Gold(I)-catalyzed decarboxylation of propargyl carbonates: Reactivity reversal of the gold catalyst from π-Lewis acidity to σ-Lewis acidity

Article abstract of DOI:10.1002/adsc.201401094

A cationic gold(I)-catalyzed decarboxylative etherification of propargyl carbonates to selectively produce propargyl ethers is reported. In the reaction the gold(I) catalyst shows a distinct σ-Lewis acidity rather than the commonly observed π-Lewis acidity, and thus catalyzes the decarboxylation of a variety of propargyl carbonates to give the corresponding propargyl ethers with high selectivity. This reaction represents a rare example of the tunable reactivity of cationic gold(I) complexes between σ-Lewis acidity and π-Lewis acidity.

Full text of DOI:10.1002/adsc.201401094

UPDATES
DOI: 10.1002/adsc.201401094
Gold(I)-Catalyzed Decarboxylation of Propargyl Carbonates:
Reactivity Reversal of the Gold Catalyst from p-Lewis Acidity to
s-Lewis Acidity
Ruwei Shen,a,* Jianjun Yang,a Shugao Zhu,b Chao Chen,a and Luling Wuc
a
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering,
Nanjing Tech University, Nanjing 210009, Peopleꢀs Republic of China
E-mail: shenrw@njtech.edu.cn
State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese
b
Academy of Sciences, Shanghai 200032, Peopleꢀs Republic of China
Department of Chemistry, Zhejiang University, Hangzhou 310028, Peopleꢀs Republic of China
c
Received: November 21, 2014; Revised: January 19, 2015; Published online: March 16, 2015
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201401094.
Abstract: A cationic gold(I)-catalyzed decarboxyla-
tive etherification of propargyl carbonates to selec-
tively produce propargyl ethers is reported. In the
reaction the gold(I) catalyst shows a distinct s-
Lewis acidity rather than the commonly observed
p-Lewis acidity, and thus catalyzes the decarboxyla-
tion of a variety of propargyl carbonates to give the
corresponding propargyl ethers with high selectivity.
This reaction represents a rare example of the tuna-
ble reactivity of cationic gold(I) complexes between
s-Lewis acidity and p-Lewis acidity.
owing to the superior p-Lewis acidic reactivity of the
cationic gold catalysts to activate carbon–carbon un-
saturated systems under mild conditions.[1] In particu-
lar, the intensively studied gold(I)-catalyzed rear-
rangement of propargyl carboxylates[2–5] and ana-
logues,[6] has emerged as a powerful strategy for the
synthesis of complex organic molecules including sev-
eral natural products.[5] Mechanistically, these reac-
tions are generally described to start from the alkyno-
ꢀ
philic activation of the C C triple bond by gold(I)
complexes followed by intramolecular 5-exo or 6-
endo attack of the carbonyl oxygen and subsequent
bond re-regulation, leading to the formation of gold
vinyl carbenoid species or allenic intermediates,[7]
which are versatile intermediates for a variety of
transformations (Scheme 1, paths a and b).[2–4] The
two reaction modes both relying on the p-Lewis
acidic reactivity of the gold(I) catalysts thus provide
huge opportunities for organic synthesis.
Keywords: decarboxylation; gold catalysis; p-Lewis
acids; s-Lewis acids; propargyl carbonates
Introduction
On the other hand, the gold catalysts also show
The past decade has undoubtedly witnessed a remark- mild s-Lewis acidity although this chemistry has so
able growth in the field of gold catalysis, partially far been less studied and applied in organic synthe-
Scheme 1. p-Lewis acidity vs. s-Lewis acidity.
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Ruwei Shen et al.
sis.[8] For example, the gold salts have long been
known as oxophilic s-Lewis acids and used to activate
carbonyl compounds.[9] Some gold salts and com-
plexes are competent to catalyze the dehydrative cou-
plings of unsaturated alcohols including allylic and
propargylic alcohols as well as diaryl alcohols with
À
carbo- or hetero-nucleophiles to form new C C or
C heteroatom bonds. Particularly, the cleavage of
[10]
À
allylic acetates by cationic gold catalysts followed by
intramolecular nucleophilic trapping has been utilized
as a valuable alternative to those catalyzed by palladi-
um complexes to produce cyclic compounds with
compensatory chemo- and stereoselectivity.[11] Fur-
thermore, recent contributions have also been made
on the cyclization of some specifically designed sub-
strates wherein the cationic gold catalysts operated as
both s-Lewis acid and p-Lewis acid (dual activa-
tion).[12] Nevertheless, it is noteworthy that very rarely
has an example been described in which the gold cat-
Scheme 2. Gold(I)-catalyzed reaction of 3-(2’-azidoaryl)-1-
arylpropargyl carbonate.
alysts shows a tunable reactivity between p-Lewis tion product 2a was produced cleanly in 80% yield
acidity and s-Lewis acidity.[13] Particularly, a catalytic when 1a was treated with a catalytic amount of
reaction of propargyl carboxylates via an overwhelm- AuCl(PPh3) and AgSbF6 in THF at 608C for 10 h
ing s-Lewis acid activation mode has not been ob- (entry 1). The nature of the solvent had a substantial
served.[14]
effect on the reaction. The commonly used solvents
In this paper we describe our findings on a highly such as DCE and toluene for a lot of cationic gold(I)-
selective cationic gold(I) complex-catalyzed decarbox- catalyzed transformations were ineffective, giving
ylation of propargyl carbonates, wherein the gold(I) a complex mixture of products including some un-
catalyst selectively functions as a s-Lewis acid, rather identified decomposition products and dimers as de-
than a p-Lewis acid that leads to the commonly ob- tected from GC-MS analysis (entries 2 and 3). It ap-
served events of 2,3- or 3,3-rearrangement (Scheme 1, pears that the coordination ability of the solvent im-
path c). We incidentally found this reaction during poses an important effect on the performance of the
the course of a systematic study on the gold(I)-cata- catalyst. Thus, the reactions using dioxane and DMF
lyzed cyclization of 3-(2’-azidoaryl)-1-arylpropargyl as the solvents gave 2a in 57% and 48% yields cleanly
carbonates.[15] As previously reported, when 3-(2’-azi- although only 70% and 69% of 1a were consumed,
dophenyl)-1-phenylpropargyl carbonate was heated to respectively (entries 4 and 5). When the reaction was
608C in DCE in the presence of 5 mol% AuCl(PPh3) conducted in DMSO, the reaction proceeded very
and 5 mol% AgSbF6 for 48 h, normally a sequence in- sluggishly and produced 2a in 18% yield with 69% of
volving 3,3-rearrangement and 6-endo-trig cyclization 1a remaining after 10 h (entry 6). The use of acetone
occurred to give a 1,3-disubsituted quinolone product. unfortunately produced a complex mixture (entry 7).
