Synthesis of carbonates directly from 1 atm CO2 and alcohols using CH2Cl2

Article abstract of DOI:10.1016/j.tet.2010.10.051

We introduced here a new one-pot, general procedure for the preparation of dialkyl carbonates from alcohols in a straightforward fashion under 1 atm pressure of CO₂ using Cs₂CO₃ and CH ₂Cl₂ as key reagents.

Full text of DOI:10.1016/j.tet.2010.10.051

Tetrahedron 66 (2010) 9675e9680
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Tetrahedron
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Synthesis of carbonates directly from 1 atm CO2 and alcohols using CH2Cl2
,b,
Yusuke Yamazaki a, Kasumi Kakuma a, Ya Du a, Susumu Saito a
*
a Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
b Institute for Advanced Research, Nagoya University, Chikusa, Nagoya 464-8601, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
We introduced here a new one-pot, general procedure for the preparation of dialkyl carbonates from
alcohols in a straightforward fashion under 1 atm pressure of CO2 using Cs2CO3 and CH2Cl2 as key
reagents.
Received 29 September 2010
Received in revised form 15 October 2010
Accepted 18 October 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Available online 10 November 2010
Keywords:
1 atm Carbon dioxide
Dichloromethane
Carbonate
Alcohol
Cesium carbonate
5ceh
1. Introduction
promoter.5a,
These two precedents were successfully imple-
mented in demand for separately preparing R0Xs in advance from the
corresponding alcohols. We report here a third synthetic method
employing M2CO3 (M¼Cs, Scheme 1, bottom), in which a range of
carbonates was produced effectively upon simple exposure of a 1 atm
pressure of CO2 to alcohols in the presence of CH2Cl2.
Recent interest in the utilization of carbon dioxide (CO2) as a syn-
thetic buildingblock hasinspired a numberofinvestigations1e5 of the
preparation of dialkyl carbonates (RO(C]O)(OR))1,4,5 from alcohols
and CO2. Carbonates have potential usage as neutral allylating,6
alkylating,7 and carbonylation7 agents, as well as fuel additives,
electrolyte solvents, etc., and in particular for poly(carbonate)s pro-
duction.1 In general, however, previous methods utilizing alcohols
and CO2, in the presence of heterogeneous or molecular catalysts,4
accommodated rather drastic conditions including high pressure
(>40 atm) and temperature (>150 ꢀC), and concomitant removal of
H2O was a fatal event to overcome the thermodynamic disadvantage
(DG>>0). In order to achieve carbonate synthesis under milder
conditions including ‘1 atm CO2’, alkyl halides (R0Xs, Scheme 1) have
been nicely adjusted, being an inevitable partner of CO2 or its
equivalents.5 During an earlier attempt, R0Xs were used as electro-
philes, wherein two molecules of an R0X underwent coupling with
COꢁ3 supplied from an alkaline metal carbonate (M2CO3; M¼Na, K, Cs)
(‘inorganic carbonate alkylation’, Scheme 1, top).5b Subsequently,
a combined usage of R0X and alcohol, the former being used as an
electrophile with the latter being a nucleophile, gave rise to either
symmetrical orunsymmetrical dialkyl carbonates (Scheme 1, middle)
in the absence or in the presence of CO2 (1e120 atm) using more or
less excess amount of base including a guanidine or M2CO3 as critical
Scheme 1. General scheme of carbonate synthesis: from alkaline metal carbonate
(M2CO3) and alkyl halide (R0X) (top); from CO2, alcohol (ROH) and R0X (middle); from
CO2 and alcohol (bottom).
2. Results and discussion
Our synthetic procedure for carbonates is very simple and
straightforward: treatment of a CH2Cl2 (3.1 equiv)dNMP suspension
of Cs2CO3 (2 equiv) with benzyl alcohol 1a (1 equiv) under an atmo-
sphere of CO2 (1 atm) at 100 ꢀC for 12 h gave, after column chroma-
tography on silica gel, the corresponding dibenzyl carbonate (2a) in
* Corresponding author. Tel./fax: þ81 52 789 5945; e-mail address: saito.susumu@
f.mbox.nagoya-u.ac.jp (S. Saito).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.10.051

9676
Y. Yamazaki et al. / Tetrahedron 66 (2010) 9675e9680
100
90
80
70
60
50
40
30
20
10
0
an isolated yield of 96%. Smaller or larger amounts of CH2Cl2 were
used to elucidate the relevance between molar equivalents of CH2Cl2
and yields of 2a (Fig. 1).
