An efficient method for the synthesis of vinylbromohydrin and vinylbromoalkoxy derivatives and cyclocarbonylation of α-allenic alcohols catalyzed by palladium chloride

Article abstract of DOI:10.1021/jo8009352

(Chemical Equation Presented) Vinylidenecyclopropanes undergo hydrobromination or alkoxybromination in the presence of N-bromosuccinimide and water or alcohols to give the corresponding vinylbromohydrin and vinylbromoalkoxy derivatives in moderate to exce

Full text of DOI:10.1021/jo8009352

An Efficient Method for the Synthesis of Vinylbromohydrin and
Vinylbromoalkoxy Derivatives and Cyclocarbonylation of r-Allenic
Alcohols Catalyzed by Palladium Chloride
Wei Li and Min Shi*
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese
Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China
mshi@mail.sioc.ac.cn
ReceiVed May 6, 2008
Vinylidenecyclopropanes undergo hydrobromination or alkoxybromination in the presence of N-
bromosuccinimide and water or alcohols to give the corresponding vinylbromohydrin and vinylbro-
moalkoxy derivatives in moderate to excellent yields at room temperature. These vinylbromohydrin
derivatives can be easily transformed to R-allenic alcohols in the presence of Et3N under mild conditions.
In addition, the cyclocarbonylation of R-allenic alcohols with CO catalyzed by palladium chloride to
give the corresponding lactones under different reaction conditions has been described.
Introduction
pioneering work has been done for this kind of particular organic
compounds involving mechanistic, theoretical, spectroscopic,
and synthetic studies as well as thermal and photochemical
Hydrobromination of olefinic compounds is a powerful
method in organic synthesis to introduce two different functional
groups (hydroxy and bromine) into organic molecules by a
single step.1 Thus far, various brominating reagents, such as
molecular bromine or N-bromosuccinimide (NBS),2 metal
bromide along with an oxidizing agent,3 and N,N-dibromo-p-
toluenesulfonamide (TsNBr2),4 have been developed to obtain
high regio- and stereoselectivity in this reaction.2-5 However,
the hydrobromination of compounds containing highly strained
cyclopropane ring moieties has been seldom reported.6,7 Vi-
nylidenecycloproanes (VDCPs) 1 are one of the most remarkable
known organic compounds. They have an allene moiety
connected by a cyclopropane ring and yet they are thermally
stable and reactive substances in organic synthesis. Much
(2) (a) ComprehensiVe Organic Transformation: A Guide to Functional
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(c) Rolston, J. H.; Yates, K. J. Am. Chem. Soc. 1969, 91, 1469–1476. (d) Dalton,
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3432. (b) Paul, R.; Tchelitcheff, S. Bull. Soc. Chim. Fr. 1948, 896–900. (c)
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* Corresponding author. Fax: 86-21-64166128.
(1) (a) Tenaglia, A.; Pardigon, O.; Buono, G. J. Org. Chem. 1996, 61, 1129–
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6698 J. Org. Chem. 2008, 73, 6698–6705
10.1021/jo8009352 CCC: $40.75 2008 American Chemical Society
Published on Web 08/01/2008

Synthesis of Vinylbromohydrin and Vinylbromoalkoxy DeriVatiVes
TABLE 1. Hydrobromination of Vinylidenecyclopropane 1a by
NBS and Water under Various Reaction Conditions
skeletal conversions since the ring-opening of cyclopropanes
can gain additional driving force by the relief of angular strain.8,9
On the other hand, homoallylic alcohols containing a vinyl
bromide moiety, such as compound 2, are useful building blocks
in organic and medicinal chemistry. For example, they could
undergo the Suzuki-Miyaura coupling reaction10 with boronic
acids to give the corresponding alcohols 3, which have been
used for the synthesis of crinane by Padwa’s group (eq 1).10b
In addition, they could undergo the Heck reaction with alkenes
(eq 1)11 and Sonogashira cross-coupling reactions with alkynes
to afford the corresponding coupling products in good yields
(eq 1).12 Moreover, Semmelhack and co-workers have achieved
intramolecular carbonylation of 2 to provide methylene lactone
4 by using a nickel carbonyl complex (eq 1).13
entrya
x
solvent
time
yield (%)b
5a
1
2
3
4
5
6
7
8
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.0
1.5
MeCN-H2O (4:1)
THF-H2O (4:1)
10 min
2 h
2 h
2 h
2 h
2 h
2 h
2 h
2 h
10 min
10 min
10 min
10 min
84
58
69
trace
55
54
27
66
58
81
90
65
90
acetone-H2O (4:1)
DMSO-H2O (4:1)
DMF-H2O (4:1)
hexane-H2O (4:1)
toluene-H2O (4:1)
CH2Cl2-H2O (4:1)
DCE-H2O (4:1)
MeCN-H2O (8:1)
MeCN-H2O (3:1)
MeCN-H2O (3:1)
MeCN-H2O (3:1)
9
10
11
12
13
a Reaction conditions: VDCP (0.18 mmol), solvent (2 mL), NBS (x
equiv), rt. b Isolated yields.
these compounds are still limited.14 In this paper, we wish to
report the hydrobromination of a variety of vinylidenecyclo-
propanes 1 by NBS and water or alcohols to give the corre-
sponding vinylbromohydrin derivatives 5 or vinylbromoalkoxy
derivatives in moderate to excellent yields under mild conditions
along with a palladium(II)-catalyzed cyclocarbonylation with
carbon monoxide.