To our surprise, however, in the presence of the same The combinations of AuCl(PPh3) with other silver
catalyst, the switch of solvent from DCE to THF un- salts were also examined. The reaction with
expectedly gave a decarboxylation product in 2 h, AuCl(PPh3) and AgOTf delivered the product in 52%
wherein the carbon-carbon triple bonds and the azido yield (entry 8), and the use of AgOTs and AgBF4
group were inert in the presence of the gold catalyst gave the product in 41% and 27% yield, respectively
(Scheme 2). This unexpected result clearly shows (entries 9 and 10). However, Ag3PO4, AgOAc and
a hitherto uncovered yet interesting divergent reactiv- AgNO3 did not show any activity (entries 11–13). Al-
ity of the gold(I) catalyst to preferentially activate the though the combination of AuCl(PPh3) and AgClO4
À
ꢀ
C O bond of the propargyl carbonates over the C C is also generally active for many cationic Au(I)-cata-
triple bonds (s-activation vs. p-activation).[16,17] lyzed reactions, it turn out to be ineffective to cata-
Herein we report the detailed results of this finding.
lyze the current reaction (entry 14). The decarboxyla-
tion could be catalyzed by AuCl(IPr) and AgSbF6
(entry 18). However, AuCl(PPh3) or AuCl(IPr) alone
did not catalyze the reaction (entries 15 and 16), and
the use of AuNTf2(PPh3) resulted in a complex mix-
Results and Discussion
We set out to conduct a detailed study by subjecting ture in which 2a was not detected (entry 19). In addi-
the simple substrate 1a to various conditions with tion, it was also interesting to observe that AgSbF6
gold(I) species. As shown in Table 1, the decarboxyla- catalyzed the reaction with low efficiency although
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Gold(I)-Catalyzed Decarboxylation of Propargyl Carbonates
Table 1. Gold(I)-catalyzed decarboxylation of 1a.[a]
Entry
Catalyst
Solvent
Time [h]
Conversion of 1a [%]
Yield of 2a [%][b]
1
2
3
4
5
6
7
8
AuCl(PPh3)/AgSbF6
AuCl(PPh3)/AgSbF6
AuCl(PPh3)/AgSbF6
AuCl(PPh3)/AgSbF6
AuCl(PPh3)/AgSbF6
AuCl(PPh3)/AgSbF6
AuCl(PPh3)/AgSbF6
AuCl(PPh3)/AgOTf
AuCl(PPh3)/AgOTs
AuCl(PPh3)/AgBF4
AuCl(PPh3)/Ag3PO4
AuCl(PPh3)/AgOAc
AuCl(PPh3)/AgNO3
AuCl(PPh3)/AgClO4
AuCl(PPh3)
THF
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
100
100
100
70
69
31
100
100
51
80 (76)
[c]
DCE
toluene
dioxane
DMF
DMSO
acetone
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
THF
–
–
[c]
57
48
18
[c]
–
52
41
27
0
0
0
7
0
0
9
10
11
12
13
14
15
16
17
18
19
38
<1
<1
5
10
0
0
45
70
100
AuCl(IPr)
AgSbF6
AuCl(IPr)/AgSbF6
AuNTf2(PPh3)
29
54
[c]
–
[a]
Reaction conditions: 1 (0.3 mmol), [Au] (0.015 mmol), [Ag] (0.015 mmol), solvent (0.6 mL).
GC yields using mesitylene as inner standard, isolated yield in parenthesis.
Complex mixture.
[b]
[c]
the silver cation was considered to be more oxophilic ever, phenyl propargyl carbonate 1o gave a complex
(entry 17). mixture (entry 16). In addition, in the case of an a-
We prepared a variety of propargyl carbonates to vinyl substituted propargyl carbonate 1p, two re-
examine the reaction scope. As shown in Table 2, the gioisomers were formed, indicative of the involve-
reactions proceeded smoothly with 1-arylpropargyl ment of an allylic cation intermediate during the reac-
carbonates having either electron-donating or elec- tion [Eq. (1)].
tron-withdrawing groups at the aryl ring, giving the
corresponding products in good yields. Heteroatoms
F, Cl, Br as well as methyl and methoxy groups were
tolerated (entries 3–8). A deuterium-labeled substrate
1a-d gave the product 2a-d in 78% yield with 94% D
still incorporated in the propargylic position (entry 2).
When methyl (2-phenylbut-3-yn-2-yl) carbonate (1h)
was employed, interestingly, a 10% yield of 4-(1-phe-
nylvinyl)-1,1’-biphenyl (2h’) was obtained (entry 9).[18]
The gold(I) catalyst also promoted the decarboxyla-
tion of 1-ethynylcyclohexyl methyl carbonate (1i)
(entry 10). However, no reaction occurred in the case
Interestingly, when we proceeded to examine the
of a 1-alkylpropargyl carbonate (entry 11). In addition reaction of internal alkynyl carbonates 3, we observed
to methyl propargyl carbonates (R1 =Me), we also ex- an interesting substitution effect. When 1,3-diphenyl-
amined the reactions of n-butyl, isopropyl, benzyl, prop-2-yn-1-yl methyl carbonate (3a) was treated with
allyl and phenyl propargyl carbonates. The reactions the gold(I) catalyst for 2 h, the decarboxylation prod-
of butyl, isopropyl, and benzyl propargyl carbonates uct 4a was produced in 18% yield, along with 28%
all proceeded smoothly and gave the expected prod- yield of (E)-chalcone (5a) (Table 3, entry 1).[19] Treat-
ucts in good yields (entries 12–14), and the reaction of ment of 4a with the gold(I) catalyst in THF did not
allyl (1-phenylprop-2-yn-1-yl) carbonate (1n) gave result in the formation of 5a. Thus, the 3,3-rearrange-
a low yield of the expected product (entry 15). How- ment of 3a to form an allenic intermediate with subse-
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Table 2. Gold(I)-catalyzed decarboxylation of propargyl car-
bonates 1.[a]
Table 3. Gold(I)-catalyzed decarboxylation of internal
alkyne carbonates.[a]
[a]
The reactions were conducted with 3 on a 0.3 mmol scale
in the presence of AuCl(PPh3) (5 mol%) and AgSbF6
(5 mol%) in THF (0.6 mL) at 608C for 2 h.