A 2.3 or 1.6 equiv of CH2Cl2 was also satisfactory, giving com-
parable yields of 2a (Table 1, entries 2 and 3), while the amounts of
CH2Cl2 lower than 0.8 equiv afforded a significantly lower yield (2a:
<54%) and without CH2Cl2, no reaction take place. The best yield of
2a was saturated in using more than 3.1 equiv of CH2Cl2. Pro-
ductivity was decreased significantly in use of a smaller amount of
Cs2CO3, such as 1 and 0.4 equiv, which gave 2a in 51% and 25% yield,
respectively. Decreasing the reaction temperature to 80 ꢀC or 60 ꢀC
again led to a decline in the carbonate yields (35% and 5%, re-
spectively). Attempts to use 200 mol % each of K2CO3, Na2CO3,
CsOH, CsHCO3 or CsCl in place of Cs2CO3 resulted in almost no re-
action (0e2%), while CsHCO3þCs2CO3 (100 mol % each) and
CsHCO3þCs2CO3þCsCl (100 mol % each) showed fair reactivity, both
yield of
2a %
0
1
2
3
4
5
molar equivalent
Fig. 1. NMR yield of 2a as a function of molar equivalent of CH2Cl2 relative to molar
amount of alcohol 1a. 1,1,2,2-tetrachloroethane was used as an internal standard,
which was added at 25 ꢀC after the reaction time of 12 h.
Table 1
Substrate scope in carbonate synthesisa
Entry
1
Alcohol 1
Time [h]
Product 2
Yieldb [%]
96
12
2
3
90c
91d
4
5
6
7
X¼OCH3 (1b)
X¼CH3 (1c)
X¼Cl (1d)
24
24
24
48
2b (X¼OCH3)
2c (X¼CH3)
2d (X¼Cl)
80 (19)
87 (12)
99
X¼CF3 (1e)
2e (X¼CF3)
47
8
9
24
24
99
93
Y¼S (1g)
2g (Y¼S)
10
24
58
11
12
13
R1¼CH3; R2¼R3¼H (1i)
R1¼H; R2¼R3¼CH3 (1j)
R1¼R3¼H; R2¼Ph (1k)
24
24
24
2i (R1¼CH3; R2¼R3¼H)
2j (R1¼H; R2¼R3¼CH3)
2k (R1¼R3¼H; R2¼Ph)
61 (16)
30 (69)
90 (7)
OH
14
15
12
12
(E)-2l (R1¼R3¼H; R2¼e(CH2)2CH]C(CH3)2)
(Z)-2l (R1¼R2¼H; R3¼e(CH2)2CH]C(CH3)2)
49 (49)
40 (47)
16
24
65 (33)
17
18
Z¼OCH3 (1n)
Z¼CH3 (1o)
24
24
2n (Z¼OCH3)
2o (Z¼CH3)
60 (20)
74 (8)
O
19
Me(CH2)7OH (1p)
24
42 (24)
Me(H2C)7O
O(CH2)7Me
a
Cs2CO3/1/CH2Cl2¼200:100:310 (mol %). Conditions: 100 ꢀC, 12e48 h in NMP.
b
c
Of isolated, purified products, corresponding to the conversion of alcohol. The values in parentheses are the isolated yields of 3.
Cs2CO3/1/CH2Cl2¼200:100:230 (mol %).
d
Cs2CO3/1/CH2Cl2¼200:100:160 (mol %).

Y. Yamazaki et al. / Tetrahedron 66 (2010) 9675e9680
9677
giving a considerably lower yield of 2a (22%) under otherwise
identical conditions. After carrying out the screening of solvent
effects, it was shown that aprotic polar solvents (DMF, DMA or
DMSO) were consistently better suited for rate enhancement (2a:
88%, 90% and 79%, respectively: 100 ꢀC, 12 h), compared with less
polar solvents (toluene or THF), which led to a very low conversion
(2a: <2%). Without NMP, the reaction did not take place (2a: <1%).
Scant reactivity (2a: <2%) was also obtained in the absence of CO2,
demonstrating that Cs2CO3 cannot be an alternative CO2 source.
Given the optimal conditions accommodating 96% yield of 2a,
(Cs2CO3 (200 mol %), CH2Cl2 (310 mol %) in NMP at 100 ꢀC) other
representative alcohols 1aep were applied in this carbonate syn-
thesis and the results are listed in Table 1. This synthetic protocol
showed substrate generality with respect to benzylic, allylic, phe-
nylethyl, and saturated alcohols 1aep (entries 1e19), but in some
cases, was contaminated with different carbonates 3 (Fig. 2). In
a series of benzylic alcohols 1aeg, substrates 1f and 1g with het-
erocyclic ring systems were well suited for this procedure (entries 8
and 9). The reaction proceeded as well no matter how electron-
withdrawing or -donating groups were attached to the aromatic
ring; however, substitution by the nitro group at the para-position
(X¼NO2) almost prohibited the reaction from proceeding. The more
electron-donating the X group, the more increased the formation of
3 (entries 4 and 5).
was recovered in 80% yield with complete preservation of the R
configuration, ascertained by chiral HPLC analysis.12 This suggests
that alcohol should merely react as nucleophile, although we could
not fully rule out the mechanistic scenario, in which alcohol worked
as electrophile undergoing double inversion or retention pathway.
Scheme 2. Carbonate formation and subsequent degradation. Cs2CO3/(R)-1q/CH2Cl2¼
200:100:310 (mol %).
