neat): 3085, 2960, 2860, 1740, 840 cmK1
.
1H NMR (400 MHz, CDCl3): 4.96 (th, JZ7.0, 1.4 Hz, 1H,
]CH), 4.92 (m, 1H, ]CH2), 4.89 (m, 1H, ]CH2), 2.80 (d,
JZ7.0 Hz, 2H, CH2), 2.12 (s, 3H, COCH3), 1.81 (s, 3H,
CH3), 1.66 (s, 3H, CH3), 1.59 (s, 3H, CH3), 0.12 (s, 9H,
Si(CH3)3).
Synthesis of 4-hydroxy-4,6,6-trimethyl-oct-7-en-2-ynoic
acid methyl ester 3f: a solution of crude silylated alcohol
(3 g, 10.5 mmol), in methanol (50 mL), is cooled down to
0 8C. Then a few drops of concentrated HCl are added, the
reaction is immediately complete. The mixture is quenched
with saturated NaHCO3 solution and extracted with
diethylether. The combined organic layers are washed
with brine, dried over MgSO4 and evaporated to give crude
3f, which is engaged in the next step without further
purification.
13C NMR (100 MHz, CDCl3): 169.9 (C]O), 148.6 (C),
147.0 (C), 142.8 (C), 132.2 (C), 120.7 (]CH), 116.6
(]CH2), 27.9 (CH2), 25.6 (CH3), 21.8 (CH3), 20.7 (CH3),
17.7 (CH3), 0.0 (Si(CH3)3).
3.2.2. Acetic acid 1-butyl-3,5,5-trimethyl-hepta-1,2,6-
trienyl ester 5b. General procedure is applied to 4b
(95 mg, 0.38 mmol, 1 equiv), with 5 mg of PtCl2
(0.02 mmol, 0.05 equiv), in 18 mL of toluene. The mixture
is heated at 40 8C during 2 h. After purification by simple
filtration over silica gel 70 mg (0.28 mmol, 74%) of 5b are
isolated.
1H NMR (400 MHz, CDCl3): 6.07 (dd, JZ17.7, 10.6 Hz,
1H, ]CH), 5.13 (d, JZ17.7 Hz, 1H, ]CHH trans), 5.07
(d, JZ10.6 Hz, 1H, ]CHH cis), 3.77 (s, 3H, OCH3), 1.86
(s, 2H, CH2), 1.50 (s, 3H, CH3), 1.29 (s, 3H, CH3), 1.09 (s,
3H, CH3).
IR (neat): 3080, 2960, 2860, 1980, 1735, 1640 cmK1
.
Synthesis of 4-acetoxy-4,6,6-trimethyl-oct-7-en-2-ynoic
acid methyl ester 4f: compound 3f (2.2 g, 10.5 mmol,
1 equiv) is acylated using the same procedure as for alcohol
1H NMR (400 MHz, CDCl3): 5.87 (dd, JZ17.4, 10.6 Hz,
1H, ]CH), 4.94 (dd, JZ17.4, 1.3 Hz, 1H, ]CHH trans),

K. Cariou et al. / Tetrahedron 60 (2004) 9745–9755
9753
4.92 (dd, JZ10.6, 1.3 Hz, 1H, ]CHH cis), 2.20 (m, 2H,
CH2), 2.12 (s, 3H, COCH3), 2.09 (s, 2H, CH2), 1.81 (s, 3H,
CH3), 1.32–1.48 (m, 4H, CH2), 1.06 (s, 3H, CH3), 1.05 (s,
3H, CH3), 0.92 (t, JZ7.2 Hz, 3H, CH3).
PtCl2 (0.02 mmol, 0.05 equiv), in 15 mL of toluene. The
mixture is heated at 80 8C during 3 h. After purification by
flash chromatography on silica gel (pentane/CH2Cl2, 8:2),
71 mg (76%) of a mixture containing: E-6c/Z-6c, 9/1, are
isolated.
13C NMR (100 MHz, CDCl3): 194.0 (C), 169.3 (C]O),
148.6 (]CH), 121.9 (C), 110.7 (]CH), 109.5 (C), 48.5
(CH2), 37.0 (C), 31.9 (CH2), 28.9 (CH2), 27.4 (CH3), 27.2
(CH3), 22.9 (CH3), 21.5 (CH3, 22.5 (CH2), 14.3 (CH3).