Although vinylbromohydrins such as compound 2 have wide
application in organic synthesis, the synthetic methods to obtain
(5) (a) Raghavan, S.; Reddy, S. R.; Tony, K. A.; Kumar, C. N.; Varma, A. K.;
Nangia, A. J. Org. Chem. 2002, 67, 5838–5841. (b) Boyes, S. A.; Hewson, A. T.
J. Chem. Soc., Perkin Trans. 1 2000, 2759–2765.
Results and Discussion
Initial examination was performed by using vinylidenecy-
clopropane 1a as the substrate to react with NBS and water in
various solvents to develop the optimal conditions and the results
of these experiments are summarized in Table 1. We found that
the corresponding vinylbromohydrin compound 5a was pro-
duced under various conditions in moderate to high yields. For
example, using 1.2 equiv of NBS in MeCN/H2O (4:1, 8:1 and
3:1) at room temperature (20 °C), the reaction proceeded
smoothly to give 5a in 84%, 81%, and 90% yields within 10
min, respectively (Table 1, entries 1, 10, and 11). However,
the reaction became sluggish to produce 5a in lower yields in
many other solvents even after extending the reaction time to
2 h (Table 1, entries 2-9). When using 1.0 and 1.5 equiv of
NBS as the brominating reagent in MeCN/H2O (3:1) at room
temperature (20 °C), the reaction proceeded smoothly to give
5a in 65% and 90% yields within 10 min, respectively (Table
1, entries 12 and 13). These results indicated that the best
reaction conditions for this transformation are to carry out the
reaction in MeCN/H2O (3:1) at room temperature in the presence
of 1.2 equiv of NBS.
With these optimized reaction conditions being identified, we
next examined the hydrobromination of a variety of vi-
nylidenecyclopropanes 1 by NBS and water. The results are
shown in Table 2. As for symmetrical vinylidenecyclopropanes
1b and 1c and unsymmetrical vinylidenecyclopropanes 1f, 1g,
and 1h having electron-donating methyl or methoxy groups on
the benzene rings, the corresponding vinylbromohydrin deriva-
tives 5b, 5c, 5f, 5g, and 5h were obtained in high yields within
(6) Krief, A.; Ronvaux, A. Synlett 1998, 491–494.
(7) Some other analogous reactions reported recently: (a) Shao, L.-X.; Shi,
M. Synlett 2006, 1269–1271. (b) Huang, X.; Fu, W.-J. Synthesis 2006, 1016–
1020.
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J. Org. Chem. Vol. 73, No. 17, 2008 6699

Li and Shi
TABLE 2. Hydrobromination of Vinylidenecyclopropanes 1 by
NBS and Water in MeCN
30 min, affording the corresponding vinylbromomethoxy 6 in
quantitative yield (Table 3, entry 1). Similarly, the alkoxybro-
mionation of 1a with ethanol and NBS gave the corresponding
vinylbromoethoxy derivative 7 in 89% yield within 5 h (Table
3, entry 2). However, the alkoxybromionation of 1a with
isopropanol and NBS became more sluggish, affording the
corresponding isopropoxy bromide 8 in 77% yield after 12 h,
presumably due to the steric hindrance of the employed alcohol
(Table 3, entry 3). Moreover, when the alkoxybromination of
1a in the mixed solvent of tert-butyl alcohol and MeCN (1:1)
with NBS was carried out under the standard conditions, none
of the corresponding tert-butoxy bromide could be isolated,
suggesting that the steric bulkiness of the employed alcohols
plays a key role in this reaction (Table 3, entry 7). Other
alcohols, such as allyl alcohol, benzyl alcohol, and propargyl
alcohol, produced the corresponding alkoxy bromides 9, 10, and
11 in moderate yields under the standard conditions (Table 3,
entries 4, 5, and 6). As for carboxylic acid or anhydride, such
as acetic acid or acetic anhydride, the corresponding product
12 was obtained in 42% or 60% yields, respectively, under the
standard conditions (Table 3, entries 8 and 9).
entry substrate
R1
R2
R3 time (min) yield (%)a of 5 + 5′
1
2
3
4
1b
1c
1d
1e
1f
1g
1h
1i
Me
MeO MeO
Cl
F
Me
MeO
H
Me
H
H
H
H
H
H
Me
H
10
10
30
30
10
10
10
20
5b, 96
5c, 88
5d, 76
5e, 81
5f + 5f′, 93
5g + 5g′, 78
5h + 5h′, 82
5i + 5i′, 78
Cl
F
H
H
Me
H
5b
6b
7b
8b
Cl
a Isolated yield. b 5f:5f′ ) 1:1, 5g:5g′ ) 2:1, 5h:5h′ ) 1:1, 5i:5i′ )
1:1.
