Robust Silver(I) Catalyst for the Carboxylative Cyclization of Propargylic Alcohols with Carbon Dioxide under Ambient Conditions

Article abstract of DOI:10.1002/adsc.201500639

Inspired by the bulkier bis(triphenylphosphine)-silver cation-induced mechanism of propargylic alcohols and carbon dioxide through the alkyl carbonate intermediate, a robust dual-component catalytic system consisting of silver acetate and tetraheptylammonium bromide was rationally developed for the synthesis of α-methylene cyclic carbonates under ambient conditions without employing any additional organic base and ligand. This is one of the most effective catalysts reported to date for this conversion, with a very high turnover number of up to 6024, probably due to the synergistic effect of Lewis basic and Lewis acidic species for the activation of both propargylic alcohol and carbon dioxide by the formation of the alkyl carbonate with a bulkier counterion. Notably, this catalyst also worked well for the carboxylative cyclization of propargylic amines with carbon dioxide with the highest turnover number of 544.

Full text of DOI:10.1002/adsc.201500639

FULL PAPERS
DOI: 10.1002/adsc.201500639
Very Important Publication
Robust Silver(I) Catalyst for the Carboxylative Cyclization of
Propargylic Alcohols with Carbon Dioxide under Ambient
Conditions
Qing-Wen Songa and Liang-Nian Hea,*
a
State Key Laboratory and Institute of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical
Science and Engineering, Nankai University, Tianjin 300071, Peopleꢀs Republic of China
Fax: (+86)-22-2350-3878; phone: (+86)-22-2350-3878; e-mail: heln@nankai.edu.cn
Received: July 3, 2015; Revised: November 11, 2015; Published online: December 17, 2015
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201500639.
Abstract: Inspired by the bulkier bis(triphenylphos- 6024, probably due to the synergistic effect of Lewis
phine)–silver cation-induced mechanism of propar- basic and Lewis acidic species for the activation of
gylic alcohols and carbon dioxide through the alkyl both propargylic alcohol and carbon dioxide by the
carbonate intermediate, a robust dual-component formation of the alkyl carbonate with a bulkier coun-
catalytic system consisting of silver acetate and tetra- terion. Notably, this catalyst also worked well for the
heptylammonium bromide was rationally developed carboxylative cyclization of propargylic amines with
for the synthesis of a-methylene cyclic carbonates carbon dioxide with the highest turnover number of
under ambient conditions without employing any ad- 544.
ditional organic base and ligand. This is one of the
most effective catalysts reported to date for this con- Keywords: bulky cations; carbon dioxide; reaction
version, with a very high turnover number of up to mechanism; silver catalysis; synthetic methods
Introduction
find wide applications in organic synthesis as shown
in Scheme 1.[4]
The chemical conversion of carbon dioxide (CO2) has
In this aspect, the carboxylative cyclization of prop-
evoked great interest in the past decades.[1] Compared argylic alcohols with CO2 is one of the most promis-
with toxic phosgene and CO, CO2 can be regarded as ing and eco-friendly routes to a-alkylidene cyclic car-
an abundant, easily available, environmentally friend- bonates.[5] However, most of the published methods
ly and renewable C1 building block for organic syn- pose some drawbacks, in particular, the requirement
thesis. In this regard, great progress has been made in of higher CO2 pressure and use of stoichiometric
catalytic conversion of CO2 with small-ring com- amounts of additional base. Accordingly, the develop-
pounds, unsaturated compounds, hydrogen, amines ment of an efficient catalyst for CO2 conversion
À
À
and so on, resulting in the formation of C C, C O under mild reaction conditions could be still highly
[2]
and C N bonds. However, its inherent thermody- desirable in both industry and academia.[6]
À
namic stability and kinetic inertness hinder the devel-
Only if we understand the underlying principles of
opment of efficient catalysts for CO2 functionaliza- the chemical transformation can highly effective cata-
tion. Generally, active organometallic reagents, and/or lytic systems be designed. The alkyl carbonate inter-
nucleophiles and high pressure/temperature are re- mediate (I) was usually postulated in the two-compo-
quired for the incorporation of CO2 into organic nent “metal-base”-catalyzed reaction of propargylic
products.[3] Although significant achievements have alcohols with CO2 (Scheme 2, I).[5a,d] In this context,
been made, chemical conversion of CO2 at atmospher- we envisioned that higher CO2 pressure and reaction
ic pressure and room temperature remains a great temperature are still indispensable presumably be-
challenge.
