Gold-catalyzed rearrangement of propargylic tert-butyl carbonates

Article abstract of DOI:10.1016/j.tet.2008.11.108

Diversely substituted 4-alkylidene-1,3-dioxolan-2-ones are efficiently synthesized by a gold(I)-catalyzed rearrangement of propargylic tert-butyl carbonates. The substrates are readily accessible and the transformation, which is performed under mild react

Full text of DOI:10.1016/j.tet.2008.11.108

Tetrahedron 65 (2009) 1889–1901
Contents lists available at ScienceDirect
Tetrahedron
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Gold-catalyzed rearrangement of propargylic tert-butyl carbonates
*
Andrea K. Buzas, Florin M. Istrate, Fabien Gagosz
Laboratoire de Synthe`se Organique, UMR 7652 CNRS/Ecole Polytechnique, Ecole Polytechnique, 91128 Palaiseau cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 1 October 2008
Received in revised form 26 November 2008
Accepted 26 November 2008
Available online 24 December 2008
Diversely substituted 4-alkylidene-1,3-dioxolan-2-ones are efficiently synthesized by a gold(I)-catalyzed
rearrangement of propargylic tert-butyl carbonates. The substrates are readily accessible and the
transformation, which is performed under mild reaction conditions using a low loading of catalyst, al-
lows the synthesis of cyclic carbonates, which would be less efficiently obtained using traditional
methods. This procedure has also been applied to the stereoselective synthesis of (E)- or (Z)-4-halo-
methylene-1,3-dioxolan-2-ones, which proved to be suitable substrates for palladium-catalyzed cross-
coupling reactions.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
the selective hydrogenation or hydroboration of 4-substituted-5-
methylene-oxazolidon-2-ones.1d Inoue and co-workers also
4-Alkylidene-1,3-dioxolan-2-ones 1 and their derivatives are
structurally interesting building blocks for organic synthesis. They
indeed represent a masked form of 1,2-hydroxyketones that can be
used as substrates in a range of transformations (Scheme 1).1
Dixneuf and co-workers have shown for instance that com-
pounds 1 were suitable substrates for the Heck reaction, thus
allowing the selective formation (Z)-4-phenylmethylene-1,3-diox-
reported the formation of substituted dihydrofuranones 4 by
a palladium-catalyzed reaction of cyclic carbonate 1 with an aro-
matic aldehyde,1e and the group of Murai described the use of
carbonate 1 for the synthesis of oxatrimethylenemethane–palla-
dium or platinum complexes 5.1f,g However, despite the synthetic
potential of 4-alkylidene-1,3-dioxolan-2-ones, the number of their
synthetic applications remains limited. This is mainly due to a lack
of general and efficient synthetic procedures to access such struc-
tural units.
4-Alkylidene-1,3-dioxolan-2-ones are indeed typically prepared
by the reaction of propargylic alcohols with carbon dioxide.2 This
transformation also requires the use of a catalyst, which can be
a metallic species (ruthenium,2a cobalt,2b copper,2c–f palladium2g–i
or silver2j,k), a phosphine2l–o or even an inorganic base.2h However,
the scope remains limited, as these transformations are generally
restricted to the use of tertiary alcohol, due to a reduced reactivity
or even a lack of reactivity in the cases of mono- and disubstituted
propargylic alcohols. Moreover, some of these procedures require
a high carbon dioxide pressure (10 MPa) and/or a high temperature
of reaction (100 ꢀC) to efficiently afford the cyclic carbonates. Given
the restrictions of these procedures, we thought that a new access
to 4-alkylidene-1,3-dioxolan-2-ones would be desirable and de-
cided to design a new route, which would allow the easy and ef-
ficient synthesis of a wide range of such compounds.
There has been an ongoing interest for gold catalysis in organic
synthesis during the last ten years, which has been recently high-
lighted by the appearance of numerous reviews in the literature.3
Gold complexes have indeed proved to be efficient and mild cata-
lysts that can selectively activate alkynes, alkenes, and allenes
toward the addition of a wide range of nucleophiles. Several gold-
catalyzed methodologies leading to various oxygen-containing
heterocycles have thus been developed.4 Following our ongoing
O
O
3
X
O
O
*
O
ref 1b,c
ref 1f,g
Ar
O
ref 1a
ref 1e
R1
R2
X= O, NAc
O
O
R
1 R2
2
O
O
R
1 R2
1
O
M
R2
Ar
5
R1
4
Scheme 1. Reported transformations of 4-alkylidene-1,3-dioxolan-2-ones 1.
olan-2-ones 2.1a The same authors also reported that cyclic carbo-
nates 1 or carbamates could be enantioselectively hydrogenated
using chiral ruthenium(II) complexes to ultimately furnish optically
active 1,2-diols carbonates and N-acyloxazolidinones 3.1b,c A similar
procedure has been recently reported by Shin and co-workers for
* Corresponding author.
E-mail address: gagosz@dcso.polytechnique.fr (F. Gagosz).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.11.108

1890
A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
Ot-Bu
O
Notably, the reaction was regiospecific since no trace of carbonate
O
O
OBoc
10, resulting from a possible 6-endo cyclization could be observed.10
Control experiments also led to the conclusion that HNTf2 and
AgNTf2 were not suitable catalysts for this transformation. In-
terestingly, the loading of the catalyst could be reduced to
0.1 mol %, when the reaction was performed on a 12 mmol and no
noticeable loss of efficiency was observed. This result contrasts
with that previously reported by Trost and co-workers who de-
scribed the synthesis of 9, in a three-step sequence, with an overall
yield of 52% (Scheme 5).12
O
Au catalyst
O
6
7
[Au]
Scheme 2. Synthetic approach to 4-methylene-1,3-dioxolan-2-ones from propargylic
carbonates.
efforts to develop new gold-catalyzed methodologies,5 we con-
jectured that a cationic gold complex could be used to promote the
rearrangement of a propargylic tert-butyl carbonate precursor 6
into the desired 4-alkylidene-1,3-dioxolan-2-one 7 (Scheme 2).6
This approach would be similar to the well-documented iodine-
mediated cyclization of allylic and homoallylic tert-butyl carbon-
ates7 and would formally correspond to the internal deprotection of
a Boc group using a gold–alkyne complex as the acidic species. It
would also differ from the majority of the previously reported
methodologies,2 since the carbonate functionality of the final
product would already be present in the structure of the substrate
under a latent form. Notably, the tert-butyloxycarbonyl group has
already proved to be a valuable nucleophilic partner for the gold-
catalyzed synthesis of oxygenated heterocycles such as butenoli-
des,8a dioxolanones,8b oxazolidinones,1d,8c,d and oxazolones.8e,f Of
special interest are the procedures reported by the groups of Shin9
and Nishizawa10 for the respective gold- and mercury-catalyzed
synthesis of dioxanones and dioxonones (Scheme 3).
This new rearrangement appears to be quite general since
a large variety of diversely substituted terminal alkynes 11a–m
reacted under the same reaction conditions (1 mol % of stable
(PPh3)AuNTf2 in dichloromethane) to furnish cyclic carbonates
12a–m in moderate to excellent yields (40–100%) (Table 1).
The reaction was rapid and a complete conversion of the sub-
strate was generally observed after 1 h, with the exception of sec-
ondary and tertiary tert-butyloxycarbonates 11f (entry 6), 11g
(entry 7), 11l (entry 12), and 11m (entry 13), which were less re-
active. In these cases, the presence of a carbocation stabilizing
group at the propargylic position of 11 (phenyl, vinyl, cyclopropyl
groups) led to the competitive formation of various side-products.
While the reaction conditions are relatively mild, the gold catalyst
seems to be acidic enough to induce a competitive fragmentation of
the C–O propargylic bond leading to undesired products. A higher
loading of (PPh3)AuNTf2 (3 mol %) or the use of the more electro-
philic gold complex [Ph3PAu(NC–CH3)]SbF6 (1 mol %) was required
in the case of cyclopropyl derivative 11g to reach completion (entry
7). Interestingly, these side-products were not observed in the case
of tertiary tert-butyloxycarbonates bearing simple alkyl groups at
the propargylic position (entries 8–11). The transformation proved
however to be compatible with various functionalities such as
a phenyl group (entries 2, 6, and 12), an alkene (entries 3, 11, and
13), a silyl ether (entry 4) or an ester (entry 11). Notably, the rear-
rangement of alkyne 11e was regioselective and exclusively fur-
nished 12e. The 5-exo cyclization proved to be a more favored
process than the 6-exo cyclization that would furnish a six-mem-
bered cyclic carbonate, as previously reported by Shin and co-
workers.9 The androstene case was particularly interesting, since
the corresponding cyclized product precipitates from the reaction
medium under the reaction conditions used (entry 11). A simple
filtration of the crude mixture furnished pure cyclic carbonate 12k
in 90% yield. The possibility of cyclizing secondary tert-butyloxy-
carbonates (entries 1–7) emphasizes the potential of this trans-
formation since the corresponding cyclic carbonates would be less
conveniently obtained using the previously reported methods.2
We next focused our attention onto a possible extension of this
transformation to the rearrangement of internal alkynes. The re-
sults of this study are presented in Table 2. Substrates 13a–g proved
to be reactive as well, while the reaction times were generally
longer and the yields lower (60–87%) than for the rearrangement of
terminal alkynes. Substrates 13a–c exclusively produced the (Z)-
isomers of desired cyclic carbonates 14a–c (entries 1–3). Substrate
13a, bearing an ester group at the alkyne terminus furnished
compound 14a as the result of a gold-catalyzed Michael type ad-
dition of the Boc group onto the activated alkyne. Once again,
(PPh3)AuNTf2 proved to be a relatively mild catalyst as attested by
the rearrangement of internal alkynes 13b and 13c for which the
second Boc group remains intact under the reaction conditions
O
Ot-Bu
O
O
O
O
Au(I) catalyst
(ref 9)
R1
R1
R2
O
R2
Ot-Bu
O
O
O
O
O
O
O
Hg(II) catalyst
(ref 10)
R2
and/or
R2
R1
R1
R1
R2
Scheme 3. Synthesis of dioxanones by Shin and dioxinones by Nishizawa.
2. Results and discussion
2.1. Synthesis of 4-alkylidene-1,3-dioxolan-2-ones
In order to validate our synthetic approach, the simple prop-
argylic tert-butyloxycarbonate 8 was first chosen as a model sub-
strate (Scheme 4). A rapid and clean conversion of 8 was observed
when the reaction was performed in dichloromethane, on a 1 mmol
scale, with 1 mol % of the bench stable (PPh3)AuNTf2.11 Cyclic
carbonate 9 was isolated in 83% yield under these conditions.
O
O
O
OBoc
O
catalyst
O
O
CH2Cl2 (0.5 M), rt
8
1 mmol
1 mmol
1 mmol
9
10
1mol% (PPh3)AuNTf2
5mol% AgNTf2
10 min
83%
O
O
1- PhSeNa
1 h
1 h
OH
2- (CH3O)2C=O, NaHCO3
O
(ref 12)
Cl
OH
5mol% HNTf2
3- O3 then norbornadiene
0.1mol% (PPh3)AuNTf2
12 mmol
5 h 81%
52%
9
Scheme 4. Rearrangement of propargylic tert-butyloxycarbonate 8.
Scheme 5. Synthesis of 9 by Trost and co-workers.