TABLE 3. Alkoxybromination of Vinylidenecyclopropane 1a with
ROH and NBS in MeCN
In addition, the reaction of N-iodosuccinimide (NIS) and 1a
in MeCN/water produced the corresponding vinyliodohydrin
derivative 13 in 20% yield under the standard conditions. The
reason the corresponding product 13 was isolated in low yield
is because it decomposes during the purification on the silica
gel column chromatography by heat and light (eq 5).
Interestingly, when molecular sieves 4Å was employed to
remove the trace amounts of water in anhydrous MeCN, the
brominated product 14 was obtained in 95% yield rather than
vinylbromohydrin derivative 5a if using 1a as the substrate (eq
6).9i The similar examinations were also employed in dry THF
and ether, providing 14 in 68% and 71% yields, respectively
(eq 6).
a Reaction conditions: VDCP (0.18 mmol), MeCN (1.0 mL), ROH
(1.0 mL), NBS (1.2 equiv), rt. b Isolated yields. c VDCP (1.28 mmol),
MeCN (1.5 mL), ROH (1.5 mL), NBS (1.2 equiv), rt. d 50 mg of MS
4Å was added.
10 min (Table 2, entries 1, 2, 5, 6, and 7). Adding moderately
electron-withdrawing chloro or fluoro groups on the benzene
rings of symmetrical vinylidenecyclopropanes 1d and 1e as well
as unsymmetrical vinylidenecyclopropane 1i afforded vinyl-
bromohydrin derivatives 5d, 5e, and 5i in moderate yields within
30 min (Table 2, entries 3, 4, and 8). As for unsymmetrical
vinylidenecyclopropanes 1f, 1g, 1h, and 1i, the corresponding
vinylbromohydrin derivatives 5f-i were obtained as isomeric
mixtures.
Encouraged by these results, we further investigated the
reactivity of vinylidenecyclopropane 1a with various alcohols
and NBS in MeCN under the standard conditions and the results
are summarized in Table 3. It was found that methoxybromi-
nation of 1a by NBS and methanol proceeded smoothly within
A plausible mechanism for this hydrobromination or alkoxy-
bromination of vinylidenecyclopropanes 1 (1a as the example)
by NBS with water or alcohols is shown in Scheme 1. First, a
three-membered cyclic bromonium ion intermediate A is formed
by the electrophilic addition of Br+ ion (generated from NBS)
6700 J. Org. Chem. Vol. 73, No. 17, 2008

Synthesis of Vinylbromohydrin and Vinylbromoalkoxy DeriVatiVes
SCHEME 1. Proposed Mechanism for the
Hydrobromination and Alkoxybromination of VDCPs 1 by
NBS and ROH
the addition of molecular sieves 4Å and subsequently performed
the reaction under the standard conditions. However, compound
18 was obtained in 12% yield along with some other unidenti-
fied complex product mixtures (Scheme 2).8t This result
suggested that the three-membered cyclic bromonium ion
intermediate A, which was generated from vinylidenecyclopro-
pane 15 with NBS, was attacked by nucleophilic reagent in the
reaction system in an SN2 pathway to give product 16 or 17,
and, in the absence of nucleophile, intermediate A′ could be
formed, which furnished compound 18 via intramolecular
Friedel-Crafts reaction along with some other unidentified
products via the other reaction pathways.
To extend the synthetic application of these vinylbromohy-
drins and alkoxybromides, we attempted to prepare R-allenic
alcohols from these simple compounds. It was found that the
vinylbromohydrins 5 can be transformed smoothly to the
corresponding R-allenic alcohols 19 in excellent yields by
removing a molecule of hydrobromide in the presence of Et3N
in DMF at 100 °C as shown in Table 4. We also attempted to
obtain the corresponding R-allenic alcohol 19a solely from 1a
in a one-pot manner by adding Et3N or KOH as base in a sealed
tube. However, it was found that a diol product 20 was formed
in 76% or 45% yield along with 19a in 23% yield or 11% yield
due to the presence of water in the reaction system, respectively
(eq 8). When methanol was employed as the cosolvent instead
of water in acetonitrile, the R-allenic ethers 21a and 21b also
could be obtained in 70% and 26% yields, respectively (eq 8).
onto 1a,4c,9i,15 which undergoes a ring-opening process to afford
the corresponding cationic intermediate B due to the highly
strained cyclopropane ring. Deprotonation of B furnishes the
corresponding vinylbromo-1,3-diene derivative 14 in the absence
of water. In the presence of nucleophilic reagents (such as H2O
or ROH), intermediate B undergoes a nucleophilic attack along
with a deprotonation process to afford the corresponding
hydrobromination derivative 5a or alkoxybromination deriva-
tives 6-12. The regioselectivity can be explained by considering
the fact that the C2dC3 double bond is more electron deficient
than the C1dC2 double bond due to the presence of the two
aromatic rings. Therefore, the C1dC2 double bond is preferential
for the electrophilic addition of Br+ ion to form the three-
membered cyclic bromonium ion intermediate A (Scheme 1).
