Hydroxy- and Alkoxycyclizations of Enynes Catalyzed by Platinum(II) Chloride

Article abstract of DOI:10.1055/s-2003-42456

The cyclization of 1-en-6-ynes catalyzed by PtCl₂ in the presence of water or alcohols affords five or six-membered ring carbocycles containing hydroxy or alkoxy functional groups in high yields. The alkoxycyclizations can also be performed wit

Full text of DOI:10.1055/s-2003-42456

2898
PRACTICAL SYNTHETIC PROCEDURES
Hydroxy- and Alkoxycyclizations of Enynes Catalyzed by Platinum(II)
Chloride
C
yclizations of Enynes
ª
C
atalze
d
by
P
Platinum(II)
C
a
hloride z Muñoz, María Méndez, Cristina Nevado, Diego J. Cárdenas,
Antonio M. Echavarren*
PSP
Departamento de Química Orgánica, Universidad Autónoma de Madrid, Cantoblanco,
28049-Madrid, Spain
Fax +34(91)3973966; E-mail: anton.echavarren@uam.es
Received 2 September 2003; revised 30 September 2003
No13
Abstract: The cyclization of 1-en-6-ynes catalyzed by PtCl2 in the presence of water or alcohols affords five or six-membered ring car-
bocycles containing hydroxy or alkoxy functional groups in high yields. The alkoxycyclizations can also be performed with AuCl3 as cat-
alyst. The reaction is stereospecific, atom-economical, and takes place in environmentally friendly solvents.
Key words: enynes, platinum, gold, cyclizations, carbenes
PhO2S
H2O
PhO2S
PhO2S
Procedure 1
Procedure 2
PhO2S
PtCl2
OH
1
3
2: 70%
MeO2C
MeO2C
OH
MeO2C
MeO2C
PtCl2
OAll
4: 95%
MeO
MeO2C
MeO2C
CO2Me
CO2Me
MeOH
PtCl2
Procedure 3
Procedure 4
5
6: 67%
MeO2C
MeO2C
MeO2C
MeO2C
acetone
PtCl2
3
7: 86%
Scheme 1
Introduction
salts or complexes of Pd(II), Ru(II), Cu(I), Ag(I), and
Au(III) are also suitable catalysts.
Cyclization of , -enynes catalyzed by transition metal
complexes leads to different cyclization products depend-
ing on the catalyst and the reaction conditions.1–5 Electro-
philic transition metal salts or complexes MXn coordinate
alkynes and activate them towards nucleophilic attack.
Thus, we found that alkynes react intramolecularly with
allylsilanes and allylstannanes to give cyclic dienes.6
PtCl2 is the best catalyst for this transformation, although
Simple alkenes and enol ethers also act as nucleophiles to-
wards alkynes and react in the presence of PtCl2 as cata-
lyst to give hydroxy- and alkoxycyclization products, in
which a molecule of water or an alcohol is incorporated in
the cyclic product (Scheme 2).7
Computational studies indicate that the enynes react with
PtCl2 or AuCl3 to give two types of cyclopropyl Pt- or Au-
carbenes as the key intermediates. The cyclopropyl metal
carbenes formed in the 5-exo-dig pathway are then at-
tacked by water or R OH with cyclopropyl cleavage at
carbons a or b to give five- I or six-membered rings II
(Scheme 3). On the other hand, migration of the metal
SYNTHESIS 2003, No. 18, pp 2898–2902
x
x.
x
x
.
