Regioselective synthesis of 1,2- and 1,3-diols from ω-hydroxy allyl acetates and carbonates via Pd complexes using boric acid and trialkyl borates

Article abstract of DOI:10.1016/j.tetlet.2005.07.135

The synthesis of 1,2- and 1,3-diols and derivatives has been achieved from ω-hydroxy π-allyl palladium complexes by using boric acid and trialkyl borates.

Full text of DOI:10.1016/j.tetlet.2005.07.135

Tetrahedron
Letters
Tetrahedron Letters 46 (2005) 6945–6948
Regioselective synthesis of 1,2- and 1,3-diols from
x-hydroxy allyl acetates and carbonates via Pd complexes
using boric acid and trialkyl borates
*
´ ˆ
Jerome Cluzeau, Patrice Capdevielle and Janine Cossy
Laboratoire de Chimie Organique, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex05, France
Received 8 June 2005; revised 25 July 2005; accepted 26 July 2005
Abstract—The synthesis of 1,2- and 1,3-diols and derivatives has been achieved from x-hydroxy p-allyl palladium complexes by
using boric acid and trialkyl borates.
ꢀ 2005 Elsevier Ltd. All rights reserved.
1,2- and 1,3-Diols and derivatives are present in a great
variety of natural products and/or biologically active
compounds.1 The most widely used method to prepare
1,2- and 1,3-diols is the nucleophilic attack of 2- or
3-hydroxy ketones or aldehydes by organometallic
species. An alternative approach is the formation of
C–O bond using transition metal-catalyzed allylic sub-
stitution. However, if the formation of C–C bonds
through palladium-catalyzed nucleophilic substitution
of allylic substrates has been found to be a useful
tool in organic synthesis, in contrast, the formation
of C–O bonds by the introduction of a hydroxyl group
is less common, although intra- and intermolecular
substitutions using alcohols, phenols,2 or carboxylic
acids3 have been reported recently. For example, car-
boxylic acids were used in a palladium-catalyzed reac-
tion of 2-allylic trichloroacetimidate to produce allylic
esters.3
R"
Pd(0)
OH
O
OH
R'O
R
n
B(OR")3
R" = H, alkyl
R
n
A
B
n = 0,1; R = alkyl, aryl
R' = Ac, CO2Et
Scheme 1. Formation of 1,2- and 1,3-diols and derivatives.
Compounds of type A were prepared using a cross-
metathesis reaction between homoallylic alcohols 1a–c
and 1,4-diacetoxybut-2-ene 2 or 1,4-diethylcarbonyloxy-
but-2-ene 3 in the presence of Grubbs catalyst7 Ru1 or
Grubbs–Hoveyda catalyst8 Ru2 (3–6 mol %) for 24 h.
Compounds 4a–e were obtained in 56–91% yield as a
5/1–10/1 E/Z ratio. The results are reported in Table 1.
Initially, the reaction of 4a with boric acid (3 equiv) was
examined in the presence of Pd(0) in THF at rt and at
50 ꢁC (Table 2, entries 1 and 2). When 4a was treated
Boric acid and alcohols with trialkyl boranes have been
employed in the palladium-catalyzed ring opening of
vinyl epoxide to produce 1,2-diols and derivatives.4–6
Here, we would like to report that the use of boric acid
and trialkyl borates can produce 1,2- and 1,3-diols and
derivatives of type B from compounds of type A, via
p-allyl palladium complexes (Scheme 1).
ꢀ
with Pd2(dba)3 CHCl3 (0.05 equiv) in the presence of
dppb (0.25 equiv) at rt or at 50 ꢁC, the expected 1,3-diol
5a was not formed. On the contrary, when Pd(PPh3)4
(0.1 equiv) in the presence of PPh3 (0.25 equiv) was used
in THF at 50 ꢁC, 4a was transformed to 1,3-diol 5a in
83% yield as a 1/1 mixture of syn and anti isomers (Table
2, entry 3). It is worth noting that the reaction did not
occur in acetonitrile or in dichloromethane (Table 2,
entries 4 and 5) as well as without Pd(0). The best con-
ditions for obtaining 1,3-diol 5a from compound 4a
seem to be Pd(PPh3)4 (10 mol %), PPh3 (25 mol %),
B(OH)3 (3 equiv), and Na2CO3 (1.5 equiv) in THF at
Keywords: Allyl alcohols; Diols; Borates; Boric acid; p-Allyl palladium
complexes.
*
Corresponding author. Tel.: +33 (0)1 40 79 44 29; fax: +33 (0)1 40 79
46 60; e-mail: janine.cossy@espci.fr
0040-4039/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2005.07.135