We also utilized other types of vinylidenecyclopropanes such
as compound 15 in this reaction to obtain other types of
vinylbromohydrins and alkoxybromides. In the presence of NBS
and H2O or NBS and methanol, 15 can be transformed rapidly
to the corresponding vinylbromohydrin 16 in 56% yield or
methoxybromide 17 in 47% yield within 10 min under the
standard conditions, respectively. We attempted to remove
the trace amount of ambient water in anhydrous MeCN with
R-Allenic alcohols have drawn much attention in organic
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Barton, T. J.; Lin, J.-B.; Ijadi-Maghsoodi, S.; Power, M. D.; Zhang, X.-P.; Ma,
Z.-X.; Shimizu, H.; Gordon, M. S. J. Am. Chem. Soc. 1995, 117, 11695–11703.
(c) Shi, L.; Narula, C. K.; Mak, K. T.; Kao, L.; Xu, Y.; Heck, R. F. J. Org.
Chem. 1983, 48, 3894–3900. (d) Cousseau, J. Synthesis 1980, 805–806. (e)
Tamao, K.; Maeda, K.; Tanaka, T.; Ito, Y. Tetrahedron Lett. 1988, 29, 6955–
6956. (f) Trost, B. M.; Pinkerton, A. B. J. Am. Chem. Soc. 2002, 124, 7376–
7389.
(15) Rodebaugh, R.; Fraser-Reid, B. Tetrahedron 1996, 52, 7663–7678.
J. Org. Chem. Vol. 73, No. 17, 2008 6701

Li and Shi
SCHEME 2. Reactions of Vinylidenecyclopropane 15 with NBS in MeCN
TABLE 4. Preparation of r-Allenic Alcohols 19 from
Vinylbromohydrins 5 in the Presence of Et3N
TABLE 5. Cyclocarbonylation of r-Allenic Alcohol 19a with CO
Catalyzed by Various Metal Complexes
yield(%)b
entrya
catalyst
base
solvent
time (h)
22a
23a
entrya
R
time (h)
yield (%)b of 19
1
2
Ru
Et
Et3N
K2CO3
dioxane
DMF
DMF
DMF
DMF
DMF
12
12
33
48
28
48
3(CO)12
Ru3(CO)12
PdCl2
3N
1
2
3
H, 5a
Me, 5b
Cl, 5c
4
3
3
19a, 99
19b, 90
19c, 90
3
4c
5c
6c
Pd(OAc)2
PtCl2
PdCl2
a General procedure: 0.10 mmol of 5 and 0.30 mmol of base in 2 mL
of DMF were stirred at 100 °C. b Isolated yield.
68
23
a General procedure: 0.1 mmol of 19a, 5 mol % of catalyst, and 0.30
mmol of base in 3 mL of DMF were stirred at 100 °C under 20 atm
CO. b Isolated yield. c No base was used.
the further transformation into novel compounds with other
functional groups in allenic chemistry.16,17a However, there have
been few reports so far on the cyclocarbonylation of R-allenic
alcohols to form lactones in the literature.18 Subsequently, we
attempted to examine the cyclocarbonylation of these R-allenic
alcohols using metal catalysts under CO atmosphere. Initially,
we examined a standard reaction of 19a (0.10 mmol) under 20
atm of carbon monoxide in the presence of Ru3(CO)12 complex
(0.005 mmol) and Et3N (0.30 mmol) in 1,4-dioxane (3 mL) at
100 °C for 12 h. None of the corresponding lactone was formed
along with the recovery of 93% of starting materials 19a (Table
5, entries 1 and 2). Next, we examined other metal catalysts
such as PdCl2 (with K2CO3), Pd(OAc)2, and PtCl2 in this
reaction, but all of them did not have catalytic abilities for the
cyclocarbonylation of 19a (Table 5, entries 3-5). Delightfully,
using PdCl2 as a catalyst in the absence of base afforded the
corresponding cyclocarbonylation reaction product 23a and 22a
as a pair of isomeric mixtures in 68% and 23% yields,
respectively (Table 5, entry 6). The structure of 23a was
unambiguously determined by X-ray diffraction and its CIF data
are presented in the Supporting Information.19
We realized that the isomeric mixtures of 2(3H)-dihydro-
furanone 22a or 2(5H)-furanone 23a could be transformed from
one to another by a 1,5-H transfer, which might occur at higher
temperature in the presence of metal complex (Table 5, entry
6).18b Therefore, we next anticipated to obtain 22a or 23a solely
by changing the reaction conditions. It was found that reducing
the reaction time to 6 h with PdCl2 (5 mol %) as a catalyst at
100 °C afforded 2(3H)-dihydrofuranone 22a solely in 31% yield
(Table 6, entry 1). Extending the time to 9 and 12 h produced
22a solely in 53% and 50% yields, respectively (Table 6, entries
2 and 3). The two isomers were both obtained again when the
reaction time was extended to 75 h, and 22a became the minor
(19) The crystal data of 23a have been deposited in CCDC as no. 662541.