2
0
0
3
Advanced online publication: 04.11.2003
DOI: 10.1055/s-2003-42456; Art ID: Z12703SS
© Georg Thieme Verlag Stuttgart · New York

PRACTICAL SYNTHETIC PROCEDURES
Cyclizations of Enynes Catalyzed by Platinium(II) Chloride
2899
PhO2S
PhO2S
MeOH
Z
OR'
PhO2S
PhO2S
[Pt(MeCN)4](BF4)2
Z
Z
R
R
OMe
R'OH
1
8: 98%
R'OH
OR'
R = Me
MeO2C
MeO2C
Z
H2O
MeO2C
MeO2C
+ MXn (cat)
R
[Pt(MeCN)2Cl2]
R'OH
Ph
Ph
H
Z
OH
R
9
10: 98%
R
Z
Z
R'O
MeO2C
MeO2C
R
Scheme 2
OMe
MeO2C
MeO2C
11: 63%
MeOH
PtCl2
MXn
XnM
MXn
MeO2C
MeO2C
R
H
5-exo-dig
6-endo-dig
a
Z
Z
Z
b
R
3
H
H
H
R
7: 34%
R'OH
R'OH
R'OH
a
b
Scheme 4
Z
Z
H
nyl compounds does not compete significantly with the
cyclization reactions. However, addition of these nucleo-
philes to the alkyne is observed with the less reactive
enynes. Thus, substrates with substituents at C-1 of the
alkyne react sluggishly in the cyclization process. Like-
wise, no cyclization was observed with enynes bearing
monosubstituted alkenes.
Z
H
R
R
R
H
OR'
OR'
OR'
I
II
III
Scheme 3
fragment towards C-2 of the alkyne (6-endo-dig pathway)
leads to derivatives of type III.8 The reaction of alkynes
with furans catalyzed by PtCl2 also involves cyclopropyl
platinum carbenes as intermediates.9
When the reactions catalyzed by PtCl2 are carried out in
non-nucleophilic solvents like 1,4-dioxane or acetone, cy-
cloisomerization by Alder ene-type transformation takes
place exclusively to give dienes in good yields (Procedure
4, Scheme 1).7
The hydroxy- and alkoxycyclization reaction is stereospe-
cific as shown in the reactions of diastereomeric enynes
12 and 14 (Scheme 5), and proceeds by the formal trans-
Scope and Limitations
The hydroxy- and alkoxycyclizations of enynes occur un-
der mild conditions with 5 mol% of PtCl2 and the nucleo-
phile as solvent (alcohol) or co-solvent (water). Other
Pt(II) complexes, such as [Pt(MeCN)2Cl2] or
[Pt(MeCN)4](BF4)2 can also be used as the catalysts
(Schemes 1 and 4). A variety of functional groups are tol-
erated on the enyne. Although most transformations are
remarkably clean, Alder ene-type reaction may take place
as a secondary process in some cases.7b Thus, for exam-
ple, malonate derivative 3 gave ene-type diene 7, in addi-
tion to the methoxycyclization derivative 11 (Scheme 4).
Diene 7 does not arise by elimination of methanol from
11. Furthermore, no addition of methanol was observed
when diene 7 was allowed to react with methanol and
PtCl2.
2
addition of the electrophile ( -alkyne-metal complex)
and the nucleophile (R OH) to the double bond in a Mark-
ovnikov manner. Similar stereoselectivity is observed in
the reactions catalyzed by AuCl3. This is a very active cat-
alyst for these cyclizations. However, due to its hygro-
scopicity, the reactions with this catalyst are less
reproducible and, occasionally, simple acid-catalyzed
transformations are observed.
Six-membered carbo- or heterocycles of type II
(Scheme 3) can also be obtained with certain enynes
(Scheme 6). Six-membered rings are favored when less
electron-withdrawing groups are at the tether of the enyne
or with enynes bearing alkenes substituted at C-2 such as
20. In this case, skeletal rearrangement (metathesis-type)
product 22 was also observed. Dienes formed by skeletal
It is noteworthy that in most cases the direct addition of
R OH or water to the alkyne to give enol ethers or carbo-
Synthesis 2003, No. 18, 2898–2902 © Thieme Stuttgart · New York

2900
M. P. Muñoz et al.
PRACTICAL SYNTHETIC PROCEDURES
cycloisomerization process to give 1,4-diene
(Scheme 3).