[b]
Isolated yields.[c] Detected by GC-MS.
entry 5). The fact that the presence of a methyl group
at the ortho-position leads to such a high chemoselec-
tivity, thus may indicate an interesting ortho-substitu-
ent effect of the substrates on the performance of the
gold(I) catalyst between s-activation and p-activation.
Table 4 show the results of some 1-arylpropargyl
carbonates with ortho-substituted aryl groups at the
3-position. Typical substrates with substituents such as
o-MeO, o-CF3, o-CN and o-N3 gave the decarboxyla-
tion products in good to high yields. As another ex-
ample, the reaction of 3f which has an ortho-methoxy-
phenyl group at the 3-position produced the decar-
boxylation product 4f cleanly in 79% yield, while the
reaction of 3-(3-methoxyphenyl)-1-phenylprop-2-ynyl
methyl carbonate that has a meta-methoxyphenyl
group also produced a mixture of decarboxylation
product and enone, further suggesting this ortho-sub-
stituent effect. Moreover, the reaction of 3k with an
ortho-bromo functionality afforded the expected
product 4k in 76% yield, and 3l with the smaller
chlorine atom gave 4l in 58% yield. However, sub-
strate 3m with an ortho-fluorine atom unfortunately
[a]
The reactions were conducted with 1 on a 0.3 mmol scale
in the presence of AuCl(PPh3) (5 mol%) and AgSbF6
(5 mol%) in THF (0.6 mL) at 608C for 10 h.
Isolated yields.
D content: 97%.
D content: 94%.
4-(1-Phenylvinyl)-1,1’-biphenyl (2h’) was isolated in 10%
yield.
[b]
[c]
[d]
[e]
[f]
GC yield using mesitylene as inner standard.
No reaction.
[g]
quent hydrolysis should be responsible for the forma- gave a very poor yield of the decarboxylation product
tion of 5a.[20] These results indicate that the gold(I) 4m along with the formation of enone by-products.
catalyst functions both as a p-Lewis acid and a s- These results further imply that the steric factor of
Lewis acid but independently in the reaction. Howev- the ortho-substituent may be responsible for the im-
er, the reaction of 3b gave a complex mixture proved chemoselectivity. This conclusion is also con-
(Table 3, entry 2). More interesting results were ob- sistent with the reaction of compound 3n with a 2,6-
served from the reactions of 3c, 3d and 3e, three simi- dimethylphenyl group, yielding the corresponding
lar substrates with different substitution patterns at product 4n in high yield. In addition, we also exam-
the phenyl ring (substituent R at the 3-position). ined the reactions of butyl, isopropyl and benzyl prop-
While the reactions of 3c and 3d with para- and meta- argyl carbonates (3j, 3g, 3o and 3p), which all gave
substituted methyl groups at the phenyl ring gave sim- the products in high yields.
ilar mixtures of decarboxylation products and enones
To further understand the mechanism, some addi-
(Table 3, entries 3 and 4), the reaction of methyl [1- tional experiments were performed and the following
phenyl-3-(ortho-tolyl) prop-2-yn-1-yl] carbonate (3e) points are noteworthy. (i) We used tert-butyl (1-phe-
proceeded smoothly and produced the decarboxyla- nylprop-2-yn-1-yl) carbonate (1q) to probe the p-
tion product 4e exclusively in 81% yield (Table 3, Lewis acidity of the gold(I) catalyst in different sol-
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Gold(I)-Catalyzed Decarboxylation of Propargyl Carbonates
Table 4. Gold(I)-catalyzed decarboxylation of propargyl carbonates 3.[a]
[a]
The reactions were conducted with 3 on a 0.3 mmol scale in the presence of AuCl(PPh3) (5 mol%) and AgSbF6 (5 mol%)
in THF (0.6 mL) at 608C for 2 h. Isolated yields are given.
Small amount of unidentified by-products were detected.
(E)-3-(4-Chlorophenyl)-1-(2-fluorophenyl)prop-2-en-1-one (5m) was isolated in 21% yield.
[b]
[c]
vents. Substrate 1q is easily cyclized to produce the
ꢀ
cyclic enol carbonate 6 via activation of the C C
triple bond followed by a 5-exo-dig cyclization and
fragmentation.[16a,b] Figure 1 shows the time course of
the gold(I)-catalyzed reactions performed in different
solvents. It is clear that the cyclization took place
quickly in DCE (ca. 0.5 h) and toluene (ca. 1 h) with
the gold(I) catalyst at 608C. However, the reaction in
THF proceeded slowly, producing 6 in 5% and 16%
yields after 2 h and 4 h, respectively. The reaction was
still incomplete after 8 h at 608C (23% GC yield).
Almost no reaction was observed when the reaction the 1,3-transposition product 9 [Eq. (2)].[21] Com-
was conducted in DMF or DMSO. These results clear- pound 9 was inert under the catalytic conditions al-
ly suggest the diminishing alkynylphilic Lewis acidity though a similar allylic carbocation might be expected
of the gold(I) catalyst with regard to the solvent to be formed during the reactions of 7 and 9 [Eq.
