Palladium(0)-catalyzed asymmetric synthesis of 2-vinylmorpholine and 2-vinylpiperazine. Influence of the biscarbonate structure on the enantioselectivity

Article abstract of DOI:10.1016/S0957-4166(00)00315-3

Palladium-catalyzed cyclization of N,N-bis(p-tolylsulfonyl)-o-phenylenediamine 2b and 2-[(2,4,6-trimethylphenyl)sulfonyl]aminophenol 2c with three allylic biscarbonates 1a-c gave quite different enantioselectivities. This indicates that the cyclization pr

Full text of DOI:10.1016/S0957-4166(00)00315-3

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 11 (2000) 3561–3568
Palladium(0)-catalyzed asymmetric synthesis of
2-vinylmorpholine and 2-vinylpiperazine. Influence of the
biscarbonate structure on the enantioselectivity
Magali Massacret,a Rajae Lakhmiri,b Paul Lhoste,a Christelle Nguefack,a
Fouad B. Ben Abdelouahab,b Rachid Fadelb and Denis Sinoua,*
aLaboratoire de Synthe`se Asyme´trique, associe´ au CNRS, CPE Lyon, Universite´ Claude Bernard Lyon 1, 43,
boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex, France
bDe´partement de Chimie, Universite´ Abdelmalek Essaadi, Faculte´ des Sciences, BP 2121, M’hannech 2,
Tetouan, Morocco
Received 14 July 2000; accepted 14 August 2000
Abstract
Palladium-catalyzed cyclization of N,N-bis(p-tolylsulfonyl)-o-phenylenediamine 2b and 2-[(2,4,6-
trimethylphenyl)sulfonyl]aminophenol 2c with three allylic biscarbonates 1a–c gave quite different enan-
tioselectivities. This indicates that the cyclization processes do not have a common intermediate, as in the
case of benzene-1,2-diol. © 2000 Elsevier Science Ltd. All rights reserved.
1. Introduction
Palladium-catalyzed cyclization processes are now widely used for the stereoselective synthesis
of carbo- and heterocyclic systems, sometimes via cascade reactions.1–8 We and others have
recently described the palladium-catalyzed asymmetric synthesis of various 2-vinyldioxanes,9
2-vinylmorpholines,10–12 and 2-vinylpiperazines,10,13,14 starting from benzene-1,2-diol, 2-
aminophenol, and 1,2-diaminobenzene, respectively, and 1,4-bis(methoxycarbonyloxy)but-2-ene.
Although the allylic biscarbonate normally used had Z stereochemistry, benzene-1,2-diol was
also condensed with the E stereoisomer. Since the same enantioselectivities were observed in
both cases, it was assumed that the syn–anti isomerization of the p-allyl palladium intermediate
obtained by the first nucleophilic substitution of the E or Z biscarbonate was fast compared to
the attack of the second nucleophile. We wish to report our studies on the use of (Z)- and
(E)-1,4-bis(methoxycarbonyloxy)but-2-ene and 3,4-bis(methoxycarbonyloxy)but-1-ene in this
cyclization reaction, and the important role played by the substituents at the nitrogen on the
enantioselectivity of this reaction.
* Corresponding author. Fax: 33 4 72 44 81 60; e-mail: sinou@univ-lyon1.fr
0957-4166/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(00)00315-3

3562
M. Massacret et al. / Tetrahedron: Asymmetry 11 (2000) 3561–3568
2. Results and discussion
The reaction of benzene-1,2-diol 2a, N,N-bis(p-tolylsulfonyl)-o-phenylenediamine 2b and
2-[(2,4,6-trimethylphenyl)sulfonyl]aminophenol 2c with the three allylic biscarbonates 1a–c
(Scheme 1) was carried out in THF at room temperature in the presence of a palladium complex
generated in situ by mixing Pd2(dba)3 with the chiral ligand. The results are summarized in
Table 1.
Scheme 1.
Table 1
Palladium-catalyzed asymmetric synthesis of compounds 3 from 1 and 2a
Entry
Substrate 2
Carbonate 1
Ligand
Product
Yieldb (%)
E.e.c (%) (config.)