7
PhO2S
PhO2S
MeOH
PhO2S
PhO2S
Ph
OMe
PtCl2
The reaction can also be applied to enol ethers as nucleo-
philes to give acetals such as 24 (Scheme 7).8 Endo-digo-
nal cyclization (products of type III, Scheme 3) was
observed in the cyclization of 25, and similar substrates
bearing enynes with substituted alkynes.
H
Ph
12
14
16
13: 77%
PhO2S
PhO2S
PhO2S
PhO2S
MeOH
Ph
OMe
PtCl2
H
TIPSO
TIPSO
TIPSO
TIPSO
MeOH
PtCl2
Ph
OMe
OMe
15: 72%
OMe
Me
MeO2C
MeO2C
23
24: 84%
MeO2C
MeO2C
MeOH
AuCl3
Ts
H
H
OMe
Ts
N
N
MeOH
AuCl3
17: 82%
(MeO)2HC
Me
OMe
25
26: 40%
Scheme 5
Scheme 7
AcO
AcO
Conclusion
MeOH
PtCl2
AcO
AcO
In summary, we have developed new methodology to ob-
tain catalytically, under very mild conditions, carbo- or
heterocycles with hydroxy or alkoxy functions at the side
chain that can be further functionalized. This general cy-
clization of 1,6-enynes, easily prepared from commercial
sources, is experimentally very simple, and occurs in en-
vironmentally friendly solvents. The reactions catalyzed
by PtCl2 in polar but non-nucleophilic solvents lead to
ene-type cycloisomerized dienes.
OMe
18
19: 63%
MeO2C
MeO2C
OMe
MeO2C
MeO2C
MeOH
PtCl2
21: 80%
+
MeO2C
MeO2C
20
PtCl2 was used as received and AuCl3 was dried at 50 °C under vac-
uum and stored under argon. [Pt(MeCN)4](BF4)2 was prepared ac-
cording to the known procedure.10 All reactions were carried out
under Ar.
22: 14%
Scheme 6
[Pt(MeCN)2Cl2]
This complex was prepared by the procedure described for the syn-
thesis of [Pt(PhCN)2Cl2].11
rearrangement2–4 are presumably derived from the same
cyclopropyl metal carbene intermediate proposed in the
alkoxycyclization mechanism (Scheme 3).
A solution of PtCl2 (200 mg, 0.75 mmol) in anhyd MeCN (10 mL)
was refluxed for 12 h. The reaction was cooled to r.t. to give a pale
yellow solid. The solid was filtered off and washed with hexane to
give the pure complex (230 mg, 88%).
Procedures
4,4-Bis(phenylsulfonyl)-7-methyloct-6-en-1-yne (1)
(a) To a suspension of NaH (60% in mineral oil, 240 mg, 10.00
mmol) in DMF (10 mL) at 0 °C was added a solution of bisphenyl-
sulfonylmethane (2.60 g, 10.00 mmol) in DMF (30 mL), followed
by prenyl bromide (1.20 mL, 10.00 mmol). The mixture was stirred
for 12 h at 23 °C. After quenching with H2O, extractive work-up
(Et2O), and chromatography (4:1 hexane–EtOAc), 5,5-bis(phenyl-
sulfonyl)-2-methyl-2-pentene was obtained as a white solid (2.90 g,
80%); mp 116–118 °C (Lit.12 mp 118 °C).
We report here general procedures for the PtCl2 catalyzed
alkoxycyclization of enynes. In Procedure 1, we describe
a representative example of hydroxycyclization reaction
from readily available enyne 1. In the second example,
Procedure 2, elaborates the addition of allyl alcohol to
enyne 3 to give an allyl-protected homoallylic alcohol 4.
