Asymmetric synthesis of optically active vinyltetrahydrofurans via palladium-catalysed cyclisation of bis(hydroxymethyl)allylic carbonates

Article abstract of DOI:10.1016/j.tetasy.2013.01.012

Optically active 3-alkyl-3-hydroxymethyl-5-vinyltetrahydrofurans were synthesised from the corresponding methyl or isobutyl carbonates of ω,ω-bis(hydroxymethyl)-α,β-unsaturated alcohols via palladium-catalysed cyclisation. The use of chiral ligands gave t

Full text of DOI:10.1016/j.tetasy.2013.01.012

Tetrahedron: Asymmetry 24 (2013) 212–216
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Asymmetric synthesis of optically active vinyltetrahydrofurans via
palladium-catalysed cyclisation of bis(hydroxymethyl)allylic carbonates
⇑
´
Beata Olszewska, Izabela Szulc, Bogusław Kryczka, Agnieszka Kubiak, Stanisław Porwanski, Anna Zawisza
´
´
Department of Organic and Applied Chemistry, University of Łódz, Tamka 12, 91-403 Łódz, Poland
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 29 November 2012
Accepted 15 January 2013
Optically active 3-alkyl-3-hydroxymethyl-5-vinyltetrahydrofurans were synthesised from the
corresponding methyl or isobutyl carbonates of -bis(hydroxymethyl)- ,b-unsaturated alcohols via
palladium-catalysed cyclisation. The use of chiral ligands gave the corresponding tetrahydrofuran
derivatives, which had er values that ranged from moderate to good.
Ó 2013 Elsevier Ltd. All rights reserved.
x,
x
a
1. Introduction
The ring-closure of methyl carbonate 1a occurred readily in THF
at room temperature in the presence of a catalytic amount of
The Pd0-catalysed intramolecular allylation of oxygen nucleo-
philes is a very useful method for the asymmetric synthesis of opti-
cally active oxygen heterocycles.1 This type of transformation
frequently occurs under mild conditions, tolerates a broad array
of functional groups and proceeds with high stereoselectivity.2
Several years ago, we presented results for the Pd0- and PdII-cat-
Pd2(dba)3, associated with dppb, which provided exclusively THF
derivatives 2a and 3a as a 15:85 mixture and in 92% overall yield
(Table 1, entry 1). The configurational assignment of compounds
2a and 3a was based on NOESY experiments.3b
Isobutyl carbonate 1b was more reactive under the same condi-
tions (Table 1, entry 2) and gave products 2a and 3a with the high-
est yield (99%) and diastereoselectivity (11:89). The Pd0-catalysed
cyclisation was extended to other allylic carbonates 1c–h bearing
different substituents. In all cases, the corresponding THFs 2b–d
and 3b–d were obtained in quite high yields (94–96%) after
1–2 h (Table 1, entries 2–8). However, it should be noted that in
all cases, the isobutyl carbonate was more reactive and led to cyclic
products with higher stereoselectivity. Only methyl and isobutyl
carbonate with the 2-naphthylmethyl substituents 1g and 1h gave
the corresponding THFs with the same yield and selectivity.
Our results led us to conclude that the rest of the carbonate
influences the course of cyclisation. The reaction mechanism
(Scheme 2) showed that the alkoxide ion generated in situ carries
the nucleophile into an ionic active form. This is why the more
alkaline ion i-BuOꢀ plays a central role in the activation of the
nucleophile and, hence, increases the yield and selectivity of the
process.
alysed cyclisation reaction of
x,x-bis(hydroxymethyl)-a,b-unsatu-
rated alcohols as well as the corresponding methyl allylic
carbonates and preliminary results concerning the asymmetric
Pd0-catalysed cyclisation of allylic carbonates.3
By extending our previous work on the use of methyl allylic car-
bonates in the synthesis of O-heterocycles,3b we herein report the
influence of the allylic carbonate (methyl or isobutyl) on hetero-
cyclisation reactions as well as the impact of chiral ligands, both
commercially available and new derivatives of carbohydrates re-
ceived in our group.
