Novel conversion of 1,2-disubstituted cis-epoxides to one-carbon homologated allylic alcohols using dimethylsulfonium methylide

Article abstract of DOI:10.1021/ol016782y

matrix presented The treatment of cis-epoxides with an excess of dimethylsulfonium methylide affords one-carbon homologated allylic alcohols in good to excellent yields.

Full text of DOI:10.1021/ol016782y

Supporting Information
Novel Conversion of 1,2-Disubstituted cis-Epoxides to One Carbon Homologated Allylic Alcohols
Using
Dimethyl Sulfonium Methylide
*
Lilian Alcaraz , Andrew Cridland, Elizabeth Kinchin
Department of Medicinal Chemistry, AstraZeneca R&D Charnwood, Bakewell Road, Loughborough
LE12 5HY, Leics
Lilian.Alcaraz@astrazeneca.com
General
n
BuLi solutions and anhydrous THF were purchased from Aldrich. All reactions were conducted in heat-
dried glassware under an atmosphere of high purity nitrogen. Solvent removal was carried out using a rotary
1
evaporator connected to a dry ice condenser. Column chromatography was performed on silica cartridges. H
1
3
1
13
1
and C NMR spectra were obtained from either a 300 MHz ( H: 300 MHz, C: 75 MHz) or 400 MHz ( H: 400
1
3
1
13
MHz, C: 100 MHz) Varian Unity Inova spectrometer. H and C shifts are given in ppm, δ scale and are
measured relative to tetramethylsilane as standard. Mass spectra were recorded on a Hewlett Packard HP 6890
or HP5973 MSD instrument. Optical rotation were recorded on an Optical Activity Ltd AA-1000 polarimeter.
1
3-methyl-3-buten-2-ol
OH
1
Colorless liquid; 91% yield; H NMR (300 MHz, CDCl ): δ 4.97 (s, 1H, C=CHH), 4.80 (s, 1H, C=CHH),
3
ppm
4
.25 (apparent quintet, 1H, J = 5.8 Hz, CHOH), 1.75 (s, 3H, CCH ), 1.45 (d, 1H, J = 4.0 Hz, OH), 1.29 (d, 3H, J
3
1
3
=
6.5 Hz, CHCH ); C NMR (CDCl , 100 MHz): δ 148.9, 109.5, 71.5, 21.7, 17.8.
3
3
ppm
In agreement with reference 1.
8-methylene tetradecan-7-ol
OH
1
Colorless oil; 88% yield; H NMR (300 MHz, CDCl ): δ 5.00 (s, 1H, C=CHH), 4.83 (d, 1H, J = 1.3 Hz,
3
ppm
C=CHH), 4.06 (dt, 1H, J = 7.2 and 4.7 Hz, CHOH), 2.02 (apparent nontuplet, 2H, J = 8.0 Hz, CH C=CH ), 1.62-
2
2
1
3
1
1
2
.40 (m, 6H, 3CH ), 1.34-1. 29 (m, 12H, 6CH ), 0.89-0.86 (m, 6H, 2CH ); C NMR (CDCl , 75 MHz): δ 152.4,
2
2
3
3
ppm
09.0, 75.5, 35.5, 31.8, 31.76, 31.4, 29.2(2C), 28.0, 25.7, 22.6(2C), 14.1(2C). MS (EPCI) m/z (rel %) 226 (1),
08 (1), 141 (54), 71 (100). Anal. Calc. for C H O C, 79.58; H, 13.36. Found: C, 79.65; H, 13.39.
1
5
30

1-(benzyloxy)-3-[(benzyloxy)methyl]-3-buten-2-ol
OH
O
O
1
Colorless oil; 90% yield; H NMR (300 MHz, CDCl ): δ 7.38-7.28 (m, 10H, Ar-H), 5.32 (s, 1H, C=CHH),
3
ppm
5
.24 (s, 1H, C=CHH), 4.56 (s, 2H, ArCH ), 4.49 (s, 2H, ArCH ), 4.45 (app. quint., 1H, J =4.1 Hz, CHOH), 4.06 (s,
2
2
2
H, CH C=CH ), 3.64 (dd 1H, J = 3.6 and 9.5 Hz, CHHCHOH), 3.49 (dd, 1H, J = 9.5 and 8.7 Hz, CHHCHOH),
2
2
1
3
2
.70 (d, 1H, J = 2.4 Hz, OH); C NMR (CDCl , 75.4 MHz): δ 144.4, 138.0, 137.9, 128.5 (2C), 128.4 (2C),
3
ppm
1
27.8 (3C), 127.8 (2C), 127.7, 114.9, 73.5, 73.4, 72.3, 72.0, 71.3. HRMS Calcd. for C H O m/z 299.1647,
1
9
23
3
found: 299.1654.