In the third procedure (Procedure 3), the stereoselective
methoxycyclization of 5 to give 6 is detailed. The last ex-
ample, Procedure 4, is a simple platinum-catalyzed enyne
(b) A solution of 5,5-bis(phenylsulfonyl)-2-methylpent-2-ene (1.24
g, 3.41 mmol) in DMF (10 mL) was added to a suspension of NaH
(60% in mineral oil, 137 mg, 3.41 mmol) in DMF (20 mL) at 0 °C,
Synthesis 2003, No. 18, 2898–2902 © Thieme Stuttgart · New York

PRACTICAL SYNTHETIC PROCEDURES
Cyclizations of Enynes Catalyzed by Platinium(II) Chloride
2901
followed by the addition of propargyl bromide (80% in toluene,
0.38 mL, 3.41 mmol). The mixture was stirred 13 h at 23 °C. After
quenching with H2O, extractive work-up (Et2O), and chromatogra-
phy (4:1 hexane-EtOAc), 1 was obtained as a white solid (1.13 g,
82%); mp 73–75 °C.
1H NMR (300 MHz, CDCl3): = 8.14–8.11 (m, 4 H), 7.74–7.71 (m,
2 H), 7.60–7.55 (m, 4 H), 5.40–5.37 (m, 1 H), 3.17 (d, J = 2.8 Hz,
2 H), 3.04 (d, J = 5.7 Hz, 2 H), 2.10 (t, J = 2.80 Hz, 1 H), 1.76 (s, 3
H), 1.57 (d, J = 5.7 Hz, 3 H).
13C NMR (75 MHz, CDCl3; DEPT): = 137.01 (C), 136.45 (C),
134.36 (CH), 131.49 (CH), 128.45 (CH), 114.81 (CH), 89.16 (C),
76.02 (C), 73.96 (CH), 27.84 (CH2), 26.11 (CH3), 20.47 (CH2),
18.24 (CH3).
(ddd, J = 13.7, 8.5, 1.6 Hz, 1 H), 2.01 (dd, J = 13.7, 9.3 Hz, 1 H),
1.19 (s, 3 H).
13C NMR (75 MHz, CDCl3): = 172.01, 171.93, 148.11, 135.76,
115.46, 110.66, 62.41, 58.56, 52.82, 52.68, 49.61, 43.45, 36.00,
29.67, 23.17, 22.67.
Anal. Calcd for C16H24O5: C, 64.84; H, 8.16. Found: C, 64.35; H,
8.75.
Dimethyl 2-(Cyclohex-2-en-1-yl)-2-(prop-2-ynyl)malonate (5)
To a suspension of NaH (60% in mineral oil, 250 mg, 6.25 mmol)
in DMF (25 mL) at 0 °C was added dimethyl propargyl malonate
(0.89 mL, 6.25 mmol). After 5 min, 3-bromocyclohexene (0.72 mL,
6.25 mmol) was added and the resulting solution was stirred for 14
h at 23 °C. After extractive work-up (Et2O) and chromatography
(9:1 hexane-EtOAc), 5 was obtained as a colorless oil (1.49 g,
95%).
Anal. Calcd for C21H22O4S2: C, 62.66; H, 5.51. Found: C, 62.80; H,
5.45.
1,1-Bis(phenylsulfonyl)-3-(1-hydroxy-1-methylethyl)-4-methyl-
enecyclopentane (2); Procedure 1
1H NMR (300 MHz, CDCl3): = 5.72 (m, 2 H), 3.76 (s, 3 H), 3.73
(s, 3 H), 3.13 (m, 1 H), 2.89 (dd, J = 16.9, 2.6 Hz, 1 H), 2.82 (dd,
J = 16.9, 2.6 Hz, 1 H), 2.01 (t, J = 2.6 Hz, 1 H), 1.95 (m, 1 H), 1.82
(m, 2 H), 1.58 (m, 1 H), 1.38 (m, 1 H).
13C NMR (75 MHz, CDCl3): = 170.08, 170.06, 129.24, 127.32,
79.54, 60.42, 52.52, 52.35, 39.04, 24.87, 24.32, 22.51, 22.28.