IR (neat): 3080, 2960, 2860, 1750, 1640, 1610 cmK1
.
1H NMR (400 MHz, CDCl3): 5.09 (s, 1H, ]CH2), 5.00 (t,
JZ7.1 Hz, 1H, ]CH), 4.91 (s, 1H, ]CH2), 3.00 (d, JZ
6.6 Hz, 2H, CH2, Z-6c), 2.67 (d, JZ6.8 Hz, 2H, CH2, E-6c),
2.09 (s, 3H, COCH3, E-6c), 2.00 (s, 3H, COCH3, Z-6c), 1.84
(s, 3H, CH3), 1.67 (s, 3H, CH3, Z-6c), 1.65 (s, 3H, CH3,
E-6c), 1.62 (s, 3H, CH3, Z-6c), 1.56 (s, 3H, CH3, E-6c), 0.75
(m, 1H, CH2), 0.57 (m, 2H, CH2), 0.47 (m, 2H, CH2).
Anal. Calcd for C16H26O2: C, 76.75; H, 10.47. Found: C,
76.57; H, 10.61.
3.2.3. Acetic acid 1-butyl-2-isopropenyl-5-methyl-hexa-
1,4-dienyl esters E-6b and Z-6b. General procedure is
applied to 4b (185 mg, 0.74 mmol, 1 equiv), with 10 mg of
PtCl2 (0.036 mmol, 0.05 equiv), in 30 mL of toluene. The
mixture is heated at 80 8C during 15 h. After purification by
flash chromatography on silica gel (pentane/Et2O, 98:2),
110 mg (60%) of a mixture containing: E-6b/Z-6b, 9/1, are
isolated.
13C NMR (100 MHz, CDCl3): 171.5 (C]O), 169.8 (C,
Z-6c), 169.4 (C, E-6c), 143.3 (C), 132.6 (C), 130.1 (C),
121.9 (]CH, Z-6c), 121.6 (]CH, E-6c), 115.9 (]CH2, E-
6c), 114.1 (]CH2, Z-6c), 29.1 (CH2), 26.0 (CH3), 22.8
(CH3), 20.8 (CH3), 18.1 (CH3), 12.2 (CH), 5.5 (2CH2).
IR (neat): 3080, 2960, 2860, 1750, 1640, 1610 cmK1
.
Anal. Calcd for C15H22O2: C, 76.88; H, 9.46. Found: C,
77.22; H, 9.85.
1H NMR (400 MHz, CDCl3): 5.01 (th, JZ7.1, 1.5 Hz, 1H,
]CH), 4.97 (m, 1H, ]CH2, E-6b), 4.95 (m, 1H, ]CH2,
Z-6b), 4.77 (m, 1H, ]CH2, E-6b), 4.68 (m, 1H, ]CH2,
Z-6b), 2.78 (d, JZ7.1 Hz, 2H, CH2, Z-6b), 2.70 (d, JZ
7.1 Hz, 2H, CH2, E-6b), 2.3 (t, JZ7.5 Hz, 2H, CH2), 2.14
(s, 3H, COCH3, E-6b), 2.03 (s, 3H, COCH3, Z-6b) 1.79 (s,
3H, CH3), 1.66 (s, 3H, CH3), 1.59 (s, 3H, CH3), 1.24–1.40
(m, 4H, CH2), 0.87 (t, JZ7.2 Hz, 3H, CH3).
3.2.6. Acetic acid 3,5,5-trimethyl-bicyclo[4.1.0]hept-2-
en-2-yl ester 7 and acetic acid 2-isopropenyl-5-methyl-
hexa-1,4-dienyl esters E-6d and Z-6d. General procedure
is applied to 4d (154 mg, 0.78 mmol, 1 equiv), with 10.5 mg
of PtCl2 (0.04 mmol, 0.05 equiv), in 30 mL of toluene. The
mixture is heated at 80 8C during 2 h. After purification by
flash chromatography on silica gel (pentane/Et2O, 95:5),
85 mg (55%) of 7 and 20 mg (13%) of a mixture containing:
E-6d/Z-6d, 75/25, are isolated.