À
effect. It appears that the p-Lewis acidity of the cata- (3)]. Thus, although the C O bond could be first acti-
lyst could be significantly suppressed in coordinating vated by the gold(I) catalyst, the generation of
solvents. (ii) Further experiments demonstrated that a stable carbocation is still rather crucial for the sub-
À
methyl prop-2-yn-1-yl carbonate, methyl (3-phenyl- sequent C O bond cleavage process. (iii) The cross-
prop-2-yn-1-yl) carbonate, cinnamyl methyl carbonate over experiment as shown in Eq. (4) indicates a step-
and methyl (1-phenylethyl) carbonate were all inert wise process to produce the propargyl carbocation
under these catalytic conditions. Particularly, the reac- species and its dissociation with the alkanolate during
tion of substrate 7 gave the decarboxylation product 8 the reaction. A process involving contacted ion pairs
in 34% yield together with a comparable amount of could be ruled out accordingly.
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Scheme 3. Proposed mechanism.
lytic species (Scheme 3a). Scheme 3b presents a ration-
ale for the ortho-substituent effect on the selective s-
activation over p-activation. Although the coordina-
tion of the C C triple bond to Ph3PAu(I) may be sig-
nificantly weakened due to the solvent effect, this co-
Figure 1. Time course for the cyclization reaction of 1q in
different solvents. Reactions were performed on a 0.3 mmol
scale in 1 mL of solvent; Yields were determined by GC
using mesitylene as inner standard; Reactions performed at
ꢀ
608C are shown as solid lines and reactions performed at ordination may still take place for carbonate 3 to
room temperature are shown as dashed lines.
form a gold(I) complex B because of the electronic
effect of the internal C C triple bond. Complex B
may have a balance with the gold(I) complex A which
ꢀ
Taken together, a plausible mechanism is proposed is resulting from the coordination of the carbonyl
in Scheme 3. The coordination of the carbonyl oxygen oxygen of 3 to the cationic Ph3PAu(I) species. A and
to Ph3PAu(I) first activates and enables the cleavage B are responsible for the decarboxylation and the 3,3-
À
of the C O bond to produce a propargyl carbocation rearrangement process, respectively. In the case of
and the Au(OCO2R)(PPh3) complex. The chemose- substrate 3 with an ortho-substituted aryl group, the
lectivity of this activation process is solvent- and sub- steric hindrance existing in the transition state C or D
strate-dependent. Loss of CO2 from Au(O- may further elevate the activation energy for the 3,3-
CO2R)(PPh3) would then produce the gold-bonded al- rearrangement process, thus preventing the formation
kanolate intermediate Au(OR)(PPh3). Reunion of the of the allenic intermediate. Therefore, the decarboxy-
propargyl carbocation with Au(OR)(PPh3) finally lation reaction proceeds preferentially to give 4 with
gives the product and regenerates the Ph3PAu(I) cata- high selectivity.
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Gold(I)-Catalyzed Decarboxylation of Propargyl Carbonates
400 MHz): d=7.56–7.54 (m, 2H), 7.40–7.38 (m, 3H), 3.82 (s,
Conclusions
3H), 2.71 (s, 1H); 13C NMR (CDCl3, 100 MHz): d=154.8,
135.8, 129.4, 128.7, 127.7, 79.6, 76.4, 69.1 (t, J=23.2 Hz),
55.1; IR (neat): n=3290, 2958, 2125, 1755, 1442, 1278, 913,
In summary, we have demonstrated that the cationic
gold(I) catalyst could selectively catalyze the decar-
boxylation of a variety of propargyl carbonates to
produce propargyl ethers. We have also observed an
interesting ortho-substituent effect of the substrate on
the reaction. It is important to note that the gold(I)
catalyst acts as a s-Lewis acid in the reaction, rather
than a p-Lewis acid that leads to the commonly ob-
served 2,3- or 3,3-rearrangement sequence. Taken to-
gether with a previous report, the study has presented
a rare example of the tunable reactivity of the gold
catalysts between s-Lewis acidity and p-Lewis acidity.
We believe that a further understanding of this tuna-
ble reactivity of the gold catalysts should be helpful
for reaction design in organic synthesis.
696 cmÀ1
; HR-MS (EI-TOF): m/z=191.0691, calcd. for
C11H9DO3 [M+]: 191.0693.
The spectroscopic data of compounds 1a–1q, 3a–3p can
be found in the Supporting Information.
General Procedure for the Gold(I)-Catalyzed
Decarboxylative Etherification of Propargyl
Carbonates
To a flame-dried Schlenk tube were added AuCl(PPh3)
(7.6 mg, 0.015 mmol), AgSbF6 (5.2 mg, 0.015 mmol) and
THF (0.2 mL) sequentially under a dry nitrogen atmos-
phere. The resulting mixture was stirred at room tempera-
ture for ca. 10 min, which was followed by the addition of
1 or 3 (0.30 mmol) with 0.4 mL of THF using a microsyringe.
The resulting mixture was then submerged in an oil bath
preheated to 608C. After complete consumption of the
starting material as monitored by TLC, silica gel (ca.
200 mg) was added and the mixture was concentrated under
reduced pressure to afford a dry powder. The sample was
purified by column chromatography on silica gel to afford 2
or 4.
(1-Deutero-1-methoxyprop-2-ynyl)benzene (2a-d): Yield:
34.3 mg (78%); oil. 1H NMR (CDCl3, 400 MHz): d=7.53–
7.51 (m, 2H), 7.38–7.35 (m, 3H), 3.44 (s, 3H), 2.65 (s, 1H);
13C NMR (CDCl3, 100 MHz): d=137.9, 128.6, 128.5, 127.3,
81.3, 75.7, 72.5 (t, J=22.1 Hz), 55.8; IR (neat): n=3292,
2928, 2104, 1450, 1256, 1082, 698 cmÀ1; HR-MS (EI-TOF):
m/z=147.0493, calcd. for C10H9DO [M+]: 147.0494.