When CH2Cl2 was replaced by 13CH2Cl2, 3q was obtained in
a comparable yield with 13CH2 fully incorporated into the structure
of 3q (Scheme 3).
O
CO2 (1 atm)
13CH2
Cs2CO3
O
O
OH
O
2q
+
13CH2Cl2/NMP
13
rac-1q
68%
25%
C-3q
°
C
100
Scheme 3. Incorporation of 13C into carbonate 3q. Cs2CO3/rac-1q/13CH2Cl2¼200:
100:310 (mol %).
We therefore envisioned that either one of IA and IB (Fig. 3)
would be formed as meta-stable intermediates upon reaction of
CH2Cl2 with alkoxide (CsOR) or carboxylate (CsO(C]O)OR, derived
from Cs2CO3þROHþCO2), respectively, so that chloromethyl ether 4
was used to see whether this could afford carbonate 2a in a rea-
sonable yield (Scheme 4). Although the reaction fairly brought
about 2a, its yield was significantly lower, suggesting that more
reactive intermediate IB is highly likely to be responsible for pro-
moting a major pathway. Unfortunately, intermediate IB was too
reactive to be detected or isolated. In addition, formaldehyde was
unable to be trapped by chemical reagents during any attempts
exerted so far. Nevertheless, we wish to emphasize that the present
protocol using CO2, alcohol and CH2Cl2 is attractive from several
notable viewpoints: e.g., productivity, substrate generality, func-
tional group tolerance, preservation of chirality, straightforward-
ness and practicality at least in lab-scale experiments.
O
Z
Z
O
O
O
O
O
O
O
X
X
3b: X = OMe
3c: X = Me
3m: Z = H
3n : Z = OMe
3o : Z = Me
R3
O
R3
CH3
O
CH3
R2
R2
R2
O
O
O
R2
O
O
O
R1
R1
3 = H
R
R
1 = Me;R2 = H;
R
(E)-3l and (Z)-3l:
R2 = -(CH2)2CH=C(CH3)2
3i :
3j :
1 = H; R2 = Me; R3 = Me
O
Me(H2C)7O
O
O(CH2)7Me
3p
Fig. 2. A series of by-products 3.
RO
CsCl
OR
In a series of allylic alcohols 1hel, the allylic olefins vicinal to the
OH group, were tolerated and remained essentially unreacted
(entries 10e15). The E and Z geometry of these olefins in 1k and 1l
was well preserved to give retention of the configuration.
CsOR
CO2, ROH
Cs2CO3
(R = Ph)
CsOR
CsCl
RO
Cl
3
The substitution by a phenyl group at the b-position of hydroxy
CsCl, CsHCO3
path a
IA
groups (1meo) (Table 1, entries 16e18) did not prevent from the
formation of the carbonates except with relatively lower yields of
2meo, accompanied by considerable amounts of 3meo. A great
difficulty in carbonate formation was observed using phenol, but
instead the formation of the acetal (PhOCH2OPh)8 predominated.
This alternative pathway could be interpreted by direct reaction of
2 equiv of the phenoxide (CsOPh) with 1 equiv of CH2Cl2 that
prevailed over the incorporation of CO2. CsF is also known to pro-
mote the O-alkylation of phenol with CH2Cl2.9 In contrast, diphenyl
carbonate1e,f was synthesized in low yields (w20%) by treatment of
a high pressure of CO2 (40 atm) with phenol, CCl4, and K2CO3 in the
presence of a stoichiometric amount of ZnCl2 at 120 ꢀC.10
CH2Cl2
CsCl
CO2, ROH
Cs2CO3
O
a
path b
CsOR
2
RO
O
IB
Cl
CsCl,
CsHCO3
CsCl, CH2O
b
Fig. 3. Possible reaction intermediates and pathways.
In order to gain further insights into the rather complicated multi-
steps that should be involved during the carbonate formation from
CO2, we carried out a set of model experiments separately. Did alco-
hols act as nucleophiles orelectrophiles? To verify thispoint, optically
Scheme 4. Reaction of 1a with chloromethyl ether 4 under 1 atm pressure of CO2.
Cs2CO3/1a/4¼200:100:100 (mol %).
pure (R)-a-phenylethyl alcohol 1q (>99% ee) was used under the
optimized conditions, which gave a mixture of 2q and 3q in >90%
total yields (Scheme 2;3qwasomitted). Subsequentlyisolated2qwas
Bearing the above working hypothesis in mind, the reaction
conditions were further optimized to obtain 2 as a sole carbonate.