To a 50 mL round bottom flask, equipped with a magnetic stirring
bar, and a reflux condenser was added 1 (2.00 g, 4.97 mmol) and
PtCl2 (66 mg, 0.25 mmol, 5 mol%). A 1:1 mixture of acetone–H2O
(20 mL) was added and the reaction was refluxed for 17 h. The mix-
ture was extracted with EtOAc, dried (MgSO4), and the organic
phase was evaporated. The crude mixture was purified by flash
chromatography (hexane–EtOAc 1:1) to give 2 as a white solid
(1.50 g, 70%); mp 125–127 °C.
1H NMR (300 MHz, CDCl3): = 8.11–8.06 (m, 2 H), 8.04–7.98 (m,
2 H), 7.76–7.69 (m, 2 H), 7.63–7.54 (m, 4 H), 5.02–5.01 (m, 1 H),
4.98 (m, 1 H), 3.48 (ddd, J = 17.4, 4.9, 3.2 Hz, 1H), 2.85–2.70 (m,
5 H), 1.64 (s, 3 H), 1.23 (s, 3 H).
Anal. Calcd for C14H18O4: C, 67.18; H, 7.25. Found: C, 67.13; H,
7.58.
Dimethyl (1R*,2R*)-2-Methoxy-9-methylenebicyc-
lo[4.3.0]nonane-7,7-dicarboxylate (6); Procedure 3
To a 25 mL round bottom flask, equipped with a magnetic stirring
bar, and a reflux condenser was added 5 (248 mg, 0.99 mmol) and
PtCl2 (13 mg, 0.05 mmol, 5 mol%). MeOH (5 mL) was added and
the mixture was refluxed for 17 h. The solvent was evaporated and
the crude mixture was purified by flash chromatography (hexane–
EtOAc, 9:1) to give 6 as a colorless oil (187 mg, 67%).
1H NMR (500 MHz, CDCl3): = 5.03 (dd, J = 5.0, 2.3 Hz, 1 H),
4.80 (dd, J = 5.1, 2.6 Hz, 1 H), 3.74 (s, 3 H), 3.73 (s, 3 H), 3.63 (dd,
J = 5.5, 2.8 Hz, 1 H), 3.38 (s, 3 H), 3.35 (dd, J = 18.4, 2.4 Hz, 1 H),
3.05 (br s, 1 H), 2.93 (dd, J = 18.5, 5.5 Hz, 1 H), 2.91 (dd, J = 18.4,
1.0 Hz, 1 H), 1.80–1.70 (m, 1 H), 1.58 (qt, J = 13.4, 3.4 Hz, 1 H),
1.43 (m, 1 H), 1.42 (m, 1 H), 1.31 (dm, J = 18.1 Hz, 1 H), 0.93 (dtd,
J = 16.6, 13.0, 3.6 Hz, 1 H).
13C NMR (75 MHz, CDCl3; DEPT): = 146.49 (C), 137.04 (C),
135.82 (C), 134.67 (CH), 134.53 (CH), 131.05 (CH), 128.70 (CH),
111.58 (CH2), 91.95 (C), 72.59 (C), 53.54 (CH), 40.57 (CH2), 33.49
(CH2), 27.27 (CH3), 26.83 (CH2).
Anal. Calcd for C21H24O5S2: C, 59.98; H, 5.75. Found: C, 59.82; H,
5.91.
Dimethyl 2-(3-Methylbut-2-enyl)-2-(prop-2-ynyl)malonate (3)13
To a suspension of NaH (60% in mineral oil, 338 mg, 14.10 mmol)
in THF (15 mL) at 0 °C, was added dimethyl propargyl malonate
(2.00 g, 11.75 mmol). After 5 min, prenyl bromide (2.11 g, 14.10
mmol) was added and the resulting solution was stirred for 6 h at 23
°C. After extractive work-up (Et2O) and chromatography (7:1 hex-
ane–EtOAc), 3 was obtained as a pale yellow oil (3.20 g, 95%).