1
2
3
4
5
6
7
8
9
10
2a
2a
2a
2b
2b
2b
2c
2c
2d
2d
1a
1b
1c
1a
1b
1c
1a
1c
1a
1c
(R)-Binap
(R)-Binap
(R)-Binap
(S)-MeOBiphep
(S)-MeOBiphep
(S)-MeOBiphep
(S)-MeOBiphep
(S)-MeOBiphep
(S)-MeOBiphep
(S)-MeOBiphep
3a
3a
3a
3b
3b
3b
3c
3c
3d
3d
60
60
60
50
20
17
52
12
95
93
37 (R)
37 (R)
37 (R)
52 (R)
37 (R)
48 (R)
64 (S)
18 (S)
38 (S)
46 (S)
a All entries carried out under N2 for 24 h in THF at 25°C in the presence of a palladium catalyst prepared in situ
by mixing Pd2(dba)3 (2.5 mol% Pd) and the chiral ligand (Pd]/[P]=1:2).
b Isolated yields after silica gel chromatography and not optimized.
c Determined by GC analysis (Chiraldex Column, type B-PH) for 3a, HPLC analysis (Chiralpak AD) for 3b and
3c, and based on specific rotation for 3d.13
Reaction of benzene-1,2-diol 2a with carbonates 1a–c in the presence of palladium(0)
associated with (R)-Binap as the chiral ligand gave the same enantioselectivity (37%) and
chemical yield (60%) for compound 3a, whatever the carbonate used (Table 1, entries 1–3).

M. Massacret et al. / Tetrahedron: Asymmetry 11 (2000) 3561–3568
3563
N,N-Bis(p-tolylsulfonyl)-o-phenylenediamine 2b reacted with carbonates 1a, 1b and 1c in the
presence of (S)-MeOBiphep as the chiral ligand, to give the 1,2,3,4-tetrahydro-2-vinylquinoxa-
line 3b in 52, 37 and 48% e.e., respectively (Table 1, entries 4, 5 and 6), and 50, 20 and 17%
yield. More importantly, condensation of 2-[(2,4,6-trimethylphenyl)sulfonyl]aminophenol 2c
with carbonates 1a and 1c, in the presence of the same ligand, gave the 3,4-dihydro-2-vinyl-1,4-
benzoxazine 3c with quite different enantioselectivities and yields: in the presence of carbonate
1a, compound 3c was obtained with 64% e.e. and 52% yield (Table 1, entry 7), whereas with
carbonate 1c, 3c was obtained with quite low e.e. (only 18%) and chemical yield (12%) (Table
1, entry 8).
Finally, condensation of N-benzyl-2-aminophenol 2d with carbonates 1a or 1c in the presence
of (S)-MeOBiphep gave 2-vinyl-1,5-benzoxazine 3d with 38 and 46% e.e. (Table 1, entries 9 and
10).
A plausible reaction pathway for the cyclization is shown in Scheme 2. The first nucleophilic
allylic substitution on the p-allyl palladium complex generated by the reaction of the biscarbon-
ate with a palladium(0) species takes place with the hydroxyl group in 2a or the amino group
in 2b–c to give an allylic carbonate 4. This intermediate reacts with palladium(0) to give a new
p-allyl palladium intermediate 5; intramolecular attack of the hydroxyl or the amino group on
this p-allyl produces the cyclized compound 3.
Scheme 2.
One of the problems in this cyclization sequence is the determination of the enantioselective
step. If the interconversion between the four possible diastereoisomeric p-allyl palladium
complexes 5 is fast compared with the cyclization reaction, then the enantioselectivity will be
determined by the stabilities of these diastereomeric complexes and their relative rate of
cyclization. However, if this interconversion is slow compared with the cyclization reaction, then
the enantioselectivity could be determined by the ability of the catalyst to differentiate the two
enantiotopic faces of compound 4. However, this implies that the palladium dissociates from the
double bond to give free compound 4 as an intermediate, before association and oxidative
addition to give intermediates 5. If the dissociation of the palladium from the double bond of
intermediate 4 is slow compared with the oxidative addition of the carbonate, then the
enantioselectivity could be determined, at least partly, by the discrimination of the double bond
for carbonate 1b. The low chemical yields observed starting from 1c could be due to some
kinetic resolution.