6946
J. Cluzeau et al. / Tetrahedron Letters 46 (2005) 6945–6948
Table 1. Preparation of compounds 4a–e using a cross-metathesis reaction
2 (10 equiv)
or 3 (8 equiv)
OH
OH
R
R'O
Mes
R
Ru1 or Ru2
(0.03 to 0.06 equiv)
1a : R=CH2CH2OBn
1b : R=CH2CH2OTBS
1c : R=Ph
4a-e
N
N
Mes
EtO2CO
AcO
N
N
Mes
Cl
Mes
Cl
Ru
Cl
Ru
O
Cl
Ph
OCO2Et
OAc
PCy3
2
3
Ru1
Ru2
Entry
1
1
Solvent, t (ꢁC)
2 or 3
Ru (equiv)
4 (yield, E/Z ratio)
OH
AcO
OBn
1a
CH2Cl2, rt
2
2
Ru2 (0.03)
4a (89%, 8/1)
OH
2
1b
CH2Cl2, rt
Ru2 (0.03)
AcO
OTBS
4b (86%, 10/1)
OH
AcO
3
4
1c
1a
CH2Cl2, rt
CH2Cl2, 40
2
3
Ru2 (0.03)
Ru1 (0.06)
4c (91%, 8/1)
OH
EtO CO
OBn
2
4d (56%, 9/1)
OH
5
1b
Toluene, 80
3
Ru1 (0.06)
EtO CO
OTBS
2
4e (81%, 5/1)
Table 2. Reaction of palladium p-allyl complexes with B(OH)3
OH
B(OH)3
OH OH
Pd(PPh3)4
R'O
R
R
4a-e
Solvent
5a-c
Entry
4
t (ꢁC)
Time (h)
5 (yield, syn/anti)
1a
2a
4a (OAc)
4a (OAc)
THF
THF
rt
50
3
3
—
—
OH OH
3b
4a (OAc)
THF
50
1
OBn
5a (83% , 1/1)
4b
5b
4a (OAc)
4a (OAc)
CH3CN
CH2Cl2
50
40
3
3
—
—
OH OH
6b
4b (OCO2Et)
THF
50
1
OTBS
5b (56%, 1/1)
OH OH
7b
4c (OCO2Et)
THF
50
1
Ph
5c (40%, 1/1)
5a (63%, 1/1)
5a (51%, 2/1)
5a (57%, 4/1)
8b
4d (OCO2Et)
4d (OCO2Et)
4d (OCO2Et)
THF
THF
CH2Cl2
50
rt
rt
1
18
18
9b
10b
a Pd2(dba)3ꢀ CHCl3 (5 mol %)/dppb (25 mol %).
b Pd(PPh3)4 (10 mol %)/PPh3 (25 mol %).
50 ꢁC for 1 h. Under these conditions, compounds 4b
and 4c were transformed into diols 5b and 5c in 56%
yield and 40% yield, respectively, in a 1/1 syn/anti ratio
(Table 2, entries 6 and 7). Furthermore, 1,3-diol 5a can
be obtained from allylic carbonate 4d in 63% yield in a
1/1 syn/anti ratio when the reaction was achieved in