1H NMR (300 MHz, CDCl3): = 4.90 (t, J = 4.0 Hz, 1 H), 3.75 (s,
6 H), 2.80 (m, 4 H), 2.01 (t, J = 2.0 Hz, 1 H), 1.70 (s, 3 H), 1.68 (s,
3 H).
13C NMR (75 MHz, CDCl3): = 172.09, 170.28, 148.00, 106.48,
75.93, 61.82, 56.03, 52.69, 52.46, 46.04, 41.80, 37.73, 24.57, 23.82,
18.55.
EI-HRMS: m/z calcd for C15H22O5: 282.1467. Found: 282.1469.
Anal. Calcd for C15H22O5: C, 63.81; H, 7.85. Found: C, 63.89; H,
8.20.
13C NMR (75 MHz, CDCl3): = 170.9, 139.9, 137.9, 117.7, 80.0,
71.5, 57.5, 51.9, 30.8, 26.9, 22.9, 18.5, 14.8.
Dimethyl 3-(Isopropenyl)-4-methylenecyclopentane-1,1-dicar-
boxylate (7);14 Procedure 4
To a 25 mL round bottom flask, equipped with a magnetic stirring
bar, was added 3 (174 mg, 0.73 mmol), PtCl2 (10 mg, 0.04 mmol, 5
mol%), and 4 Å molecular sieves. Acetone (5 mL) was added and
the mixture was stirred at 23 °C for 18 h. The crude mixture was fil-
tered through Celite and the solvent was evaporated. The crude mix-
ture was purified by flash chromatography (hexane–EtOAc, 10:1)
to give the known 714 as a colorless oil (150 mg, 86%).
1H NMR (300 MHz, CDCl3): = 5.02 (q, J = 2.7 Hz, 1 H), 4.83 (s,
2 H), 4.80 (q, J = 2.7 Hz, 1 H), 3.74 (s, 6 H), 3.28 (tt, J = 7.5, 2.7
Hz, 1 H), 3.08 (td, J = 16.8, 1.1 Hz, 1 H), 2.91 (tdd, J = 16.8, 2.7 Hz,
1 H), 2.53 (ddd, J = 12.0, 7.5, 1.6 Hz, 1 H), 2.12 (dd, J = 12.0, 2.7
Hz, 1 H), 1.65 (3 H).
Dimethyl 3-(1-Allyloxy-1-methylethyl)-4-methylenecyclopen-
tane-1,1-dicarboxylate (4); Procedure 2
To a 50 mL round bottom flask, equipped with a magnetic stirring
bar, and a reflux condenser was added 3 (1.50 g, 6.28 mmol) and
PtCl2 (83 mg, 0.31 mmol, 5 mol%). Allylic alcohol (10 mL) was
added and the mixture was refluxed for 17 h. The solvent was evap-
orated and the crude mixture was purified by flash chromatography
(hexane–EtOAc, 5:1) to give 4 as a yellow oil (1.77 g, 95%).
1H NMR (300 MHz, CDCl3): = 5.87 [dquint (dq), J = 16.97, 5.25
Hz, 1 H], 5.24 (dq, J = 17.0, 1.62 Hz, 1 H), 5.08 (dq, J = 10.5, 1.6
Hz, 1 H), 5.02 (m, 1 H), 4.98 (m, 1 H), 3.89 (dq, J = 5.3, 1.6 Hz, 2
H), 3.71 (s, 3 H), 3.70 (s, 3 H), 2.86 (m, 2 H), 2.81 (m, 1 H), 2.54
13C NMR (75 MHz, CDCl3): = 172.07, 171.97, 149.19, 144.65,
113.44, 108.06, 58.70, 52.74, 51.06, 40.88, 38.61, 18.10.
Synthesis 2003, No. 18, 2898–2902 © Thieme Stuttgart · New York

2902
M. P. Muñoz et al.
PRACTICAL SYNTHETIC PROCEDURES
(5) Transition-metal catalyzed reaction of enol ethers with
alkynes: (a) Iwasawa, N.; Maeyama, K.; Kusama, H. Org.