Empirical formul: C22H22O2; formula weight: 318.40; crystal color, habit:
colorless, prismatic; crystal dDimensions: 0.498 × 0.357 × 0.311 mm3; crystal
system: monoclinic; lattice type: primitive; lattice parameters: a ) 11.6537(18)
Å, b ) 14.736(2) Å, c ) 11.9299(18) Å, R ) 90°, ꢀ ) 119.237(2)°, γ ) 90°,
(18) (a) Yoneda, E.; Kaneko, T.; Zhang, S.-W.; Onitsuka, K.; Takahashi, S.
Org. Lett. 2000, 2, 441–443. (b) Yoneda, E.; Zhang, S.-W.; Zhou, D.-Y.;
Onitsuka, K.; Takahashi, S. J. Org. Chem. 2003, 68, 8571–8576.
V ) 1787.7(5) Å3; space group: P2(1)/c; Z ) 4; Dcalc ) 1.183 g/cm3; F000
680; diffractometer: Rigaku AFC7R; residuals: R; Rw: 0.0511, 0.1346.
)
6702 J. Org. Chem. Vol. 73, No. 17, 2008

Synthesis of Vinylbromohydrin and Vinylbromoalkoxy DeriVatiVes
TABLE 6. Cyclocarbonylation of r-Allenic Alcohol 19a Catalyzed
by PdCl2 in the Absence of Bases
TABLE 7. Cyclocarbonylation of r-Allenic Alcohols 19 Catalyzed
by PdCl2
yield (%)b
yield (%)b
entrya
ligand
temp (°C)
time (h)
22a
23a
entrya
R
ligand temp (°C) time (h)
22
23
1
2
3
4
5
6
7
8
9
c
c
c
c
100
100
100
100
120
120
150
150
150
6
9
12
31
53
50
3
d
d
trace
trace
trace
53
60
57
1
2
3
4
Me, 19b dppp
70
80
28
30
28
28
22b, 61
22c, 62
d
d
Cl, 19c
Me, 19b
Cl, 19c
dppp
75
c
c
150
150
d
d
23b, 74
23c, 75
PPh3
dppb
c
PPh3
dppp
100
100
28
28
28
a General procedure: 0.1 mmol of 19, 10 mol % of catalyst, and 20
mol % of ligand in 3 mL of DMF were stirred under 20 atm CO.
b Isolated yield. c No ligand was used. d The product was not detected.
d
d
72
57
complex
10
c
70
28
no reaction
SCHEME 3. Proposed Mechanism for the
Cyclocarbonylation of r-Allenic Alcohols19
11
12
PPh3
dppp
70
70
28
28
63
70
d
d
a General procedure: 0.1 mmol of 19a, 10 mol % of catalyst, and 20
mol % of ligand in 3 mL of DMF were stirred under 20 atm CO.
b Isolated yield. c No ligand was used. d None of the product was
isolated.
product in only 3% yield along with 2(5H)-furanone 23a in 53%
yield (Table 6, entry 4). Adding phosphine ligands such as PPh3
and 1,4-bis(diphenylphosphino)butane (dppb), enhancing the
temperature, and extending the reaction time facilitated
the formation of 23a (Table 6, entries 5 and 6). To reduce the
reaction time, we raised the reaction temperature to 150 °C,
and found that product 23a was obtained solely in 72% yield
in the absence of ligand and in 57% yield in the presence of
PPh3 within 28 h, respectively, although using 1,3-bis(diphe-
nylphosphino)propane (dppp) as a ligand afforded complex
product mixtures under otherwise identical conditions, suggest-
ing that 23a might be derived from 22a upon heating at >100
°C (Table 6, entries 7-9). Encouraged by these results, we also
attempted to obtain 22a solely at lower temperature. When the
temperature was turned down to 70 °C, no reaction occurred in
the presence of PdCl2 (Table 6, entry 10). However, we were
pleased to find that product 22a could be obtained in good yields
(63% and 70%) by adding PPh3 or 1,3-bis(diphenylphosphino)-
propane (dppp) as a ligand at 70 °C within 28 h (Table 6, entries
11 and 12). These results can be explained by the fact that CO
insertion into a Pd-C bond occurs more rapidly for those
alkylpalladium phosphine complexes.20a
According to the above results, we turned our attention to
examine the generality of the present catalytic system using
R-allenyl alcohols 19b and 19c that contain electron-donating
groups and electron-withdrawing groups on the benzene rings,
respectively, and the results of these experiments are sum-
marized in Table 7. In the presence of PdCl2 and dppp, the
cyclocarbonylation of 19b and 19c proceeded smoothly at lower
temperature (70 and 80 °C) to give the corresponding lactones
22b and 22c in moderate yields (Table 7, entries 1 and 2). On
the other hand, in the absence of ligand, the cyclocarbonylation
of 19b and 19c catalyzed by PdCl2 at 150 °C afforded the
corresponding lactones 21b and 21c in good yields (Table 7,
entries 3 and 4). Therefore, using the phosphine ligand and
changing the reaction temperature and reaction time, the
selective cyclocarbonylation of R-allenic alcohols 19 could be
realized in the presence of PdCl2.