3564
M. Massacret et al. / Tetrahedron: Asymmetry 11 (2000) 3561–3568
Since the same enantioselectivity was obtained in the cyclization of benzene-1,2-diol 2a with
carbonates 1a–c whatever the carbonate used, this indicates that intermediate 4a is probably the
same, starting from each carbonate, and that the equilibrium between the diastereomeric
complexes is fast compared with the cyclization reaction in this case.15 The same behavior was
observed for the condensation of N-benzyl-2-aminophenol 2d with carbonates 1a and 1c.
Conversely, quite different enantioselectivities were obtained in the condensation of N,N-
bis(p-tolylsulfonyl)-o-phenylenediamine 2b or 2-[(2,4,6-trimethylphenyl)sulfonyl]aminophenol 2c
with these carbonates; this is an indication that in these cases the enantioselectivity is probably
not only due to the differentiation of the two enantiotopic faces of intermediates 4b–c by the
chiral catalyst, and that the structure of the starting biscarbonate as well as the sulfonyl group
probably has some influence on both the enantioselectivity and the chemical yield of the
cyclization reaction.
In order to have more information about the reasons for these quite different enantioselectiv-
ities, we prepared the intermediates 4b–c of configuration Z and E, and submitted them to the
cyclization conditions.
Compounds 4b–c were prepared via a Mitsunobu coupling reaction between the monocarbon-
ate of butene-1,4-diol of configuration E or Z and the corresponding 2-(arylsulfonyl-
amino)phenol 2b, or bis(arylsulfonylamino)benzene 2c, respectively (Scheme 3). No isomeriza-
tion of the double bond of the olefins was observed. The stereochemistry of this double bond
was unambiguously assigned by 13C NMR spectroscopy. For compound 4b, we observed the
ꢀOCH2ꢀ signals at l 62.6 and 66.9 ppm for the (Z)- and (E)-isomers, respectively, and the
ꢀNCH2ꢀ signals at l 48.8 and 53.6 ppm, respectively, in agreement with this stereochemistry.
The ꢀOCH2ꢀ signals for (Z)-4c and (E)-4c are at l 63.5 and 67.1 ppm, and the ꢀNCH2ꢀ signals
appeared at l 48.2 and 52.4 ppm, respectively.
Scheme 3. b: Y=Z=NSO2C6H4-p-CH3; c: Y=NSO2C6H2-2,4,6-triCH3; Z=O
The cyclization reaction was carried out as previously described and the results are summa-
rized in Table 2. The cyclization of compounds (E)-4b and (Z)-4b gave 1,2,3,4-tetrahydro-2-
vinylquinoxaline 3b in 45 and 17% yield, respectively, with enantioselectivities of up to 18% (R)
Table 2
Palladium-catalyzed cyclization of compounds 4a
Entry
Compound
Product
Ligand
Yieldb (%)
E.e.c % (config.)
1
2
3
4
(E)-4b
(Z)-4b
(E)-4c
(Z)-4c
3b
3b
3c
3c
(S)-MeOBiphep
(S)-MeOBiphep
(S)-MeOBiphep
(S)-MeOBiphep
45
17
53
21
18 (R)
9 (R)
16 (S)
28 (R)
a All entries carried out under N2 for 24 h in THF at 25°C in the presence of a palladium catalyst prepared in situ
by mixing Pd2(dba)3 (2.5 mol% Pd) and the chiral ligand (Pd]/[P]=1:2).
b Isolated yields after silica gel chromatography and not optimized.
c Determined by HPLC analysis (Chiralpak AD) for 3b–c.