During such attempts, it was revealed that addition of water or
degradated by a b
-aminoalcohol11 into the parent alcohol 1q, which

9678
Y. Yamazaki et al. / Tetrahedron 66 (2010) 9675e9680
rather acidic environments (pH¼5ꢂ0.02) adjusted by an aqueous
buffer (citric acid/NaOH) at 125 ꢀC, facilitated the decomposition of 2
and 3 into CO2 and 1. Finally, exactly the same reaction conditions
(100 ꢀC) described in Table 1 for each substrate (first step) were
followed by addition of Na2SO4 (50 mol % with respect to the molar
amount of starting alcohol) and subsequently raising the tempera-
ture to 125 ꢀC under argon (second step) uniformly increased the
yield of 2 (Table 2). As a few exceptions, no improvement was ob-
served with alcohols 1b and 1o having a more electron-donating
group (entries 1 and 7). In all attempts, undesirable carbonate 3 was
converted notonly into respective 2, but also into CO2 and the parent
alcohol 1 even after such an effort to re-optimize the conditions. In
contrast, when the reaction of (E)-1l with CO2 was started at 125 ꢀC
(as the first step), which was kept through the end (12 h), the yield of
(E)-2l (57%) was better than that in Table 1 (entry 12) but worse than
inTable 2 (entry 4); formation of (E)-3l was not observed in this case.
chromatography was performed using silica gel (silica gel 60,
230e400 mesh, Merck). TLC was performed using pre-coated silica
gel plate (silica gel 60 F254, Merck) and products were observed
under UV light or with either phosphomolybdic acid reagent. 1H
NMR and 13C NMR spectra were recorded on a JEOL ECA-600 spec-
trometer, operating in CDCl3 at 600 MHz. Chemical shifts and cou-
pling constants are presented in parts per million
d relative to
tetramethylsilane and hertz, respectively. High resolution mass
spectra was obtained on JEOL JMS-700. Chiral high performance
liquid chromatography analysis was conducted using Shimadzu
LC-10AD coupled with photo diode array-detector SPD-M20A and
chrial column of CHIRALCEL OD-H (Daicel chemical industries, LTD.).
2a, 2c, 2d, 2f, 2h, 2i, 2k, 2m, 2n, 2o, and 2q are all known compounds
(For references, see Electronic Supplementary data). The available
spectral and analytical data for all new compounds are shown below.
Table 2
4.2. Typical procedure: the synthesis of carbonate 2a (Table 1)
Improved one-pot preparation of carbonate 2a
Entry
Alcohol 1
Yieldb [%]
of 2 (3)
Product 2c
Yieldd
of 2 [%]
Recoverye
of 1 [%]
To an anhydrous 1-methyl-2-pyrrolidinone (NMP) (1 mL) solution
of benzyl alcohol (1a) (217 mg, 2 mmol) were added cesium car-
bonate (1303 mg, 4 mmol) and dichloromethane (400 mL, 6.2 mmol)
1
2
3
4
5
6
7
8
9
1b
1i
1j
(E)-1l
(Z)-1l
1m
1n
1o
1p
80 (19)
61 (16)
30 (69)
49 (49)
40 (47)
65 (33)
60 (20)
74 (8)
2b
2i
2j
(E)-2l
(Z)-2l
2m
2n
2o
2p
66
63
74
79
66
67
25
77
60
33
36
25
19
33
32
74
22
39
under argon atmosphere at room temperature. A 1 L balloon charged
with CO2 gas was equipped to the reaction tube, and the mixture was
subjected to the freeze (ꢁ196 ꢀC)ethaw (25 ꢀC) cycle (ꢃ3) to replace
the argon atmosphere by CO2 (filled in 1 L balloon). The mixture was
stirred for 12 h at 100 ꢀC in a closed system. The reaction mixture
was quenched with saturated aq NH4Cl(10 mL), and then the mixture
was extracted with EtOAc (10 mLꢃ3). The organic layer was dried
over Na2SO4 and filtered. Evaporation of the filtrate solvents followed
by flash column chromatography on silica gel (eluent: hexane/EtOAc,
10:1) afforded 2a (232.5 mg, 0.96 mmol, 96%) as a colorless oil.
42 (24)
a
Cs2CO3/1/CH2Cl2¼200:100:310 (mol %). Conditions: first step: 100 ꢀC, 12e24 h
in NMP as in Table 1, then; second step: the mixture being further reacted for 6 h at
125 ꢀC under Ar after adding Na2SO4 (50 mol %).
b
Of the first step, the same values as in Table 1.
Of the second step.
Of isolated, purified products obtained after the total (first and second) steps,
c
d
based on the conversion % of 1.
e
Determined by 1H NMR using 1,1,2,2-tetrachloroethane as an internal standard.
4.3. Typical procedure: the improved synthesis of carbonate
(E)-2l (Table 2)
3. Conclusions
To an anhydrous 1-methyl-2-pyrrolidinone (NMP) (1 mL) solution
of geraniol ((E)-1l) (351
(1303 mg, 4 mmol) and dichloromethane (400
m
L, 2 mmol) were added cesium carbonate
In summary, we introduced a new one-pot procedure for the
preparation of carbonates from alcohols in a straightforward fashion
under 1 atm pressure of CO2 using Cs2CO3 and CH2Cl2. A set of multi-
steps involving IB, and another set of distinct steps involving IA, might
be involved in the overall process, both affording carbonates. The re-
action was demonstrated to preserve E or Z geometry of the olefin of
allylic alcohols as well as a stereogenic center of alcohol. Bycontrast, in
useofalkylhalides(R0X,Scheme 1)previouslyreported,5 theseaspects
were not necessarily guaranteed. To be emphasized is that separately
preparing RX from the corresponding ROH is not needed. The more
detailed reaction mechanism, as well as a possibility of replacement of
the CH2Cl2 by other reagents that mimic a potential function of CH2Cl2,
are to be addressed in a next improvement. In addition, an attempt to
expand the substrate scope to the autoclave synthesis of more im-
portant classes of low molecular weight carbonates, such as dimethyl
carbonate (DMC)7 is now underway in our laboratory.