A possible mechanism for the cyclocarbonylation of R-allenic
alcohols (19a as the example) is outlined in Scheme 3.
Palladium(0), generated from Pd(II) and carbon monoxide, can
insert into the C-O bond of 19a to give intermediate C via
oxidative addition,21a,22a which can further form the alkenylpal-
ladium intermediate E via allylpalladium intermediate D. The
oxidative addition of Pd(0) complexes to allylic alcohols to form
(21) (a) Piotti, M. E.; Alper, H. J. Org. Chem. 1994, 59, 1956–1957. (b)
Yu, W.-Y.; Alper, H. J. Org. Chem. 1997, 62, 5684–5687. (c) Xiao, W.-J.; Alper,
H. J. Org. Chem. 2005, 70, 1802–1807.
(22) Some other examples of insertion of carbon monoxide into carbon-
heteroatom bonds catalyzed by palladium complexes: (a) Crudden, C. M.; Alper,
H. J. Org. Chem. 1995, 60, 5579–5587. (b) Imada, Y.; Nishimura, K.; Murahashi,
S.-I. Tetrahedron 1994, 50, 453–464. (c) Imada, Y.; Alper, H. J. Org. Chem.
1996, 61, 6766–6767.
(20) (a) Dekker, G. P. C. M.; Elsevier, C. J.; Vrieze, K.; van Leeuwen,
P. W. N. M. Organometallics 1992, 11, 1598–1603. (b) Dekker, G. P. C. M.;
Elsevier, C. J.; Vrieze, K.; van Leeuwen, P. W. N. M. J. Organomet. Chem.
1992, 430, 357–372.
J. Org. Chem. Vol. 73, No. 17, 2008 6703

Li and Shi
SCHEME 4. A Control Experiment on the Transformation
of 22a to 23a in the Presence of PdCl2
mohydrin derivatives 5 can be easily transformed to R-allenic
alcohols 19 in the presence of Et3N. In addition, the cyclocar-
bonylation of R-allenic alcohols 19 with CO catalyzed by
palladium chloride to give lactones 22 or 23 under different
reaction conditions has been described. Efforts are underway
to elucidate the mechanistic details and the scope and limitations
of these reactions in the laboratory.
Experimental Section
1
General Remarks. H NMR spectra were recorded on a 300
allylpalladium complexes has been proposed by Trost and
Verhoeven,23 and the same type of intermediate like D, where
the π-allyl group is directly attached to the double bond, has
been suggested for the reaction of allenyl esters and carbonates
using Pd(0) catalysts.24 The formation of the conjugate diene
would be the driving force for the conversion of the π-bonded
complex D to the σ-bonded complex E.21a The insertion of CO
into the Pd-OH bond produces intermediate F, which generates
a cyclopalladium complex G by an intramolecular oxidative
addition of OH to the double bond. This may explain why the
cyclocarbonylation cannot occur in the presence of base because
NEt3 or K2CO3 can inhibit the intramolecular oxidative addition
of OH to the double bond in intermediate F by forming a salt.
Moreover, the existence of intermediate F can be proved by
the isolation of trace amount of acid 24a in a large scale
cyclocarbonylation of 19a,25 which should be derived from the
reductive elimination of intermediate F. The double bond at
the γ-position of Pd is essential for the cyclocarbonylation of
19a to be able to take place since many other types of R-allenic
alcohols cannot undergo such a cyclocarbonylation in the
presence of palladium complexes under similar conditions.18,23
The reductive elimination of intermediate G gives the corre-
sponding lactone product 2(3H)-dihydrofuranone 22a and
regenerates the Pd(0) species. 2(3H)-Dihydrofuranone 22a can
be transformed to the corresponding 2(5H)-furanone 23a in the
presence of palladium complex at higher temperatures (100-150
°C) via a 1,5-H transfer (Scheme 3). This transformation is
proved in a control experiment by employing 2(3H)-dihydro-
furanone 22a and PdCl2 (8 mol %) in DMF at 150 °C under
CO atmosphere or ambient atmosphere, affording the corre-
sponding 2(5H)-furanone 23a in 89% or 82% yield, respectively
(Scheme 4). It also should be noted that upon heating at 150
°C, 22a could not be transformed to 23a, suggesting that PdCl2
is essential in this transformation.