2. Results and discussion
New isobutyl carbonates 1b, 1d, 1f and 1h were prepared
according to the procedure described for methyl carbonates 1a,
1c, 1e and 1g, that is, by palladium-catalysed alkylation of
substituted dimethyl malonates with the monoacetate of
but-1,4-diol, followed by protection of the hydroxyl function with
a tert-butyldimethylsilyl group, then reduction of the diester,
deprotection of the tert-butyldimethyl ether and finally condensa-
tion with isobutyl chloroformate.3b The cyclisation was first stud-
ied with bis(hydroxymethyl) allylic carbonate 1a as the substrate
(Scheme 1).
Previous studies on the Pd0-catalysed asymmetric cyclisation of
methyl carbonates containing two enantiotopic hydroxymethyl
groups have shown that the use of chiral ligands in association
with Pd affords the corresponding THF stereoisomers with low to
moderate er values.3b The best results were obtained in the pres-
ence of (R,S)-Josiphos as the ligand at 55 °C, when the minor diaste-
reoisomer 2a was obtained with an enantiomeric ratio (er) of
15:85, while the major diastereoisomer 3a exhibited an er of
64:36 (Table 2, entry 1).3b
Under the same conditions isobutyl carbonate 1b gave products
⇑
Corresponding author. Tel.: +48 42 6355764; fax: +48 42 6655162.
E-mail address: azawisza@chemia.uni.lodz.pl (A. Zawisza).
2a and 3a with
a similar yield as well as diastereo- and
0957-4166/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetasy.2013.01.012

B. Olszewska et al. / Tetrahedron: Asymmetry 24 (2013) 212–216
213
R1
O
C
HOH2
OCO2R2
Pd2(dba)3, dppb
THF, rt
HOH2C
R1
HOH2C
R1
+
CH2OH
O
1
2
2a: R1 = C6H5
3a: R1 = C6H5
1a
: R = C6H5, R = Me
1b: R1 = C6H5, R2 = i-Bu
1
1
2b:
3b:
R = 2-CH3C6H4
R = 2-CH3C6H4
1
2
2c: R1 = 4-CH3C6H4
3c: R1 = 4-CH3C6H4
1c
: R = 2-CH3C6H4, R = Me
1d: R1 = 2-CH3C6H4, R2 = i-Bu
1
1
2d:
3d:
R = 2-C10H7
R = 2-C10H7
1
2
1e
: R = 4-CH3C6H4, R = Me
1f: R1 = 4-CH3C6H4, R2 = i-Bu
1
: R = 2-C10H7, R2 = Me
1g
1h: R1 = 2-C10H7, R2 = i-Bu
Scheme 1. Pd0-catalysed synthesis of tetrahydrofurans 2 and 3.
Table 1
Pd0-catalysed allylic cyclisation of substrates 1a–h according to Scheme 1a
products 2a and 3a in a good yield of 98% after 72 h with 22:78 dia-
stereoselectivity in favour of stereoisomer 2a (Table 2, entry 6).
The minor isomer was obtained with a higher er of 89:11, while
the major isomer had an er of 27:73. The results obtained for the
Pd0-catalysed cyclisation of methyl carbonate 1c and isobutyl car-
bonate 1d bearing the o-tolyl substituent in the presence of Trost’s
ligand again showed a higher efficiency of the isobutyl carbonate
(Table 2, entries 7–8). Both carbonates 1c and 1d gave cyclisation
products with the same diastereoselectivity (2b/3b 15:85), but
the er was better for isobutyl carbonate 1d (er of 2b 64:36 and
er of 3b 69:31). Additionally, the minor steroisomer 2b was ob-
tained with a reversal of configuration going from 1c (42:58) to
1d (64:36). The use of (R,S)-Josiphos as the chiral ligand gave very
good diastereoselectivity (2b/3b 5:95) in excellent yield (98%) after
20 h at 55 °C (Table 2, entry 9). The er value of the major isomer
was very low (58:42) while that of the minor isomer was 21:79.
Conversely, the phosphorus amidite ligand L1 showed good selec-
tivity only for the major isomer 3b (er 70:30) (Table 2, entry 10).
Cyclisation of isobutyl carbonate 1d in the presence of carbohy-
drate ligands L2–L4 was successful only with the phosphine-amide
ligand L2 (Table 2, entries 11–14). When the reaction was per-
formed at 25 °C, we observed the best selectivity after 72 h: the
minor diastereoisomer 2b was obtained with an enantiomeric ratio
of 86:14 and the major diastereoisomer 3b showed an er of 19:81
(Table 2, entry 11). Increasing the temperature to 55 °C gave the
cyclised products in 98% yield in less time (20 h), but resulted in
a decrease in enantioselectivity (Table 2, entry 12). The same reac-
tion in the presence of carbohydrate urea ligand L3 derived from
cellobiose and phosphine-imine ligand L4 derived from glucosa-
mine,5 afforded practically a 1:1 mixture of enantiomers of both
diastereoisomers 2b and 3b (Table 2, entries 13, 14).