mL, 6.2 mmol) under
argon atmosphere at room temperature. A 1 L balloon charged with
CO2 gas was equipped to the reaction tube, and the mixture was
subjected to the freeze (ꢁ196 ꢀC)ethaw (25 ꢀC) cycle (ꢃ3) to replace
the argon atmosphere by CO2 (filled in 1 L balloon). The mixture was
stirred at 100 ꢀC in this closed system. After stirring for 12 h, The CO2
gas in balloon was replaced by argon gas, followed by the addition of
anhydrous Na2SO4 (142 mg, 1 mmol) to the reaction mixture. The
resulting mixture was stirred at 125 ꢀC for 6 h. The reaction was
quenched with saturated aq NH4Cl(10 mL), and then the mixture was
extracted with EtOAc (10 mLꢃ3). The organic layer was dried over
Na2SO4 and filtered. Evaporation of the filtrate solvents followed by
flash column chromatography on silica gel (eluent: hexane/EtOAc,
10:1) afforded (E)-2l (264 mg, 0.79 mmol, 79%) as a colorless oil.
4.3.1. Bis((4-methoxyphenyl)methyl) carbonate (2b). Rf (17% EtOAc/
hexane) 0.37; 1H NMR (CDCl3, 400 MHz)
d
7.29 (d, J¼8.8 Hz, 2H),
4. Experimental
4.1. General
6.86 (d, J¼8.8 Hz, 2 H), 5.07 (s, 2H), 3.76 (s, 3H); 13C NMR (CDCl3,
100 MHz)
d 159.7, 155.0, 130.1, 127.3, 113.8, 69.3, 55.1. HRMS (FAB)
calcd for C17H18O5 (MþNaþ): 325.1046. Found m/z¼325.1048.
All reactions were carried out under argon atmosphere and in
dried up glassware by means of standard Schlenk techniques unless
otherwise noted. All reagents were purchased from Aldrich, Wako,
TCI, Kanto and used without further purification except for benzyl
alcohol, which is simply distilled under reduced pressure. Column
4.3.2. 4-Methoxybenzyl (4-methoxybenzyloxy)methyl carbonate (3b).
Rf (10% EtOAc/hexane) 0.31; 1H NMR (CDCl3, 400 MHz)
d 7.34 (d,
J¼8.3 Hz, 2H), 7.25 (d, J¼8.6 Hz, 2 H), 6.90 (d, J¼8.5 Hz, 2H), 6.87 (d,
J¼8.5 Hz, 2H), 5.32 (s, 2H), 5.12 (s, 2H), 4.64 (s, 2H), 3.81 (s, 3H), 3.80
(s, 3H); 13C NMR (CDCl3, 100 MHz)
d 159.9, 159.5, 154.5, 130.4, 129.7,

Y. Yamazaki et al. / Tetrahedron 66 (2010) 9675e9680
9679
128.6, 127.1, 114.0,114.0, 90.9, 71.3, 69.6, 55.3, 55.2. HRMS (FAB) calcd
117.5, 90.9, 66.1, 64.8, 39.5, 39.5, 26.2, 26.2, 25.6, 17.6, 16.5, 16.4. HRMS
for C18H20O4 (MþNaþ): 355.1158. Found m/z¼355.1148.
(FAB) calcd for C22H36O4 (MþNaþ): 387.2511. Found m/z¼387.2493.
4.3.3. 4-Methylbenzyl (4-methylbenzyloxy)methyl carbonate (3c). Rf
4.3.12. Bis((Z)-3,7-dimethylocta-2,6-dienyl) carbonate ((Z)-2l). Rf (17%
(10% EtOAc/hexane) 0.29; 1H NMR (CDCl3, 270 MHz)
d
7.31e7.13 (m,
J¼8H), 5.34 (s, 2 H), 5.15 (s, 2H), 4.67 (s, 2H), 2.36 (s, 3H), 2.34 (s,
3H); 13C NMR (CDCl3, 100 MHz)
154.5, 138.5, 137.8, 133.5, 132.0,
EtOAc/hexane) 0.69; 1HNMR(CDCl3, 270 MHz)
d
5.38(t, J¼6.9 Hz, 2H),
5.09 (t, J¼5.6 Hz, 2H), 4.61 (d, J¼7.3 Hz, 4H), 2.16e1.99 (m, 8H),1.76 (s,
6H),1.68 (s, 6H),1.60 (s, 6H); 13C NMR (CDCl3,100 MHz)
155.3,143.0,
d
d
129.3, 129.2, 128.6, 128.1, 91.1, 71.5, 69.7, 21.2, 21.2. HRMS (FAB)
132.2,123.5,118.8,64.2,32.1, 26.6,25.6, 23.5,17.6.HRMS(FAB)calcdfor
calcd for C18H20O4 (MþNaþ): 323.1259. Found m/z¼323.1256.
