Sequential gold-catalyzed reactions of 1-phenylprop-2-yn-1-ol with 1,3-dicarbonyl compounds

Article abstract of DOI:10.1016/j.jorganchem.2008.12.013

A variety of sequential gold-catalyzed reactions of 1-phenylprop-2-yn-1-ol with 1,3-dicarbonyl compounds are directed towards different outcomes by a suitable choice of the catalytic system, feature of 1,3-dicarbonyl and reaction conditions.

Full text of DOI:10.1016/j.jorganchem.2008.12.013

Journal of Organometallic Chemistry 694 (2009) 576–582
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Sequential gold-catalyzed reactions of 1-phenylprop-2-yn-1-ol
with 1,3-dicarbonyl compounds
a
b
a
Antonio Arcadi a, , Maria Alfonsi , Marco Chiarini , Fabio Marinelli
*
a Department of Chemistry, Chemical Engineering and Materials, University of L’Aquila, Via Vetoio, Coppito Due, I-67100 L’Aquila, Italy
b Department of Food Science, University of Teramo, Via Carlo Lerici 1, Mosciano Sant’Angelo, I-64023 Teramo, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 October 2008
Received in revised form 4 December 2008
Accepted 4 December 2008
Available online 16 December 2008
A variety of sequential gold-catalyzed reactions of 1-phenylprop-2-yn-1-ol with 1,3-dicarbonyl com-
pounds are directed towards different outcomes by a suitable choice of the catalytic system, feature of
1,3-dicarbonyl and reaction conditions.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Gold catalysis
Propargylic alcohols
1,3-Dicarbonyl compounds
Sequential reactions
1. Introduction
reaction of secondary propargylic alcohols was carried out with
cyclic 1,3-diones the nature of the resulting products was found
Gold catalysts are assuming growing popularity in organic syn-
thesis [1]. In contrast to classic Lewis acids, which are known to
to be dependent on the ring size of the dicarbonyl compound em-
ployed: whereas furan-ring formation has been selectively ob-
tained starting from acyclic 1,3-dicarbonyl compounds and 1,3-
cyclohexanediones (Scheme 2a), the use of 1,3-cyclopentanedione
leads, instead, to products via a pyran-ring formation (Scheme 2b)
[8].
form strong
ate as bifunctional Lewis acids activating either (or both) carbon–
carbon multiple bonds via -bonding and/or forming -complexes
r-complexes, the salts of transition metals can oper-
p
r
by coordinating with heteroatoms [2]. Although gold catalysis has
attained a substantial advance in the nucleophilic activations of al-
kynes and alkenes, only limited examples have focused on the acti-
vation of pre-electrophiles [3]. In particular, an effective bidentate
chelation of gold catalysts to propargylic alcohols has been re-
ported providing an excellent reactivity for the Meyer–Schuster
rearrangement under mild conditions [4]. Moreover, gold catalysts
may also act as propargylic alcohol-activating agents in propargylic
substitution reactions (Scheme 1) [5].
Recently, efficient methods for the preparation of tetrasubsti-
tuted furans through propargylation of 1,3-dicarbonyl com-
pounds-cyclization tandem processes have been developed. It
was discovered that InCl3, could catalyze that transformation effi-
ciently while simple iron, copper and silver salts were proven to be
ineffective [6]. Moreover, a process, which proceeds in a one-pot
manner, involves the initial propargylation of the 1,3-dicarbonyl
compound promoted by trifluoroacetic acid, and subsequent cyclo-
As an extension of our studies of gold catalysis in promoting
sequential reaction by accomplishing a dual role catalysis through
a twofold coordination of a lone pair of heteroatoms and
p-elec-
trons of C–C multiple bonds [9], we decided to investigate the use
of gold as an alternative catalyst in the reaction of propargylic
alcohols with 1,3-dicarbonyl compounds. The development of
novel synthetic routes, allowing the facile assembly of more
complex scaffolds from readily available and inexpensive precur-
sors, still remains an important objective for synthetic organic
chemists. Hereafter we report the preliminary results of our
investigation.
2. Results and discussion
At the outset, we tested Au(III) catalysts in the reaction of 1-
phenylprop-2-yn-1-ol 1 with 2,4-pentanedione 2a. Au(III) catalysts
have been reported to give the best results compared to Au(I) cat-
alysts in promoting the selective nucleophilic substitution of prop-
argylic alcohols [5a]. Surprisingly, a mixture of products was
isolated in different organic solvents at different temperatures
(Scheme 3; Table, entries 1–8). By contrast when the reaction
isomerization of the resulting c-ketoalkyne catalyzed by a ruthe-
nium(II) complex [7]. When the ruthenium/TFA catalyzed
* Corresponding author. Tel.: +39 0862433774; fax: +39 0862433753.