A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
1891
Table 1
Reaction scope for the transformation of terminal alkynes 11a–m
O
O
OBoc
O
1 mol% (PPh3)AuNTf2
CH2Cl2 (0.5 M), rt
R1
R1
R2
R2
12
11
Entry
1
Substrate 11
Product 12
Time
Yielda
O
O
OBoc
Me
O
11a
11b
12a
12b
15 min
94
Me
O
O
OBoc
O
2
3
5 min
100
Ph
Ph
O
OBoc
dr = 1:1
O
O
11c
11d
12c
12d
10 min
91 dr¼1:1
O
O
OBoc
4
5 min
96
O
TIPSO
TIPSO
O
OBoc
O
5
6
11e
11f
12e
12f
5 min
10 h
95
74
O
O
OBoc
O
O
Ph
Ph
O
OBoc
49b
49c
O
5 h
1 h
7
11g
12g
O
O
O
OBoc
Me
O
8
9
11h
11i
12h
12i
5 min
5 min
85
98
Me
Et
Me
Et
Me
O
O
OBoc
Me
O
Me
O
O
OBoc
O
10
11j
12j
30 min
96
O
O
OBoc
O
11
12
11k
11l
12k
12l
10 min
90
76
AcO
AcO
O
O
OBoc
Me
O
17 h
Ph
Ph
Me
(continued on next page)

1892
A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
Table 1 (continued)
Entry
Substrate 11
Product 12
Time
18 h
Yielda
40
O
O
OBoc
13
11m
12m
O
Me
Me
a
Isolated yield.
With 3 mol % of (PPh3)AuNTf2.
With 1 mol % of [Ph3PAu(NC–CH3)]SbF6.
b
c
(entries 2 and 3). Thus, remarkably, unsymmetrical substrate 13b,
stereoselectively produces 14b as the result of a Thorpe–Ingold
effect favoring a faster cyclization of the more substituted tert-
butyloxycarbonate. Curiously, tert-butyloxycarbonates 13d–g did
not react under the same reaction conditions (entries 4–7). The
rearrangement was however effective when the more electrophilic
gold complex [(p-CF3Ph)3P]AuNTf2 was used as the catalyst. Under
these new conditions, exo-methylene compounds 12a and 14e–g
were obtained in moderate yields (60–68%) following an un-
expected reaction pathway. The cyclic carbonate motif in com-
pounds 12a and 14e–g was indeed shifted from one carbon in
comparison with the structures of the compounds obtained in the
cases studied previously. The reactions of substrates 13f and 13g,
possessing an asymmetric center at the propargylic position, pro-
duced diastereoisomeric mixtures of cyclic carbonates. Even if the
selectivity was modest, it notably increased as a function of the
steric hindrance induced by the group located at the propargylic
position (compare entry 6 with entry 7).
Disappointing results were obtained in the case of internal al-
kynes 13h and 13i (entries 8 and 9), whatever the catalyst used. In
the first case, the substrate was unreactive, while numerous
products derived from the degradation of the Boc group were
formed when TMS derivative 13i was used as the substrate. While
alkyne 13j was described in our preliminary communication6 as
leading to cyclic carbonate 14j, reexamination of NMR spectra led to
the conclusion that the structure of the product had been initially
misassigned (Scheme 6). Rearrangement of 13j, in the presence of
1 mol % of (PPh3)AuNTf2 actually furnished compound 16 as the
result of a 1,3-tert-butoxycarbonyl migration followed by the
hydrolysis of the resulting tert-butoxycarbonyloxyallene 15 by
traces of water.13
Table 2
Reaction scope for the transformation of internal alkynes 13a–i
OBoc
1 mol% (PR3)AuNTf2
R1
14
R2
CH2Cl2 (0.5 M), rt
R3
13
Entry
1b
Substrate 13
Product 14
Time
Yielda
87
O
OBoc
O
Me
Me
Me
Me
O
13a
13b
14a 2 h
CO2Et
CO2Et
O
O
OBoc
O
2b
14b 50 min 62
14c 30 min 77
OBoc
OBoc
O
OBoc
OBoc
O
3b
13c
13d
O
Me
Me
OBoc
OBoc
O
4c
12a 24 h
62
O
O
Me
Et
Me
Et
2.2. Mechanistic proposal
OBoc
OBoc
O
O
The results obtained during the scope of the transformation led
to the conclusion that the structure of the cyclic carbonates (17 or
18) furnished by the gold-catalyzed rearrangement of propargylic
tert-butyloxycarbonates 13 was significantly dependant on the
nature of the substituent attached at the alkyne terminus
(Scheme 7).14
A mechanistic proposal that accounts for the formation of cyclic
carbonates of type 17 is given in Scheme 8. Gold(I)-activation of the
alkyne moiety in substrate 19 promotes the nucleophilic addition of
5c
13e
13f
14e 24 h
14f 20 h
60
O
O
O
6c
68 dr¼1:1.6
O
OBoc
O
O
7c
13g
13h
13i
14g 20 h
66 dr¼1:3.9
O
Ph
Ph
O
O
OBoc
OBoc
O
O
1% (PPh3)AuNTf2
CH2Cl2, rt, 30 min
BocO
O
8b,c
d
20 h
d
d
O
N
N
N
O
Ph
13j
14j
O
O
1,3-shift
9b,c
d
3 h
OBoc
N
O
hydrolysis
O
TMS
O
a
Isolated yield.
With (PPh3)AuNTf2.
With [(p-CF3Ph)3P]AuNTf2.
94%
15
16
b
c
Scheme 6. Rearrangement of propargylic tert-butyloxycarbonate 13j.

A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
1893
O
O
O
O
OBoc
O
O
Au
CH2Cl2, rt
+
R3
O
19
O
R1
R1
or
O
R2
O
R3
R2
R3 18
R
O
13
17
R1, R2= H
O
R
Scheme 7. Divergence in the rearrangement of propargylic tert-butyloxycarbonates.
+
Au
O
R
O
+
Au
HO
Au
O
O
20
O
O
19
O
O
O
O
O
R
O
R
R
O
O
H
Au
+
R
H
25
+
+
Au
O
O
O
R
O
+
O
O
O
R
+
Au
HO
O
R
Au
20
+
Au
Au 23
O
O
24
- Au +
O
O
O
O
+
R
+
H
R
Boc
+
H
Au
22
26
H
21
R'
Scheme 8. Mechanistic proposal for the formation of cyclic carbonate of type 17.
Scheme 10. Mechanistic proposal for the formation of cyclic carbonate of type 18.
leading to the formation of a 1,3-diene 26, as recently reported by
Zhang and co-workers.15 The formation of such dienes was not
observed during the rearrangement of substrates 13f and 13g, for
which this 1,2-hydride shift would be especially favored. This se-
lectivity may result from a greater stability of intermediate 24
compared to 23.14
the tert-butyloxycarbonyl group that leads to the formation of the
intermediate cationic species 20. A selective fragmentation of
the C–O bond of the tert-butyloxy group subsequently furnishes the
neutral vinyl–gold species 21 with release of isobutene. A final
protodemetallation step finally gives cyclic carbonate 22. This
mechanism seems to be favored in the case of terminal alkynes (see
Table 1) or alkynes possessing electron-withdrawing groups (see
Table 2, entry 1). Substrates possessing a second propargylic BocO
group are also rearranged following this reaction pathway (see
Table 2, entries 2 and 3).
The anti addition of the tert-butyloxycarbonyl group onto the
activated alkyne combined with the stereoselective proto-
demetallation step are in agreement with the stereospecific for-
mation of compounds 14a–c (see Table 2, entries 1–3). The
exclusive formation of compound 8(D) during the rearrangement of
80% deuterated alkyne 9(D) is also in agreement with this mecha-
nistic proposal (Scheme 9).
A plausible reaction pathway that may explain the formation of
cyclic carbonates of type 18 is presented in Scheme 10. After an
identical nucleophilic addition of the tert-butyloxycarbonyl group
onto the activated alkyne, the fragmentation of the internal C–O
bond in intermediate 20 could alternatively occur to give the sta-
bilized gold carbene 23 (Scheme 10). A subsequent cyclization of
the Boc group, followed by a sequence of fragmentation and pro-
todemetallation would finally furnish cyclic carbonate 25.
This mechanism can account for the selectivity observed in the
case of substrates 13f and 13g (see Table 2). Interestingly, the for-
mation of intermediate 23 might be followed by a 1,2-hydride shift
2.3. Synthesis of 4-(Z-halomethylene)-1,3-dioxolan-2-ones
Vinyl bromides and iodides are synthetically useful building
blocks that can be used in a range of transformations, among which
transition metal-catalyzed cross-coupling reactions occupy a pre-
dominant place. We were particularly intrigued to see if the pro-
tocol used for the rearrangement of terminal propargylic tert-butyl
carbonates could also be applied to the formation of haloalkenes 28
using as substrates haloalkynes 27 (Scheme 11).
This approach would be particularly interesting for two main
reasons. Following the same mechanistic proposal than that pro-
posed for the rearrangement of terminal alkynes (see Scheme 8),
this procedure would allow the stereoselective formation of (Z)-
haloalkenes. Secondly, it is noteworthy that these isomers could not
be obtained following the methods previously developed for the
direct iodocyclization of similar homopropargylic tert-butyl
carbonates16 since the use of a source of electrophilic iodine ex-
clusively furnishes the opposite (E)-isomers (Scheme 12). It is also
stereoselective protodemetallation
H+
O
O
H+
BocO
27
O
X
H
O
O
O
X
O
(80%)
D
BocO
O
1% (PPh3)AuNTf2
CH2Cl2, rt, 5 min
X
AuL
X= Br, I
O
D
(80%)
28
LAu
H+
Scheme 11. Synthetic approach to 4-(Z-halomethylene)-1,3-dioxolan-2-ones.
8(D)
9(D)
80%
Scheme 9. Rearrangement of propargylic tert-butyloxycarbonate 8(D).