M. Massacret et al. / Tetrahedron: Asymmetry 11 (2000) 3561–3568
3565
and 9% (R), respectively (Table 2, entries 1 and 2); it is to be noticed that these enantioselectiv-
ities are lower than those obtained by the direct condensation of N,N-bis(p-tolylsulfonyl)-o-
phenylenediamine 2b with carbonates 1a–c. When the cyclization was performed on compounds
(E)-4c and (Z)-4c, 3,4-dihydro-2-vinyl-1,4-benzoxazine 3c was obtained in 53 and 21% yield,
respectively (Table 2, entries 3 and 4); however, the (E) isomer gave the (S) enantiomer in 16%
e.e., although the (Z) isomer gave the (R) enantiomer in 28% e.e.
The results obtained starting from intermediates 4 deserve some comments. In the case of
intermediates 4b and 4c, the cyclization of the two stereoisomers led to different enantioselectiv-
ities, and even for 4c, to the opposite configuration for the cyclized product 3c. So, in these
cases, the asymmetric induction derives from the chiral recognition of the enantiotopic faces of
the substrate 4b or 4c during the formation of the p-allyl palladium complex; moreover, the
interconversion of the diastereoisomeric p-allyl palladium complexes is necessarily slow com-
pared with the cyclization reaction. We also noticed that the intermolecular reaction between
2b–c and 1 leading to 3b–c gave higher enantioselectivities in the (R) enantiomer than starting
from the intermediate 4b–c. This difference in enantioselectivity implies that, in these two cases,
there is probably no dissociation of the palladium complex, after the first nucleophilic allylic
substitution of the amino group on the p-allyl palladium complex generated by the reaction of
the biscarbonate with a palladium(0) species. This very low interconversion between the
diastereoisomeric p-allyl palladium complexes as well as the non-dissociation of the palladium
complex from intermediate 4 is probably due to the presence of the sulfonyl group, which could
coordinate to the palladium complex. The same enantioselectivities obtained in the condensation
of N-benzyl-2-aminophenol 2d are in agreement with this hypothesis.
3. Conclusion
In conclusion, we have shown that the asymmetric cyclization between various allylic
biscarbonates and various aminophenols or diaminobenzenes depends strongly on the stereo-
chemistry of the biscarbonate as well as on the substituents of the nitrogen. We assumed that
the sulfonyl groups probably coordinate to the palladium complex during the catalytic cycle,
and that there is no common intermediate for these cyclizations.
4. Experimental
4.1. General
1H NMR (200 MHz) and 13C NMR (50 MHz) spectra were obtained using a Bru¨ker AM 200
spectrometer. Chemical shifts are reported on the l scale with reference to tetramethylsilane as
an internal standard. Silica gel column chromatography was carried out using Merck silica gel
60 Gerudan (40–63 mm). GC analyses were recorded with a Shimadzu capillary gas chromatog-
raph equipped with a Chiraldex™, type B-PH (30 m×0.32 mm) capillary column. Analytical
HPLC was performed using a Shimadzu instrument with a UV detector and equipped with a
Chiralpak AD column (eluent: n-hexane/2-propanol, 80:20). Reactions involving organometallic
catalysis were carried out in Schlenk tubes under an inert atmosphere. Tetrahydrofuran was
distilled from sodium/benzophenone. The following compounds were prepared according to

3566
M. Massacret et al. / Tetrahedron: Asymmetry 11 (2000) 3561–3568
literature procedures: (Z)- and (E)-1,4-bis(methoxycarbonyloxy)but-2-ene 1a and 1b,16 3,4-bis-
(methoxycarbonyloxy)but-1-ene 1c,16 N,N-bis(p-tolylsulfonyl)-o-phenylenediamine 2b,17 N-
benzyl-2-aminophenol
2d.18
(S)-6,6%-Dimethoxy-2,2%-bis(diphenylphosphanyl)-1,1%-biphenyl
(MeOBiphep) was a gift from Dr. Schmid (Hofmann La Roche, Basle, Switzerland).