E-mail address: arcadi@univaq.it (A. Arcadi).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.12.013

A. Arcadi et al. / Journal of Organometallic Chemistry 694 (2009) 576–582
577
R1
O
R1
R2
OH
R3
R2
R3
OH
HO
R1
Au
[Au]
R1
R2
R3
R2
R3
Nu
NuH
R1
R2
- H2O
R3
Scheme 1.
O
R4
O
a
R1
OH
R3
R4
[Ru]
CF3COOH
O
R3
O
O
+
R1
R3 R4
R1
O
R2
R2
R2
R1
b
O
OH
O
O
[Ru]/CF3COOH
+
R1
R2
R2
O
Scheme 2.
Ph
H
O
O
O
CH3
H3C
Ph
O
O
O
O
CH3
CH3 CH3
CH3
CH3
OH
O
H3C
Ph
2a
O
+
+
Ph
CH3
Catalyst
CH3
H
5a
1
5a'
4a
Scheme 3.
was catalyzed by [AuClPPh3]/AgOTf the furan 5a was isolated as
the only reaction product in 80% yield (Table 1, entry 9). AgOTf
should help generate a more electrophilic gold species. AgOTf
alone did not efficiently catalyze the reaction under the same con-
ditions (Table 1, entry 10).
and alkyl ketone fragments gave rise only to the formation of furan
derivatives (Scheme 4).
In the presence of Ph3PAuCl (5 mol%)/AgOTf (10 mol%), as cata-
lytic system, the reaction of 1 (2 equiv.) with 2b (1 equiv.) led, in
good yield, the tetrasubstituted furan 5b derived from the cycliza-
When the reaction was studied by using other 1,3-dicarbonyl
compounds, we observed a variety of intriguing results. The reac-
tion of 1 with the 1-phenyl-1,3-butanedione 2b containing aryl
O
O
CH3 Ph
H3C
Ph
2b
H3C
Ph
O
O
O
O
Table 1
CH3
Ph
Ph3PAuCl/AgOTf
Ph
1
Gold-catalyzed reaction of 1 with 2a.
+
THF, 60 °C,
4 h
Entry 2a/
Solvent Catalyst
Temperature
(°C)/time (h)
Yield
of 4a
(%)a
Yield
of 5a
(%)a
Yield
of 5a0
(%)a
CH3
1
(70% yield)
5b
(8% yield)
5b''
1
2
3
4
5
6
7
8
9
10
3
3
5
5
Neat
THF
THF
THF
DCE
NaAuCl4 ꢀ 2H2O 75/1
–
44
14
18
–
45
–
–
–
–
–
–
28
16
32
22
–
HAuCl4 ꢀ 3H2O
HAuCl4 ꢀ 3H2O
HAuCl4 ꢀ 3H2O
HAuCl4 ꢀ 3H2O
HAuCl4 ꢀ 3H2O
HAuCl4 ꢀ 3H2O
HAuCl4 ꢀ 3H2O
PPh3AuCl/
60/0.5
rt/2.5
60/5
60/24
60/5
60/5.5
60/24
60/4
Ph
2b
.
HAuCl4 3H2O
(5 mol %)
O
–
21
–
–
80
Ph
1
5
CH3CN
5b'' (20% yield) +
H
THF, 60 °C,
24 h
0.5 THF
1.2 Neat
17
–
CH3
O
5
THF
AgOTf
5b' (21% yield)
10
5
THF
AgOTf
60/24
22
aYields refer to single runs, and are given for pure isolated products.
Scheme 4.

578
A. Arcadi et al. / Journal of Organometallic Chemistry 694 (2009) 576–582
On the other hand, the Au(III)-catalyzed formation of the trisub-
O
OPh
stituted furan 5b0 should involve the competitive allenylation
(Scheme 6) of the 1,3-dicarbonyl/cyclization reaction with a mech-
anism that proceeds by an SN20 pathway [10]. The regioselectivity
of the nucleophilic trapping can depend on the competition
between an SN20 or a cationic mechanism. This latter mechanism
can be favored by Au(PPh3)+ [11].