1894
A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
Table 3
O
(E)-selectivity
Reaction scope for the formation of 4-(Z-halogenomethylene)-1,3-dioxolan-2-ones
32a–g
OBoc
O
O
IBr, CH2Cl2
(ref 16)
O
O
R
R
OBoc
O
I
1 mol% (PPh3)AuNTf2
CH2Cl2 (0.5 M), rt
R1
R1
R2
R2
32
Scheme 12. Literature precedent for the iodocyclization of homopropargylic tert-butyl
X
carbonates.
X
31
Entry
1
Substrate 31
Product 32
Time
Yielda
important to note that these haloalkenes could not be obtained
using the mercury-catalyzed reaction developed by Nishizawa.10
We chose simple bromoalkyne 29 as a model substrate to study
the feasibility of the transformation (Scheme 13). To our delight, the
desired reaction did happen with 1 mol % of (PPh3)AuNTf2 using
dichloromethane as the solvent and bromoalkyne 30 was formed in
87% yield with a complete (Z) selectivity.
O
O
OBoc
O
31a
32a 20 min 87
Br
Br
O
OBoc
O
This procedure was applied to a series of diversely substituted
haloalkynes, and the results are presented in Table 3. The reaction
proved to be rapid in all the cases. The presence of a halogen atom
at the alkyne terminus did not induce a change in the kinetics of the
cyclization (compare results of Table 3 with those of Table 1).
Bromoalkyne 31a, possessing an extra methyl substituent at the
propargylic position, cyclized more rapidly and (Z)-bromoalkyne
32a was isolated in an excellent 95% yield. Since iodoalkenes are
generally more desirable than their bromo analogs for transition
metal-catalyzed cross-coupling reactions, we focused more par-
ticularly our attention on the transformation of iodoalkynes. Re-
sults presented in entries 2–7 demonstrate that a range of
secondary and tertiary iodoalkynes bearing a variety of sub-
stituents could be selectively rearranged to the corresponding (Z)-
iodoalkenes 32b–g in generally good yields. A phenyl group (entry
3), an alkene (entry 4) or a silyl ether (entry 5) was compatible
functionalities. A disappointing result was however obtained in the
case of alkyne 31f possessing a cyclopropyl group at the propargylic
position. Only traces of the corresponding iodoalkene 32f were
obtained when (PPh3)AuNTf2 was used as the catalyst. The more
electrophilic [Ph3PAu(NC–CH3)]SbF6 complex was required to im-
prove the formation of 32f, which could be isolated in a modest 32%
yield. As previously suggested, (PPh3)AuNTf2 might be acidic
enough to activate the OBoc group and cause the degradation of the
substrate by formation of a positive charge at the propargylic po-
sition. This process would be especially favored in this case due to
the presence of the cyclopropyl ring.
O
2
3
31b
31c
32b 10 min 95
I
I
O
O
OBoc
O
32c 5 min 99
Ph
Ph
I
I
OBoc
O
O
O
4
31d
32d 5 min 97 dr¼1:1
I
dr = 1:1
I
O
O
OBoc
O
5
31e
31f
32e 5 min 69
TIPSO
I
OTIPS
I
O
OBoc
O
6b
32f 1 h
32
O
I
I
O
O
OBoc
O
7
31g
32g 5 min 83
I
I
2.4. Synthesis of 4-(E-iodomethylene)-1,3-dioxolan-2-ones
a
Isolated yield.
With 1 mol % of [Ph3PAu(NC–CH3)]SbF6.
b
We next envisaged to synthesize the (E)-isomers of 4-iodo-
methylene-1,3-dioxolan-2-ones, which one could not be obtained
by the rearrangement of iodoalkynes derivatives, due to the
stereospecificity of the transformation. The development of an-
other gold-catalyzed reaction allowing the stereoselective forma-
tion of the (E) isomers would however be synthetically useful since
either one or the other isomer could be selectively obtained from
the same propargylic tert-butyl carbonate precursor. Our synthetic
approach is depicted in Scheme 14. Since a stereoselective proto-
demetallation was proposed as the last step in the rearrangement
of propargylic tert-butyl carbonates into 4-methylene-1,3-dioxo-
lan-2-ones (Scheme 8), we envisaged to trap the intermediate
vinyl–gold species 33 by a source of an electrophilic iodine before
the protonation occurs.17
NIS was chosen as the electrophile17 and the reaction attempted
using alkyne 11j as the substrate (Scheme 15). Using the conditions
previously developed for the simple rearrangement of propargylic
protodemetallation
O
O
H+
H+
O
O
H
I
BocO
O
O
O
"I+"
O
OBoc
O
AuL
33
O
1% (PPh3)AuNTf2
CH2Cl2, rt, 1h
O
LAu
O
I+
Br
Br
29
30
87%
iododemetallation
Scheme 13. Formation of (Z)-bromoalkene 30.
Scheme 14. Synthetic approach to 4-(E-iodomethylene)-1,3-dioxolan-2-ones.

A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
1895
Table 4
O
O
Reaction scope for the formation of 4-(E-iodomethylene)-1,3-dioxolan-2-ones 35
O
O
OBoc
1% (PPh3)AuNTf2
NIS (1.2 equiv), rt
O
O
O
O
OBoc
O
I
1 mol% (PPh3)AuNTf2
11j
I
R1
R1
12j
34
NIS (1.2 eq.)
Acetone (0.5 M), rt
solvent:
35
36
dichloromethane 5 min
48%
-
48%
95%
Entry
1
Substrate 35
Product 36
Time
Yielda
35
acetone
5 min
O
O
Scheme 15. Formation of (E)-iodoalkene 34.
OBoc
O
35a
35b
35c
36a 5 min
I
tert-butyl carbonates (1 mol % of (PPh3)AuNTf2, dichloromethane as
the solvent) with a slight excess of NIS (1.2 equiv), the reaction was
very rapid and a 1:1 mixture of the desired (E)-iodinated product
34 and the protodemetallated product 12j was formed. In order to
improve the formation of 34, the reaction was attempted using
a more polar solvent. We indeed hypothesized that the protonation
should be slowed down in a polar solvent thus favoring the trap-
ping of the vinyl–gold intermediate by NIS. Gratifyingly, the use of
acetone as the solvent had a dramatic effect on the selectivity while
the rate of the reaction remains the same. Compound 34 was ex-
clusively and stereoselectively formed under these conditions and
isolated in 95% yield.
While the iodine-mediated cyclization of allylic and homoallylic
tert-butyl carbonates is well documented,7 no example of the same
transformation applied to propargylic derivatives has been repor-
ted. Mathew and co-workers have however described the direct
iodocyclization of a series of homopropargylic tert-butyl carbonates
using IBr as the source of electrophilic iodine (Scheme 12).16 In
order to evaluate the role of the gold catalyst during this reaction,
a control experiment was performed (Scheme 16). Under the same
reaction conditions with a twofold excess of NIS and without
(PPh3)AuNTf2, the formation of iodoalkene 34 was slow. This
compound could however be isolated in 82% yield after 48 h.
Even if this control experiment does not prove that iodoalkene
34 is formed after an iododemetallation step when the gold com-
plex is used, the difference observed in the kinetics reflects the
major role played by this complex in the transformation. In-
cidentally, such an iododemetallation step has been invoked in
a series of other gold mediated transformations.17
O
O
O
OBoc
2
3
36b 45 min 66
Ph
Ph
I
O
O
OBoc
O
I
36c
15 min 64
TIPSO
OTIPS
O
O
I
OBoc
OBoc
4b
35d
35e
36d 1 h
76
O
5
d
5 min
d
OBoc
6
35f
d
15 min
d
a
Isolated yield.
With 1 mol % of [Ph3PAu(NC–CH3)]SbF6.
b
yields were improved to 66% and 64%, while the reaction times
were increased (entries 2 and 3). It is particularly noteworthy that
only limited desilylation occurred in the case of substrate 35c due
to the mildness of the reaction conditions used. Cyclopropyl de-
rivative 35d also furnished the desired iodoalkene 36d in a good
76% yield (entry 4). As in the case of the simple rearrangement
(Table 1, entry 7), the use of the more electrophilic [Ph3PAu(NC–
CH3)]SbF6 gold complex was however required to obtain a com-
plete conversion of 35d. This transformation is however not
a general process as indicated by the results obtained when the
transformation was attempted using substrates 35e and 35f (en-
tries 5 and 6). In these cases, the corresponding iodoalkenes could
not be isolated and only degradation products were obtained. This
contrasting reactivity remains unclear even if the occurrence of
competitive side reactions initiated by the interaction of NIS with
the alkene might be invoked for substrate 35e.
A rapid exploration of the scope of the reaction was next per-
formed using diversely substituted secondary propargylic alcohol
derivatives 35a–f (Table 4). While the yield was excellent when
tertiary propargylic alcohol derivative 11j was used as the substrate
(Scheme 15), iodoalkenes 36a–d were only obtained in low to
moderate yields (35–76%), but with a complete stereoselectivity. It
is interesting to note that in most cases, the iodocyclization was
a slower process than the simple cyclization (compare the results in
Table 1 with those in Table 4), perhaps the consequence of a lower
activity of the gold complex in acetone than in dichloromethane.
Even if the reaction was rapid in the case of monomethyl
substituted substrate 35a, it was however surprisingly inefficient,
and compound 36a was isolated in a low 35% yield (entry 1). With
a longer side chain such as in the case of alkynes 35b and 35c, the
O
OBoc
O
NIS (2 equiv)
acetone, rt
2.5. Palladium cross-coupling reactions
O
11j
Having in hand a series of 4-halogenomethylene-1,3-dioxolan-
2-ones, we attempted to use these compounds as substrates in
palladium cross-coupling reactions. We first focused our attention
on the Sonogashira coupling. This transformation has already been
successfully applied to the coupling of various alkynes with cyclic
I
34
3 h
48h
5%
83%
Scheme 16. Control experiment for the formation of (E)-iodoalkene 34.