Entry
Carbonate
Yield (2+3)b (%)
2/3c (%)
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
92
99
94
96
95
96
94
95
15:85
11:89
15:85
10:90
17:83
13:87
13:87
13:87
1g
1h
a
b
c
[1]/[Pd2(dba)3]/[dppb] = 40:1:2.2, THF, rt, 1–2 h.
Yield refers to isolated pure products after column chromatography.
Determined by 1H NMR spectroscopy.
enantioselectivity (Table 2, entry 2). Ring-closure of the methyl
carbonate 1a occurred quickly (1 h) at room temperature in the
presence of the (R,R)-Trost ligand and quantitatively provided THFs
2a and 3a as a 20:80 mixture of diastereoisomers in favour of ste-
reoisomer 2a. The major diastereoisomer 3a was obtained with an
er of 59:41, while the minor diastereoisomer 2a showed an er of
43:57 (Table 2, entry 3).
The use of isobutyl carbonate 1b under the same conditions
afforded an identical yield (99%) and diastereoselectivity (2a/3a
20:80), although the minor isomer 2a showed the opposite ratio
(er values of 67:33). The major isomer 3a was obtained with higher
selectivity (er 71:29) in comparison with methyl carbonate 1a
(59:41) (Table 2, entry 4).
Asymmetric cyclisation of isobutyl carbonate 1b was performed
in the presence of the phosphorus amidite ligand L1 (Fig. 1).
Cyclisation of 1b at room temperature afforded a 19:81 mixture
of diastereoisomers 2a and 3a in 99% yield after 20 h (Table 2,
entry 5). The minor isomer was obtained with an er of 20:80 while
the major isomer exhibited an er of 76:24. Cyclisation of com-
pound 1b was also carried out in the presence of the carbohydrate
ligand L2, prepared according to the procedure described by Si-
nou.4 This cyclisation required a longer reaction time and gave
When we compared the reactivity of the methyl and isobutyl
carbonate with a p-tolyl substituent in the presence of (R,R)-Trost’s
ligand, we again obtained better results for the isobutyl carbonate
1f (Table 2, entries 15–16). The reaction performed at room tem-
perature gave cyclised products in 93% yields after 1 h with 7:93
diastereoselectivity in favour of diastereoisomer 2c. Both isomers,
[Pd0]/L
+ R2OH
OH2C
OCO2R2
HOH2C
R1
HOH2C
2 + 3
- R2OH
(-CO2)
HOH2C
HOH2C
R1
CH2OH
[Pd]+
[Pd]+
R2O
R1
1
Scheme 2. Mechanism of the Pd0-catalysed cyclisation.

214
B. Olszewska et al. / Tetrahedron: Asymmetry 24 (2013) 212–216
Table 2
Effect of carbonates and ligands on the Pd0-catalysed asymmetric allylic alkylationa
Entry
Carbonate
Ligand
Time (h)
Temp (°C)
Yield 2+3b
2/3c
er of 2d
er of 3d
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
1a
1b
1a
1b
1b
1b
1c
1d
1d
1d
1d
1d
1d
1d
1e
1f
(R,S)-Josiphos
(R,S)-Josiphos
(R,R)-Trost
(R,R)-Trost
L1
L2
(R,R)-Trost
(R,R)-Trost
(R,S)-Josiphos
L1
L2
L2
L3
L4
(R,R)-Trost
(R,R)-Trost
(R,S)-Josiphos
L1
(R,S)-Josiphos
L1
20
20
1
55
55
25
25
25
25
25
25
55
25
25
55
25
25
25
25
55
25
55
25
25
83
83
99
99
99
98
92
95
98
96
97
98
74
68
95
93
92
94
98
95
98
18:82
20:80
20:80
20:80
19:81
22:78
15:85
15:85
5:95
10:90
25:75
20:80
15:85
12:88
17:83
7:93
15:85
18:82
43:57
67:33
20:80
89:11
42:58
64:36
21:79
43:57
86:14
77:23
45:55
56:44
48:52
63:37
22:78
18:82
18:82
79:21
88:12
64:36
60:40
59:41
71:29
76:24
27:73
60:40
69:31
58:42
70:30
19:81
33:67
48:52
50:50
62:38
70:30
59:41
75:25
60:40
15:85
20:80
1
20
72
1
1
20
20
72
20
72
96
1
1
1f
1f
1h
1h
1h
20
20
72
20
72
25:75
20:80
14:86
13:87
13:87
L2
a
b
c
[1]/[Pd2(dba)3]/[ligand] = 40:1:2.2 (4.4), THF.