J. Cluzeau et al. / Tetrahedron Letters 46 (2005) 6945–6948
6947
THF at 50 ꢁC (Table 2, entry 8). As carbonates are more
reactive than acetates and in order to improve the dia-
stereoselectivity, the reaction was performed on carbon-
ate 4d at rt in the presence of Pd(PPh3)4. Diol 5a was
isolated in 51% yield and the syn/anti ratio was slightly
increased to 2/1 in favor of the syn isomer (Table 2,
entry 9). Furthermore, the syn/anti ratio was increased
to 4/1 when the reaction was performed in CH2Cl2 at
rt (Table 2, entry 10).9,10
It is worth noting that for allylic acetates 9 and 10, the
presence of a hydroxy group is necessary to produce
the corresponding allylic alcohol or ether (Table 4,
entries 4 and 5). In contrast, with allylic carbonates,
the hydroxy group does not seem necessary as allylic
carbonate 11 was transformed to ether 15 (60%), which
corresponds to the substitution of the carbonate on the
less hindered carbon, whereas the presence of a hydroxyl
group directs the attack of the OR group on the p-allyl
palladium complex at the more substituted carbon.
Monoprotected 1,3-diols can be useful in the synthesis
of various natural products. In order to produce these
diols, allylic acetate 4a was treated with trimethyl borate
(3 equiv) or tribenzyl borate (3 equiv) in the presence of
Pd(PPh3)4 (0.1 equiv) and PPh3 (0.25 equiv) in THF at
50 ꢁC. Unfortunately, the desired products 6a and 6b
were not obtained. However, treatment of the allylic car-
bonate 4d, under the conditions used to transform 4a in
5a, provided the monoprotected 1,3-diols. The reaction
is general as methyl ether 6a11 and benzyl ether 6b were
isolated in 93% and 74% yield when 4d was treated with
trimethyl borate and tribenzyl borate, respectively
(Table 3, entries 3 and 4). When 4d and 4e were treated
at rt in CH2Cl2 with trimethyl borate, 6a (76%) and 6c
(70%) were isolated in a 2/1 syn/anti ratio (Table 3,
entries 5 and 6).
Table 4. Formation of 1,2-diols and derivatives
Entry Substrate
B(OR)3
Product
(yield, syn/anti)
OH
OH
B(OH)3
1
OCO2Et
7
OH
12 (57%a, 6/1)
OH
2
7
B(OMe)3
OMe
13 (64%, 6/1)
OCO2Et
3
4
B(OMe)3
B(OH)3
14 (78%O, 1/1)
OH
8
OAc
b
—
In order to explore the scope and limitation of the method,
the reaction was tested on compounds 7–11 in the
presence of Pd(PPh3)4 in THF at 50 ꢁC. 1,2-Diols 12
can be obtained in 57% yield (syn/anti = 6/1) when 7
was treated with boric acid and the corresponding
monomethyl ether derivative 13 was isolated in 64%
yield (syn/anti = 6/1) when trimethyl borate was used.12
On the contrary, 1,4-diol was not formed when 8 was
treated with trimethyl borate as the intramolecular reac-
tion was faster than the intermolecular reaction and the
disubstituted tetrahydrofuran 1413 was isolated in 78%
yield as an equimolecular mixture of cis/trans isomers.
9
b
5
6
B(OMe)3
B(OMe)3
—
OAc
10
OCO2Et
OMe
15 (60%)
11
a
29% of starting material was recovered.
b 100% of starting material was recovered.
Table 3. Synthesis of monoprotected 1,3-diols
B(OR")3
OH
OR" OH
Pd(PPh3)4
R'O
R
R
4
6a-c
Entry
4
B(OR00)3
Solvent, t (ꢁC)
Time (h)
6 (yield, syn/anti)
1
2
4a (OAc)
4a (OAc)
B(OMe)3
B(OBn)3
THF, 50
THF, 50
3
3
—
—
MeO OH
3
4
5
6
4d (OCO2Et)
4d (OCO2Et)
4d (OCO2Et)
4e (OCO2Et)
B(OMe)3
B(OBn)3
B(OMe)3
B(OMe)3
THF, 50
1
1
2
2
OBn
6a (93%, 1/1)
BnO OH
THF, 50
OBn
6b (74%, 1/1)
MeO OH
CH2Cl2, rt
CH2Cl2, rt
OBn
6a (76%, 2/1)
MeO OH
OTBS
6c (70%, 2/1)