1896
A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
O
O
O
O
O
n
O
O
O
(ref 19)
R
n
O
O
3.5h
79%
O
O
I
O
O
I
Ph
Sonogashira coupling
Ph B(OH)2
34
O
O
R
R
40
(ref 18)
(ref 21)
Pd(PPh3)4, K2CO3
I
R
toluene, 80 °C
O
O
O
O
N
O
I
O
N
O
2.5h
40%
O
TIPSO
TIPSO
I
O
Ph
36c
41
O
O
Sonogashira coupling
?
R
O
Scheme 19. Examples of Suzuki cross-coupling reaction with 4-(iodomethylene)-1,3-
dioxolan-2-ones.
O
O
R
I
Scheme 17. Literature precedents for the Sonogashira cross-coupling reaction of
substrates structurally closed to dioxolanones.
reaction between (Z)-iodoalkene 32a and phenylacetylene, which
was relatively efficient when only 10 equiv of triethylamine were
used, only furnished degradation products when the base was used
as the solvent. We were also surprised by the reactivity of (E)-
iodoalkene 36a. While (Z) isomer 32b reacted with triisopropyl-
pent-4-ynyloxy-silane to give enyne 39c in 67% yield, the reaction
with (E) isomer 36a only led to degradation products under the
same reaction conditions.
Attempts to perform Suzuki cross-coupling reactions with
dioxolanones derivatives were also successful (Scheme 19).22
Enynes 34 and 36c reacted for instance with phenylboronic acid in
the presence of tetrakis(triphenylphosphine)palladium(0) and po-
tassium carbonate in toluene at 80 ꢀC to give dioxolanones 40 and
41 in, respectively, 79% and 40% yield. However, the reaction proved
to be more sluggish for this coupling probably due to the higher
temperature used and the instability of the vinylcarbonate func-
tionality under the basic conditions used.
derivatives furanones,18 dihydrofuranones,19 tetrahydropyr-
anones19,20 or oxazolidinones21 and could therefore be envisaged in
the case of dioxolanones (Scheme 17).
The results of this study are summarized in Scheme 18. To our
delight, the reaction of (Z)-iodoalkene 32g with phenylacetylene
under classical Sonogashira reaction conditions led to the forma-
tion of enyne 37, which was isolated in a moderate 61% yield.
Surprisingly, the reaction of the isomeric (E)-iodoalkene 34 was
more efficient and furnished the corresponding enyne 38 in an
excellent 94% yield. Various alkynes could be used as partners in
the Sonogashira coupling as attested by the transformation of
iodoalkene 32b into enynes 39a–c (67–72% yield).22
Interestingly, the quantity of triethylamine used for the Sono-
gashira cross-coupling proved to be highly important. Indeed, the
In summary, we have shown that gold(I) complexes efficiently
catalyze the formation of a variety of 4-(alkylidene)-1,3-dioxolan-
2-ones from readily available propargylic tert-butyl carbonates. The
loading of the catalyst is low (1 mol %) and the reaction conditions
mild enough to insure a compatibility with diversely substituted
substrates. The structure of the cyclic carbonates obtained also
appears to be dependant on the nature of the substituent attached
at the terminus of the alkyne. An extension of the procedure to the
stereoselective formation of (E)- or (Z)-4-(halomethylene)-1,3-
dioxolan-2-ones has also been developed, using, respectively,
haloalkynes or terminal alkynes as the substrates. These trans-
formations furnished valuable haloalkenes, which proved to be
suitable substrates for Sonogashira and Suzuki cross-coupling
reactions.
O
O
O
O
Ph
O
O
PdCl2(PPh3)2, CuI
Et3N (10 eq), THF, rt, 30 min
61%
I
Ph
32g
37
O
O
O
O
Ph
O
I
O
PdCl2(PPh3)2, CuI
Et3N (10 eq), THF, rt, 20 min
94%
34
38
Ph
O
O
O
O
3. Experimental
O
R
O
PdCl2(PPh3)2, CuI
3.1. General information
Et3N (10 eq), THF, rt
I
R
32b
39a-c
Commercially available reagents were used as received with-
out further purification. Dry Et2O and THF were obtained by
distillation from Na/benzophenone and dry CH2Cl2 from CaH2.
Flash column chromatography was performed over silica gel 60 by
n-C5H11
R=
67%
1.5 h
39a
Ph
20 min 72% 39b
Merck (40–63 m
m). 1H NMR and 13C NMR spectra were recorded
(CH2)3OTIPS
18h 67%
39c
on a Bruker Avance 400 MHz spectrometer using residue solvent
peaks as internal standards. Infrared spectra were recorded with
a Perkin–Elmer FT-1600 spectrometer. Mass spectra were recor-
O
O
Ph
ded with a Hewlett–Packard HP-5890
B spectrometer using
O
PdCl2(PPh3)2, CuI
electron ionization (EIþ) or chemical ionization with ammonia
(CIþ, NH3) methods. High resolution mass spectra were recorded
with a Jeol GCmate II spectrometer using the electron ionization
(EIþ) method. R3P-Au-NTf2 catalysts were synthesized as pre-
viously described.11
degradation
Et3N (solvent), rt
I
32b
Scheme 18. Attempts of Sonogashira cross-coupling reaction with 4-(iodomethylene)-
1,3-dioxolan-2-ones.