Lett. 2001, 3, 3871. (b) Kusama, H.; Yamabe, N.; Iwasawa,
N. Org. Lett. 2002, 4, 2569. (c) Iwasawa, N.; Miura, T.;
Kiyota, K.; Kusama, H.; Lee, K. Org. Lett. 2002, 4, 4463.
(d) Dankwardt, J. W. Tetrahedron Lett. 2001, 42, 5809.
(6) (a) Fernández-Rivas, C.; Méndez, M.; Echavarren, A. M. J.
Am. Chem. Soc. 2000, 122, 1221. (b) Fernández-Rivas, C.;
Méndez, M.; Nieto-Oberhuber, C.; Echavarren, A. M. J.
Org. Chem. 2002, 67, 5197.
(7) (a) Méndez, M.; Muñoz, M. P.; Echavarren, A. M. J. Am.
Chem. Soc. 2000, 122, 11549. (b) Méndez, M.; Muñoz, M.
P.; Nevado, C.; Cárdenas, D. J.; Echavarren, A. M. J. Am.
Chem. Soc. 2001, 123, 10511.
(8) Nevado, C.; Cárdenas, D. J.; Echavarren, A. M. Chem.–Eur.
J. 2003, 9, 2627.
(9) (a) Martín-Matute, B.; Cárdenas, D. J.; Echavarren, A. M.
Angew. Chem. Int. Ed. 2001, 40, 4754. (b) Martín-Matute,
B.; Nevado, C.; Cárdenas, D. J.; Echavarren, A. M. J. Am.
Chem. Soc. 2003, 125, 5757.
(10) de Renzi, A.; Panunzi, A.; Vitagliano, A. J. Chem. Soc.,
Chem. Commun. 1976, 47.
(11) Braunstein, P.; Bender, R.; Jud, J. Inorg. Synth. 1989, 26,
341.
(12) Benedetti, F.; Berti, F.; Fabrissin, S.; Gianferraro, T.; Rialiti,
A. J. Org. Chem. 1991, 56, 3530.
Acknowledgments
We are grateful to the DGES (Project PB97-0002-C2-02) for sup-
port of this research, to the MEC for predoctoral fellowships to
M.M., M.P.M., and the CAM for a fellowship to C.N. We also thank
Johnson Matthey PLC for a generous gift of PtCl2.
References
(1) Aubert, C.; Buisine, O.; Malacria, M. Chem. Rev. 2002, 102,
813.
(2) (a) Chatani, N.; Morimoto, T.; Muto, T.; Murai, S. J. Am.
Chem. Soc. 1994, 116, 6049. (b) Chatani, N.; Furukawa, N.;
Sakurai, H.; Murai, S. Organometallics 1996, 15, 901.
(c) Chatani, N.; Kataoka, K.; Sakurai, H.; Murai, S.;
Furukawa, N.; Seki, Y. J. Am. Chem. Soc. 1998, 120, 9104.
(3) (a) Fürstner, A.; Szillat, H.; Gabor, B.; Mynott, R. J. Am.
Chem. Soc. 1998, 120, 8305. (b) Fürstner, A.; Szillat, H.;
Stelzer, F. J. Am. Chem. Soc. 2000, 122, 6785. (c) Fürstner,
A.; Stelzer, F.; Szillat, H. J. Am. Chem. Soc. 2001, 123,
11863.
(4) (a) Trost, B. M.; Doherty, G. A. J. Am. Chem. Soc. 2000,
122, 3801. (b) Trost, B. M.; Toste, D. F.; Pinkerton, A. B.
Chem. Rev. 2001, 101, 2067.
(13) Trost, B. M.; Braslau, R. Tetrahedron Lett. 1988, 29, 1231.
(14) Castaño, A. M.; Ruano, M.; Echavarren, A. M. Tetrahedron
Lett. 1996, 37, 6591.
Synthesis 2003, No. 18, 2898–2902 © Thieme Stuttgart · New York