cause the strong interaction between the base-H+ and
1
2
À
ꢀ
As is well-known, a-alkylidene cyclic carbonates HC CC(R R )OCO2 species reduces the nucleophi-
are an important class of heterocyclic frameworks in licity of alkyl carbonic anion (I). Most recently, we
natural products with potential bioactivities and also have successfully developed an efficient single-com-
ponent catalyst, i.e., [(PPh3)2Ag]2CO3, which enables
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Qing-Wen Song and Liang-Nian He
sumably going through the proposed intermediate
(III) (Scheme 2). This is a thermodynamically favour-
able step[7] and thus provides an attractive access to
various organic carbonates without utilization of any
base and ligand under solvent-free conditions.
Results and Discussion
2-Methylbut-3-yn-2-ol (1a) was chosen as the model
substrate to optimize the reaction conditions, as sum-
marized in Table 1. Various silver(I) compounds capa-
ble of activating the carbon-carbon triple bond were
investigated in combination with quaternary ammoni-
um salts. Initially, several easily available salts such as
KOAc, (n-C7H15)4NBr, (n-C7H15)4NOAc and AgOAc
Table 1. Optimization of the reaction conditions for the car-
boxylative cyclization of 1a with CO2.[a]
Entry Catalyst
Co-Catalyst
Yield [%][b]
1
KOAc
–
0
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20[c]
21[d]
22[e]
(n-C7H15)4NBr
(n-C7H15)4NOAc
AgOAc
Ag2O
Ag2CO3
AgOAc
AgNO3
AgBr
–
–
–
0
0
0
45
25
89
0
0
0
<1
65
6
22
85
Scheme 1. Applications of a-alkylidene cyclic carbonates.
(n-C7H15)4NBr
(n-C7H15)4NBr
(n-C7H15)4NBr
(n-C7H15)4NBr
(n-C7H15)4NBr
(n-C7H15)4NBr
(n-C7H15)4NOAc
(n-C7H15)4NOAc
(CH3)4NBr
(C2H5)4NBr
(n-C4H9)4NBr
KOAc
AgBr
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
AgOAc
Scheme 2. Activation modes involving a two-component
“metal+base” catalytic system (base=tertiary amine) (I),
a single-component bifunctional catalyst (II), and a bulkier
(n-C7H15)4N+-inspired intermediate (III) in this work.
n-C16H33(CH3)3NBr 16
PhCH2(C2H5)3NBr 64
(n-C4H9)4NCl
(n-C4H9)4PBr
(n-C7H15)4NBr
(n-C7H15)4NBr
(n-C7H15)4NBr
83
85
96
27
98
the reaction to perform smoothly under ambient con-
ditions[5k] through the formation of intermediate (II)
(Scheme 2).
The bulkier cation [(Ph3P)2Ag(I)]+ can stabilize the
carbonic anion and enhance the nucleophilicity of
alkyl carbonate intermediate in comparison with the
base-H+ species. We hypothesized that an ideal cata-
lytic system would be a kind of bifunctional one with
both Lewis acidic and Lewis basic sites in combina-
tion with the bulkier cation. Herein we disclose
a robust catalytic system consisting of (n-C7H15)4NBr
and AgOAc for the synthesis of a-alkylidene cyclic
carbonates with a high turnover number (TON), pre-
[a]
Unless otherwise specified, all the reactions were per-
formed with 1a (0.421 g, 5 mmol), Cat. (1 mol%), Co-
Cat. (1 mol%), neat, CO2 balloon, 608C, 12 h.