A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
1897
3.2. Au(I)-catalyzed formation of 4-alkylidene-1,3-dioxolan-
2-ones
(ddd, J¼2.7, 6.0, 17.2 Hz, 1H), 2.77 (ddd, J¼2.7, 4.5, 17.2 Hz, 1H), 2.18
(t, J¼2.7 Hz, 1H). 13C NMR (100 MHz, CDCl3):
d 151.7, 151.6, 88.2,
76.7, 76.0, 72.6, 25.3. IR (CCl4): cmꢁ1 3310, 1850, 1685, 1328, 1288,
1129, 1075. MS (CIþ, NH3): m/z 156 (MNHþ4 ). HRMS (EIþ): m/z cal-
culated for C7H6O3: 138.0317, found: 138.0320.
General procedure: To
a solution of propargylic tert-butyl
carbonate (1 equiv) in dichloromethane (0.5 M) at room tempera-
ture was added the gold catalyst (0.01 equiv). The mixture was
stirred at room temperature and monitored periodically by TLC.
Upon completion, the mixture was either directly filtered through
a silica pad pre-impregnated with dichloromethane or evaporated
and then chromatographed with a petroleum ether/diethyl ether
mixture to give the expected product.
3.2.7. 5-Methylene-4-phenyl-1,3-dioxolan-2-one (12f)
Yield: 74%. Pale yellow oil. 1H NMR (400 MHz, CDCl3):
d 7.52–7.48
(m, 3H), 7.47–7.44 (m, 2H), 6.13 (dd, J¼2.1, 2.5 Hz,1H), 5.03 (dd, J¼2.5,
4.0 Hz, 1H), 4.35 (dd, J¼2.1, 4.0 Hz, 1H). 13C NMR (100 MHz, CDCl3):
d
153.1,151.9,134.9,130.3,129.3,127.4, 89.3, 81.4. IR(CCl4):cmꢁ11845,
1711, 1684, 1301, 1261, 1127, 1040. MS (CIþ, NH3): m/z 194 (MNH4þ).
HRMS (EIþ): m/z calculated for C10H8O3: 176.0473, found: 176.0480.
3.2.1. 4-Methylene-1,3-dioxolan-2-one (9)
Yield: 83%. Solid. 1H NMR (400 MHz, CDCl3):
d
5.01 (t, J¼2.3 Hz,
2H), 4.93–4.90 (m, 1H), 4.45–4.43 (m, 1H). 13C NMR (100 MHz,
3.2.8. 4-Cyclopropyl-5-methylene-1,3-dioxolan-2-one (12g)
CDCl3):
d
152.7, 148.9, 87.4, 67.6. IR (CCl4): cmꢁ1 2925, 1855, 1708,
Yield: 49%. Pale yellow oil. 1H NMR (400 MHz, CDCl3):
d 4.88 (dd,
1681, 1283, 1119, 1067. Mp (ꢀC): 28–29. MS (CIþ, NH3) m/z 118
(MNHþ4 ). HRMS (EIþ) m/z calculated for C4H4O3: 100.0160, found:
100.0159.
J¼2.5, 3.6 Hz,1H), 4.57 (dd, J¼2.1, 8.4 Hz,1H), 4.50 (dd, J¼2.0, 3.7 Hz,
1H), 1.35–1.19 (m, 1H), 0.81–0.71 (m, 2H), 0.64–0.53 (m, 1H), 0.55–
0.44 (m, 1H). 13C NMR (100 MHz, CDCl3):
d 152.7, 151.9, 87.4, 84.0,
14.3, 2.6, 2.2. IR (CCl4): cmꢁ1 3088, 3013, 2966, 2927, 2860, 1843,
1681, 1378, 1320, 1277, 1181, 1130, 1045. MS (EIþ): m/z 140 (Mþ).
HRMS (EIþ): m/z calculated for C7H8O3: 140.0474, found: 140.0478.
3.2.2. 4-Methyl-5-methylene-1,3-dioxolan-2-one (12a)
Yield: 94%. Yellow oil. 1H NMR (400 MHz, CDCl3):
d
5.28–5.19 (m,
1H), 4.85–4.78 (m, 1H), 4.37–4.33 (m, 1H), 1.59–1.54 (m, 3H). 13C
NMR (100 MHz, CDCl3):
d
154.5, 151.8, 86.5, 76.2, 20.3. IR (CCl4):
3.2.9. 4,4-Dimethyl-5-methylene-1,3-dioxolan-2-one (12h)
cmꢁ1 2989, 2934, 1844, 1707, 1682, 1317, 1279, 1145, 1085, 1003. MS
(CIþ, NH3): m/z 132 (MNHþ4 ), 102, 85. HRMS (EIþ): m/z calculated for
C5H6O3: 114.0317, found: 114.0313.
Yield: 85%. Solid. 1H NMR (400 MHz, CDCl3):
d
4.74 (d, J¼3.9 Hz,
1H), 4.31 (d, J¼3.9 Hz, 1H), 1.60 (s, 6H). 13C NMR (100 MHz, CDCl3):
d
158.6, 151.2, 85.2, 84.6, 27.4. IR (CCl4): cmꢁ1 2988, 190þ6, 1838,
1708, 1678, 1258, 1173, 1080, 1025. Mp (ꢀC): 28–29. MS (CI , NH3):
m/z 146 (MNHþ4 ). HRMS (EIþ): m/z calculated for C6H8O3: 128.0473,
found: 128.0475.
3.2.3. 4-Methylene-5-phenethyl-1,3-dioxolan-2-one (12b)
Yield: quant. Yellow oil. 1H NMR (400 MHz, CDCl3):
d 7.36–7.32
(m, 2H), 7.27–7.21 (m, 3H), 5.17–5.14 (m, 1H), 4.89 (dd, J¼2.4, 4.0 Hz,
1H), 4.37 (dd, J¼2.0, 4.0 Hz, 1H), 2.93–2.75 (m, 2H), 2.20–2.09 (m,
3.2.10. 4-Ethyl-4-methyl-5-methylene-1,3-dioxolan-2-one (12i)
2H). 13C NMR (100 MHz, CDCl3):
d
153.1, 151.9, 139.5, 128.6, 128.3,
Yield: 98%. Colorless oil. 1H NMR (400 MHz, CDCl3):
d 4.82 (d,
126.4, 86.8, 78.6, 36.5, 30.2. IR (CCl4): cmꢁ1 3065, 3028, 2950, 2930,
2862, 1842, 1705, 1681, 1497, 1452, 1341, 1282, 1131, 1085, 1045,
1004. MS (EIþ): m/z 204 (Mþ), 160, 145, 117, 105. HRMS (EIþ): m/z
calculated for C12H12O3: 204.0787, found: 204.0781.
J¼3.9 Hz, 1H), 4.27 (d, J¼3.9 Hz, 1H), 1.92 (dd, J¼7.4, 14.7 Hz, 1H),
1.76 (dd, J¼7.4, 14.7 Hz, 1H), 1.59 (s, 3H), 0.99 (t, J¼7.4 Hz, 3H). 13C
NMR (100 MHz, CDCl3):
d 157.2, 151.4, 87.5, 85.5, 33.2, 25.8, 7.1. IR
(CCl4): cmꢁ1 2980, 2935, 2839, 1703, 1677, 1291, 1229, 1151, 1090,
1040. MS (CIþ, NH3) m/z 160 (MNHþ4 ), 139, 117, 102, 85. HRMS (EIþ):
m/z calculated for C7H10O3: 142.0630, found: 142.0624.
3.2.4. 4-(2,6-Dimethyl-hept-5-enyl)-5-methylene-1,3-dioxolan-2-
one (12c)
Yield: 91%. Yellow oil (isolated as
astereoisomers). 1H NMR (400 MHz, CDCl3) for the mixture of di-
astereoisomers: 5.23–5.16 (m, 1H), 5.11–5.06 (m, 1H), 4.85–4.83
a
1:1 mixture of di-
3.2.11. 4-Methylene-1,3-dioxa-spiro[4.5]decan-2-one (12j)
Yield: 96%. Heavy oil. 1H NMR (400 MHz, CDCl3):
d
4.81 (d,
d
J¼3.8 Hz, 1H), 4.33 (d, J¼3.8 Hz, 1H), 2.07–2.03 (m, 2H), 1.84–1.58
(m, 1H), 4.33–4.31 (m, 1H), 2.09–1.93 (m, 2H), 1.94–1.13 (m, 5H),
(m, 8H). 13C NMR (100 MHz, CDCl3):
d 158.5, 151.2, 86.2, 85.3, 36.3,
1.69 (s, 3H), 1.61 (s, 3H), 1.00 (d, J¼6.3 Hz, 3H). 13C NMR (100 MHz,
24.1, 21.4. IR (CCl4): cmꢁ1 2942, 2862, 1842, 1703, 1676, 1264, 1196,
1128, 1059, 1022. MS (CIþ, NH3) m/z 186 (MNHþ4 ). HRMS (EIþ): m/z
calculated for C9H12O3: 168.0786, found: 168.0791.
CDCl3) for the mixture of diastereoisomers:
d 154.0, 154.0, 152.0,
131.8, 131.8, 123.9, 123.9, 86.6, 86.5, 78.6, 78.1, 42.5, 42.5, 37.2, 36.1,
29.2, 28.6, 25.6, 25.2, 25.1, 19.8, 18.7, 17.6, 17.6. IR (CCl4): cmꢁ1 2965,
2925, 2859, 1834, 1703, 1680, 1452, 1378, 1340, 1282, 1135, 1077,
1017. MS (EIþ): m/z 224 (Mþ). HRMS (EIþ): m/z calculated for
C13H20O3: 224.1413, found: 224.1420.
3.2.12. Androstene derivative (12k)
Yield: 90%. Crystalline. 1H NMR (400 MHz, CDCl3):
d 5.28 (d,
J¼4.8 Hz, 1H), 4.83 (d, J¼3.8 Hz, 1H), 4.55–4.42 (m, 1H), 4.31 (d,
J¼3.8 Hz, 1H), 2.43–2.14 (m, 3H), 2.10–1.94 (m, 2H), 1.94 (s, 3H), 1.93
(br d, J¼10.5 Hz, 2H), 1.71–1.60 (m, 1H), 1.54–1.26 (m, 8H), 1.29–1.17
(m, 1H), 1.07–1.01 (m, 1H), 0.95 (s, 3H), 0.90 (s, 3H), 1.00–0.82 (m,
3.2.5. 4-Methylene-5-(4-triisopropylsilanyloxy-butyl)-1,3-
dioxolan-2-one (12d)
Yield: 96%. Yellow oil. 1H NMR (400 MHz, CDCl3):
d
5.19–5.16 (m,
1H). 13C NMR (100 MHz, CDCl3):
d 170.2, 157.6, 151.3, 139.6, 121.6,
1H), 4.86 (dd, J¼2.4, 3.9 Hz, 1H), 4.35 (dd, J¼1.9, 3.9 Hz, 1H), 3.71 (t,
96.8, 88.8, 73.4, 49.2, 49.0, 47.1, 37.9, 36.7, 36.4, 34.1, 31.8, 31.2, 30.9,
27.5, 22.9, 21.2, 20.0, 19.1, 14.0. IR (CCl4): cmꢁ1 2949, 2907, 183þ5,
1735, 1674, 1369, 1245, 1137, 1080, 1030. Mp (ꢀC): 195–200. MS (CI ,
NH3) m/z 419 (MNHþ4 ), 355, 339. HRMS (EIþ): m/z calculated for
C24H32O5: 400.2250, found: 400.2257.
J¼5.8 Hz, 2H), 1.97–1.77 (m, 2H), 1.68–1.50 (m, 4H), 1.13–1.01 (m,
21H). 13C NMR (100 MHz, CDCl3):
d 153.4, 152.0, 86.7, 79.8, 62.8,
34.6, 32.1, 20.6, 17.9, 11.9. IR (CCl4): cmꢁ1 2945, 2865, 2727, 2251,
1842, 1746, 1704, 1681, 1462, 1383, 1338, 1280, 1105, 1011. MS (EIþ):
m/z 328 (Mþ), 286, 242, 223, 211, 199. HRMS (EIþ): m/z calculated
for C17H32O4Si: 328.2070, found: 328.2083.
3.2.13. 4-Methyl-5-methylene-4-phenyl-1,3-dioxolan-2-one (12l)
Yield: 76%. Heavy yellow oil. 1H NMR (400 MHz, CDCl3):
d
7.41–
7.27 (m, 5H), 4.86 (d, J¼4.0 Hz,1H), 4.38 (d, J¼4.0 Hz,1H),1.88 (s, 3H).
13C NMR (100 MHz, CDCl3):
157.5, 151.2, 139.3, 129.2, 128.9, 124.8,
88.2, 87.2, 27.6. IR (CCl4): cmꢁ1 3660, 3065, 2991, 2935, 1843, 1680,
3.2.6. 4-Methylene-5-prop-2-ynyl-1,3-dioxolan-2-one (12e)
Yield: 95%. Colorless oil. 1H NMR (400 MHz, CDCl3):
d
5.31–5.27
d
(m, 1H), 5.00 (dd, J¼2.3, 4.1 Hz, 1H), 4.62 (dd, J¼1.9, 4.1 Hz, 1H), 2.88