2
2-methylene cyclopentanol
OH
1
Colorless oil; 91% yield; H NMR (300 MHz, CDCl ): δ 5.14 (d, 1H, J = 2.4 Hz, C=CHH), 5.02 (d, 1H, J
3
ppm
=
2.4 Hz, C=CHH), 4.42 (app. q, 1H, J = 4.8 Hz, CHOH), 2.56-2.41 (m, 1H, CHHC=CH ), 2.38-2.25 (m, 1H,
2
1
3
CHHC=CH ), 2.01-1.75 (m, 2H, CH CHOH), 1.74-1.50 (m, 2H, CH CH CH ), 1.42 (d, 1H, J=5.4Hz, OH); C NMR
2
2
2
2
2
(
CDCl , 100 MHz): δ 155.3, 107.5, 75.1, 35.6, 30.3, 21.7.
3
ppm
In agreement with reference 2.
Tetrahydro-4-methylene-3-furanol
O
OH
1
Colorless oil; 92 % yield; H NMR (300 MHz, CDCl ): δ 5.35-5.33 (m, 1H, C=CHH), 5.15 (app. q, 1H, J
3
ppm
=
2.0 Hz, C=CHH), 4.62-4.56 (m, 1H, CHOH), 4.50 (dt, 1H, J = 13.5 and 2.0 Hz, CHHC=CH ), 4.28 (dt, 1H, J =
2
1
3.5 and 2.4 Hz, CHHC=CH ), 3.93 (dd, 1H, J = 5.0 and 9.9 Hz, CHHCHOH), 3.78 (dd, 1H, J = 9.9 and 3.3 Hz,
2
1
3
CHHCHOH), 1.74 (d, 1H, J = 6.5 Hz, OH); C NMR (CDCl , 75 MHz): δ 150.4, 107.9, 75.1, 72.7, 70.0. Anal.
3
ppm
Calc. for C H O C, 59.98; H, 8.05. Found: C, 60.14; H, 8.21.
5
8
2

tert-butyl 3-hydroxy-4-methylene-1-pyrrolidinecarboxylate
O
N
O
OH
1
Colorless oil; 83% yield; H NMR (300 MHz, D -DMSO): δ 5.34 (d, 1H, J = 5.2 Hz, OH), 5.13 (s, 1H,
6
ppm
C=CHH), 5.05 (s, 1H, C=CHH), 4.44 (app. q, 1H, J = 6.5 Hz, CHOH), 3.94-3.82 (m, 2H, CH C=CH ), 3.57-3.51
2
2
1
3
o
(
m, 1H, CHHCHOH), 3.04-2.98 (m, 1H, CHHCHOH), 1.40 (s, 9H, C(CH ) ); C NMR (D -DMSO (90 C), 75
3
3
6
MHz): δppm 153.7, 148.6, 107.3, 78.5, 70.3, 53.2, 48.8, 28.2(3C). MS (EPCI) m/z (rel %) 199 (1), 143 (22), 126
(
19), 82 (19), 57 (100). Anal. Calc. for C H NO C, 60.28; H, 8.60; N, 7.03. Found: C, 60.11; H, 8.64; N, 6.99.
1
0
17
3
3
2-methylene cyclohexanol
OH
1
Colorless oil; 86% yield; H NMR (300 MHz, CDCl ): δ 4.89 (s, 1H, C=CHH), 4.76 (s, 1H, C=CHH),
3
ppm
4
.09-4.07 (m, 1H, CHOH), 2.41-2.39 (m, 1H, CH ), 2.03-2.00 (m, 2H, CH ), 1.83-1.79 (m, 1H, CH ), 1.68-1.64
2
2
2
1
3
(
m, 1H, CH ), 1.55 (d, 1H, J = 4.2 Hz, OH), 1.51-1.27 (m, 3H, CH ); C NMR (CDCl , 100 MHz): δ 151.6,
2
2
3
ppm
105.0, 72.6, 36.6, 33.5, 27.7, 23.7. MS (EPCI) m/z (rel %) 112 (54), 97 (94), 83 (100).