Determined by 1H NMR with 1,1,2,2-tetrachloroethane
as the internal standard.
(n-C7H15)4NBr (29.4 mg, 1.2 mol%).
AgOAc (24.8 mg, 3 mol%), (n-C7H15)4NBr (88.2 mg,
3.6 mol%), 258C.
[b]
[c]
[d]
[e]
AgOAc (42 mg, 5 mol%), (n-C7H15)4NBr (147 mg,
6 mol%), 258C.
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Robust Silver(I) Catalyst for the Carboxylative Cyclization
Table 2. Substrate scope.[a]
were found to have no catalytic activity under neat
conditions (Table 1, entries 1–4). Gratifyingly, a two-
component system consisting of 1 mol% Ag2O and
(n-C7H15)4NBr gave a-alkylidene cyclic carbonate 2a
in 45% yield (entry 5). Ag2CO3 displayed a lower ac-
tivity than Ag2O under otherwise identical conditions
(entry 6 vs. 5). In previous studies, AgOAc in combi-
nation with a basic nitrogen ligand was highly effec-
tive for internal propargylic alcohols[5e] but showed
low activity for terminal propargylic alcohols.[5k] Inter-
estingly, AgOAc and (n-C7H15)4NBr in this study dis-
played excellent activity, affording 2a in 89% yield
(entry 7). However, an acidic silver salt, for example,
AgNO3 or AgBr, was ineffective (entries 8 and 9),
suggesting a crucial role of the anion in proton trans-
fer. It is also worth mentioning that KOAc instead of
AgOAc showed no activity, indicating that activation
of the carbon-carbon triple bond could be a prequisite
for the reaction (entry 10 vs. 7). On the other hand,
insoluble AgBr was inactive (entry 11). In contrast,
soluble AgOAc performed well (entry 12).
Furthermore, several quaternary ammonium salts
were investigated as co-catalysts (entries 13–18). As
a result, the yield of 2a increased in the order
(CH3)4N+ <(C2H5)4N+ <(n-C4H9)4N+ <(n-C7H15)4N+
(entries 13–15 and 7). In addition, the unsymmetrical
tetraalkylammonium cation bearing one longer alkyl
showed better performance than that with a less
bulky cation evidently (entries 16, 17 vs. 13, 14). The
bulkier tetraheptylammonium cation might form
looser ion pairs with alkyl carbonic anion, as support-
ed by a DFT study (see the Supporting Information,
Figure S1), and thus can enhance the nucleophilicity
of the alkyl carbonic anion, being in agreement with
the published results.[8] On the other hand, (n-
C4H9)4NCl and (n-C4H9)4PBr were found to have
comparable activity with (n-C4H9)4NBr (entry 18, 19
vs. 7). A further improved result was obtained by
using 1.2 mol% (n-C7H15)4NBr (entry 20 vs. 7). Inter-
estingly, the reaction could proceed smoothly even at
room temperature. On further elevating the catalyst
[a]
Reaction conditions for protocol A:
AgOAc (4.2 mg, 1 mol%), (n-C7H15)4NBr (14.7 mg,
1.2 mol%) at 608C; protocol B: 1 (2.5 mmol), AgOAc
(21.0 mg, 5 mol%), (n-C7H15)4NBr (73.5 mg, 6 mol%) at
258C for 12 h.
NMR yield.
Isolated yield.
AgOAc (8.3 mg, 2 mol%), (n-C7H15)4NBr (29.4 mg,
2.4 mol%), 48 h.
AgOAc (42 mg, 10 mol%), (n-C7H15)4NBr (147 mg,
12 mol%), 24 h.
36 h.
1 (2.5 mmol),
[b]
[c]
[d]
[e]
[f]
loading, 2a was obtained almost quantitatively (en- mounted by increasing the catalyst amount and pro-
tries 21 and 22).
longing the reaction time.