C21H34O3 (MþNaþ): 357.2406. Found m/z¼357.2395.
4.3.4. Bis(4-(trifluoromethyl)benzyl) carbonate (2e). Rf (33% EtOAc/
4.3.13. (Z)-3,7-Dimethylocta-2,6-dienyl ((Z)-3,7-dimethylocta-2,6-di-
hexane) 0.63; 1H NMR (CDCl3, 270 MHz)
d
7.63 (d, J¼7.9 Hz, 4H),
enyloxy)methyl carbonate ((Z)-3l). Rf (17% EtOAc/hexane) 0.62; 1H
7.50 (d, J¼7.9 Hz, 4 H), 5.23 (s, 4H); 13C NMR (CDCl3, 400 MHz)
NMR (CDCl3, 270 MHz) d 5.47e5.30 (m, 2H), 5.28 (s, 2H), 5.10e5.09
d
154.8, 139.0, 130.9, 130.6, 128.3, 127.8, 125.7, 125.7, 125.6, 125.6,
(m, 2H), 4.64 (d, J¼7.3 Hz, 2H), 4.10e4.05 (m, 2H), 2.09e2.08 (m, 8H),
125.4, 125.3, 122.6, 68.9. HRMS (FAB) calcd for C17H12F6O3
1.75 (s, 3H), 1.69 (s, 3H), 1.67 (s, 3H), 1.60 (s, 9H); 13C NMR (CDCl3,
(MþNaþ): 401.0588. Found m/z¼401.0579.
100 MHz) d 154.6, 143.5, 140.0, 132.5, 130.9, 128.8, 124.4, 123.6, 121.2,
120.2, 66.0, 63.6, 32.2, 31.9, 26.6, 26.5, 25.7, 25.6, 23.5, 23.4,17.6. HRMS
4.3.5. Bis(thiophen-2-ylmethyl) carbonate (2g). Rf (10% EtOAc/hex-
(FAB) calcd for C22H36O4 (MþNaþ): 387.2511. Found m/z¼387.2493.
ane) 0.61; 1H NMR (CDCl3, 270 MHz)
d
7.35 (dd, J¼5.3,1.0 Hz, 2H), 7.15
(d, J¼3.3 Hz, 2H), 7.00 (dd,J¼3.6, Hz, 2H), 5.33 (s, 4H);13C NMR(CDCl3,
4.3.14. Phenethoxymethyl phenethyl carbonate (3m). Rf (17% EtOAc/
100 MHz)
d
155.3,137.4,129.5,127.9,127.5, 64.4. HRMS (FAB) calcd for
hexane) 0.55; 1H NMR (CDCl3, 270 MHz)
d 7.19e7.32 (m,10H), 5.24 (s,
C11H20O3S2 (MþNaþ): 276.9969. Found m/z¼276.9965.
2H), 4.34 (t, J¼7.2 Hz, 2H), 3.86 (t, J¼6.9 Hz, 2H), 2.97 (t, J¼6.9 Hz, 2H),
2.89 (t, J¼7.2 Hz, 2H); 13C NMR (CDCl3,100 MHz)
d 155.3, 139.0, 137.9,
129.7, 129.7, 129.3, 129.2, 127.5, 127.1, 93.0, 72.1, 69.2, 36.9, 35.8. HRMS
4.3.6. 2-Methylallyl (2-methylallyloxy)methyl carbonate (3i). Rf (17%
EtOAc/hexane) 0.60; 1H NMR (CDCl3, 270 MHz)
d
5.32 (s, 2H), 5.02
(d, J¼8.6 Hz, 2H), 4.95 (d, J¼9.6 Hz, 2H), 4.58 (s, 2H), 4.11 (s, 2H),
1.79 (s, 3H), 1.75 (s, 3H); 13C NMR (CDCl3, 100 MHz)
154.5, 140.8,
(FAB) calcd for C18H20O4 (MþNaþ): 323.1259. Found m/z¼323.1256.
d
4.3.15. Bis(4-methoxyphenethyl) carbonate (2n). Rf (10% EtOAc/hex-
139.2, 113.7, 113.3, 91.3, 73.8, 71.2, 19.4, 19.3. Desirable HRMS (FAB)
peak sets data were unable to be obtained due to strong instability
of 3i under a range of HRMS measurement conditions.
ane) 0.49; 1H NMR (CDCl3, 270 MHz)
d 7.15e7.10 (m, 4H), 6.87e6.81
(m, 4H), 4.28 (t, J¼7.2 Hz, 4H), 3.78 (s, 6H), 1.26 (t, J¼7.2 Hz, 4H); 13C
NMR (CDCl3, 100 MHz)
d 158.4, 155.1, 129.9, 129.2, 114.0, 113.8, 68.5,
55.2, 34.3. HRMS (FAB) calcd for C19H22O5 (MþNaþ): 353.1365.