Ph
Ph
CH3
OH
H3C
Ph
OH
A different sequence of gold-catalyzed reactions was observed
when 1 was reacted with the 1,3-diphenylpropanedione 2c in
the presence of Ph3PauCl (5 mol%)/AgOTf (10 mol%). In this
transformation, hydrative alkylation occurs regioselectively lead-
ing 4b in good yield (Scheme 7) [12].
5b
5b''
Very likely, the Au(PPh3)+ coordination with 1 promotes the
generation of a carbocation, which is subsequently trapped by
the dicarbonyl 2c to form the substitution product 3b. Next, regio-
selective hydration occurs. The competition of the gold-catalyzed
hydration of intermediates 3 versus their gold-catalyzed cycliza-
tion to furans may depends on a combination of electronic, coordi-
nating, and medium factors. In order to confirm that, we prepared,
according to the literature [13], the substitution product 3a–b, and
then treated them with a catalytic amount of gold catalysts
(5 mol%) (Scheme 8).
Scheme 5.
H
O
O
O
R
R
Ph
R
R
H
O
1
H
HO
O
5'
R
R
The results observed show that the amount of water, in the
reaction medium, plays a pivotal role to direct the reaction towards
the hydrative pathway. Indeed 3a undergoes NaAuCl4 ꢀ 2H2O cata-
lyzed hydration in high yield in aqueous CH3CN at 60 °C. By using
anhydrous THF instead of aqueous CH3CN, cyclization of 3a occurs
to give the furan derivative 5a. The formation of the derivative 4
can be also observed by using the Ph3PAuCl/AgOTf catalytic system
in THF/H2O with the derivative 3b which is less prone to undergo
the annulation reaction. Indeed, the Au(I)-catalyzed cyclization of
3b requires long reaction time: after 8 h we isolated 5c in 65%
yield, but the starting 3b was also recovered in 35% yield. The prod-
uct 5c is only accessible by a two step synthesis.
To compare the feature of the catalysis by gold versus the re-
ported ruthenium/TFA-catalyzed coupling of secondary propargy-
lic alcohols with cyclic 1,3-diones [8], we investigated the
reaction of 1 with 1,3-cyclohexanediones 2d–e and 1,3-cyclopen-
tanedione 2f, respectively. In our cases, the 6,7-dihydro-5H-benzo-
furan-4-one derivative 5d has been isolated in moderate yield only
in the presence of Au(III) catalysts. Attempts to promote related
coupling reaction under Au(I) catalysis resulted in the formation
of more complicated reaction mixtures from which the 9-((E)-sty-
ryl)-3,4,5,6,7,9-hexahydro-2H-xantene-1,8-dione 6a has been sep-
arated by uncharacterized byproducts. The formation of 6a occurs,
also, to some extent under Au(III) catalysis (Scheme 9).
Scheme 6.
O
O
Ph Ph
2c
O
Ph
Ph3PAuCl/AgOTf
CH3
1
O
O
THF, 60 °C, 3 h
Ph Ph
4b (62% yield)
Scheme 7.
tion involving the oxygen of the alkyl ketone fragment. Regioiso-
meric furan 5b00 was isolated as minor byproduct. Surprisingly,
by using HAuCl4 ꢀ 3H2O as catalyst we observed a loss of efficiency
and different products distribution. The formation of the tetrasub-
stituted furans 5b and 5b00 can be readily explained through the
exo-dig annulation reaction of the two isomeric enol intermediates
arising from the nucleophilic substitution reaction of 1 with 2b
(Scheme 5).
H
Ph
NaAuCl4. 2H2O
4a (12 % yield) + 5a (70 % yield)
THF, 60 °C, 3 h
NaAuCl4. 2H2O
4a (95% yield)
O
O
CH3CN/H2O (10/1)
60 °C, 6 h
CH3 CH3
3a
H
Ph
O
Ph3PAuCl/AgOTf
THF, 60 °C, 8 h
Ph
Ph3PAuCl/AgOTf
4b (90% yield)
CH3
Ph
O
O
THF/ H2O, 60 °C, 3 h
Ph
O
Ph Ph
5c (65% yield)
3b
Scheme 8.