Having established the optimized reaction condi-
To further validate the efficaciousness of this meth-
tions, we next examined the substrate scope of this odology, a gram-scale experiment was performed with
carboxylative cyclization as listed in Table 2. Terminal a lower catalyst amount as depicted in Scheme 3. To
propargylic alcohols with both alkyl and aryl substitu- our delighted, over 60% 2a yield was obtained with
ents at the propargylic position (1a–1g) underwent a high TON of up to 6024.
the reaction smoothly with CO2 at atmospheric pres-
sure to afford the corresponding a-alkylidene cyclic
carbonates (2a–2g) in excellent yields. Herein, two
procedures were employed as indicated in Table 2. As
a result, both protocols (low catalytic loading or low
temperature) were effective. Propargylic alcohols
with n-C6H13, cyclohexyl, vinyl and phenyl substitu-
ents showed relatively poor reactivity especially at
room temperature. Yet, such a problem could be sur- Scheme 3. Evaluation of the catalytic activity.
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Qing-Wen Song and Liang-Nian He
ethisterone) was also successfully prepared through
a ring-opening amination (Scheme 4, step 2).
The catalytic role of AgOAc/(n-C7H15)4NBr was
further elucidated. The interaction of propargylic al-
cohol 1a with CO2 was monitored by 1H and
13C NMR techniques (Figure 2). The proton signal of
the hydroxy group in 1a became broad and was shift-
ed from d=2.66 to 5.93 ppm (Figure 2a and b), sug-
gesting hydrogen bond formation between the acetic
group and 1a,[12] resulting in activation of propargylic
alcohol, and thus enhancement of the nucleophilicity
of the hydroxy group. As seen in Figure 2c and d,
changes in carbon peaks could be attributed to the in-
teraction of the silver salt with the carbon-carbon
triple bond, leading to the activation of propargylic
alcohol.[13]
A
tentative mechanism for the AgOAc/(n-
C7H15)4NBr-catalyzed fixation of atmospheric CO2
with propargylic alcohols is illustrated in Scheme 5.
Initially, the propargylic alcohol reacts with CO2 to
generate the propargylic carbonate intermediate in
which CO2 is activated by a hydroxy group[6a] with the
aid of AgOAc and (n-C7H15)4NBr. Notably, the bulki-
er cation, i.e., (nC7H15)4N+ plays a key role in stabiliz-
ing the carbonic anion and enhancing the nucleophi-
Scheme 4. Structure modifications of ethisterone.
Ethisterone is the first orally active progestin.[9] The licity of the carbonate intermediate. Then, an intra-
structural modification of ethisterone could be inter- molecular nucleophilic cyclization proceeds at the sil-
ꢀ
esting due to its significance for pharmaceutical ver(I)-activated C C bond, followed by protonation
chemistry.[10] The present AgOAc/(n-C7H15)4NBr-cata- with regeneration of the catalytic species.
lyzed carboxylative cyclization of propargylic alcohol
The synthesis of oxazolidinones through the car-
with CO2 was also applied to the synthesis of a compli- boxylative cyclization of propargylic amines and CO2
cated molecule with several functional groups such as is one of the most attractive synthetic methods.[14,6f]
ethisterone (Scheme 4, step 1) to afford the ACC- To futher display the effectiveness of the present cata-
ethisterone (a-alkylene cyclic carbonate ethisterone) lytic system, the carboxylative cyclization of propar-
with retention of the configuration. The configuration gylic amines with CO2 was further examined
of ACC-ethisterone was unambiguously confirmed by (Scheme 6). To our delight, the current protocol was
single-crystal X-ray analysis (Figure 1).[11] In addition, efficiently performed to give oxazolidinones 4a–4c
b-oxopropylcarbamate-modified ethisterone (OPC- with almost quantitative yields even at ambient condi-
tions. In the case of 3c, the TON reached up to 544
which is the highest among the reported results to
date.