Yield refers to isolated pure products after column chromatography.
Determined by 1H NMR spectroscopy.
d
Enantioselectivity (er) was measured by chiral stationary phase HPLC on a Chiralpak AD column (25 cm ꢁ 4.6 mm); flow rate = 0.5 ml minꢀ1; hexane/i-propanol (90:10),
tR = 18.7 min and tR = 22.8 min for 2a and tR = 17.2 min and tR = 18.7 min for 3a; hexane/i-propanol (85:15), tR = 12.3 min and tR = 16.8 min for 2b and tR = 12.2 min and
tR = 14.6 min for 3b; hexane/i-propanol (95:5), tR = 24.7 min and tR = 33.3 min for 2c and tR = 23.2 min and tR = 25.1 min for 3c; hexane/i-propanol (95:5), tR = 42.4 min and
tR = 44.7 min for 2d and hexane/i-propanol (98:2), tR = 84.6 min and tR = 88.6 min for 3d; the first value corresponds to the enantiomer being eluted first.
Ph
H
O
O
O
O
cHex
Ph2P
Ph2P
NH
HN
PPh2
P
N
Fe
CH3
Ph
(R,S)-Josiphos
(R,R)-Trost's ligand
L1 (S,S,aS)
OAc
O
OAc
O
OTMS
OAc
O
O
AcO
AcO
AcO
AcO
TMSO
TMSO
O
OAc
O
N
H
N
H
AcO
HN
N
OAc
OTMS
PPh2
OAc
Ph2P
CH
O
Ph2P
L2
L4
L3
Figure 1. Ligands used herein.
minor 2c and major 3c, were obtained with similar enantioselec-
tivity, 63:37 and 70:30 for 2c and 3c, respectively (Table 2, entry
16). Cyclisation of isobutyl carbonate 1f in the presence of (R,S)-
Josiphos as the chiral ligand afforded good selectivity only for the
minor isomer 2c (er 22:78) (Table 2, entry 17). The best results
were obtained for the reaction carried out in the presence of the
phosphorus amidite ligand L1 (er 18:82 for 2c and er 75:25 for
3c) (Table 2, entry 18).
Finally, the asymmetric cyclisation of the isobutyl carbonate
with a 2-naphthylmethyl substituent 1h was performed in the
presence (R,S)-Josiphos as the chiral ligand (Table 2, entry 19). Cyc-
lisation at 55 °C afforded a 14:86 mixture of stereoisomers. Good er

B. Olszewska et al. / Tetrahedron: Asymmetry 24 (2013) 212–216
215
values for the two stereoisomers 2d and 3d were obtained: 18:82
and 60:40 for 2d and 3d, respectively. Ligand L1 gave better selec-
tivity (79:21 for 2d and 15:85 for 3d) (Table 2, entry 20), but the
best results were obtained for carbohydrate ligand L2. The reaction
required a longer reaction time but afforded 2d and 3d in very
good yield (98%) after 72 h with good selectivity (2d/3d 13:87)
and high er values, 88:12 for 2d and 20:80 for 3d (Table 2, entry
21).