1898
A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
1294, 1222, 1071. MS (CIþ, NH3): m/z 208 (MNHþ4 ), 157, 140. HRMS
(EIþ): m/z calculated for C11H10O3: 190.0630, found: 190.0622.
(dd, J¼2.0, 3.8 Hz, 1H), 3.7 (qd, J¼3.8, 7.2 Hz, 1H), 1.53 (d, J¼7.2 Hz,
3H). 13C NMR (100 MHz, CDCl3):
d 152.0, 151.1, 137.6, 128.7, 128.6,
127.9, 88.4, 83.4, 43.5, 15.4. IR (CCl4): cmꢁ1 2976, 1844, 1681, 1133,
1047. MS (CIþ, NH3): m/z 222 (MNHþ4 ). HRMS (EIþ): m/z calculated
for C12H12O3: 204.0786, found: 204.0788.
3.2.14. 4-Methyl-5-methylene-4-vinyl-1,3-dioxolan-2-one (12m)
Yield: 40%. Yellow oil. 1H NMR (400 MHz, CDCl3):
d 5.94 (d,
J¼10.6, 17.1 Hz, 1H), 5.49 (d, J¼17.1 Hz, 1H), 5.33 (d, J¼10.6 Hz, 1H),
Minor isomer: 1H NMR (400 MHz, CDCl3):
d 7.43–7.30 (m, 5H),
4.88 (d, J¼3.9 Hz, 1H), 4.34 (d, J¼3.9 Hz, 1H), 1.69 (s, 3H). 13C NMR
5.29 (ddd, J¼2.1, 2.1, 5.6 Hz, 1H), 4.86 (dd, J¼2.1, 3.9 Hz, 1H), 4.05
(100 MHz, CDCl3):
d 156.1, 151.0, 136.1, 116.6, 87.2, 85.7, 25.5. IR
(dd, J¼2.1, 3.9 Hz, 1H), 3.13 (qd, J¼5.6, 7.1 Hz, 1H), 1.47 (d, J¼7.1 Hz,
(CCl4): cmꢁ1 3671, 3097, 2988, 2931, 2864, 1843, 1754, 1679, 1291,
1227, 1125, 1023. MS (CIþ, NH3) m/z 158 (MNHþ4 ). HRMS (EIþ) m/z
calculated for C7H8O3: 140.0473, found: 140.0476.
3H). 13C NMR (100 MHz, CDCl3):
d 152.0, 151.8, 139.9, 129.0, 128.9,
127.8, 88.4, 83.4, 44.6, 15.6. IR (CCl4): cmꢁ1 2978, 1843, 1681, 1131,
1050. MS (CIþ, NH3): m/z 222 (MNHþ4 ). HRMS (EIþ): m/z calculated
for C12H12O3: 204.0786, found: 204.0787.
3.2.15. [5,5-Dimethyl-2-oxo-1,3-dioxolan-(4E)-ylidene]-acetic acid
ethyl ester (14a)
3.2.21. 3-Acryloyl-oxazolidin-2-one (16)
Yield: 87%. White solid. 1H NMR (400 MHz, CDCl3):
d
5.17 (br s,
Yield: 94%. White solid. 1H NMR (400 MHz, CDCl3):
d 7.54 (dd,
1H), 4.26 (d, J¼6.8 Hz, 2H), 1.69 (s, 6H), 1.35 (t, J¼6.8 Hz, 3H). 13C
J¼10.5, 17.0 Hz, 1H), 6.60 (dd, J¼1.8, 17.0 Hz, 1H), 5.95 (dd, J¼1.8,
NMR (100 MHz, CDCl3):
d 163.3, 163.1, 149.9, 93.4, 85.5, 60.9, 27.3,
17.0 Hz, 1H), 4.49 (t, J¼8.0 Hz, 2H), 4.13 (t, J¼8.0 Hz, 2H). 13C NMR
14.2. IR (CCl4): cmꢁ1 3050, 2984, 1854, 1719, 1694, 1262. Mp (ꢀC):
77–78. MS (CIþ, NH3): m/z 218 (MNH4þ), 201 (MHþ). HRMS (EIþ): m/
z calculated for C9H12O5: 200.0685, found: 200.0688.
(100 MHz, CDCl3): d 165.07 (2C), 153.4, 131.8, 127.0, 62.2, 42.6. IR
(CCl4): cmꢁ1 1791, 1693, 1408, 1382, 1324, 1257, 1220. Mp (ꢀC): 73–
74. MS (CIþ, NH3): m/z 159, 142. HRMS (EIþ): m/z calculated for
C7H7NO5: 185.0324, found: 185.0321.
3.2.16. tert-Butyl (E)-2-(2-oxo-1,3-dioxolan-4-ylidene)ethyl
carbonate (14b)
3.2.22. 4-[1-Bromo-meth-(Z)-ylidene]-1,3-dioxolan-2-one (30)
Yield: 62%. Pale yellow oil. 1H NMR (400 MHz, CDCl3):
d
4.9 (dd,
Yield: 87%. Colorless crystals. 1H NMR (400 MHz, CDCl3):
d 5.5 (t,
J¼1.4, 3.4 Hz, 2H), 4.96–4.91 (m, 1H), 4.63 (dd, J¼1.4, 7.2 Hz, 2H),
J¼2.1 Hz, 1H), 5.02 (d, J¼2.1 Hz, 2H). 13C NMR (100 MHz, CDCl3):
1.41 (s, 9H). 13C NMR (100 MHz, CDCl3):
d
153.0, 151.9, 145.6, 97.4,
d
151.1, 145.0, 78.9, 67.5. Mp (ꢀC): 100–103. MS (CIþ, NH3): m/z 196
82.51, 67.4, 59.9, 27.7. IR (CCl4): cmꢁ1 2980, 1855, 1724, 1391, 1366,
1269, 1167, 1094, 1052. MS (CIþ, NH3): m/z 248 (MNH4þ), 192. HRMS
(EIþ): m/z calculated for C10H14O6: 230.0790, found: 230.0795.
(MNHþ4 ), 192, 188, 178, 169, 156. HRMS (EIþ): m/z calculated for
C4H3BrO3: 177.9266, found: 177.9262.
3.2.23. 4-[1-Bromo-meth-(Z)-ylidene]-5-methyl-1,3-dioxolan-2-
3.2.17. tert-Butyl (E)-2-(5-methyl-2-oxo-1,3-dioxolan-4-
one (32a)
ylidene)ethyl carbonate (14c)
Yield: 87%. Yellow crystals. 1H NMR (400 MHz, CDCl3):
d 5.44 (d,
Yield: 77%. Pale yellow oil. 1H NMR (400 MHz, CDCl3):
d
5.26–
J¼2.0 Hz, 1H), 5.28 (qd, J¼2.0, 6.5 Hz, 1H), 1.62 (d, J¼6.5 Hz, 3H). 13C
5.21 (m, 1H), 4.87 (td, J¼1.9, 7.3 Hz, 1H), 4.63 (dd, J¼1.2, 7.3 Hz, 2H),
NMR (100 MHz, CDCl3): d 150.7, 150.4, 79.0, 76.4, 20.3. IR (CCl4):
1.53 (d, J¼6.5 Hz, 3H), 1.42 (s, 9H). 13C NMR (100 MHz, CDCl3):
cmꢁ1 3098, 2989, 2933, 1857, 1689, 1379, 1325, 1288, 1164, 1140,
1103, 1078, 1035. MS (EIþ): m/z 194, 192 (Mþ), 150, 148, 120, 122.
HRMS (EIþ): m/z calculated for C5H5O3Br: 191.9422, found:
191.9419.
d
153.0, 151.2, 151.1, 96.8, 82.5, 76.1, 59.9, 27.6, 20.2. IR (CCl4): cmꢁ1
3683, 2981, 2933, 1847, 1742, 1271, 1144, 1099, 1029. MS (CIþ, NH3):
m/z 262 (MNHþ4 ), 218, 206. HRMS (EIþ): m/z calculated for
C11H14O6: 244.0947, found: 244.0944.
3.2.24. 4-[1-Iodo-meth-(Z)-ylidene]-5-methyl-1,3-dioxolan-2-one
3.2.18. 4-Methyl-5-methylene-1,3-dioxolan-2-one (14e)
(32b)
Yield: 60%. Yellow oil. 1H NMR (400 MHz, CDCl3):
d
5.17–5.13 (m,
Yield: 95%. Yellow crystals. 1H NMR (400 MHz, CDCl3):
d 5.38 (d,
1H), 4.86 (dd, J¼2.4, 3.9 Hz, 1H), 4.35 (dd, J¼2.4, 3.9 Hz, 1H), 2.00–
J¼1.9 Hz, 1H), 5.29 (qd, J¼1.9, 6.5 Hz, 1H), 1.61 (d, J¼6.5 Hz, 3H). 13C
1.74 (m, 2H), 1.04 (t, J¼7.3 Hz, 3H). 13C NMR (100 MHz, CDCl3):
NMR (100 MHz, CDCl3):
d 154.9, 150.2, 76.8, 45.8, 20.2. IR (CCl4):
d
153.0, 152.1, 86.7, 80.6, 27.7, 7.8. IR (CCl4): cmꢁ1 2976, 2937, 1843,
cmꢁ1 3086, 2988, 2933, 2867, 1844, 1675, 1447, 1379, 1324, 1276,
1140, 1103, 1076, 1033. MS (EIþ): m/z 240 (Mþ). HRMS (EIþ): m/z
calculated for C5H5O3I: 239.9248, found: 239.9280.
1705, 1681, 1334, 1282, 1139, 1091. MS (CIþ, NH3): m/z 146 (MNH4þ),
139, 117, 102. HRMS (EIþ): m/z calculated for C6H8O3: 128.0473,
found: 128.0478.
3.2.25. 4-[1-Iodo-meth-(Z)-ylidene]-5-phenethyl-1,3-dioxolan-2-
3.2.19. 4-(1-Methyl-allyl)-5-methylene-1,3-dioxolan-2-one (14f)
Yield: 68% (isolated as a mixture of syn and anti isomers,
dr¼1:1.6). 1H NMR (400 MHz, CDCl3) for the mixture of isomers:
one (32c)
Yield: 99%. Yellow oil. 1H NMR (400 MHz, CDCl3):
d 7.33 (t,
J¼7.0 Hz, 2H), 7.25 (t, J¼7.4 Hz, 1H), 7.20 (d, J¼6.9 Hz, 2H), 5.35 (d,
d
5.81–5.72 (m, 1Hminorþ1Hmajor), 5.29–5.10 (m, 3Hminorþ3Hmajor),
J¼1.9 Hz, 1H), 5.15 (td, J¼1.8, 5.9 Hz, 1H), 2.94–2.78 (m, 2H), 2.22–
4.95–4.91 (m, 1Hminorþ1Hmajor), 4.45 (dd, J¼1.8, 3.9 Hz, 1Hminor),
4.42 (dd, J¼1.8, 3.9 Hz, 1Hmajor), 2.72–2.56 (m, 1Hminorþ1Hmajor),
1.23 (d, J¼6.9 Hz, 3Hmajor), 1.15 (d, J¼7.0 Hz, 3Hminor). 13C NMR
2.15 (m, 2H). 13C NMR (100 MHz, CDCl3):
d 153.6, 150.3, 139.1, 128.7,
128.3, 126.6, 79.3, 45.9, 36.3, 30.1. IR (CCl4): cmꢁ1 3085, 3028, 2973,
2930, 2863, 1849, 1674, 1601, 1497, 1451, 1341, 1279, 1145, 1110, 1081,
1034. MS (EIþ): m/z 330 (Mþ), 285, 267, 203. HRMS (EIþ): m/z cal-
culated for C12H11O3I: 329.9753, found: 329.9748.
(100 MHz, CDCl3) for the major isomer:
d
152.1, 151.3, 134.4, 119.1,
87.9, 82.7, 41.4, 14.2; for the minor isomer:
d 152.1, 151.4, 136.4, 118.3,
88.0, 82.4, 42.1, 13.5. IR (CCl4): cmꢁ1 2977, 1845, 1705, 1680, 1332,
1288, 1132, 1055. MS (CIþ, NH3): m/z 172 (MNHþ4 ). HRMS (EIþ): m/z
calculated for C8H10O3: 154.0630, found: 154.0627.
3.2.26. 4-(2,6-Dimethyl-hept-5-enyl)-5-methylene-1,3-dioxolan-2-
one (32d)
Yield: 97%. Pink oil (isolated as
astereoisomers). 1H NMR (400 MHz, CDCl3) for the mixture of di-
astereoisomers:
5.13–5.09 (m, 1H), 2.13–1.92 (m, 3H), 1.85–1.17 (m, 4H), 1.74 (s, 3H),
1.65 (s, 3H), 1.06–1.01 (m, 3H). 13C NMR (100 MHz, CDCl3) for the
a 1:1 mixture of di-
3.2.20. 4-Methylene-5-(1-phenyl-ethyl)-1,3-dioxolan-2-one (14g)
Yield: 66% (separable mixture of syn and anti isomers, dr¼1:3.9).
d
5.38 (d, J¼1.9 Hz, 1H), 5.28–5.23 (m, 1H),
Major isomer: 1H NMR (400 MHz, CDCl3):
d
7.42–7.27 (m, 5H),
5.35 (ddd, J¼2.0, 2.0, 3.8 Hz, 1H), 4.83 (dd, J¼2.0, 3.8 Hz, 1H), 4.20