Conclusions
In summary, we have established an elegant protocol
for expeditious chemical fixation of atmospheric CO2
to generate various a-alkylidene cyclic carbonates or
oxazolidinones under ambient conditions. On the
basis of a mechanistic understanding of the bulkier
cation [(Ph3P)2Ag(I)]+-catalyzed carboxylative cycli-
zation of propargylic alcohols with CO2, the robust
dual-activation catalyst system, i.e., AgOAc/(n-
C7H15)4NBr, which could simultaneously activate CO2,
a carbon-carbon triple bond, and a nucleophile (alco-
hols, amines etc.), was successfully developed. Taking
the carboxylative cyclization of 2-methylbut-3-yn-2-ol
Figure 1. X-ray crystal structure of ACC-ethisterone. Hydro-
gen atoms are omitted for clarity.
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Robust Silver(I) Catalyst for the Carboxylative Cyclization
Figure 2. 1 H, 13C NMR spectroscopic study: a, c for propargylic alcohol 1a and b, d for a mixture of 1a/AgOAc/(n-
C7H15)4NBr: 1a (0.1 mmol), AgOAc (1 equiv.), (n-C7H15)4NBr (1 equiv.) in CDCl3 (0.6 mL).
with CO2 as an example, a TON of up to 6024 was
achieved. This clean approach represents a promising
strategy for the development of the highly efficient
chemical conversion of CO2 to produce valuable
chemicals at atmospheric pressure.
Experimental Section
General Procedure for the Synthesis of a-Alkylidene
Cyclic Carbonates
Scheme 5. Plausible reaction mechanism.
Taking the carboxylative cyclization of 2-methylbut-3-yn-2-
ol with CO2 as an example: a 10-mL Schlenk tube equipped
with a stirrer bar was charged with AgOAc (4.2 mg,
1 mol%), (n-C7H15)4NBr (14.7 mg, 1.2 mol%), and 1a
(211 mg, 2.5 mmol) under neat conditions. Next, the Schlenk
tube was attached to a balloon filled with CO2 (99.99%
purity). Then, the reaction mixture was stirred at 608C for
12 h [or protocol B: AgOAc (21 mg, 5 mol%), (n-
C7H15)4NBr (74 mg, 6 mol%), 258C]. On carefully releasing
Scheme 6. AgOAc/(n-C7H15)4NBr-promoted chemical fixa-
tion of CO2 with propargylic amines.
the CO2 after the reaction, the mixture was washed with
CHCl3 (1 mL). The organic phase was analyzed by H NMR
1
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Qing-Wen Song and Liang-Nian He
with 1,1,2,2-tetrachloroethane as the internal standard or
concentrated under vacuum and purified by flash column
chromatography on silica gel (petroleum ether/ethyl ace-
tate=100:1–20:1) to give the pure product. Note: 1 mmol
ethisterone was used for the reaction in Scheme 4.
(s, 1H), 4.87 (d, J=3.6 Hz, 1H), 4.31 (d, J=4.0 Hz, 1H),
2.90–2.82 (1H), 2.43–2.29 (5H), 2.15–2.00 (m, 2H), 1.92–
1.89 (1H), 1.77–1.51 (6H), 1.45–1.39 (2H), 1.34–1.26 (1H),
1.20 (s, 3H), 1.14–1.06 (1H), 1.02 (s, 3H), 0.95–0.90 (1H);
13C NMR (CDCl3, 100.6 MHz): d=199.0, 170.0, 157.5, 151.2,
123.9, 96.6, 89.0, 52.9, 48.3, 35.5, 35.4, 34.0, 33.7, 32.3, 31.2,
30.8, 22.7, 20.0, 17.2, 14.1; HR-MS (ESI): m/z=379.1879,
4,4-Dimethyl-5-methylene-1,3-dioxolan-2-one (2a): yield:
1
321 mg (95%); colourless oil; H NMR (CDCl3, 400 MHz):
+
calcd. for C22H28NaO4 [M+Na]+: 379.1880.
d=4.75–4.31 (dd, J=4.0 Hz, 2H, CH2), 1.59 (s, 6H, 2CH3);
13C NMR (CDCl3, 100.6 MHz): d=158.6, 151.2 (C=O), 85.2,
84.6, 27.5; MS (EI, 70 eV): m/z (%)=128.10 (2.81), 85.10
(6.49), 84.10 (100), 83.10 (3.54), 69.10 (48.16); IR (neat): n=
3023, 2991, 1825, 1687, 1271, 1086, 1032, 856 cmÀ1.