In agreement with reference 3.
6-methylene-1,3-dioxepan-5-ol
O
O
OH
1
Colorless oil; 81% yield; H NMR (300 MHz, CDCl ): δ 5.16 (s, 1H, C=CHH), 5.04 (s, 1H, C=CHH),
3
ppm
4
.99 (d, 1H, J = 6.7 Hz, OCHHO), 4.64 (d, 1H, J = 6.7 Hz, OCHHO), 4.54 (d, 1H, J = 14.0 Hz, CHHC=CH ), 4.33
2
(
bd, 1H, J = 4.0 Hz, CHOH), 4.26 (dd, 1H, J = 1.5 and 14.0 Hz, CHHC=CH ), 3.95 (dd, 1H, J = 4.0 and 11.9 Hz,
2
1
3
CHHCHOH), 3.66 (dd, 1H, J = 1.7 and 11.9 Hz, CHHCHOH), 2.66 (bs, 1H, OH); C NMR (CDCl , 75 MHz): δ
3
ppm
1
48.1, 114.3, 95.6, 74.6, 72.7, 70.5. Anal. Calc. for C H O C, 55.37; H, 7.74. Found: C, 55.48; H, 7.79.
6
10
3
4
1,2-dihydro-2-anthracenol
OH

1
White crystals; 75% yield; H NMR (300 MHz, CDCl ): δ 7.79-7.73 (m, 2H, Ar-H), 7.62 (s, 1H, Ar-H),
3
ppm
7.56 (s, 1H, Ar-H), 7.48-7.38 (m, 2H, Ar-H), 6.73 (d, 1H, J = 9.6 Hz, ArCH=CH), 6.21 (dd, 1H, J = 4.2 and 9.6
Hz, ArCH=CH), 4.60 (app. quint., 1H, J = 6.0 Hz, CHOH), 3.20 (d, 2H, J = 6.0 Hz, CH ).
2
See reference 4.
4-(benzyloxy)-2-methylene-1,3-butanediol (±-1) and 3-[(benzyloxy)methyl]-3-butene-1,2-diol (±)-2
OH
OH
OH
BnO
+
BnO
OH
±)-1
(
3:1
(±)-2
1
Inseparable mixture of isomers in ratio 3:1 (based on crude NMR); 85% yield; 1: H NMR (300 MHz,
CDCl ): δ 7.37-7.29 (m, 5H, Ar-H), 5.19 (s, 1H, C=CHH), 5.17 (s, 1H, C=CHH), 4.59 (s, 2H, PhCH ), 4.55-4.45
3
ppm
2
(
m, 1H, CHOH), 4.21-4.18 (m, 2H, CH OH), 3.63 (dd, 1H, J = 9.6 and 3.8 Hz, BnOCHH), 3.55 (dd, 1H, J = 9.6
2
1
and 7.7 Hz, BnOCHH), 2.73 (d, 1H, J = 3.8 Hz, OH), 2.21 (t, 1H, J = 6.2 Hz, OH); and 2: H NMR (300 MHz,
CDCl ): δ 7.37-7.29 (m, 5H, Ar-H), 5.31 (s, 1H, C=CHH), 5.25 (s, 1H, C=CHH), 4.54 (s, 2H, PhCH ), 4.33
3
ppm
2
(
app. q, 1H, J = 6.0 Hz, CHOH), 4.11 (dd, 1H, J = 11.7 and 1.8, CHHC=CH ), 4.03 (dd, 1H, J = 11.7 and 1.8 Hz,
2
CHHC=CH ), 3.73-3.64 (m, 2H, CH OH), 2.66 (d, 1H, J = 5.6 Hz, OH), 2.36 (t, 1H, J = 6.0 Hz, OH). HRMS
2
2
Calcd. for C H O m/z 209.1178, found: 209.1164.