4.2. 2-[(2,4,6-Trimethylphenyl)sulfonyl]aminophenol 2c
To a solution of 2-aminophenol (545 mg, 5 mmol) and C5H5N (435 mg, 5.5 mmol) in CH2Cl2
(5 mL) at 0°C was slowly added 2,4,6-trimethylphenylsulfonyl chloride (1.2 g, 5.5 mmol). After
24 h at room temperature, H2O (2 mL) was added; separation of the organic phase followed by
evaporation of the solvent and recrystallization in ethanol afforded 658 mg of compound 2c
1
(yield 45%). Mp: 112–113°C. H NMR (CDCl3): l 2.23 (s, 3H, Me), 2.58 (s, 6H, Me), 6.72–6.84
(m, 2H, Har), 6.90–6.98 (m, 3H, Har), 7.19 (dd, J 7.9 and 1.6 Hz, 1H, Har), 8.31 (bs, 2H, OH,
NH). 13C (CDCl3): l 21.1 (Me), 23.2 (Me), 117.0, 121.0, 122.7, 125.5, 128.3, 132.2, 132.5, 139.8,
143.1 and 151.0 (Car). Anal. calcd for C15H17NO3S (294.37): C, 61.84; H, 5.88. Found: C, 61.56;
H, 5.83.
4.3. General procedure for the preparation of compounds 4
To a mixture of 2b–c (0.69 mmol), (Z)- or (E)-4-(methoxycarbonyloxy)but-2-enol (100 mg,
0.69 mmol), and diethyl azodicarboxylate (120 mg, 0.69 mmol) in THF (8 mL) was added at 0°C
triphenylphosphine (181 mg, 0.69 mmol). After being stirred for 12 h at room temperature, the
solvent was evaporated. Chromatography of the residue on silica gel gave compound 4.
4.3.1. (Z)-4-[N-Tosyl-N-(2-tosylaminophenyl)]amino-1-(methoxycarbonyloxy)but-2-ene (Z)-4b
1
Yield 49%; Rf 0.62 (eluent: petroleum ether/ethyl acetate, 1:1). H NMR (CDCl3): l 1.6 (bs,
1H, NH), 2.38 (s, 3H, Me), 2.44 (s, 3H, Me), 3.74 (s, 3H, OMe), 4.22–4.36 (m, 4H, CH2),
5.20–5.42 (m, 2H, ꢀCHꢁ), 6.17–7.29 (m, 4H, Har), 7.45 (d, J 8.3 Hz, 2H, Har), 7.62 (d, J 8.3 Hz,
2H, Har), 7.83 (d, J 8.3 Hz, 4H, Har). 13C (CDCl3) l 21.6 (Me), 48.8 (CH2N), 54.9 (OMe), 62.6
(CH2O), 120.2, 123.9, 127.4, 127.8, 128.3, 128.7, 129.6, 129.7, 133.4, 136.9, 137.1, 144.0, 144.6
(ꢀCHꢁ, Car), 155.5 (CO).
4.3.2. (E)-4-[N-Tosyl-N-(2-tosylaminophenyl)]amino-1-(methoxycarbonyloxy)but-2-ene (E)-4b
1
Yield 51%; Rf 0.62 (eluent: petroleum ether/ethyl acetate, 1:1). H NMR (CDCl3) l 1.5 (bs,
1H, NH), 2.39 (s, 3H, Me), 2.44 (s, 3H, Me), 3.75 (s, 3H, OMe), 4.05–4.37 (m, 4H, CH2),
5.32–5.46 (m, 2H, ꢀCHꢁ), 6.17–7.29 (m, 4H, Har), 7.45 (d, J 8.3 Hz, 2H, Har), 7.62 (d, J 8.3 Hz,
2H, Har), 7.83 (d, J 8.3 Hz, 4H, Har). 13C (CDCl3) l 21.5 (Me), 21.6 (Me), 53.6 (CH2N), 54.9
(OMe), 66.9 (CH2O), 120.1, 123.8, 127.5, 128.2, 128.4, 128.6, 129.3, 129.5, 129.7, 133.7, 137.0,
144.0, 144.5 (ꢀCHꢁ, Car), 155.4 (CO).