MHz spectrometer in CDCl3 with tetramethylsilane as the internal
standard. Infrared spectra were measured on a spectrometer. Mass
spectra were recorded by the EI method, and HRMS was measured
on a Kratos Analytical Concept mass spectrometer (EI or MALDI).
Satisfactory CHN microanalyses were obtained with an analyzer.
Melting points are uncorrected. All reactions were monitored by
TLC with silica gel coated plates. Flash Column Chromatography
was carried out with 300-400 mesh silica gel at increased pressure.
General Procedure for the Synthesis of Vinylbromohydrins.
To a solution of vinylidenecyclopropanes (0.18 mmol) in MeCN
(1.8 mL) was added 0.6 mL of water with a syringe. Then, 40 mg
of NBS (1.2 equiv, 0.22 mmol) was added in one portion and the
mixture was stirred for another 10 min at room temperature. The
reaction mixture was quenched by addition of 10 mL of water then
extracted with ether (3 × 10 mL), and the combined organic phases
were washed with brine (1 × 20 mL) and dried over anhydrous
MgSO4. The products were purified by flash column chromatog-
raphy with petroleum ether-EtOAc (5%).
4-Bromo-2-methyl-5,5-diphenyl-3-(propan-2-ylidene)pent-4-
1
en-2-ol, 5a. A white solid, mp 108-110 °C. H NMR (CDCl3,
300 MHz, TMS) δ 1.23 (s, 3H, CH3), 1.46 (s, 3H, CH3), 1.59 (s,
1H, OH), 1.94 (s, 3H, CH3), 1.97 (s, 3H, CH3), 7.18-7.38 (m,
10H, Ar). 13C NMR (CDCl3, 75 MHz, TMS) δ 21.7, 25.0, 30.3,
30.4, 72.9, 124.0, 127.3, 127.4, 127.9, 128.1, 128.4, 129.1, 137.4,
140.0, 140.6, 141.2, 143.2. IR (CH2Cl2) ν 3080, 3027, 2928, 2853,
1730, 1628, 1596, 1492, 1443, 1371, 1277, 1120, 1074, 1031, 965,
900, 790, 771, 758, 745, 697, 597, 567 cm-1. MS (%) m/e 353
(M+ - H2O, 1), 290 (M+ - Br, 6), 273 (M+ - Br - H2O), 233
(29), 232 (100), 217 (36), 215 (26), 202 (18), 91 (17), 59 (26).
HRMS (EI) for C21H21Br (M - H2O) 352.0827, found 352.0825.
Anal. Calcd for C21H23OBr: C, 67.93; H, 6.24. Found: C, 67.99;
H, 6.20.
General Procedure for the Synthesis of r-Allenic Alcohols.
To a solution of 5 (0.10 mmol) in DMF (3.0 mL) was added 3.0
equiv of Et3N with a syringe, and the resulting mixture was stirred
for 3-4 h at 100 °C, followed by addition of water (5 mL), and
extracted with ether (3 × 10 mL). The combined organic phases
were washed with brine (1 × 20 mL) and dried over anhydrous
MgSO4. The products were purified by a flash column chromatog-
raphy with petroleum ether-EtOAc (5%).
Conclusion
We have disclosed in this paper that the hydrobromination
or alkoxybromination of vinylidenecyclopropanes 1 could be
achieved in the presence of NBS and water or alcohols under
mild conditions. By this synthetic approach, the corresponding
vinylbromohydrin derivatives 5 or vinylbromoalkoxy derivatives
6-12 can be obtained in moderate to excellent yields. A
considerable range of aromatic groups-substituted VDCPs 1 has
been examined in the reaction, providing an efficient route to
the synthesis of various vinylbromohydrin or vinylbromoalkoxy
derivatives according to different substrates. These vinylbro-
2-Methyl-5,5-diphenyl-3-(prop-1-en-2-yl)penta-3,4-dien-2-
1
ol, 19a. A white solid, mp 124-126 °C. H NMR (CDCl3, 300
MHz, TMS) δ 1.56 (s, 6H, 2CH3), 1.95 (s, 3H, CH3), 5.15 (dd, J
) 1.2 Hz, J ) 1.5 Hz, 1H), 5.46 (s, 1H), 7.25-7.35 (m, 10H, Ar).
13C NMR (CDCl3, 75 MHz, TMS) δ 24.6, 30.5, 72.4, 111.9, 115.4,
118.3, 127.2, 128.1, 128.5, 136.6, 137.8, 204.3. IR (CH2Cl2) ν 3568,
3448, 2974, 2928, 1919, 1616, 1597, 1492, 1449, 1375, 1173, 1106,
1030, 900, 827, 767, 695, 636, 577, 550 cm-1. MS (%) m/e 290
(M+, 8), 257 (11), 232 (100), 217 (69), 202 (30), 189 (12), 165
(17), 59 (58), 43 (54). Anal. Calcd for C21H22O: C, 86.85; H, 7.64.