Found m/z¼353.1356.
4.3.7. Bis(3-methylbut-2-enyl) carbonate (2j). Rf (17% EtOAc/hex-
ane) 0.77; 1H NMR (CDCl3, 400 MHz)
d
5.37 (t, J¼7.3 Hz, 2H), 4.64 (d,
J¼7.1 Hz, 4H), 1.76 (s, 6H), 1.72 (s, 6H); 13C NMR (CDCl3, 100 MHz)
4.3.16. (4-Methoxyphenethoxy)methyl 4-methoxyphenethyl carbon-
d
155.4, 139.8, 118.2, 64.5, 25.8, 18.1. HRMS (FAB) calcd for C11H18O3
ate (3n). Rf (10% EtOAc/hexane) 0.29; 1H NMR (CDCl3, 270 MHz)
(MþNaþ): 221.1154. Found m/z¼221.1158.
d 7.16e7.12 (m, 2H), 7.12e7.09 (m, 2H), 6.86e6.83 (m, 2H), 6.82e6.80
(m, 2H), 5.25 (s, 2H), 4.30 (t, J¼7.2 Hz, 2H), 3.83 (t, J¼6.9 Hz, 2H), 3.76
4.3.8. 3-Methylbut-2-enyl (3-methylbut-2-enyloxy)methyl carbonate
(s, 6H), 2.91 (t, J¼7.2 Hz, 2H), 2.83, (t, J¼6.9 Hz, 2H); 13C NMR (CDCl3,
(3j). Rf (17% EtOAc/hexane) 0.66; 1H NMR (CDCl3, 270 MHz)
100 MHz) d 158.3, 158.1, 154.4, 130.1, 129.8, 129.8, 129.0, 113.9, 113.8,
d
5.42e5.26 (m, 2H), 5.29 (s, 2H), 4.66 (d, J¼7.3 Hz, 2H), 4.19 (d,
92.2, 71.5, 68.5, 55.1, 35.1, 34.1. Desirable HRMS (FAB) peak sets data
were unable to be obtained due to strong instability of 3n under
a range of HRMS measurement conditions.
J¼6.9 Hz, 2H), 1.77 (s, 3H), 1.76 (s, 3H), 1.73 (s, 3H), 1.68 (s, 3H); 13C
NMR (CDCl3, 100 MHz)
d 154.7, 140.2, 138.8, 119.6, 117.9, 91.0, 66.2,
64.7, 25.8, 18.1, 18.0. HRMS (FAB) calcd for C12H20O4 (MþNaþ):
251.1259. Found m/z¼251.1251.
4.3.17. Bis(4-methylphenethyl) carbonate (2o). Rf (17% EtOAc/hex-
ane) 0.63; 1H NMR (CDCl3, 270 MHz)
d
7.10 (s,10H), 4.28 (t, J¼7.2 Hz,
4.3.9. Cinnamyl cinnamyloxymethyl carbonate (3k). Rf (17% EtOAc/
4H), 2.92 (t, J¼7.2 Hz, 4H), 2.32 (s, 6H); 13C NMR (CDCl3, 100 MHz)
hexane) 0.11; 1H NMR (CDCl3, 270 MHz)
d
7.41e7.22 (m, 10H), 6.67
d 155.1, 136.2, 135.2, 134.3, 134.1, 129.2, 128.8, 68.4, 34.7, 21.0. HRMS
(t, J¼15.8 Hz, 2H), 6.35e6.21 (m, 2H), 5.39 (s, 2H), 4.81 (dd, J¼6.6,
(FAB) calcd for C19H22O3 (MþNaþ): 321.1467. Found m/z¼321.1472.
1.3 Hz, 2H), 4.38 (dd, J¼6.3, 1.3, 2H); 13C NMR (CDCl3, 100 MHz)
d
154.5, 136.3, 136.0, 135.1, 133.6, 128.6, 128.6, 128.2, 127.9, 126.7,
4.3.18. (4-Methylphenethoxy)methyl 4-methylphenethyl carbonate
126.6, 124.3, 122.1, 91.2, 70.6, 68.5. HRMS (FAB) calcd for C20H20O4
(3o). Rf (17% EtOAc/hexane) 0.54; 1H NMR (CDCl3, 270 MHz)
d 5.24
(MþNaþ): 347.1259. Found m/z¼347.1259.