4.3.3. (Z)-4-[N-(2-Hydroxyphenyl)-N-(2,4,6-trimethylphenyl)sulfonyl]amino-1-(methoxycarbonyl-
oxy)but-2-ene (Z) 4c
1
Yield 42%; Rf 0.31 (eluent: petroleum ether/ethyl acetate, 3:1). H NMR (CDCl3) l 2.20 (s,
3H, Me), 2.32 (s, 6H, 2×Me), 3.67 (s, 3H, OMe), 4.33–4.47 (m, 4H, CH2), 5.57–5.60 (m, 2H,

M. Massacret et al. / Tetrahedron: Asymmetry 11 (2000) 3561–3568
3567
ꢀCHꢁ), 6.57–6.63 (m, 2H, Har), 6.80–6.92 (m, 3H, Har), 7.07–7.28 (m, 1H, Har), 7.19 (s, 1H,
OH). 13C (CDCl3) l 21.7 (Me), 23.8 (2×Me), 48.2 (CH2N), 55.6 (OMe), 63.5 (CH2O), 118.9,
121.8, 125.5, 128.7, 129.4, 131.0, 131.3, 132.8, 141.1, 143.9, 149.0, 155.7 (ꢀCHꢁ, Car), 156.2 (CO).
Anal. calcd for C21H25NO6S (419.49): C, 60.13; H, 6.01. Found C, 59.65; H, 6.13.
4.3.4. (E)-4-[N-(2-Hydroxyphenyl)-N-(2,4,6-trimethylphenyl)sulfonyl]amino-1-(methoxycarbonyl-
oxy)but-2-ene (E) 4c
1
Yield 45%; Rf 0.31 (eluent: petroleum ether/ethyl acetate, 3:1). H NMR (CDCl3) l 2.26 (s,
3H, Me), 2.39 (s, 3H, Me), 2.52 (s, 3H, Me), 3.75 (s, 3H, OMe), 4.33–4.47 (m, 4H, CH2),
5.58–5.74 (m, 2H, ꢀCHꢁ), 6.47–7.33 (m, 7H, OH, Har). 13C (CDCl3) l 21.0 (Me), 23.0 (2×Me),
52.4 (CH2N), 54.9 (OMe), 67.1 (CH2O), 116.6, 120.7, 122.9, 124.8, 127.7, 128.8, 130.4, 132.0,
139.6, 140.3, 142.8, 143.2, 150.4 (ꢀCHꢁ, Car), 154.8 (CO).
4.4. General procedure for the cyclization reaction
A solution of tris(dibenzylideneacetone)dipalladium (5.8 mg, 6.3×10−3 mmol) and the chiral
ligand (12.5×10−3 mmol) in 3 mL of THF was stirred at room temperature for 30 min. To the
solution were added the substrate 2 (0.25 mmol) and the biscarbonate 1 (0.35 mmol), or
compound 4 (0.25 mmol), dissolved in 3 mL of THF. The mixture was stirred at room
temperature for 24 h. The solution was concentrated under reduced pressure and the residue was
chromatographed on silica gel to give the cyclized product 3. The enantioselectivity was
determined by GPC analysis using a chiral stationary phase column Chiraldex™ type B-PH (30
m×0.32) at 85°C for compound 3a,9 by HPLC analysis with a chiral stationary phase column
(Chiralpax AD, eluent: n-hexane/2-propanol, 80:20) for compounds 3b–c, according to the
procedure previously described.12,14
4.4.1. 4-(2,4,6-Trimethylphenyl)sulfonyl-2-vinyl-3,4-dihydro-2H-1,4-benzoxazine 3c
Oil; Rf 0.77 (eluent: petroleum ether/ethyl acetate, 4:1); [h]2D0=−27.8 (c 2, CHCl3) (64% e.e.).