Found: C, 86.55; H, 7.88.
General Procedure for the Cyclocarbonylation of r-Allenic
Alcohols Catalyzed by PdCl2 to Give 2(3H)-Furanones. To a
solution of 19 (0.10 mmol) in DMF (3.0 mL) were added PdCl2
(10 mol%) and dppp (20 mol%), and the resulting mixture was
stirred for 28 h at 70-80 °C under 20 atm of carbon monoxide.
The reaction was quenched by addition of water (5 mL) and
(23) Trost, B. M.; Verhoeven, T. R. J. Am. Chem. Soc. 1980, 102, 4730–
4743, and references cited therein.
(24) Nokami, J.; Maihara, A.; Tsuji, J. Tetrahedron Lett. 1990, 31, 5629–
5630.
(25) A trace of acid 22a can be obtained in a large scale cyclocarbonylation
with use of 0.3 mmol of 18a under the standard conditions.
6704 J. Org. Chem. Vol. 73, No. 17, 2008

Synthesis of Vinylbromohydrin and Vinylbromoalkoxy DeriVatiVes
extracted with ether (3 × 10 mL), and the combined organic phases
were washed with brine (1 × 20 mL) and dried over anhydrous
MgSO4. The products were purified by a flash column chromatog-
raphy with petroleum ether-EtOAc (10%).
22.1, 24.7, 27.2, 83.7, 122.6, 128.0, 129.1, 129.6, 129.9, 131.4,
136.0, 137.4, 138.3, 139.0, 140.8, 153.0, 168.0. IR (CH2Cl2) ν 3023,
2976, 2924, 2859, 1747, 1650, 1605, 1510, 1463, 1371, 1253, 1188,
1089, 1069, 1036, 1010, 926, 824, 804, 734, 537 cm-1. MS (%)
m/e 346 (M+, 51), 331 (58), 313 (15), 288 (19), 273 (100), 260
(11), 245 (14), 229 (12), 213 (15). HRMS (EI) for C24H26O2
346.1933, found 346.1936.
3-(Diphenylmethylene)-5,5-dimethyl-4-(propan-2-ylidene)-di-
hydrofuran-2(3H)-one, 22a. A light yellow solid, mp 128-130
1
°C. H NMR (CDCl3, 300 MHz, TMS) δ 1.05 (s, 3H, CH3), 1.68
(s, 3H, CH3), 1.71 (s, 6H, 2CH3), 7.11-7.14 (m, 2H, Ar), 7.24-7.38
(m, 8H, Ar). 13C NMR (CDCl3, 75 MHz, TMS) δ 22.1, 24.7, 27.2,
83.9, 123.7, 127.3, 128.3, 128.5, 128.9, 129.8, 130.6, 131.3, 135.6,
140.1, 143.6, 152.6, 167.7. IR (CH2Cl2) ν 3057, 2976, 2926, 2853,
1757, 1490, 1444, 1368, 1283, 1246, 1202, 1091, 1070, 1009, 941,
762, 753, 697, 652, 590 cm-1. MS (%) m/e 318 (M+, 16), 303
(18), 257 (66), 245 (51), 215 (33), 199 (100), 165 (13), 105 (41),
77 (39). Anal. Calcd for C22H22O2: C, 82.99; H, 6.96. Found: C,
82.68; H, 6.93.
Acknowledgment. We thank the Shanghai Municipal Com-
mittee of Science and Technology (04JC14083, 06XD14005)
and the National Natural Science Foundation of China (20472096,
203900502, 20672127, and 20732008).
Supporting Information Available: Detailed experimental
1
procedures, H and 13C NMR spectroscopic data for vinylbro-
mohydrin derivatives 5 and vinylbromoalkoxy derivatives 6-12,
compounds 14, 16-18, R-allenic alcohols 19 and 20 as well as
the lactone products 22 and 23, X-ray crystal structure of 23a.
These materials are available free of charge via the Internet at
http://pubs.acs.org.
3-(Di-p-tolylmethylene)-5,5-dimethyl-4-(propan-2-ylidene)di-
hydrofuran-2(3H)-one, 22b. A light yellow solid, mp 114-116
1
°C. H NMR (CDCl3, 300 MHz, TMS) δ 1.05 (s, 3H, CH3), 1.68
(s, 3H, CH3), 1.70 (s, 6H, 2CH3), 2.33 (s, 3H, CH3), 2.37 (s, 3H,
CH3), 7.01 (d, J ) 8.1 Hz, 2H, Ar), 7.07 (d, J ) 8.1 Hz, 2H, Ar),
7.25 (s, 4H, Ar). 13C NMR (CDCl3, 75 MHz, TMS) δ 21.3, 21.5,
JO8009352
J. Org. Chem. Vol. 73, No. 17, 2008 6705