A. Arcadi et al. / Journal of Organometallic Chemistry 694 (2009) 576–582
579
In summary, gold-catalyzed sequential C-alkylation/cyclization,
C-alkylation/hydration and O-alkylation/hydration reactions of 1-
phenyl-prop-2-yn-1-ol with 1,3-dicarbonyl compounds are direc-
ted by a suitable choice of the gold catalytic system, substrates
and reaction conditions. In the presence of 1,3-cyclohexandione
derivatives a cascade gold-catalyzed reaction of 1-phenylprop-
2-yn-1-ol can accomplish the formation 3,4,5,6,7,9-hexahydro-
2H-xantene-1,8-dione derivatives. Further investigation on the
application of the gold-catalyzed reactions of propargylic alcohols
with 1,3-dicarbonyls is ongoing and will be reported in due course.
O
Ph
O
O
O
Ph
O
2d
+
1
H3C
.
O
O
NaAuCl4 2H2O
THF, 60 °C, 24 h
6a (27% yield)
5d (44 % yield)
2d
6a (27% yield)
1
Ph3PAuCl/AgOTf
THF, 60 °C, 2 h
3. Experimental
Scheme 9.
Temperatures are reported as bath temperature. Solvents used in
extraction and purification were distilled prior to use. Compounds
were visualized on analytical thin-layer chromatograms (TLC) by
UV light (254 nm). The products, after usual work-up, were purified
by flash chromatography on silica gel (230–400 mesh) eluting with
n-hexane/ethyl acetate mixtures. 1H NMR and 13C NMR spectra
were recorded with a Bruker AC 200 E spectrometer or Varian Mer-
cury 300. Mass spectra were recorded with a Varian Saturn 2100 T
GC/MS instrument. IR were recorded with a Perkin–Elmer 683 spec-
trometer. Only the most significant IR absorptions are given. All
starting materials, catalysts, and solvents if not otherwise stated,
are commercially available and were used as purchased, without
further purification. The products 4b [12b], 5a [7], 5d [8], 6a–b
[14] were known and where determined using comparison of their
physical and spectral data with those reported in literature.
O
H
2d
6a (74% yield)
Ph3PAuCl/AgOTf
THF, 60 °C, 5 h
Ph
Scheme 10.
O
Ph
O
O
O
2e
1
Ph3PAuCl/AgOTf
THF, 60 °C, 2 h
3.1. HAuCl4 ꢀ 3H2O catalyzed reaction of 1-phenylprop-2-yn-1-ol 1
with 2,4-pentanedione (2a)
O
6b (63 % yield)
To a solution of 1-phenylprop-2-yn-1-ol 1 (0.88 mmol, 90 mg)
in THF (1 mL) were added the 1,3-dicarbonyl compound 2a
(2.04 mmol, 204 mg) and HAuCl4 ꢀ 3H2O (0.034 mmol, 13 mg).
The mixture was stirred at 60 °C and monitored by TLC or GC–
MS. After 0.5 h, the solvent was removed by evaporation. The res-
idue was purified by chromatography on silica gel (230–400 mesh)
eluting with n-hexane/ethyl acetate mixture 95/5 to afford the
pure derivatives 4a and 5a0.
Scheme 11.
O
O
O
O
CH3
O
2f
1
Ph
Ph3PAuCl/AgOTf
THF, 60 °C, 2 h
3.2. 3-Acetyl-4-phenyl-hexane-2,5-dione (4a)
7 (53 % yield)
69 mg; 44% yield; IR (neat):
m .
= 1750, 1700, 740, 690 cmꢁ1 1H
Scheme 12.
NMR (CDCl3, 300.20 MHz) d = 1.88 (s, 3H), 2.08 (s, 3H), 2.28 (s,
3H), 4.52 (d, J = 11.4 Hz, 1H), 4.64 (d, J = 11.4 Hz, 1H), 7.22 (m,
2H), 7.32 (m, 3H). 13C NMR (CDCl3, 75.49 MHz) d = 28.6, 30.1,
30.7, 58.6, 70.3, 128.2, 128.6, 129.3, 143.2, 201.6, 202.5, 205.9.
MS (70 EV, EI, relative intensity): 214 [(MꢁH2O)+, 100].
Considering that 6a has been previously prepared by the reac-
tion of cyclohexan-1,3-dione 2d with cinnamaldehyde, it can be
suggested that 1 can also undergo fast gold-catalyzed Meyer-
Schuster rearrangement to give the cinnamaldehyde, which
subsequently generates 6a [14]. To shed a light on this aspect,
we reacted cynnamaldehyde with 2d under our reaction condi-
tions and we isolated the derivative 6a in good yield (Scheme 10).