1
2
17
3
1-(benzyloxy)-3-[(trityloxy)methyl]-3-buten-2-ol 3 and 3-[(benzyloxy)methyl]-1-(trityloxy)-3-buten-2-ol 4
OH
OTr
OTr
BnO
BnO
+
1:5
OH
3
4
Two isomers in ratio 1:5 (based on crude NMR). Purification yielded two thick yellow oils:
1
3
(11% yield): H NMR (300 MHz, CDCl ): δ 7.42 (d, 6H, J = 8.4 Hz, Ar-H), 7.31-7.24 (m, 14H, Ar-H),
3
ppm
5
.36 (s, 1H, C=CHH), 5.30 (s, 1H, C=CHH), 4.48 (s, 2H, PhCH ), 4.41-4.37 (m, 1H, CHOH), 3.68 (d, 1H, J =
2
1
1.0 Hz, CHHC=CH ), 3.61 (d, 1H, J = 11.0 Hz, CHHC=CH ), 3.50 (dd, 1H, J = 9.9 and 3.7 Hz, BnOCHH), 3.36
2
2
1
3
(
dd, 1H, J = 9.9 and 7.9 Hz, BnOCHH), 2.57 (d, 1H, J = 3.8 Hz, OH); C NMR (CDCl , 100 MHz): δ
144.1,
3
ppm
1
43.9 (3C), 138.9, 128.6 (6C), 128.4 (2C), 127.8 (6C), 127.7 (2C), 127.1, 127.0 (3C), 113.1, 87.2, 73.4, 73.2,
1.9, 64.9. Anal. Calc. for C H O C, 82.64; H, 6.71. Found: C, 82.58; H, 6.72.
7
3
1
30
3

1
4
(57% yield): H NMR (300 MHz, CDCl ): δ 7.42 (d, 6H, J = 8.4 Hz, Ar-H), 7.31-7.20 (m, 14H, Ar-H),
3
ppm
5
.25 (s, 1H, C=CHH), 5.19 (s, 1H, C=CHH), 4.37 (s, 2H, PhCH ), 4.38-4.32 (m, 1H, CHOH), 3.94 (s, 2H,
2
BnOCH ), 3.32 (dd, 1H, J = 9.4 and 4.4 Hz, CHHOTr), 3.24 (dd, 1H, J = 9.4 and 7.1 Hz, CHHOTr), 2.71 (d, 1H,
2
1
3
J = 4.6 Hz, OH); C NMR (CDCl , 75 MHz): δ 144.5, 143.8 (3C), 137.9, 128.7 (6C), 128.4 (2C), 127.9 (6C),
3
ppm
1
27.7, (2C), 127.6, 127.1 (3C), 114.9, 86.8, 72.6, 72.3, 71.3, 66.7. Anal. Calc. for C H O C, 82.64; H, 6.71.
3
1
30
3
Found: C, 82.73; H, 6.78.
2-({[tert-butyl(dimethyl)silyl]oxy}methyl)-1-penten-3-ol 5 and 1-{[tert-butyl(dimethyl)silyl]oxy}-3-ethyl-3-
buten-2-ol 6
OH
OTBS
OTBS
+
OH
5
1:2
6
Purification yielded two colourless oils in ratio 1:2 (based on crude NMR):
1
5
(24% yield): H NMR (300 MHz, CDCl ): δ 5.10 (s, 1H, C=CHH) 5.05 (s, 1H, C=CHH), 4.30 (d, 1H, J
3
ppm
=
13.1, CHHO), 4.19 (d, 1H, J = 13.1 Hz, CHHO), 4.08 (dt, 1H, J = 5.4 and 6.0 Hz, CHOH), 2.43 (d, 1H, J = 5.4
Hz, OH), 1.65 (app. quintet, 2H, J = 7.3 Hz, CH CH ), 0.91 (s, 9H, C(CH ) ), 0.85 (t, 3H, J = 6.4 Hz, CH ), 0.09
2
3
3
3
3
1
3
(
s, 6H, Si(CH ) ; C NMR (CDCl , 100 MHz): δ 149.2, 111.3, 75.7, 64.5, 28.5, 25.8(3C), 18.2, 10.0, -5.5(2C).
3
2
3
ppm
Anal. Calc. for C H O Si C, 62.55; H, 11.37. Found: C, 62.76; H, 11.25.