OPC-ethisterone: yield: 408 mg (96%); white solid; mp.
169–1708C; 1H NMR (CDCl3, 400 MHz): d=5.71 (s, 1H),
3.38–3.29 (m, 2H), 3.28–3.18 (m, 1H), 2.80–2.72 (m, 1H),
2.41–2.24 (4H), 2.08 (s, 3H), 2.00–1.95 (m, 1H), 1.87–1.76
(m, 3H), 1.69–1.56 (m, 5H), 1.49–1.32 (m, 4H), 1.20 (t, J=
6.8 Hz, J=7.2 Hz, 3H), 1.17 (s, 3H), 1.12 (t, J=7.2 Hz, J=
6.8 Hz, 3H), 1.05 (s, 3H), 0.97–0.84 (m, 2H); 13C NMR
(CDCl3, 100.6 MHz): d=208.8, 199.3, 170.7, 155.3, 124.0,
95.4, 52.9, 47.1, 47.0, 42.1, 41.6, 38.4, 35.7, 35.6, 33.9, 33.2,
32.7, 31.4, 27.1, 24.7, 20.6, 17.3, 15.4, 14.3, 13.6; HR-MS
4-Ethyl-4-methyl-5-methylene-1,3-dioxolan-2-one
(2b):
yield: 354 mg (97%); colourless oil; 1H NMR (CDCl3,
400 MHz): d=4.80 (d, J=4.0 Hz, 1H), 4.26 (d, J=4.0 Hz,
1H), 1.94–1.70 (m, 2H), 1.57 (s, 3H), 0.97 (t, 3H); 13C NMR
(CDCl3, 100.6 MHz): d=157.2, 151.4, 87.5, 85.4, 33.1, 25.7,
7.1; GC-MS (EI, 70 eV): m/z (%)=143.10 (6), 113.05 (16),
98.10 (30), 83.05 (75), 70.10 (100).
+
(ESI): m/z=452.2772, calcd. for C26H39NNaO4 [M+Na]+:
452.2771.
4-Hexyl-4-methyl-5-methylene-1,3-dioxolan-2-one
(2c):
yield: 498 mg (90%); colourless oil; 1H NMR (CDCl3,
400 MHz): d=4.77 (d, J=4.0 Hz, 1H), 4.26 (d, J=4.0 Hz,
1H), 1.89–1.64 (m, 2H), 1.57 (s, 3H), 1.26–1.37 (m, 8H),
0.86 (t, 3H); 13C NMR (CDCl3, 100.6 MHz): d=157.7, 151.5,
87.2, 85.4, 40.4, 31.4, 28.9, 26.3, 22.8, 22.4, 13.9; GC-MS (EI,
70 eV) m/z (%)=199.15 ([M+H]+, 2), 139.2 (13), 112.15
(35), 111.15 (51), 97.10 (68), 85.10 (30), 84.10 (45), 83.10
(72), 82.10 (29), 72.10 (75), 70.15 (93), 69.10 (100).
4-Isobutyl-4-methyl-5-methylene-1,3-dioxolan-2-one (2d):
yield: 428 mg (96%); colourless oil; 1H NMR (CDCl3,
400 MHz): d=4.79–4.26 (dd, 2H), 1.87–1.62 (m, 3H), 1.57
(s, 3H), 0.96 (6H); 13C NMR (CDCl3, 100.6 MHz): d=158.1,
151.4, 87.3, 85.5, 48.3, 26.9, 24.2, 23.8, 23.5; GC-MS (EI,
70 eV) m/z (%)=114.10 (8), 113.10 (8), 111.15 (19), 84.15
(37), 83.15 (15), 70.10 (10), 69.10 (100).