6948
J. Cluzeau et al. / Tetrahedron Letters 46 (2005) 6945–6948
Formation of 1,3-Diols
Supplementary data
LnPd
R"
R"
OH OH
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tetlet.
2005.07.135.
O
R"
LnPd
O
B
R
O
O
R
B
R
O
O
O
O
R"
anti
R"
R"
D
C
References and notes
OH OH
LnPd
O
1. Norcross, R. D.; Paterson, I. Chem. Rev. 1995, 95, 2041–
2114.
2. Lopez, F.; Ohmura, T.; Hartwig, J. F. J. Am. Chem. Soc.
2003, 125, 3426–3427.
3. Kirsch, S. F.; Overman, L. E. J. Am. Chem. Soc. 2005,
127, 2866–2867.
R"
R"
R
R
O
O
B
syn
E
O
"R
Formation of 1,2-Diols
4. Xiao-Qiang, Y.; Atsushi, H.; Masaaki, M. Chem. Lett.
2004, 33, 764–765.
5. Trost, B. M.; McEachern, E. J.; Toste, F. D. J. Am. Chem.
Soc. 1998, 120, 12702–12703.
6. Trost, B. M.; Brown, B. S.; McEachern, E. J.; Kuhn, O.
Chem. Eur. J. 2003, 9, 4442–4451.
7. Scholl, M.; Ding, S.; Woo Lee, C.; Grubbs, R. H. Org.
Lett. 1999, 1, 953–956.
O
H
OH
B
O
R
O
R
O
"R
OH
syn
H
LnPd
F
8. Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J., Jr.;
Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791–
799.
9. The syn relationship was proved by the chemical shift of
(CH3)2C in the diol acetonide by 13C NMR. (a) Evans, D.
A.; Rieger, D. L.; Gage, J. R. Tetrahedron Lett. 1990, 31,
7099–7100; (b) Rychnovsky, S. D.; Rogers, B.; Yang, G.
J. Org. Chem. 1993, 58, 3511–3515.
O
H
OH
B
O
O
R
O
R
"R
OH
PdLn
anti
G
10. General procedure for the reaction using B(OR)3: Com-
pound of type 4 (1 equiv) was dissolved in THF or CH2Cl2
(0.05 M). Trialkyl borate or boric acid (3 equiv) and
Na2CO3 (1.5 equiv) were added and the mixture was
stirred for 1 h. Pd(PPh3)4 (0.1 equiv) and PPh3 (0.25 equiv)
were then added and the mixture was stirred until
completion of the reaction (monitoring by TLC). The
reaction was then diluted with Et2O and washed with a
saturated aqueous NaHCO3 solution, 0.1 M aqueous HCl
solution, and brine. The organic phase was dried over
anhydrous Na2SO4, filtered, and concentrated. The reac-
tion mixture was purified by flash chromatography.
11. 1-Benzyloxy-5-methoxy-hept-6-en-3-ol (6a): Compound
4d (50 mg, 0.15 mmol, 1 equiv) was treated with
B(OMe)3 (52 lL, 0.46 mmol, 3 equiv) in THF (3 mL) at
50 ꢁC. Product 6a was obtained as a 1/1 mixture of
diastereomers (93%). Rf = 0.31 (70/30 hexane/EtOAc); 1H
NMR d (CDCl3) 7.32 (m, 5H), 5.70 (m, 1H), 5.26–5.18
(m, 2H), 4.51 (s, 3H), 4.00 and 3.98 (2br s, 1H), 3.90–3.76
(m, 1H), 3.68 (m, 2H), 3.29 and 3.28 (2s, 3H), 1.81–1.54
(m, 4H); 13C NMR d (CDCl3) 138.3 (·2), 138.1, 138.0,
128.4 (·2), 127.7, 127.6, 117.6, 116.9, 83.1, 80.1, 73.3, 73.2,
69.0, 68.8, 67.9, 67.5, 56.4, 56.1, 42.7, 42.6, 37.3, 36.9. IR
(cmꢁ1) 3447, 2923, 2856, 1496, 1453, 1420, 1362, 1205,
1092, 1027, 992, 925, 808, 735, 696. MS (IE) m/z 218
(M+ꢁCH3OꢁH).
Scheme 2. Proposed transition states for the syn/anti selectivity.
The poor diastereoselectivity in the synthesis of 1,3-diols
can be explained by a six-membered chair transition
state where the borate is complexed by the free hydroxy
group (Scheme 2). In the C, D, and E transition states,
1,3-diaxial interactions and/or interactions with the
palladium complex are present and the stability of all
the intermediates should be similar, leading to a low
syn/anti ratio.
For the formation of 1,2-diols, the five-membered ring
transition state G is disfavored by a A1,3-strain or a
1,2-diaxial interaction, favoring the transition state F,
which is responsible for the formation of the syn
isomers.
In conclusion, we have developed a new palladium-cat-
alyzed formation of 1,2- and 1,3-diols as well as the for-
mation of monoprotected diols from x-hydroxy allylic
acetates and carbonates using boric acid and trialkyl
borates.
12. The relative stereochemistry of the diols was determined
1
by comparison with the reported H and 13C NMR data.
Acknowledgments
Lombardo, M.; Morganti, S.; Trombini, C. J. Org. Chem.
2003, 68, 997–1006.
One of us (J. Cluzeau) thanks the CNRS for a postdoc-
toral grant.
13. Wilson, S. R.; Augelli-Szafran, C. E. Tetrahedron 1988, 44,
3983–3995.