1-Bromo-2-(1-methoxyprop-2-ynyl)benzene (2b): Yield:
47.9 mg (71%); oil. 1H NMR (CDCl3, 400 MHz): d=7.74
(dd, J=8.0, 1.6 Hz, 1H), 7.57 (dd, J=8.0, 0.8 Hz, 1H), 7.38–
7.34 (m, 1H), 7.22–7.18 (m, 1H), 5.37 (d, J=2.4 Hz, 1H),
3.50 (s, 3H), 2.63 (s, J=2.4 Hz, 1H); 13C NMR (CDCl3,
100 MHz): d=137.3, 132.9, 130.1, 129.1, 127.8, 123.4, 80.7,
75.7, 72.1, 56.7; IR (neat): n=3295, 2115, 1469, 1195, 1081,
988, 754 cmÀ1; HR-MS (EI-TOF): m/z=223.9833, calcd. for
C10H9OBr [M+]: 223.9837.
Experimental Section
General Information
Unless otherwise specified, all reactions were performed
under a dry N2 atmosphere. Anhydrous solvents were dis-
tilled prior to use: THF, dioxane and toluene were distilled
from sodium using benzophenone as the indicator; DCE,
DMF and DMSO were distilled from CaH2. The starting
materials 1 and 3 were prepared following known proce-
dures.[15] AuCl(PPh3) and AuCl(IPr) were purchased from
commercial sources and used as received while
AuNTf2(PPh3) was prepared following a literature proce-
dure.[22] Flash chromatography was performed on silica gel
using petroleum ether and EtOAc as eluent. Petroleum
ether refers to the fraction with the boiling point in the
range 60–908C. Analytical gas chromatography (GC) was
carried out with a flame ionization detector on a Shimadazu
1
GC2014 model. H and 13C NMR spectra were recorded on
a Bruker Advance 400 spectrometer. Chemical shifts (ppm)
were recorded with tetramethylsilane (TMS) as the internal
reference standard. Chemical shifts are expressed in ppm
and J values are given in Hz. HR-mass spectra were ob-
tained from the Analytical Center of the Department of
Chemistry of Zhejiang University, People’s Republic of
China.
1-Fluoro-4-(1-methoxyprop-2-ynyl)benzene (2c): Yield:
1
32.0 mg; oil. H NMR (CDCl3, 400 MHz): d=7.51–7.47 (m,
2H), 7.08–7.04 (m, 2H), 5.06 (d, J=2.0 Hz, 1H), 3.44 (s,
3H), 2.66 (d, J=2.0 Hz, 1H); 13C NMR (CDCl3, 100 MHz):
d=162.8 (d, J=245.7 Hz), 133.9 (d, J=3.1 Hz), 129.2 (d, J=
8.2 Hz), 115.4 (d, J=21.1 Hz), 81.0, 76.0, 72.1, 55.9; IR
(neat): n=3305, 2111, 1509, 1225, 1083 cmÀ1; HR-MS (EI-
TOF): m/z=164.0642, calcd. for C10H9OF [M+]: 164.0637.
1-(1-Methoxyprop-2-ynyl)-4-methylbenzene (2d): Yield:
Typical Procedure for the Preparation of Propargyl
Carbonates[15]
To a solution of 1-deutero-1-phenylprop-2-yn-1-ol (665 mg,
5.0 mmol), pyridine (1.63 mL, 20 mmol), and N,N-dimethyl-
pyridin-4-amine (DMAP) (122 mg, 1.0 mmol) in CH2Cl2
(10 mL) was added methyl chloroformate (1.54 mL,
20 mmol) at À208C. The reaction was allowed to warm to
room temperature and stirred overnight. The reaction mix-
ture was then diluted with CH2Cl2, and the CH2Cl2 solution
was washed with a saturated aqueous CuSO4 solution,
water, dried over anhydrous Na2SO4, filtered and concen-
trated. The residue was purified by column chromatography
on silica gel to afford methyl 1-deutero-1-phenylprop-2-ynyl
carbonate (1a-d); yield: 764 mg (80%). 1H NMR (CDCl3,
1
37.4 mg (78%); oil. H NMR (CDCl3, 400 MHz): d=7.39 (d,
J=8.0 Hz, 2H), 7.18 (d, J=8.0 Hz, 2H), 5.05 (d, J=2.0 Hz,
1H), 3.42 (s, 3H), 2.64 (d, J=2.0 Hz, 1H), 2.35 (s, 3H);
13C NMR (CDCl3, 100 MHz): d=138.4, 135.1, 129.2, 127.3,
81.5, 75.5, 72.6, 55.8, 21.2; IR (neat): n=3289, 2925, 2113,
1448, 1280, 1180, 1082 cmÀ1; HR-MS (EI-TOF): m/z=
160.0891, calcd. for C11H22O [M+]: 160.0888.
1-Methoxy-2-(1-methoxyprop-2-ynyl)benzene (2e): Yield:
42.2 mg (78%); oil. 1H NMR (CDCl3, 400 MHz): d=7.65–
7.63 (m, 1H), 7.33–7.29 (m, 1H), 7.02–6.98 (m, 1H), 6.90 (d,
J=8.0 Hz, 1H), 5.48 (d, J=2.0 Hz, 1H), 3.86 (s, 3H), 3.45
Adv. Synth. Catal. 2015, 357, 1259 – 1269
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UPDATES
Ruwei Shen et al.
(s, 3H), 2.56 (d, J=2.4 Hz, 1H); 13C NMR (CDCl3,
100 MHz): d=156.7, 129.9, 128.4, 126.5, 120.7, 110.8, 81.8,
74.5, 66.8, 56.3, 55.7; IR (neat): n=3289, 2112, 1601, 1493,
1463, 1246, 1027 cmÀ1; HR-MS (EI-TOF): m/z=176.0839,
calcd. for C11H12O2 [M+]: 176.0837.
1H), 1.29 (d, J=6.0 Hz, 6H); 13C NMR (CDCl3, 100 MHz):
d=137.7, 134.1, 134.0, 131.7 (q, J=30.4 Hz), 131.4, 128.7,
128.6, 128.3, 125.8 (q, J=5.0 Hz), 123.5 (q, J=272.5 Hz),
120.8 (d, J=2.0 Hz), 93.2, 82.8, 70.2, 68.7, 23.0, 21.4; IR
(neat): n=2972, 1489, 1319, 1136, 1034, 766 cmÀ1; HR-MS
(EI-TOF): m/z=352.0845, calcd. for C19H16OClF3 [M+]:
352.0842.