4.2.2. (E)-5-(2-Methylbenzyl-6-hydroxy-5-(hydroxymethyl)hex-
2-en-1-yl isobutyl carbonate 1d
Colourless oil, 473 mg, 54% yield. Rf = 0.51 (ethyl acetate/petro-
leum ether, 1:1). 1H NMR (600 MHz, CDCl3): d = 0.87 (d, 6H, J = 6.7,
CH(CH3)2), 1.85–1.95 (m, 1H, CH(CH3)2), 2.12 (d, 2H, J = 7.5, CH2–
CH@), 2.26 (s, 3H, CH3Ph), 2.30 (s, 2H, 2OH), 2.63 (s, 2H, PhCH2),
3.54 (s, 4H, 2CH2OH), 3.83 (d, 2H, J = 6.5, CH2CH(CH3)2), 4.49 (dd,
2H, J = 6.4, 0.7, CH2O), 5.60 (dtt, 1H, J = 15.2, 6.5, 1.3, CH@), 5.81
(dtt, 1H, J = 15.2, 7.5, 1.2, CH@), 7.05–7.20 (m, 4H, C6H4). 13C
NMR (150 MHz, CDCl3): d = 19.1 (CH(CH3)2), 20.5 (CH3), 27.0
(CH(CH3)2), 35.1 (CH2–CH@), 36.0 (PhCH2), 44.3 (C(CH2OH)2),
67.0 (CH2OH), 68.3 (CH2O), 74.3 (CH2CH(CH3)2), 125.8, 126.6,
127.1, 130.9, 131.4, 132.6, 136.2. 137.3 (C6H4, CH@CH), 155.5
(CO). C20H30O5 (350.21): calcd C 68.54, H 8.63; found C 68.32, H
8.45.
3. Conclusion
In conclusion, we have developed a simple and efficient meth-
odology for the synthesis of substituted tetrahydrofurans via the
Pd0-catalysed cyclisation of allylic carbonates. The reactions affor-
ded a mixture of stereoisomers with excellent yields and good dia-
stereoselectivities and enantioselectivities. Using as a starting
material isobutyl carbonates, we observed significantly higher
reactivities and selectivities in comparison with methyl carbon-
ates. The best results were obtained in the asymmetric cyclisation
in the presence of a catalytic amount of Pd2(dba)3 associated with
phosphorus amidite ligand L1 and phosphine-amide ligand L2
4.2.3. (E)-5-(4-Methylbenzyl-6-hydroxy-5-(hydroxymethyl)hex-
2-en-1-yl isobutyl carbonate 1f
Colourless oil, 779 mg, 89% yield. Rf = 0.82 (ethyl acetate/petro-
leum ether, 4:1). 1H NMR (600 MHz, CDCl3): d = 0.89 (d, 6H, J = 6.8,
CH(CH3)2), 1.50 (s, 2H, 2OH), 1.85–2.00 (m, 1H, CH(CH3)2), 2.02 (d,
2H, J = 7.8, CH2–CH@), 2.25 (s, 3H, CH3Ph), 2.55 (s, 2H, PhCH2), 3.50
(s, 4H, 2CH2OH), 3.85 (d, 2H, J = 6.4, CH2CH(CH3)2), 4.52 (dd, 2H,
J = 6.4, 1.1, CH2O), 5.63 (dtt, 1H, J = 15.4, 6.4, 1.2, CH@), 5.85 (dtt,
1H, J = 15.4, 7.5, 1.1, CH@), 7.15–7.25 (m, 4H, C6H4). 13C NMR
(150 MHz, CDCl3): d = 18.9 (CH(CH3)2), 21.0 (CH3), 27.8 (CH(CH3)2),
35.0 (CH2–CH@), 37.6 (PhCH2), 43.1 (C(CH2OH)2), 67.8 (CH2OH),
68.1 (CH2O), 74.1 (CH2CH(CH3)2), 127.0, 128.9, 130.4, 131.2,
134.2, 135.9 (C6H4, CH@CH), 155.3 (CO). C20H30O5 (350.21): calcd
C 68.54, H 8.63; found C 68.34, H 8.42.
derived from D-glucosamine (er values up to 89:11).