1
2
26
2
1
6
(53% yield): H NMR (300 MHz, CDCl ): δ 5.10 (s, 1H, C=CHH), 4.92 (s, 1H, C=CHH), 4.14 (dt, 1H,
3
ppm
J = 8.2 and 4.1 Hz, CHOH), 3.70 (dd, 1H, J = 10.0 and 3.5 Hz, CHHCHOH), 3.46 (dd, 1H, J = 10.0 and 8.3 Hz,
CHHCHOH), 2.64 (d, 1H, J = 2.9 Hz, OH), 2.18-1.95 (m, 2H, CH CH ), 0.91 (s, 9H, C(CH ) ), 0.85 (t, 3H, J = 6.3
2
3
3 3
1
3
Hz, CH ), 0.10 (s, 3H, SiCH ), 0.08 (s, 3H, SiCH ). C NMR (CDCl , 100 MHz): δ 150.8, 108.5, 74.1, 68.7,
3
3
3
3
ppm
2
5.0, 25.8(3C), 18.3, 12.7, -5.5(2C). Anal. Calc. for C H O Si C, 62.55; H, 11.37. Found: C, 62.5; H, 11.36.
1
2
26
2
2-[(trityloxy)methyl]-1-penten-3-ol (7) and 3-ethyl-1-(trityloxy)-3-buten-2-ol 8
OH
OTr
OTr
+
1:3
OH
7
8
Purification yielded two colourless oils in ratio 1:3 (based on crude NMR):
1
7
(20 yield%): H NMR (300 MHz, CDCl ): δ 7.47 (d, 6H, J = 10 Hz, Ar-H), 7.33-7.22 (m, 9H, Ar-H),
3
ppm
5.30 (d, 1H, J = 1.3 Hz, C=CHH), 5.17 (s, 1H, C=CHH), 4.05 (dt, 1H, J = 5.0 and 6.0 Hz, CHOH), 3.69 (bs, 2H,
CH OTr), 2.07 (d, 1H, J = 5.0 Hz, OH), 1.47 (apparent quin, 2H, J = 7.4 Hz, CH CH ), 0.84 (t, 3H, J = 7.4 Hz,
2
2
3

1
3
CH ); C NMR (CDCl , 75.4 Hz): δppm 147.9, 143.8 (3C), 128.6 (6C), 127.9 (6C), 127.1 (3C), 112.4, 87.3, 75.5,
3
3
6
4.9, 28.4, 9.9. Anal. Calc. for C H O C, 83.76; H, 7.31. Found: C, 83.54; H, 7.45.
2
5
26
2
1
8
(57 yield%): H NMR (300 MHz, CDCl ): δ 7.45 (d, 6H, J = 10 Hz, Ar-H) 7.34-7.24 (m, 9H, Ar-H),
3
ppm
5
3
2
.06 (s, 1H, C=CHH), 4.88 (s, 1H, C=CHH), 4.18 (dt, 1H, J = 7.7 and 3.5 Hz, CHOH), 3.27 (dd, 1H, J = 9.6 and
.7 Hz, CHHOTr), 3.15 (dd, 1H, J = 9.6 and 7.7 Hz, CHHOTr), 2.45 (d, 1H, J = 3.5 Hz, OH), 2.02-1.78 (m,
1
3
H,CH CH ), 0.97 (t, 3H, J = 7.4 Hz, CH ); C NMR (CDCl , 75.4 MHz): δ 149.8, 143.9 (3C), 128.6 (6C), 127.9
2
3
3
3
ppm
(
6C), 127.1 (3C), 109.6, 86.9, 73.9, 67.1, 25.0, 12.1. Anal. Calc. for C H O C, 83.76; H, 7.31. Found: C,
2
5
26
2
83.63; H, 7.28.
2-{[tert-butyl(dimethyl)silyl]oxy}-6-methylenecyclohexanol
OTBS
OH
(±)-
1
Purification yielded a pale yellow oil; 80% yield; H NMR (300 MHz, CDCl ): δ 5.06 (q, 1H, J = 1.8 Hz,
3
ppm
C=CHH), 4.83 (q, 1H, J = 1.8 Hz, C=CHH), 3.84 (dd, 1H, J = 1.8 and 8.5 Hz, CHOH), 3.32 (ddd, 1H, J = 4.4, 8.5
and 10.4 Hz, CHOSi), 2.52 (d, 1H, J = 1.8 Hz, OH), 2.36-2.28 (m, 1H, CH ), 2.04-1.98 (m, 1H, CH ), 1.96-1.87
2
2
(
m, 1H, CH ), 1.78-1.69 (m, 1H, CH ), 1.53-1.40 (m, 1H, CH CHHCH ), 1.36-1.21 (m, 1H, CH CHHCH ), 0.91 (s,
2
2
2
2
2
2
1
3
9
H, C(CH ) ), 0.11 (s, 3H, SiCH ), 0.09 (s, 3H, SiCH ); C NMR (CDCl , 75.4 MHz): δ 146.8, 106.4, 77.6,
3
3
3
3
3
ppm
7
7.5, 33.7, 33.5, 25.8(3C), 24.3, 18.0, -4.2, -4.4. HRMS Calcd. for C H O Si m/z 243.1780, found: 243.1796.