13C NMR (100 MHz, CDCl3): 169.1 (C]O), 144.1 (C),
142.9 (C), 132.0 (C), 129.8 (C), 121.4 (]CH), 114.7
(]CH2), 30.3 (CH2), 29.7 (CH2), 28.0 (CH2), 25.7 (CH3),
22.6 (CH3), 22.4 (CH2), 20.9 (CH3), 17.7 (CH3), 13.9 (CH3).
3.2.7. Acetic acid 3,5,5-trimethyl-bicyclo[4.1.0]hept-2-
en-2-yl ester 7. IR (neat): 3075, 2950, 2870, 1750, 1450,
1610 cmK1
.
3.2.4. Acetic acid 1-cyclopropyl-3,5,5-trimethyl-hepta-
1,2,6-trienyl ester 5c. General procedure is applied to 4c
(147 mg, 0.63 mmol, 1 equiv), with 8.5 mg of PtCl2
(0.03 mmol, 0.05 equiv), in 25 mL of toluene. The mixture
is heated at 40 8C during 1 h. After purification by simple
filtration over silica gel 110 mg (0.47 mmol, 75%) of 5c are
isolated.
1H NMR (400 MHz, CDCl3): 2.22 (s, 3H, COCH3), 1.82 (d,
JZ16.5 Hz, 1H, CH2), 1.57 (dd, JZ16.5, 2.0 Hz, 1H, CH2),
1.50 (s, 3H, CH3), 1.19–1.12 (m, 2H, CH2), 1.12 (s, 3H,
CH3), 1.07 (s, 3H, CH3), 0.85–0.64 (m, 2H, CH2).
13C NMR (100 MHz, CDCl3): 169.3 (C]O), 142.3 (C),
112.9 (C), 40.5 (CH2), 29.5 (CH3), 28.6 (CH3), 28.0 (C),
26.4 (CH3), 20.8 (CH3), 16.5 (CH), 13.4 (CH), 9.7 (CH2).
IR (neat): 3080, 2960, 2870, 1940, 1750, 1640 cmK1
.
1H NMR (400 MHz, CDCl3): 5.85 (dd, JZ17.5, 10.7 Hz,
1H, ]CH), 4.93 (dd, JZ17.5, 1.5 Hz, 1H, ]CHH trans),
4.90 (dd, JZ10.7, 1.5 Hz, 1H, ]CHH cis), 2.12 (s, 3H,
COCH3), 2.07 (s, 2H, CH2), 1.78 (s, 3H, CH3), 1.45 (m, 1H,
CH), 1.05 (s, 3H, CH3), 1.04 (s, 3H, CH3), 0.70 (m, 2H,
CH2), 0.50 (m, 2H, CH2).
3.2.8. Acetic acid 2-isopropenyl-5-methyl-hexa-1,4-di-
enyl esters E-6d and Z-6d. IR (neat): 3080, 2960, 2860,
1750, 1640, 1610 cmK1
.
1H NMR (400 MHz, CDCl3): 7.41 (s, 1H, ]CH, E-6d),
6.96 (s, 1H, ]CH, Z-6d), 5.09 (m, 1H, CH, Z-6d), 5.07 (s,
1H, ]CH2), 5.05 (m, 1H, ]CH, E-6d), 4.98 (s, 1H,
]CH2), 3.08 (d, JZ6.8 Hz, 2H, CH2, E-6d), 2.82 (d, JZ
6.8 Hz, 2H, CH2, Z-6d), 2.20 (s, 3H, COCH3, E-6d), 2.14 (s,
3H, COCH3, Z-6d), 1.97 (s, 3H, CH3, Z-6d), 1.92 (s, 3H,
CH3, E-6d), 1.74 (s, 3H, CH3, E-6d), 1.72 (s, 3H, CH3,
Z-6d), 1.70 (s, 3H, CH3, E-6d), 1.64 (s, 3H, CH3, Z-6d).
13C NMR (100 MHz, CDCl3): 193.2 (C), 168.9 (C]O),
148.1 (]CH), 123.4 (C), 110.5 (]CH2), 110.0 (C), 48.0
(CH2), 37.0 (C), 27.1 (CH3), 26.8 (CH3), 22.6 (CH3), 21.1
(CH3), 12.0 (CH), 6.0 (CH2), 5.5 (CH2).