4. Experimental
4.1. General
All solvents and reagents were purchased from Sigma–Aldrich
and used as supplied, without additional purification. NMR spectra
were recorded in CDCl3 on Brucer Avance III (600 MHz for 1H NMR,
150 MHz for 13C NMR), coupling constants are reported in Hz.
Chromatographic purification of compounds was achieved with
230–400 mesh size silica gel. The progress of the reactions was
monitored by silica gel thin layer chromatography plates (Merck
TLC Silicagel 60 F254). The enantiomeric ratio was determined by
4.2.4. (E)-5-(2-Naphthylmethyl-6-hydroxy-5-(hydroxymethyl)-
hex-2-en-1-yl isobutyl carbonate 1h
Colourless oil, 560 mg, 58% yield. Rf = 0.63 (ethyl acetate/petro-
leum ether, 3:1). 1H NMR (600 MHz, CDCl3): d = 0.87 (d, 6H, J = 6.7,
CH(CH3)2), 1.89–2.00 (m, 1H, CH(CH3)2), 2.02 (d, 2H, J = 7.5, CH2–
CH@), 2.38 (s, 2H, 2OH), 2.76 (s, 2H, CH2C10H7), 3.53 (s, 4H,
2CH2OH), 3.85 (d, 2H, J = 6.7, CH2CH(CH3)2), 4.53 (d, 2H, J = 6.4,
CH2O), 5.62 (dt, 1H, J = 15.2, 6.4, CH@), 5.88 (dt, 1H, J = 15.2, 7.5,
CH@), 7.28–7.273 (m, 7H, C10H7). 13C NMR (150 MHz, CDCl3):
d = 19.1 (CH(CH3)2), 28.0 (CH(CH3)2), 35.2 (CH2–CH@), 38.2
(CH2C10H7), 44.6 (C(CH2OH)2), 67.1 (CH2OH), 68.2 (CH2O), 74.3
(CH2CH(CH3)2), 125.6, 126.1, 127.3, 127.7, 127.8, 129.2, 129.3,
131.3, 132.4, 133.6, 135.1, 135.3 (C10H7, CH@CH), 155.5 (CO).
HPLC (ProStar Varian) employing
a Chiralpak AD column
(25 cm ꢁ 4.6 mm).
4.2. Typical procedure for the synthesis of isobutyl carbonates
1b, 1d, 1f, 1h
A solution of the corresponding triol3b (2.5 mmol) in CH2Cl2
(50 mL) cooled to 0 °C was treated with pyridine (0.4 mL,
5.0 mmol) and isobutyl chloroformate (0.32 mL, 2.5 mmol). After
2–4 h at room temperature, the reaction mixture was quenched
with water (10 mL) and extracted with CH2Cl2 (2 ꢁ 50 mL). The
combined organic phases were dried (Na2SO4) and evaporated un-
der reduced pressure. The crude product was purified by flash
chromatography on silica gel to give allylic carbonates 1b, 1d, 1f
and 1h.
C23H30O5 (386.21): calcd C 71.48, H 7.82; found C 70.99, H 7.53.
4.3. Synthesis of N-[(1S,2S)-2-(Diphenylphosphino)cyclohexyl]-
N0-(2,3,6,20,30,40,6-hexa-O-acetyl-b-
-cellobiose)urea L3
D
To a solution of 2,3,6,20,30,40,6-hexa-O-acetyl-b-
D-azidocellobi-
ose6 (669 mg, 1 mmol) in methylene chloride (8 mL), triphenyl-
phosphine (865 mg, 3.3 mmol) was added. The mixture was
stirred at room temperature for 30 min and then flushed
with CO2. Next, (1S,2S)-2-(diphenylphosphino)cyclohexylamine
(283 mg, 1 mmol) was added. The mixture was then stirred and
flushed with CO2 at room temperature 24 h. The solution was next
evaporated to dryness and the solid residue was purified by flash
chromatography on silica gel, eluting with a ethyl acetate/hexane,
9:1 (Rf = 0.80). White solid, 897 mg, 95% yield, mp 109–110.5 °C;
4.2.1. (E)-5-Benzyl-6-hydroxy-5-(hydroxymethyl)hex-2-en-1-yl
isobutyl carbonate 1b
Colourless oil, 378 mg, 45% yield. Rf = 0.71 (ethyl acetate/petro-
leum ether, 4:1). 1H NMR (600 MHz, CDCl3): d = 0.98 (d, 6H, J = 6.7,
CH(CH3)2), 1.98–2.02 (m, 1H, CH(CH3)2), 2.10 (d, 2H, J = 7.3, CH2–
CH@), 2.26 (s, 2H, 2OH), 2.70 (s, 2H, PhCH2), 3.59 (d, 4H, J = 5.5,
2CH2OH), 3.95 (d, 2H, J = 6.7, CH2CH(CH3)2), 4.62 (d, 2H, J = 6.4,
CH2O), 5.72 (dt, 1H, J = 15.3, 6.4, CH@), 5.94 (dt, 1H, J = 15.3, 7.6,
CH@), 7.2–7.35 (m, 5H, C6H5). 13C NMR (150 MHz, CDCl3):
d = 18.9 (CH(CH3)2), 27.8 (CH(CH3)2), 35.0 (CH2–CH@), 38.0
(PhCH2), 43.1 (C(CH2OH)2), 67.7 (CH2OH), 68.1 (CH2O), 74.1
(CH2CH(CH3)2), 126.4, 127.1, 128.2, 130.5, 132.1, 137.4 (C6H5,
CH@CH), 155.3 (CO). C19H28O5 (336.19): calcd. C 67.83, H 8.39;
found C 67.54, H 8.51.