General Procedure for the Synthesis of
Oxazolidinones
Taking the carboxylative cyclization of N-benzylprop-2-yn-1-
amine and CO2 as an example: a 10-mL Schlenk tube
equipped with a stirrer bar was charged with AgOAc
(1.7 mg, 2 mol%), (n-C7H15)4NBr (5.9 mg, 2.4 mol%), N-
benzylprop-2-yn-1-amine (72.6 mg, 0.5 mmol) and DMSO
(0.3 mL). Next, the Schlenk tube was attached to a balloon
filled with CO2. Then, the reaction mixture was stirred at
258C for the preset time. The CO2 was carefully released
after the reaction. The organic phase was analyzed by
1H NMR with 1,1,2,2-tetrachloroethane as the internal stan-
dard or concentrated under vacuum and purified by flash
column chromatography on silica gel (petroleum ether/ethyl
acetate=20:1–5:1) to give the pure product.
4-Methylene-1,3-dioxaspiro[4.5]decan-2-one (2e): yield:
1
423 mg (87%); colourless oil; H NMR (CDCl3, 400 MHz):
5-Benzylidene-3-butyl-4-phenyloxazolidin-2-one
(4a):
d=4.73 (d, J=4.0 Hz, 1H), 4.28 (d, J=4.0 Hz, 1H), 1.98–
1.95 (m, 2H), 1.70–1.59 (m, 7H), 1.34–1.20 (m, 1H);
13C NMR (CDCl3, 100.6 MHz): d=158.4, 151.2, 86.2, 85.3,
36.2, 24.0, 21.4; GC-MS (EI, 70 eV): m/z (%)=124.10 (9),
109.10 (15), 95.10 (15), 82.10 (49), 81.15 (50), 80.10 (20),
67.10 (100).
1
yield: 141 mg (94%); H NMR (CDCl3, 400 MHz): d=7.39–
7.27 (m, 5H), 4.76–4.74 (1H), 4.47 (s, 2H), 4.25–4.23 (1H),
4.03–4.02 (2H); 13C NMR (CDCl3, 100.6 MHz): d=155.6,
148.9, 134.9, 129.0, 128.23, 128.15, 86.8, 47.8, 47.2; GC-MS
(EI, 70 eV): m/z (%)=189.20 (13.18), 92.15 (15.37), 91.15
(100), 65.10 (11.34).
4-Methyl-5-methylene-4-vinyl-1,3-dioxolan-2-one
(2f):
3-Benzyl-4,4-dimethyl-5-methyleneoxazolidin-2-one (4b):
yield: 112 mg (97%); light brown oil; 1H NMR (CDCl3,
400 MHz): d=7.33–7.27 (m, 5H), 4.66 (1H), 4.45 (s, 2H),
4.22 (1H), 1.30 (6H); 13C NMR (CDCl3, 100.6 MHz): d=
160.7, 154.8, 137.6, 128.6, 127.72, 127.69, 84.1, 61.5, 44.0,
27.6; GC-MS (EI, 70 eV): m/z (%)=217.25 (4.67), 202.20
(19.34), 132.20 (7.04), 91.15 (100), 65.10 (8.80).