The formation of 3,4,5,6,7,9-hexahydro-2H-xantene-1,8-dione
derivatives in satisfactory synthetic yields through the gold-cata-
lyzed cascade reaction can be accomplished by a suitable choice
of the 1/1,3-cyclohexanedione derivative ratio (i.e. 6b was isolated
in 63% yield by reacting an excess of 1 with 2e (1/2e = 2) in anhy-
drous THF at 60 °C under the presence of Ph3PauCl (5 mol%)/AgOTf
(10 mol%) catalytic system (Scheme 11).
3.3. 1-(5-Benzyl-2-methyl-furan-3-yl)-ethanone (5a0)
41 mg; 28% yield; IR (neat):
m .
= 1670, 1550, 670 cmꢁ1 1H NMR
(CDCl3, 200 MHz) d = 2.30 (s, 3H), 2.53 (s, 3H), 3.90 (s, 2H), 6.19 (s,
2H), 7.22–7.36 (m, 5H). 13C NMR (CDCl3, 50.3 MHz) d = 14.3, 29.0,
34.1, 106.8, 122.0, 126.7, 128.5, 131.6, 137.3, 152.4, 157.3, 194.1.
MS (70 EV, EI, relative intensity): 214 [M+, 100], 199 (73), 171
(30).
Remarkably, in contrast to the reactions with 1,3-cyclohexan-
ediones, when 1,3-cyclopentanedione is used as a substrate the
sequential gold-catalyzed O-propargylation/hydration reaction
prevails to give as main reaction product the 3-(2-oxo-1-phenyl-
propxy)-cyclopent-2-enone 7 (Scheme 12).
3.4. Ph3PAuCl/AgOTf catalyzed reaction of 1-phenylprop-2-yn-1-ol 1
with 2,4-pentanedione (2a)
To a solution of 1-phenylprop-2-yn-1-ol 1 (1.52 mmol, 200 mg)
in THF (2 mL) were added the 1,3-dicarbonyl compound 2a

580
A. Arcadi et al. / Journal of Organometallic Chemistry 694 (2009) 576–582
(7.06 mmol, 758 mg), Ph3PAuCl (0.036 mmol, 37 mg) and AgOTf
(0.152 mmol, 40 mg). The mixture was stirred at 60 °C and moni-
tored by TLC or GC–MS. After 4.0 h, the solvent was removed by
evaporation. The residue was purified by chromatography on silica
gel (230–400 mesh) eluting with n-hexane/ethyl acetate mixture
95/5 to afford the pure 5a (258 mg, 80% yield).
3.11. Gold(III) catalyzed hydration reaction of 3-(1-phenylprop-2-
ynyl)-pentane-2,4-dione (3a)
To a solution of 3-(1-phenylprop-2-ynyl)-pentane-2,4-dione
(3a) (0.41 mmol, 89 mg) in CH3CN (2 mL) were added water
(0.2 mL) and NaAuCl4 ꢀ 2H2O (0.020 mmol, 8 mg). The mixture
was stirred at 60 °C and monitored by TLC or GC–MS. After 6.0 h,
the mixture was filtered through a short pad of florisil (EtOAc)
and the solvents were evaporated under reduced pressure to give
the corresponding derivative 4a (90 mg, 94% yield).
3.5. Ph3PAuCl/AgOTf catalyzed reaction of 1-phenylprop-2-yn-1-ol 1
with 1-phenyl-1,3-butanedione (2b)
To a solution of 1-phenylprop-2-yn-1-ol 1 (2.17 mmol, 293 mg)
in THF (2 mL) were added the 1,3-dicarbonyl compound 2b
(1.09 mmol, 180 mg), Ph3PAuCl (0.055 mmol, 27 mg) and AgOTf
(0.11 mmol, 28 mg). The mixture was stirred at 60 °C and moni-
tored by TLC or GC–MS. After 4.0 h, the solvent was removed by
evaporation. The residue was purified by chromatography on silica
gel (230-400 mesh) eluting with n-hexane/ethyl acetate mixture
85/15 to afford the pure derivatives 5b and 5b00.
3.12. Ph3PAuCl/AgOTf catalyzed hydration reaction of 1,3-diphenyl-2-
(1-phenylprop-2-ynyl)-propane-1,3-dione (3b)
To
a solution of 1,3-diphenyl-2-(1-phenylprop-2-ynyl)-pro-
pane-1,3-dione (3b) (0.30 mmol, 100 mg) in anhydrous THF
(2 mL) were added water (2.95 mmol, 53 mg), Ph3PAuCl
(0.015 mmol, 8 mg) and AgOTf (0.029 mmol, 8 mg). The mixture
was stirred at 60 °C and monitored by TLC or GC–MS. After 6.0 h,
the mixture was filtered through a short pad of florisil (EtOAc)
and the solvents were evaporated under reduced pressure to give
the corresponding derivative 4b (96 mg, 90% yield).