3.2.5. Acetic acid 1-cyclopropyl-2-isopropenyl-5-methyl-
hexa-1,4-dienyl esters E-6c and Z-6c. General procedure is
applied to 4c (93 mg, 0.4 mmol, 1 equiv), with 5.3 mg of
13C NMR (100 MHz, CDCl3): 167.9 (C]O), 139.8 (C),
133.0 (]CH), 126.0 (C), 122.3 (]CH), 115.1 (C), 113.5

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K. Cariou et al. / Tetrahedron 60 (2004) 9745–9755
(CH2), 25.7 (CH3), 24.9 (CH2), 20.9 (CH3), 20.6 (CH3), 17.8
(CH3).
JZ10.6, 1.4 Hz, 1H, ]CHH cis, 8), 4.98 (s, 1H, ]CH2,
6f), 4.92 (m, 1H, ]CH, 6f), 4.70 (s, 1H, ]CH2, 6f), 3.71 (s,
3H, OCH3, 6f), 3.69 (s, 3H, OCH3, 8), 2.91 (d, JZ7.2 Hz,
2H, CH2, 6f), 2.34 (s, 3H, COCH3, 8), 2.23 (s, 3H, COCH3,
6f), 1.94 (s, 3H, CH3), 1.85 (s, 3H, CH3), 1.70 (s, 3H, CH3,
6f), 1.64 (s, 3H, CH3, 6f), 1.22 (s, 6H, CH3, 8).
3.2.9. Acetic acid 3,5,5-trimethyl-1-phenyl-hepta-1,2,6-
trienyl ester 5e and acetic acid 2-isopropenyl-5-methyl-
1-phenyl-hexa-1,4-dienyl ester E-6e and Z-6e. General
procedure is applied to 4e (50 mg, 0.18 mmol, 1 equiv),
with 2.5 mg of PtCl2 (0.009 mmol, 0.05 equiv), in 8 mL of
toluene. The mixture is stirred at rt during 60 h. After
purification by flash chromatography on silica gel (pentane/
Et2O, 99:1), 35 mg (70%) of a mixture containing: 5e/E-6e/
Z-6e, 55/41/4, are isolated.
13C NMR (50 MHz, CDCl3): 169.6 (C]O), 168.6 (C]O),
165.5 (C]O), 160.5 (C]O), 146.3 (]CH, 8), 144.7 (C),
143.4 (]CH, 8), 143.0 (]CH), 134.5 (C), 130.3 (C), 128.9
(C), 128.7 (C), 129.3 (C), 119.2 (]CH, 6f), 113.7 (]CH2,
8), 111.6 (]CH2, 6f), 104.6 (]CH, 8), 52.2 (OCH3), 51.7
(OCH3), 39.0 (3C, 8), 30.9 (CH2, 6f), 29.2 (2 CH3, 8), 26.1
(CH3, 6f), 22.5 (CH3), 21.3 (CH3), 20.8 (CH3), 15.7 (CH3),
14.2 (CH3).
3.2.10. Acetic acid 3,5,5-trimethyl-1-phenyl-hepta-1,2,6-
trienyl ester 5e. IR (neat): 3090, 3060, 2970, 2860, 1950,
1750, 1640, 1610 cmK1
.
3.2.13. Acetic acid 2-isopropenyl-1-phenyl-hexa-1,4-di-
enyl ester E-10 and Z-10. General procedure is applied to 9
(270 mg, 1.05 mmol, 1 equiv), with 14 mg of PtCl2
(0.052 mmol, 0.05 equiv), in 40 mL of toluene. The mixture
is heated at 80 8C during 15 h. After purification by flash
chromatography on silica gel (pentane/CH2Cl2, 8:2),
170 mg (63%) of a mixture containing: E-10/Z-10, 9/1,
were isolated.
1H NMR (400 MHz, CDCl3): 7.41 (m, 2H, HAr), 7.25 (m,
3H, HAr), 5.86 (dd, JZ17.4, 10.6 Hz, 1H, ]CH), 4.94 (dd,
JZ17.4, 1.5 Hz, 1H, ]CHH trans), 4.89 (dd, JZ10.6,
1.5 Hz, 1H, ]CHH cis), 2.27 (s, 3H, COCH3), 2.23 (s, 2H,
CH2), 1.94 (s, 3H, CH3), 1.08 (s, 3H, CH3), 1.07 (s, 3H,
CH3).