A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
1899
mixture of diastereoisomers:
d
154.4, 154.3, 150.3, 131.9, 123.8,
3.3.3. 4-[1-Iodo-meth-(E)-ylidene]-5-phenethyl-1,3-dioxolan-2-
one (36b)
Yield: 66%. Pink oil. 1H NMR (400 MHz, CDCl3):
123.8, 79.2, 78.8, 45.7, 45.5, 42.2, 37.0, 36.1, 29.0, 28.5, 25.6, 25.1,
25.0, 19.7, 18.7, 17.6, 17.6. IR (CCl4): cmꢁ1 3086, 2961, 2925, 2856,
1853, 1674, 1455, 1377, 1338, 1279, 1143, 1079. MS (EIþ): m/z 350
(Mþ), 319, 264, 237, 223. HRMS (EIþ): m/z calculated for C13H19O3I:
350.0379, found: 350.0388.
d
7.36–7.32 (m,
2H), 7.27–7.24 (m, 3H), 5.93 (d, J¼2.2 Hz, 1H), 5.16 (dt, J¼2.3, 8.3 Hz,
1H), 2.91–2.84 (m, 1H), 2.80–2.73 (m, 1H), 2.57–2.49 (m, 1H), 2.30–
2.20 (m, 1H). 13C NMR (100 MHz, CDCl3):
d 151.2, 150.0, 139.2, 128.6,
128.4, 126.5, 80.5, 50.6, 33.2, 29.9. IR (CCl4): cmꢁ1 3085, 3029, 2954,
2927, 2859, 1843, 1670, 1498, 1453, 1332, 1281, 1144, 1103, 1077,
1035, 1004. MS (EIþ): m/z 330 (Mþ), 285, 220, 205. HRMS (EIþ): m/z
calculated for C12H11O3I: 329.9753, found: 329.9753.
3.2.27. 4-[1-Iodo-meth-(Z)-ylidene]-5-(4-triisopropyl silanyloxy-
butyl)-1,3-dioxolan-2-one (32e)
Yield: 69%. Yellow oil. 1H NMR (400 MHz, CDCl3):
d 5.35 (d,
J¼1.8 Hz, 1H), 5.21–5.17 (m, 1H), 3.71 (t, J¼5.5 Hz, 2H), 1.97–1.81 (m,
2H), 1.67–1.48 (m, 4H), 1.15–0.94 (m, 21H). 13C NMR (100 MHz,
3.3.4. 4-[1-Iodo-meth-(E)-ylidene]-5-(4-triisopropyl silanyloxy-
CDCl3):
d
153.8, 150.4, 80.4, 62.6, 45.6, 34.4, 32.0, 20.5, 17.9, 11.9. IR
butyl)-1,3-dioxolan-2-one (36c)
(CCl4): cmꢁ1 3086, 2945, 2894, 2865, 1853, 1674, 1463, 1383, 1339,
1280, 1141, 1110, 1068, 1014. MS (EIþ): m/z 454 (Mþ), 411, 368, 337.
HRMS (EIþ): m/z calculated for C17H31O4SiI: 454.1037, found:
454.1041.
Yield: 64%. Yellow oil. 1H NMR (400 MHz, CDCl3):
d 5.91 (d,
J¼2.2 Hz, 1H), 5.20 (dt, J¼2.5, 7.5 Hz, 1H), 3.71 (t, J¼5.9 Hz, 2H),
2.23–2.14 (m, 1H), 2.04–1.94 (m, 1H), 1.67–1.52 (m, 4H), 1.12–1.02
(m, 21H). 13C NMR (100 MHz, CDCl3):
d 151.3, 150.4, 81.5, 62.6, 50.3,
32.1, 31.5, 20.1, 18.0, 11.9. IR (CCl4): cmꢁ1 3311, 3085, 2961, 2865,
2727, 2238,1858,1744,1670,1462,1383,1333,1277,1254,1118,1017.
MS (EIþ): m/z 454 (Mþ), 411, 368, 337, 325. HRMS (EIþ): m/z cal-
culated for C17H31O4SiI: 454.1037, found: 454.1036.
3.2.28. 4-Cyclopropyl-5-[1-iodo-meth-(Z)-ylidene]-1,3-dioxolan-2-
one (32f)
Yield: 32%. Orange oil. 1H NMR (400 MHz, CDCl3):
d 5.52 (d,
J¼1.8 Hz, 1H), 4.53 (dd, J¼1.7, 8.7 Hz, 1H), 1.28–1.21 (m, 1H), 0.84–
0.76 (m, 2H), 0.64–0.55 (m, 1H), 0.55–0.43 (m, 1H). 13C NMR
3.3.5. 4-Cyclopropyl-5-[1-iodo-meth-(E)-ylidene]-1,3-dioxolan-2-
(100 MHz, CDCl3):
d
153.4, 150.2, 84.8, 46.7, 14.2, 3.0, 2.5. IR (CCl4):
one (36d)
cmꢁ1 3089, 3012, 2926, 2855, 1855, 1674, 1320, 1274, 1142, 1107,
1037. MS (EIþ): m/z 266 (Mþ), 222, 205, 192, 180. HRMS (EIþ): m/z
calculated for C7H7O3I: 265.9440, found: 265.9447.
Yield: 76%. Pink oil. 1H NMR (400 MHz, CDCl3):
d 6.00 (d,
J¼2.1 Hz, 1H), 4.83 (dd, J¼2.0, 7.1 Hz, 1H), 1.41–1.29 (m, 1H), 0.91–
0.78 (m, 2H), 0.76–0.68 (m, 1H), 0.61–0.55 (m, 1H). 13C NMR
(100 MHz, CDCl3):
d 151.1, 150.9, 83.8, 51.1, 13.1, 5.7, 2.4. IR (CCl4):
3.2.29. 4-[1-Iodo-meth-(Z)-ylidene]-1,3-dioxa-spiro[4.5]decan-2-
cmꢁ1 3085, 3015, 2927, 2856, 1839, 1670, 1311, 1270, 1139, 1103,
1031, 1020. MS (EIþ): m/z 266 (Mþ), 222, 207, 192. HRMS (EIþ): m/z
calculated for C7H7O3I: 265.9440, found: 265.9434.
one (32g)
Yield: 83%. White solid. 1H NMR (400 MHz, CDCl3):
d 5.34 (s,1H),
2.06 (br d, J¼9.2 Hz, 2H), 1.82–1.64 (m, 7H), 1.41–1.30 (m, 1H). 13C
NMR (100 MHz, CDCl3):
d
159.1, 149.8, 87.5, 45.3, 36.5, 24.2, 21.6. IR
3.4. Pd-catalyzed transformations of iodo-alkylidene-1,3-
dioxolan-2-ones
(CCl4): cmꢁ1 2943, 1846, 1668, 1192, 1048. Mp (ꢀC): 133–134. MS
(CIþ, NH3): m/z 312 (MNHþ4 ). HRMS (EIþ): m/z calculated for
C9H11IO3: 293.9753, found: 293.9751.
General procedure for the Sonogashira coupling: To a solution of
halogenated derivative (1 equiv) in THF (0.25 M) were added the
corresponding terminal alkyne (2 equiv), PdCl2(PPh3)2 (0.2 equiv),
CuI (0.04 equiv), and NEt3 (10 equiv). The mixture was stirred at
room temperature and monitored periodically by TLC. Upon com-
pletion, it was quenched with a saturated solution of NH4Cl, the
aqueous layer was extracted twice with diethyl ether and the
combined organic layers were washed with brine, dried over
MgSO4, and evaporated under vacuum. The crude mixture was then
loaded onto a silica gel column and chromatographed with the
appropriate mixture of petroleum ether and diethyl ether to give
the expected product.
3.3. Au(I)-catalyzed formation of (E)-iodo-alkylidene-1,3-
dioxolan-2-ones
General procedure: To a solution of propargylic tert-butyl carbo-
nate (1 equiv) in acetone (0.5 M) at room temperature were added
N-iodosuccinimide (1.2 equiv) and the gold catalyst (0.01 equiv).
The mixture was stirred at room temperature and monitored peri-
odically by TLC. Upon completion, the mixture was evaporated and
then chromatographed with the appropriate mixture of petroleum
ether and diethyl ether to give the expected product.
3.3.1. 4-[1-Iodo-meth-(E)-ylidene]-1,3-dioxa-spiro[4.5]decan-2-
3.4.1. 4-[3-Phenyl-prop-2-yn-(Z)-ylidene]-1,3-dioxa-
one (34)
spiro[4.5]decan-2-one (37)
Yield: 95%. 1H NMR (400 MHz, CDCl3):
d
5.87 (s, 1H), 2.49 (td,
Yield: 61%. Yellow crystals. 1H NMR (400 MHz, CDCl3):
d 7.49–
J¼4.6, 13.9 Hz, 2H), 1.95 (br d, J¼13.9 Hz, 2H), 1.83–1.66 (m, 5H),
7.44 (m, 2H), 7.35–7.32 (m, 3H), 5.01 (s, 1H), 2.06 (d, J¼12.3 Hz, 2H),
1.44–1.27 (m, 1H). 13C NMR (100 MHz, CDCl3):
d
153.4, 150.1, 88.2,
1.80–1.58 (m, 7H), 1.38–1.26 (m, 1H). 13C NMR (100 MHz, CDCl3):
47.6, 32.6, 24.2, 21.4. IR (CCl4): cmꢁ1 2944, 2864, 1841, 1658, 1264,
1204,1128,1057. Mp (ꢀC): 135–136. MS (CIþ, NH3): m/z 312 (MNHþ4 ).
HRMS (EIþ): m/z calculated for C9H11IO3: 293.9753, found:
293.9753.
d 160.3, 150.5, 131.4, 128.5, 128.3, 122.7, 95.5, 86.9, 83.0, 80.5, 36.4,
24.2, 21.5. IR (CCl4): cmꢁ1 3056, 2943, 2863, 1844, 1679, 1492, 1447,
1346, 1260, 1191, 1126, 1052, 1007. MS (EIþ): m/z 268 (Mþ), 196, 167,
149. HRMS (EIþ): m/z calculated for C17H16O3: 268.1100, found:
268.1097.
3.3.2. 4-[1-Iodo-meth-(E)-ylidene]-5-methyl-1,3-dioxolan-2-one
(36a)
3.4.2. 4-[3-Phenyl-prop-2-yn-(E)-ylidene]-1,3-dioxa-
Yield: 35%. Yellow oil. 1H NMR (400 MHz, CDCl3):
d
5.91 (d,
spiro[4.5]decan-2-one (38)
13
J¼2.2 Hz, 1H), 5.26 (qd, J¼2.2, 6.5 Hz, 1H), 1.73 (d, J¼6.5 Hz, 3H).
C
Yield: 94%. Yellow crystals. 1H NMR (400 MHz, CDCl3):
d 7.42–
NMR (100 MHz, CDCl3):
d
151.4,151.1, 78.0, 50.1,18.4. IR (CCl4): cmꢁ1
7.37 (m, 2H), 7.41–7.36 (m, 3H), 5.86 (s, 1H), 2.42 (td, J¼3.5, 14.1 Hz,
3085, 2988, 2933, 2866, 1841, 1673, 1450, 1376, 1318, 1279, 1139,
1119, 1073, 1035. MS (EIþ): m/z 240 (Mþ), 196. HRMS (EIþ): m/z
calculated for C5H5O3I: 239.9248, found: 239.9272.
2H), 2.01 (d, J¼13.9 Hz, 2H),1.86–1.65 (m, 5H),1.38–1.27 (m,1H). 13C
NMR (100 MHz, CDCl3):
d 161.1, 150.4, 130.8, 128.5, 128.4, 122.6,
95.6, 88.0, 84.5, 81.3, 33.3, 24.5, 21.4. IR (CCl4): cmꢁ1 3060, 2942,