(s, 2H), 4.32 (t, J¼7.2 Hz, 2H), 3.85 (t, J¼6.9 Hz, 2H), 2.9 (t, J¼7.3 Hz,
2H), 2.86 (t, J¼6.9 Hz, 2H), 2.31 (s, 6H); 13C NMR (CDCl3, 100 MHz)
4.3.10. Bis((E)-3,7-dimethylocta-2,6-dienyl) carbonate ((E)-2l). Rf
d 154.5, 136.2, 135.8,135.0,134.0, 129.2, 129.1, 128.8, 128.7, 92.2, 74.1,
(17% EtOAc/hexane) 0.68; 1H NMR (CDCl3, 400 MHz)
d
5.38 (t,
71.4, 68.5, 35.6, 34.6. HRMS (FAB) calcd for C20H24O4 (MþNaþ):
351.1572. Found m/z¼351.1561.
J¼6.4 Hz, 2H), 5.08 (t, J¼5.4 Hz, 2 H), 4.65 (d, J¼7.1 Hz, 4H), 2.10e2.05
(m, 8H),1.71 (s, 6H),1.68 (s, 6H),1.60 (s, 6H); 13CNMR(CDCl3,100 MHz)
d
155.4,143.0, 131.9, 123.7, 117.8, 64.6, 39.5, 26.2, 25.7,17.7, 16.5. HRMS
4.3.19. Dioctyl carbonate (2p). Rf (10% EtOAc/hexane) 0.75; 1H NMR
(FAB) calcd for C21H34O3 (MþNaþ): 357.2406. Found m/z¼357.2402.
(CDCl3, 270 MHz)
d
4.12 (t, J¼6.6 Hz, 4H), 1.66 (septet, J¼6.6 Hz, 4H),
1.42e1.22 (m, 20H), 0.87 (t, J¼6.3 Hz, 6H); 13C NMR (CDCl3,
4.3.11. (E)-3,7-Dimethylocta-2,6-dienyl ((E)-3,7-dimethylocta-2,6-dien-
100 MHz) d 155.5, 68.1, 31.8, 29.20, 29.16, 28.7, 25.7, 22.6,14.1. HRMS
yloxy)methyl carbonate ((E)-3l). Rf (17% EtOAc/hexane) 0.59; 1H NMR
(FAB) calcd for C17H34O3 (MþNaþ): 309.2406. Found m/z¼309.2407.
(CDCl3, 400 MHz)
d
5.39 (t, J¼6.4 Hz, 1H), 5.33 (t, J¼6.1 Hz, 1H), 5.29 (s,
2H), 5.09e5.06 (m, 2H), 4.68 (d, J¼7.3 Hz, 2H), 4.22 (d, J¼6.8 Hz, 2H),
4.3.20. Octyl octyloxymethyl carbonate (3p). Rf (10% EtOAc/hexane)
2.11e2.05 (m, 8H), 1.72 (s, 3H), 1.68 (s, 9H), 1.60 (s, 6H); 13C NMR
0.65; 1H NMR (CDCl3, 270 MHz)
3.66 (t, J¼6.6 Hz, 2H), 1.75e1.53 (m, 4H), 1.46e1.17 (m, 20H), 0.88 (t,
d
5.28 (s, 2H), 4.16 (t, J¼6.6 Hz, 2H),
(CDCl3, 100 MHz) d 154.6, 143.3, 142.0, 131.8, 131.7, 123.8, 123.6, 119.2,

9680
Y. Yamazaki et al. / Tetrahedron 66 (2010) 9675e9680
J¼6.3 Hz, 6H); 13C NMR (CDCl3, 100 MHz)
d
154.7, 92.3, 70.8, 68.3,
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4.3.21. (1-Phenylethoxy)methyl 1-phenylethyl carbonate (3q). Rf (10%
EtOAc/hexane) 0.16; 1H NMR (CDCl3, 270 MHz)
d 7.37e7.25 (m, 10H),
5.74e5.70 (m, 1H), 5.38 (dd, J¼6.3, 11.2 Hz, 1H), 5.01 (dd, J¼6.3,
15.5 Hz, 1H), 4.81e4.78 (m, 1H), 1.61e1.44 (m, 6H); 13C NMR (CDCl3,
ꢀ
Dibenedetto, A.; Fracchiolla, E.; Giannoccaro, P.; Pastore, C.; Papai, I.;
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CO2, the 13C NMR signal of 3q-d2 at 90.0 ppm showed significantly
strong intensity. HRMS (FAB) calcd for C18H20O4 (MþNaþ): 323.1259.
Found m/z¼323.1251. Data of chiral HPLC analysis of 1-phenyl-
ethenol (1q): chiral column: OD-H; eluent: hexane:i-PrOH¼20:1;
retention time: tR¼11.8 min ((R)-isomer); tR¼13.1 min ((S)-isomer)
at a flow rate of 1.0 mL/min.
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This work was supported by a Grant-in-Aid for Basic Research
(B) and Scientific Research on Priority Areas ‘Advanced Molecular
Transformations of Carbon Resource’ from the Ministry of Educa-
tion, Culture, Science, Sports and Technology of Japan, and by funds
from Asahi Glass, Asahi Kasei Chemicals, Daiso, Kuraray, Mitsubishi
Chemical, Mitsui Chemicals, Nissan Chemical Ind., and Sumitomo
Chemical. SS also greatly appreciates Prof. R. Noyori (Nagoya Uni-
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Supplementary data
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Supplementary data including 1H and 13C NMR spectra of all
new compounds for this article is available. Supplementary data
associated with this article can be found in online version at
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InChIKeys of the most important compounds described in this
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