13C NMR (100 MHz, CDCl3): 195.3 (C), 168.8 (C]O),
147.9 (]CH), 132.2 (C), 128.3 (2CHAr), 127.8 (2CHAr),
124.5 (CHAr), 120.7 (C), 112.6 (C), 110.7 (CH2), 48.0
(CH2), 27.1 (CH3), 26.9 (CH3), 22.1 (CH3), 21.0 (CH3).
IR (neat): 3090, 3020, 2970, 2860, 1760, 1640 cmK1
.
1H NMR (400 MHz, CDCl3): 7.28–7.41 (m, 5H, HAr), 6.48
(dd, JZ17.4, 11.1 Hz, 1H, ]CH), 5.32 (dd, JZ17.4,
1.0 Hz, 1H, ]CHH, trans), 5.10 (dd, JZ11.1, 1.0 Hz, 1H,
]CHH, cis), 5.09 (m, 1H, ]CH), 3.04 (d, JZ6.6 Hz, 2H,
CH2, E-10), 2.99 (d, JZ6.6 Hz, 2H, CH2, Z-10), 2.16 (s, 3H,
COCH3, E-10), 2.08 (s, 3H, COCH3, Z-10), 1.73 (s, 3H,
CH3), 1.71 (s, 3H, CH3).
3.2.11. Acetic acid 2-isopropenyl-5-methyl-1-phenyl-
hexa-1,4-dienyl ester E-6e and Z-6e. 1H NMR
(400 MHz, CDCl3): 7.41 (m, 2H, HAr), 7.25 (m, 3H, HAr),
5.10 (m, 1H, ]CH), 4.90 (m, 1H, ]CH2), 4.79 (m, 1H,
]CH2), 2.93 (d, JZ7.0 Hz, 2H, CH2, E-6e), 2.90 (d, JZ
7.0 Hz, 2H, CH2, Z-6e), 2.16 (s, 3H, COCH3, E-6e), 2.08 (s,
3H, COCH3, Z-6e), 1.74 (s, 3H, CH3), 1.71 (s, 3H, CH3),
1.66 (s, 3H, CH3).
13C NMR (100 MHz, CDCl3): 169.8 (C]O), 146.4 (C),
135.2 (C), 133.6 (]CH), 131.8 (C), 129.5 (2CHAr), 128.5
(CHAr), 128.1 (2CHAr), 127.5 (C), 122.0 (]CH), 115.5
(]CH2), 25.7 (CH2), 25.7 (CH3), 20.9 (CH3), 17.9 (CH3).
13C NMR (100 MHz, CDCl3): 169.1 (C]O), 142.6 (C),
141.8 (C), 136.3 (C), 132.6 (C), 132.1 (C), 128.3 (2CHAr),
127.8 (3CHAr), 120.7 (]CH), 116.8 (]CH2), 30.1 (CH2),
25.7 (CH3), 22.6 (CH3), 20.9 (CH3), 17.8 (CH3).
Acknowledgements
3.2.12. 3-Acetoxy-4,6,6-trimethyl-octa-2,4,7-trienoic
acid methyl ester 8 and 2-acetoxy-3-isopropenyl-6-
methyl-hepta-2,5-dienoic acid methyl esters E-6f and
Z-6f. General procedure is applied to 4f (260 mg, 1.1 mmol,
1 equiv), with 14.5 mg of PtCl2 (0.054 mmol, 0.05 equiv),
in 40 mL of toluene. The mixture is heated at 80 8C during
20 h. After purification by flash chromatography on silica
gel (pentane/Et2O, 95:5), 115 mg (43%) a mixture contain-
ing: 8/6f, 45/55, are isolated.
`
E.M. thanks the Ministere de la Recherche for an AMX
grant. M.M. is member of Institut Universitaire de France,
and we thank IUF for generous support of this research.
References and notes
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´
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Fu¨rstner, A. Chemtracts-Org. Chem. 2003, 16, 397. (c) Lloyd-
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`
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