1H NMR (CDCl3) l 2.33 (s, 3H, Me), 2.57 (s, 6H, Me), 3.12 (dd, J 14.3 and 9.6 Hz, 1H, H-3a),
4.12 (dd, J 14.3 and 2.5 Hz, 1H, H-3eq), 4.50–4.58 (m, 1H, H-2), 5.34 (dd, J 10.5 and 1.1 Hz,
1H, ꢁCH2),), 5.43 (dd, J 17.3 and 1.4 Hz, 1H, ꢁCH2), 5.87 (ddd, J 17.3, 10.5 and 5.9 Hz, 1H,
ꢀCHꢁ), 6.74–6.82 (m, 1H, Har), 6.92–7.09 (m, 5H, Har). 13C (CDCl3) l 21.8 (Me), 23.7 (2×Me),
48.0 (CH2N), 74.7 (CHO), 118.4, 119.6, 121.3, 124.5, 124.9, 126.9, 133.2, 134.4, 134.5, 140.9,
144.1, 148.1 (ꢀCHꢁCH2, Car). Anal. calcd for C19H21NO3S (343.37): C, 66.44; H, 6.16. Found:
C, 66.21; H, 6.35.
Acknowledgements
One of us (M. M.) thanks the MESR for a fellowship.
References
1. (a) Oppolzer, W. Angew. Chem., Int. Ed. Engl. 1989, 28, 38–52. (b) Oppolzer, W. In Comprehensive Organic
Synthesis; Trost, B. M.; Fleming, I.; Paquette, L. A., Eds.; Pergamon Press: Oxford, 1991; Vol. 5, pp. 29–61.

3568
M. Massacret et al. / Tetrahedron: Asymmetry 11 (2000) 3561–3568
2. Grigg, R. J. Heterocycl. Chem. 1994, 31, 631–639.
3. De Meijere, A.; Meyer, F. E. Angew. Chem., Int. Ed. Engl. 1994, 33, 2379–2411.
4. Thebtaranonth, C.; Thebtaranonth, Y. Cyclization Reactions; CRC Press: London, 1994; pp. 255–330.
5. Tietze, L. F. Chem. Ind. (London) 1995, 453–457.
6. (a) Heumann, A.; Reglier, M. Tetrahedron 1995, 51, 975–1015. (b) 1996, 52, 9289–9346.
7. Negishi, E.; Coperet, C.; Ma, S.; Liou, S. Y.; Lin, F. Chem. Rev. 1996, 96, 365–393.
8. Ojima, I.; Tzamarioudaki, M.; Li, Z.; Donovan, R. J. Chem. Rev. 1996, 96, 635–662.
9. (a) Massacret, M.; Goux, C.; Lhoste, P.; Sinou, D. Tetrahedron Lett. 1994, 35, 6093–6096. (b) Massacret, M.;
Lhoste, P.; Lakhmiri, R.; Parella, T.; Sinou, D. Eur. J. Org. Chem. 1999, 2665–2673.
10. Uozomi, T.; Tanahashi, A.; Hayashi, T. J. Org. Chem. 1993, 58, 6826–6832.
11. Yamazaki, A.; Achiwa, I.; Achiwa, K. Tetrahedron: Asymmetry 1996, 7, 403–406.
12. Lhoste, P.; Massacret, M.; Sinou, D. Bull. Soc. Chim. Fr. 1997, 134, 343–347.
13. Yamazaki, A.; Achiwa, K. Tetrahedron: Asymmetry 1995, 6, 1021–1024.
14. Massacret, M.; Lhoste, P.; Sinou, D. Eur. J. Org. Chem. 1999, 129–134.
15. (a) Trost, B. M.; Krische, M. J.; Radinov, R.; Zanoni, G. J. Am. Chem. Soc. 1996, 118, 6297–6298. (b) Pfaltz,
A.; Roch, G. Tetrahedron: Asymmetry 1996, 7, 2213–2216. (c) Trost, B. M.; Asakawa, N. Synthesis 1999,
1491–1494.
16. Tsuda, T.; Kioy, T.; Saegusa, T. J. Org. Chem. 1990, 55, 3388–3390.
17. Amundsen, L. H. J. Am. Chem. Soc. 1937, 59, 1466–1467.
18. Boothroy, B.; Clark, E. R. J. Chem. Soc. 1953, 1499–1504.
.