½
a 2D0
ꢂ
¼ ꢀ24:8 (c 0.5, CH2Cl2); 1H NMR (600 MHz, CDCl3): d = 0.92–
1.02 (m, 1H, H-500b), 1.28–1.35 (m, 3H, H-600b, H-400b, H-300b),
1.60–1.86 (m, 3H, H-500a, H-400a, H-300a), 1.97, 1.99, 2.00, 2.00,
2.02, 2.08, 2.09 (7s, 21H, 7CH3, Ac), 2.14–2.22 (m, 2H, H-100,
H-600a), 3.48–3.58 (m, 1H, H-200), 3.64 (ddd, 1H, J5 ,4 = 9.6,
0
0
J5 6 a = 4.4, J5 ,6 b = 2.4, H-50), 3.74 (ddd, 1H, J5,4 = 9.2, J5,6a = 1.8,
0
0
0
0

216
B. Olszewska et al. / Tetrahedron: Asymmetry 24 (2013) 212–216
0
0
J5,6b = 4.8, H-5, J6 b,5 ), 3.80 (t, 1H, J4,3 = 9.3, J4,5 = 9.2, H-4), 4.05 (dd,
ral ligand (0.055 mmol or 0.11 mmol) in THF (3 mL) for 0.5 h. This
solution was then added under argon to a Schlenk tube containing
the allylic carbonate 1a–h (1 mmol) dissolved in anhydrous THF
(3 mL). The solution was stirred at 25 °C (or 55 °C). After being stir-
red for the indicated time, the solvent was evaporated, and the res-
idue was purified by column chromatography on silica gel.
1H, J6 b,6 a = 12.0, J6 b,5 = 2.4, H-60b), 4.19 (dd, 1H, J6b,6a = 12.0,
0
0
0
0
J6b,5 = 4.8, H-6b), 4.37 (dd, 1H, J6 a,6 b = 12.0, J6 a,5 = 4.4, H-60a),
4.45 (dd, 1H, J6a,6b = 12.0, J6a,5 = 1.8, H-6a), 4.53 (d, 1H, J1’,2’ = 7.9,
0
0
0
0
00
H-1’), 4.69 (d, 1H, JNH,2 = 8.0, NH), 4.82 (t, 1H, J2,1 = 9.3, J2,3 = 9.3,
H-2), 4.94 (dd, 1H, J2 ,3 = 9.3, J2 ,1 = 7.9, H-20), 4.99 (d,1H,
JNH,1 = 9.3, NH), 5.09 (t, 1H, J4’,3’ = 9.6, J4’,5’ = 9.6, H-4’), 5.16 (t, 1H,
0
0
0
0
J3 ,2 = 9.3, J3 ,4 = 9.6, H-30,), 5.19 (t, 1H, J1,NH = 9.3, J1,2 = 9.3, H-1),
5.29 (t, 1H, J3,2 = 9.3, J3,4 = 9.3, H-3), 7.31–7.46 (m, 10H, 2C6H5).
13C NMR (150 MHz, CDCl3): d = 20.5, 20.6, 20.8, 20.9 (CH3, Ac),
24.4 (C-300), 25.4 (C-400), 27.3 (C-500), 34.2 (C-600), 41.1 (d, JC-
P = 11.8, C-100), 51.1 (d, JC-P = 16.5, C-200), 61.6 (C-60), 62.1 (C-6),
67.9 (C-4), 71.0 (C-2), 71.6 (C-20), 72.0 (C-50), 72.6 (C-3), 73.0 (C-
30), 74.3 (C-5), 76.3 (C-4), 80.1 (C-1), 100.6 (C-1’), 128.1, 128.2,
128.3, 128.5, 128.6, 129.00 (C6H5), 132.4 (d, J = 17.6, C6H5), 134.5
(d, J = 20.5, C6H5), 135.2 (d, J = 17.0, C6H5), 136.9 (d, J = 13.0,
C6H5), 155.1 (CO, Urea), 169.0, 169.3, 169.4, 170.2, 170.3, 170.5,
171.3 (CO, Ac). C45H57N2O18P (944.91): calcd C 57.20, H 6.08, N
2.96; found C 57.14, H 6.09, N 2.98.