3-Benzyl-5-methyleneoxazolidin-2-one (4c): yield: 94 mg
(98%); light brown oil; 1H NMR (CDCl3, 400 MHz): d=
7.39–7.27 (m, 5H), 4.76–4.74 (1H), 4.47 (s, 2H), 4.25–4.23
(1H), 4.03–4.02 (2H); 13C NMR (CDCl3, 100.6 MHz): d=
155.6, 148.9, 134.9, 129.0, 128.23, 128.15, 86.8, 47.8, 47.2;
GC-MS (EI, 70 eV): m/z (%)=189.20 (13.18), 92.15 (15.37),
91.15 (100), 65.10 (11.34).
yield: 356 mg (89%); colourless oil; 1H NMR (CDCl3,
400 MHz): d=5.96–5.89 (m, 1H), 5.48–5.29 (dd, 2H), 4.85–
4.33 (dd, 2H), 1.67 (s, 3H); 13C NMR (CDCl3, 100.6 MHz):
d=156.0, 151.0, 136.0, 116.5, 87.2, 85.7, 25.5; GC-MS (EI,
70 eV): m/z (%)=96.15 (16), 95.15 (50), 81.10 (51), 68.10
(39), 67.10 (100).
4-Methyl-5-methylene-4-phenyl-1,3-dioxolan-2-one (2g):
1
yield: 471 mg (67%); greenish-yellow oil; H NMR (CDCl3,
400 MHz): d=7.49–7.47 (m, 2H), 7.44–7.38 (m, 3H), 4.95
(d, J=4.0 Hz, 1H), 4.48 (d, J=4.0 Hz, 1H), 1.97 (s, 3H);
13C NMR (CDCl3, 100.6 MHz): d=157.2, 151.0, 139.1, 129.0,
128.8, 124.5, 88.1, 87.0, 27.3; GC-MS (EI, 70 eV): m/z (%)=
146.10 (13), 131.10 (19), 118.15 (100), 117.15 (82), 103.10
(52), 78.10 (32), 77.10 (43).
ACC-ethisterone: yield: 337 mg (94%); colourless crystals
[acetone/hexane=1:5 v/v]; mp 170–1718C; IR (KBr): n=
2971, 2944, 2912, 2859, 1820, 1677, 1458, 1291, 1260, 1133,
1
1037, 1027, 864 cmÀ1; H NMR (CDCl3, 400 MHz): d=5.67
1256
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Adv. Synth. Catal. 2016, 358, 1251 – 1258

FULL PAPERS
Robust Silver(I) Catalyst for the Carboxylative Cyclization
2028; i) Q. W. Song, B. Yu, X. D. Li, R. Ma, Z. F. Diao,
Acknowledgements
R. G. Li, W. Li, L. N. He, Green Chem. 2014, 16, 1633–
1638; j) Y. B. Wang, D. S. Sun, H. Zhou, W. Z. Zhang,
X. B. Lu, Green Chem. 2014, 16, 2266–2272; k) Q. W.
Song, W. Q. Chen, R. Ma, A. Yu, Q. Y. Li, Y. Chang,
L. N. He, ChemSusChem 2015, 8, 821–827.
This work was supported by funds from the National Natural
Sciences Foundation of China, Specialized Research Fund
for the Doctoral Program of Higher Education
(20130031110013), MOE Innovation Team of China
(IRT13022) and the “111” Project of Ministry of Education
of China (project No. B06005).
[6] For typical examples of fixing atmospheric pressure of
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[13] The carbon peaks shifted apparently in the position of
ꢀ
C C [from d=(88.69 and 70.10) to (89.70 and 68.75)
ppm] and propargylic position (from d=64.90 to
63.99 ppm), mainly due to the electronic effect of the
activation of hydroxy and silver towards the unsaturat-
ed bond. The CH3 (d=1.54 ppm) group was unaffected.
Other unlabelled peaks were assigned as follows: (n-
1
C7H15)4NOAc, H NMR (CDCl3, 400 MHz): d=3.32 (t,
J=8.4 Hz, 8H, 4 -CH2-N), 1.90 (s, 3H, CH3COO), 1.61
(m, 8H, 4 -CH2-), 1.27 (m, 32H, 16 -CH2-), 0.82 (t, J=
6.6 Hz, 12H, 4 CH3-); 13C NMR (CDCl3, 100.6 MHz):
d=176.5, 58.9, 31.4, 28.7, 26.3, 25.2, 22.3, 22.1, 13.9.
1258
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ꢁ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2016, 358, 1251 – 1258