1-Bromo-3-(1-methoxyprop-2-ynyl)benzene (2f): Yield:
1
50.6 mg (75%); oil. H NMR (CDCl3, 400 MHz): d=7.67 (s,
1H), 7.47–7.43 (m, 2H), 7.26–7.22 (m, 1H), 5.05 (d, J=
2.0 Hz, 1H), 3.44 (s, 3H), 2.67 (d, J=2.0 Hz, 1H); 13C NMR
(CDCl3, 100 MHz): d=140.2, 131.6, 130.4, 130.1, 125.9,
122.6, 80.6, 76.3, 72.0, 56.0; IR (neat): n=3296, 2937, 2115,
2-(3-Methoxy-3-phenylprop-1-ynyl)benzonitrile
(4h):
1
Yield: 45.2 mg (61%); oil. H NMR (CDCl3, 400 MHz): d=
7.68–7.57 (m, 5H), 7.45–7.37 (m, 4H), 5.41 (s, 1H), 3.56 (s,
3H). 13C NMR (CDCl3, 100 MHz): d=137.7, 132.7, 132.6,
132.4, 128.7, 128.6, 127.6, 126.5, 117.5, 115.6, 93.4, 83.7, 73.4,
56.2; IR (neat): n=2230, 1455, 1258, 1074, 762 cmÀ1; HR-
MS (EI-TOF): m/z=247.1003, calcd. for C17H13NO [M+]:
247.0997.
1474, 1190, 1082, 677 cmÀ1
; HR-MS (EI-TOF): m/z=
223.9837, calcd. for C10H9OBr [M+]: 223.9837.
1-Chloro-4-(1-methoxyprop-2-ynyl)benzene (2g): Yield:
1
43.2 mg (80%); oil. H NMR (CDCl3, 400 MHz): d=7.45 (d,
J=8.4 Hz, 2H), 7.34 (d, J=8.4 Hz, 2H), 5.06 (d, J=2.4 Hz,
1H), 3.43 (s, 3H), 2.66 (d, J=2.4 Hz, 1H); 13C NMR
(CDCl3, 100 MHz): d=136.6, 134.4, 128.7, 80.8, 76.1, 72.0,
55.9; IR (neat): n=3295, 2924, 2212, 1591, 1450, 1125,
1-Azido-2-[3-butoxy-3-(4-chlorophenyl)prop-1-yn-1-yl]-4-
chlorobenzene (4j): Yield: 76.0 mg (68%); oil. 1H NMR
(CDCl3, 400 MHz): d=7.52 (d, J=8.4 Hz, 2H), 7.41 (d, J=
2.4 Hz, 1H), 7.36 (d, J=8.4 Hz, 2H), 7.31–7.28 (m, 1H),
7.03 (d, J=8.8 Hz, 1H), 5.37 (s, 1H), 3.78–3.72 (m, 1H),
3.59–3.54 (m, 1H), 1.68–1.61 (m, 2H), 1.47–1.37 (m, 2H),
0.93 (t, J=7.6 Hz, 3H); 13C NMR (CDCl3, 100 MHz): d=
139.0, 136.1, 133.2, 132.3, 129.0, 128.8, 127.8, 127.7, 118.9,
115.0, 93.1, 80.9, 70.2, 67.5, 30.7, 18.4, 12.8; IR (neat): n=
2119, 1486, 1394, 1303, 1089, 809 cmÀ1; HR-MS (EI-TOF):
m/z=345.0695, calcd. for C19H17NOCl2 [M+ÀN2]: 345.0687.
1-Bromo-2-(3-methoxy-3-para-tolylprop-1-ynyl)benzene
(4k): Yield: 71.7 mg (76%); oil. 1H NMR (CDCl3,
400 MHz): d=7.58 (d, J=8.0 Hz, 1H), 7.52–7.48 (m, 3H),
7.27–7.15 (m, 4H), 5.35 (s, 1H), 3.51 (s, 3H), 2.36 (s, 3H);
13C NMR (CDCl3, 100 MHz): d=138.3, 135.2, 133.6, 132.4,
129.6, 129.2, 127.7, 127.0, 125.7, 124.8, 91.5, 86.1, 73.3, 55.8,
21.2; IR (neat): n=2954, 1470, 1440, 1256, 1026, 921,
700 cmÀ1
; HR-MS (EI-TOF): m/z=180.0344, calcd. for
C10H9OCl [M+]: 180.0342.
(1-Butoxyprop-2-ynyl)benzene (2k). Yield: 45.1 mg
(81%); oil. 1H NMR (CDCl3, 400 MHz): d=7.51 (d, J=
7.6 Hz, 2H), 7.38–7.30 (m, 3H), 5.15 (d, J=2.0 Hz, 1H),
3.70–3.64 (m, 1H), 3.52–3.47 (m, 1H), 2.61 (d, J=2.0 Hz,
1H), 1.65–1.58 (m, 2H), 1.45–1.35 (m, 2H), 0.91 (t, J=
7.2 Hz, 3H); 13C NMR (CDCl3, 100 MHz): d=138.5, 128.5,
128.4, 127.3, 82.0, 75.3, 71.3, 68.3, 31.7, 19.4, 13.9; IR (neat):
n=3291, 2113, 1456, 1250, 928 cmÀ1; HR-MS (EI-TOF): m/
z=188.1203, calcd. for C13H16O [M+]: 188.1201.
Collected data from a mixture of (E)-(3-methoxypent-1-
en-4-ynyl)benzene (2p, 60 mol%) and (E)-(1-methoxypent-
2-en-4-ynyl)benzene (2p’, 40 mol%): Total yield: 30.0 mg
(58%); oil. 1H NMR (CDCl3, 400 MHz): d=7.41–7.25 (m,
5H), 6.32–6.26 (m, 0.6H), 6.10–6.05 (m, 0.4H), 5.76–5.63
(m, 1H), 5.29 (d, J=9.2 Hz, 0.4H), 4.66 (d, J=6.0 Hz,
0.6H), 3.39 (s, 1.2H), 3.32 (s, 1.8H), 3.20 (dd, J=2.0, 0.8 Hz,
0.4H), 2.88 (d, J=2.4 Hz, 0.6H); HR-MS (EI-TOF): m/z=
172.0883, calcd. for C12H12O [M+]: 172.0888.