0
0
0
0
Acknowledgement
This work was partly financed by the European Union within
the European Regional Development Fund (POIG.01.01.02-14-
102/09).
References
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Samanta, S. Heterocycles 2010, 81, 517–584; (e) Sadig, J. E. R.; Willis, M. C.
Synthesis 2011, 1, 1–22.
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4.4. Synthesis of 1,3,4,6-tetra-O-trimethylsilyl-2-deoxy-2-{[2-
(diphenylphosphino)benzoyl]imino}-a-D-glucopyranose L4
In a Schlenk tube under nitrogen, 2-amino-2-deoxy-1,3,3,6-tet-
ra-O-trimethylsilyl-
-glucopyranose7 (1 g, 2.1 mmol) and 2-
a-D
(diphenylphosphino)benzaldehyde (621 mg, 2.1 mmol) were stir-
red in toluene (40 mL) at 60 °C for 12 h. After concentration, the
residue was purified by flash chromatography on silica gel, eluting
with ethyl acetate/hexane, 5:1 (Rf = 0.82). Yellow oil, 1.2 g, 77%
yield, ½a 2D0
ꢂ
¼ þ41:6 (c 0.5, CHCl3); 1H NMR (600 MHz, CDCl3):
d = 0.10, 0.18, 0.25, 0.31 (4s, 36H, 4OSi(CH3)3), 3.25 (dd, 1H,
J = 9.4, 3.2, H-2), 3.71 (dd, 1H, J = 9.6, 8.6, H-4), 3.84–3.90 (m, 2H,
H-6, H-60), 3.99 (ddd, 1H, J = 9.6, 3.7, 2.8, H-5), 4.41 (dd, 1H,
J = 9.4, 8.6, H-3), 4.80 (d, 1H, J = 3.2, H-1), 7.35–7.52 (m, 13H,
C6H5), 8.34–8.36 (m, 1H, C6H5), 9.19 (d, 1H, J = 6.1, NCH). 13C
NMR (150 MHz, CDCl3): d = 0.0, 0.2, 1.1, 1.5 (4OSi(CH3)3), 62.5 (C-
6), 72.5, 72.8 (C-4, C-5), 74.6 (C-2), 77.0 (C-3), 95.4 (C-1), 127.3
(d, J = 4.4, C6H5), 128.4, 128.7, 128.8, 129.0, 129.1, 130.6, 133,7,
133.9, 134.0, 134.1, 134.2, 134.3, (C6H5), 136.2 (d, J = 5,6, C6H5),
136.7 (d, J = 9.9, C6H5), 138.0 (d, J = 18.8, C6H5), 139.7 (d, J = 17.8,
C6H5), 161.1 (d, J = 27.5, NCH). C37H58NO5PSi4 (740.18): calcd C
60.04, H 7.90, N 1.89; found C 60.01, H 7.86, N 1.96.
3. (a) Zawisza, A.; Sinou, D. Tetrahedron Lett. 2006, 47, 3271–3274; (b) Zawisza, A.;
Fenêt, B.; Sinou, D. Eur. J. Org. Chem. 2007, 2296–2309.
4. Tollabi, M.; Framery, E.; Goux-Henry, C.; Sinou, D. Tetrahedron: Asymmetry 2003,
14, 3329–3333.
´
5. Carbohydrate urea ligand L3 was obtained by Porwanski who soon publish a
paper on a series of carbohydrate urea ligands derived from cellobiose, lactose
and glucose.
6. Petö, C.; Batta, G.; Györgydeak, Z.; Sztaricskai, F. Liebigs Ann. Chem. 1991, 505–
507.
7. Irmak, M.; Groschner, A.; Boysen, M. M. K. Chem. Commun. 2007, 177–179.
4.5. General procedure for the Pd0-catalysed reaction
The catalytic system was prepared by stirring Pd2(dba)3
(22.9 mg, 0.025 mmol) and dppb (23.5 mg, 0.055 mmol) or the chi-