1900
A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
2860, 1842, 1670, 1492, 1446, 1352,1264, 1213, 1177, 1126, 1072, 995.
MS (EIþ): m/z 268 (Mþ), 224, 196, 167. HRMS (EIþ): m/z calculated
for C17H16O3: 268.1100, found: 268.1112.
3028, 2945, 2893, 2865, 1838, 1691, 1462, 1381, 1344, 1225, 1179,
1123, 1070, 1018. MS (EIþ): m/z 404 (Mþ), 359, 331. HRMS (EIþ): m/z
calculated for C23H36O4Si: 404.2383, found: 404.2365.
3.4.3. 4-Methyl-5-oct-2-yn-(Z)-ylidene-1,3-dioxolan-2-one (39a)
Acknowledgements
Yield: 67%. Yellow oil. 1H NMR (400 MHz, CDCl3):
d 5.30 (q,
J¼6.5 Hz, 1H), 4.82 (q, J¼2.2 Hz, 1H), 2.35 (td, J¼2.2, 7.1 Hz, 2H), 1.58
The authors wish to thank Prof. S. Z. Zard, Dr. B. Quiclet-Sire, and
Dr. I. Hanna for helpful discussions, Eric Talbot for performing initial
experiments on Pd cross-coupling reactions, and Rhodia Chimie
Fine for a donation of HNTf2.
(d, J¼6.5 Hz, 3H), 1.58–1.51 (m, 2H), 1.41–1.26 (m, 4H), 0.91 (t,
J¼7.1 Hz, 3H). 13C NMR (100 MHz, CDCl3):
d 155.3, 151.2, 97.4, 84.5,
76.3, 71.2, 31.0, 28.1, 22.1, 20.4,19.5,13.9. IR (CCl4): cmꢁ1 2932, 2863,
2222, 1853, 1690, 1457, 1375, 1355, 1330, 1307, 1214, 1140, 1103,
1078, 1031. MS (EIþ): m/z 208 (Mþ), 161, 149, 121, 117, 107. HRMS
(EIþ): m/z calculated for C12H16O3: 208.1100, found: 208.1104.
References and notes
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3.4.4. 4-Methyl-5-[3-phenyl-prop-2-yn-(Z)-ylidene]-1,3-dioxolan-
2-one (39b)
Yield: 72%. Yellow crystals. 1H NMR (400 MHz, CDCl3):
d 7.48–
7.45 (m, 2H), 7.35–7.30 (m, 3H), 5.37 (qd, J¼2.0, 6.5 Hz, 1H), 5.07 (d,
J¼2.0 Hz, 1H), 1.63 (d, J¼6.5 Hz, 3H). 13C NMR (100 MHz, CDCl3):
d
156.1, 151.0, 131.5, 128.3, 122.6, 95.6, 84.1, 80.1, 76.5, 20.3. IR (CCl4):
cmꢁ1 3059, 2983, 2959, 2928, 2865, 1851, 1687, 1306, 1206, 1138,
1102, 1081, 1041. MS (EIþ): m/z 214 (Mþ), 142, 141, 115. HRMS (EIþ):
m/z calculated for C13H10O3: 214.0630, found: 214.0623.
3.4.5. 4-Methyl-5-[6-triisopropylsilanyloxy-hex-2-yn-(Z)-ylidene]-
1,3-dioxolan-2-one (39c)
Yield: 67%. Brown oil. 1H NMR (400 MHz, CDCl3):
d 5.30 (q,
J¼6.4 Hz, 1H), 4.81 (q, J¼2.1 Hz, 1H), 3.78 (t, J¼6.0 Hz, 2H), 2.48 (td,
J¼1.9, 7.0 Hz, 2H), 1.80–1.74 (m, 2H), 1.57 (d, J¼6.5 Hz, 3H), 1.12–1.00
(m, 21H). 13C NMR (100 MHz, CDCl3):
d 155.4, 151.1, 97.0, 84.4, 76.3,
71.3, 61.7, 31.7, 20.4, 17.9, 17.6, 16.0, 12.2, 11.9. IR (CCl4): cmꢁ1 2944,
2894, 2865, 1847, 1691, 1463, 1307, 1213, 1138, 1105, 1078, 1031. MS
(EIþ): m/z 352 (Mþ), 309, 265, 237, 223. HRMS (EIþ): m/z calculated
for C19H32O4Si: 352.2070, found: 352.2071.
General procedure for the Suzuki coupling: To a solution of halo-
genated derivative (1 equiv) in toluene (0.5 M) was added K2CO3
powder (2.5 equiv), phenylboronic acid (1.1 equiv), and tetrakis(-
triphenylphosphine)palladium(0) (0.05 equiv). The mixture was
stirred at 80 ꢀC and monitored periodically by TLC. Upon comple-
tion, it was quenched with a saturated solution of NH4Cl, the
aqueous layer was extracted twice with diethyl ether and the
combined organic layers were washed with brine, dried over
MgSO4, and evaporated under vacuum. The crude mixture was then
loaded onto a silica gel column and chromatographed with the
appropriate mixture of petroleum ether and diethyl ether to give
the expected product.
3.4.6. 4-[1-Phenyl-meth-(E)-ylidene]-1,3-dioxa-spiro[4.5]decan-2-
one (40)
Yield: 79%. Yellow crystals. 1H NMR (400 MHz, CDCl3):
d 7.38–
7.30 (m, 3H), 7.22 (d, J¼7.2 Hz, 2H), 6.45 (s, 1H), 1.98–1.93 (m, 2H),
1.80–1.59 (m, 7H), 1.05–0.93 (m, 1H). 13C NMR (100 MHz, CDCl3):
d
152.3, 151.3, 132.0, 129.3, 128.3, 127.7, 105.4, 87.2, 35.2, 24.2, 21.3.
IR (CCl4): cmꢁ1 3060, 3027, 2941, 2861, 1826, 1694, 1448, 1350, 1267,
1214, 1157, 1130, 1056, 1002. MS (EIþ): m/z 244 (Mþ), 200, 185.
HRMS (EIþ): m/z calculated for C15H16O3: 244.1100, found:
244.1096.
3.4.7. 4-[1-Phenyl-meth-(E)-ylidene]-5-(4-triisopropylsilanyloxy-
7. See for instance: (a) Duan, J.; Smith, A. B., III. J. Org. Chem. 1993, 58, 3703–3711;
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butyl)-1,3-dioxolan-2-one (41)
Yield: 40%. Yellow oil. 1H NMR (400 MHz, CDCl3):
d 7.36 (t,
J¼7.7 Hz, 2H), 7.27 (t, J¼8.0 Hz, 1H), 7.15 (d, J¼7.3 Hz, 2H), 6.37 (d,
J¼2.2 Hz,1H), 5.70 (dt, J¼2.6, 7.6 Hz,1H), 3.61 (t, J¼5.7 Hz, 2H),1.91–
1.83 (m,1H),1.72–1.62 (m,1H),1.57–1.43 (m, 4H),1.11–0.99 (m, 21H).
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13C NMR (100 MHz, CDCl3):
d
151.9, 147.6, 132.2, 128.9, 127.8, 127.5,
105.6, 79.8, 62.6, 32.0, 31.6, 20.4, 17.9, 11.9. IR (CCl4): cmꢁ1 3062,

A.K. Buzas et al. / Tetrahedron 65 (2009) 1889–1901
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