755 cmÀ1
; HR-MS (EI-TOF): m/z=314.0308, calcd. for
C17H15OBr [M+]: 314.0306.
2-[3-(2-Bromophenyl)-3-methoxyprop-1-ynyl]-1,4-dichlor-
1
obenzene (4l): Yield: 64.2 mg (58%); oil. H NMR (CDCl3,
400 MHz): d=7.83 (dd, J=7.6, 1.6 Hz, 1H), 7.59 (d, J=
8.4 Hz, 1H), 7.48 (d, J=2.4 Hz, 1H), 7.40–7.32 (m, 2H),
7.26–7.20 (m, 2H), 5.65 (s, 1H), 3.59 (s, 3H). 13C NMR
(CDCl3, 100 MHz): d=137.3, 134.6, 133.1, 133.0, 132.3,
130.3, 130.2, 129.8, 129.4, 127.8, 123.9, 123.5, 92.6, 83.2, 72.7,
56.8; IR (neat): n=2927, 1469, 1096, 1007, 753 cmÀ1; HR-
MS (EI-TOF): m/z=367.9365, calcd. for C16H11OBrCl2
[M+]: 367.9370.
1-(3-Methoxy-3-phenylprop-1-ynyl)-2-methylbenzene (4e):
1
Yield: 57.3 mg (81%); oil. H NMR (CDCl3, 400 MHz): d=
7.60–7.59 (m, 2H), 7.46–7.34 (m, 4H), 7.23–7.19 (m, 2H),
7.15–7.11 (m, 1H), 5.36 (s, 1H), 3.51 (s, 3H), 2.45 (s, 3H);
13C NMR (CDCl3, 100 MHz): d=140.4, 138.7, 132.2, 129.5,
128.6, 128.55, 128.47, 127.6, 125.6, 122.4, 90.6, 86.8, 73.7,
55.9, 20.8; IR (neat): n=2219, 1486, 1454, 1277, 1082,
1-[3-(4-Chlorophenyl)-3-methoxyprop-1-ynyl]-2-fluoro-
758 cmÀ1
;
HR-MS (EI-TOF): m/z=236.1205, calcd. for
benzene (4m): Yield: 20.8 mg (25%); oil. H NMR (CDCl3,
1
C17H16O [M+]: 236.1201.
400 MHz): d=7.54–7.52 (m, 2H), 7.48–7.44 (m, 1H), 7.38–
7.30 (m, 3H), 7.12–7.07 (m, 2H), 5.33 (s, 1H), 3.50 (s, 3H);
13C NMR (CDCl3, 100 MHz): d=163.0 (J=249.6 Hz), 136.8,
134.4, 133.6 (J=1.5 Hz), 130.5 (J=8.0 Hz), 128.9, 128.7,
123.9 (J=3.5 Hz), 115.6 (J=22.3 Hz), 110.9 (J=15.3 Hz),
91.3 (J=3.3 Hz), 81.6, 72.8, 55.9; IR (neat): n=2231, 1492,
1-Methoxy-2-(3-methoxy-3-phenylprop-1-ynyl)benzene
1
(4f): Yield: 59.5 mg (79%); oil. H NMR (CDCl3, 400 MHz):
d=7.64 (d, J=7.2 Hz, 2H), 7.47–7.29 (m, 5H), 6.93–6.88 (m,
2H), 5.40 (s, 1H), 3.89 (s, 3H), 3.52 (s, 3H); 13C NMR
(CDCl3, 100 MHz): d=160.4, 138.6, 133.7, 130.0, 128.5,
128.4, 127.7, 120.4, 111.9, 110.7, 90.6, 84.3, 73.6, 55.8, 55.7;
1454, 1089, 1016, 757 cmÀ1
; HR-MS (EI-TOF): m/z=
IR (neat): n=2226, 1596, 1493, 1455, 1260, 1076, 753 cmÀ1
;
274.0561, calcd. for C16H12OClF [M+]: 274.0561.
HR-MS (EI-TOF): m/z=252.1154, calcd. for C17H16O2 [M+]:
252.1150.
2-[3-(4-Fluorophenyl)-3-methoxyprop-1-ynyl]-1,3-dime-
thylbenzene (4n): Yield: 64.3 mg (80%); oil. 1H NMR
(CDCl3, 400 MHz): d=7.61–7.57 (m, 2H), 7.15–7.06 (m,
5H), 5.41 (s, 1H), 3.53 (s, 3H), 2.45 (s, 6H); 13C NMR
(CDCl3, 100 MHz): d=162.7 (d, J=245.9 Hz), 140.5, 130.7
(d, J=3.2 Hz), 129.3 (d, J=7.8 Hz), 128.1, 126.7, 122.2, 115.3
(d, J=21.8 Hz), 94.7, 85.7, 73.0, 55.8, 21.2; IR (neat): n=
1-[3-(4-Chlorophenyl)-3-isopropoxyprop-1-yn-1-yl]-2-(tri-
fluoromethyl)benzene (4g): Yield: 69.0 mg (71%); oil.
1H NMR (CDCl3, 400 MHz): d=7.66 (d, J=7.6 Hz, 1H),
7.60 (d, J=7.6 Hz, 1H), 7.54–7.47 (m, 3H), 7.44–7.40 (m,
1H), 7.36 (d, J=8.4 Hz, 2H), 5.45 (s, 1H), 4.18–4.09 (m,
1266
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ꢁ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2015, 357, 1259 – 1269

UPDATES
Gold(I)-Catalyzed Decarboxylation of Propargyl Carbonates
1468, 1225, 1092, 835 cmÀ1
;
HR-MS (EI-TOF): m/z=
(20133221120003), Jiangsu Provincial NSFC (BK20130924)
268.1266, calcd. for C18H17OF [M+]: 268.1263.
and Foundation of Jiangsu Educational Committee of China
(13KJB150019) is gratefully acknowledged. This work was
also partially supported by the Project of Priority Academic
Program Development of Jiangsu Higher Education Institu-
tions (PAPD).The authors also thank one of the reviewers
for his/her helpful suggestions on the improvement of the
paper.