1
3
27
2
2-{[tert-butyl(dimethyl)silyl]oxy}-6-methylenecyclohexanol
OTBS
OH
(±)-
1
Pale yellow oil; 71% yield; H NMR (300 MHz, CDCl ): δ 4.94 (s, 1H, C=CHH), 4.86 (s, 1H, C=CHH),
3
ppm
4
2
1
.02 (app t, 1H, J = 4.0 Hz, CHOH), 3.78 (dt, 1H, J = 8.3 and 3.8 Hz, SiOCH), 2.40 (d, 1H, J = 4.4 Hz, OH),
.36-2.28 (m, 1H, CHHC=CH ), 2.02 (dt, 1H, J = 5.4 and 13.6 Hz, CHHC=CH ), 1.80-1.65 (m, 2H, CH ), 1.63-
2
2
2
.56 (m, 1H, CH CHHCH ), 1.36-1.28 (m, 1H, CH CHHCH ), 0.90 (s, 9H, C(CH ) ), 0.08 (d, 6H, J = 3.1 Hz,
2
2
2
2
3 3
1
3
Si(CH ) ); C NMR (CDCl , 100 MHz): δ 147.8, 110.5, 75.1, 73.3, 30.8, 30.0, 25.7(3C), 23.1, 18.1, -4.2, -4.4.
3
2
3
ppm
HRMS Calcd. for C H O Si m/z 243.1780, found: 243.1766.
1
3
27
2

1
Relevant signals for the TBS migrated compound (5 to 10 % unseparable): H NMR (300 MHz, CDCl ): δ
3
ppm
4.92 (s, 1H, C=CHH), 4.84 (s, 1H, C=CHH), 4.14 (d, 1H, J = 3.0 Hz, SiOCH), 3.78 (app sept, 1H, J = 3.0 Hz,
1
3
CHOH), 2.20 (d, 1H, J = 6.0 Hz, OH); C NMR (CDCl , 100 MHz): δ 147.8, 109.8, 75.8, 72.4, 31.6, 30.1,
3
ppm
25.7(3C), 22.9, 18.1, -4.2, -4.4.
α-L-ribo-hexopyranoside, methyl 2-deoxy-2-methylene-4,6-O-(phenylmethylene)
MeO
O
MeO
O
O
O
1
O
Ph
O
Ph
O
OH
2
7
1
Thick oil; 91% yield; [α] +62.4° (c 0.23, CHCl ); H NMR (300 MHz, CD OD): δ 7.55-7.51 (m, 2H, Ar-
D
3
3
ppm
H), 7.38-7.33 (m, 3H, Ar-H), 5.66 (s, 1H, CHPh), 5.33 (d, 1H, J = 1.0 Hz, C=CHH), 5.27 (d, 1H, J = 1.0 Hz,
C=CHH), 5.00 (s, 1H, CHOCH ), 4.49 (d, 1H, J = 3.1 Hz, CHOH), 4.33-4.27 (m, 2H, CHCH and CHH ), 3.75
3
2
eq.
3
1
(
app t, 1H, J = 11.8 Hz, CHH ), 3.63 (dd, 1H, J = 3.1 and 9.0 Hz, CHCHOH), 3.42 (s, 3H, OCH ); C NMR
ax.
3
(
CDCl , 75 MHz): δ 144.1, 139.3, 130.0, 129.1(2C), 127.7(2C), 119.5, 103.4, 103.2, 82.0, 71.8, 70.4, 59.3,
3
ppm
5
5.4. HRMS Calcd. for C H O m/z 279.1232, found: 279.1238.
1
5
19
5
References:
1
-Feeder, N.; Hutton, G.; Nelson, A.; Stuart, W. J. Chem. Soc. Perkin Trans. 1 1999, 23, 3413-3424.
-Joshi, V.S. et al Tetrahedron 1968, 24, 5817-5830.
2
3
- Eid, C.N.; Konopelski, J.P. Tetrahedron 1991, 47, 975-992.
-Dehaen, W.; Corens, D.; L’abbe, G. Synthesis 1996, 201-203.
4