1-(3-Isopropoxy-3-phenylprop-1-ynyl)-2-methylbenzene
(4o): Yield: 60.3 mg (76%); oil. 1H NMR (CDCl3,
400 MHz): d=7.62 (d, J=7.2 Hz, 2H), 7.46–7.35 (m, 4H),
7.23–7.12 (m, 3H), 5.50 (s, 1H), 4.18–4.09 (m, 1H), 2.45 (s,
3H), 1.30 (dd, J=6.4, 6.0 Hz, 6H); 13C NMR (CDCl3,
100 MHz): d=140.3, 139.7, 132.1, 129.4, 128.5, 128.4, 128.2,
127.4, 125.5, 122.6, 91.9, 85.7, 69.8, 69.6, 23.1, 21.7, 20.8; IR
(neat): n=2222, 1486, 1454, 1120, 1046, 757, 670 cmÀ1; HR-
MS (EI-TOF): m/z=264.1512, calcd. for C19H20O [M+]:
264.1514.
References
1-[3-(Benzyloxy)-3-phenylprop-1-ynyl]-2-methylbenzene
(4p): Yield: 73.0 mg (78%); oil. 1H NMR (CDCl3,
400 MHz): d=7.61 (d, J=6.8 Hz, 2H), 7.48–7.32 (m, 9H),
7.24–7.13 (m, 3H), 5.50 (s, 1H), 4.81 (d, J=12.0 Hz, 1H),
4.76 (d, J=12.0 Hz, 1H), 2.47 (s, 3H); 13C NMR (CDCl3,
100 MHz): d=140.3, 138.8, 137.8, 132.2, 129.4, 128.54,
128.49, 128.42, 128.37, 128.2, 127.8, 127.6, 125.5, 122.4, 90.7,
86.9, 71.1, 70.0, 20.8; IR (neat): n=2221, 1486, 1454, 1120,
1046, 757, 697 cmÀ1; HR-MS (ESI): m/z=312.1516, calcd.
for C23H20O [M+]: 312.1514.
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A. M. Schuster, M. Rudolph, F. Rominger, C. A. Gade,
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Gold(I)-Catalyzed Reaction of 1-(4-
Chlorophenyl)allyl Methyl Carbonate (7)
To a flame-dried Schlenk tube were added AuCl(PPh3)
(7.6 mg, 0.015 mmol), AgSbF6 (5.2 mg, 0.015 mmol) and
THF (0.2 mL) sequentially under a dry nitrogen atmos-
phere. The resulting mixture was stirred at room tempera-
ture for ca. 10 min, which was followed by the addition of 1-
(4-chlorophenyl)allyl methyl carbonate (67.8 mg, 0.3 mmol)
in 0.4 mL of THF using a microsyringe. The resulting mix-
ture was then submerged in an oil bath preheated to 608C.
After complete consumption of the starting material, the
mixture was concentrated after the addition of ca. 200 mg of
silica gel under reduced pressure to afford a dry powder.
The sample was purified by column chromatography on
silica gel to afford 8 (yield: 18.6 mg, 34%) and 9 (yield:
23.7 mg, 35%).
(E)-1-Chloro-4-(3-methoxyprop-1-enyl)benzene
(8):
1H NMR (CDCl3, 400 MHz): d=7.33–7.26 (m, 4H), 6.57 (d,
J=16.0 Hz, 1H), 6.26 (dt, J=16.0, 6.0 Hz, 1H), 4.08 (dd, J=
6.0, 1.2 Hz, 2H), 3.39 (s, 3H); 13C NMR (CDCl3, 100 MHz):
d=135.2, 133.3, 131.0, 128.7, 127.7, 126.7, 72.9, 58.1; IR
(neat): n=2924, 1491, 1090, 968 cmÀ1; HR-MS (EI-TOF): m/
z=182.0499, calcd. for C10H11OCl [M+]: 182.0498.
(E)-3-(4-Chlorophenyl)allyl
methyl
carbonate
(9):
1H NMR (CDCl3, 400 MHz): d=7.33–7.26 (m, 4H), 6.63 (d,
J=16.0 Hz, 1H), 6.26 (dt, J=16.0, 6.4 Hz, 1H), 4.78 (dd, J=
6.4, 1.2 Hz, 2H), 3.81 (s, 3H); 13C NMR (CDCl3, 100 MHz):
d=155.6, 134.5, 133.9, 133.4, 128.8, 127.9, 123.1, 68.1, 54.9;
IR (neat): n=2925, 1754, 1493, 1262, 1092 cmÀ1; HR-MS
(EI-TOF): m/z=226.0395, calcd. for C11H11OCl [M+]:
226.0397.
[4] For selected examples of gold-catalyzed reactions in-
volving 3,3-rearangements, see: a) L. Zhang, J. Am.
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Zhang, S. Wang, J. Am. Chem. Soc. 2006, 128, 1442–
1443; d) N. Marion, S. Diez-Gonzalez, P. de Fremont,
A. R. Noble, S. P. Nolan, Angew. Chem. 2006, 118,
Acknowledgements
The financial support from the National Natural Science
Foundation of China (Project No. 21302095), Research Fund
for the Doctoral Program of Higher Education of China
Adv. Synth. Catal. 2015, 357, 1259 – 1269
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UPDATES
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3729–3732; Angew. Chem. Int. Ed. 2006, 45, 3647–3650;
e) T. Luo, S. L. Schreiber, Angew. Chem. 2007, 119,
8398–8401; Angew. Chem. Int. Ed. 2007, 46, 8250–8253;
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Adv. Synth. Catal. 2015, 357, 1259 – 1269

UPDATES
Gold(I)-Catalyzed Decarboxylation of Propargyl Carbonates
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substrates initiated by activation of the triple bonds
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also obtained from the reaction. While the initial spec-
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carbonyl groups with chemical shifts around 153–
Adv. Synth. Catal. 2015, 357, 1259 – 1269
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1269