3.6. (2,5-Dimethyl-4-phenyl-furan-3-yl)-phenyl-methanone (5b)
210 mg; 70% yield; IR (neat):
m .
= 1650, 1580, 710, 680 cmꢁ1 1H
NMR (CDCl3, 300.20 MHz) d = 2.29 (s, 3H), 2.31 (s, 3H), 7.08–7.65
(m, 10H). 13C NMR (CDCl3, 75.49 MHz) d = 11.8, 12.4, 34.1, 121.5,
126.2, 127.2, 127.5, 127.7, 128.9, 129.2, 132.1, 132.5, 138.1,
146.6, 154.5, 192.2. MS (70 EV, EI, relative intensity): 276 [M+,
100], 199 (23), 105 (45).
3.13. (Methyl-2,4-diphenyl-furan-3-yl)-phenyl-methanone (5c)
65 mg; 65% yield; IR (neat):
m .
= 1650, 1590, 670 cmꢁ1 1H NMR
(CDCl3, 200 MHz) d = 2.45 (s, 3H), 7.13–7.83 (m, 15H). 13C NMR
(CDCl3, 50.3 MHz) d = 12.3, 121.8, 123.5, 126.2, 126.9, 127.2,
128,1, 128.2, 128.4, 129.2, 129.8, 132.3, 133.1, 137.6, 148.1,
150.8, 193.7 MS (70 EV, EI, relative intensity): 238 [M+, 100], 261
(22), 105 (32).
3.7. 1-(5-Methyl-2,4-diphenyl-furan-3-yl)-ethanone (5b00)
22 mg; 8% yield; IR (neat):
m .
= 1690, 1600, 730, 690 cmꢁ1 1H
NMR (CDCl3, 200 MHz) d = 2.20 (s, 3H), 2.35 (s, 3H), 7.16–
7.48 (m, 10H). MS (70 EV, EI, relative intensity): 276 [M+, 70],
261 (100).
3.14. Ph3PAuCl/AgOTf catalyzed reaction of trans-cynnamaldehyde
with cyclohexan-1,3-dione (2d)
To a solution of trans-cynnamaldehyde (0.78 mmol, 100 mg) in
anhydrous THF (2 mL) were added the 1,3-dicarbonyl compound
2d (2.27 mmol, 255 mg), Ph3PAuCl (0.04 mmol, 19 mg) and AgOTf
(0.08 mmol, 19 mg). The mixture was stirred at 60 °C and moni-
tored by TLC or GC–MS. After 6.0 h, the solvent was removed by
evaporation. The residue was purified by chromatography on silica
gel (230–400 mesh) eluting with n-hexane/ethyl acetate mixture
50/50 to afford the pure derivative 6a (180 mg, 74% yield).
3.8. HAuCl4 ꢀ 3H2O Catalyzed reaction of 1-phenylprop-2-yn-1-ol 1a
with 1-phenyl-1,3-butanedione (2b)
To a solution of 1-phenylprop-2-yn-1-ol 1 (1.11 mmol, 147 mg)
in THF (1 mL) were added the 1,3-dicarbonyl compound 2a
(0.55 mmol, 90 mg) and HAuCl4 ꢀ 3H2O (0.028 mmol, 11 mg). The
mixture was stirred at 60 °C and monitored by TLC or GC–MS. After
24 h, the solvent was removed by evaporation. The residue was
purified by chromatography on silica gel (230-400 mesh) eluting
with n-hexane/ethyl acetate mixture 85/15 to afford the pure
derivatives 5b00 (30 mg; 20% yield) and 5b0.
3.15. Ph3PAuCl/AgOTf catalyzed reaction of 1-phenylprop-2-yn-1-ol 1
with dimedone (2e)
3.9. 1-(5-Benzyl-2-phenyl-furan-3-yl)-ethanone (5b0)
To a solution of 1-phenylprop-2-yn-1-ol 1 (1.51 mmol, 200 mg)
in anhydrous THF (2 mL) were added the 1,3-dicarbonyl compound
2e (0,76 mmol, 106 mg), Ph3PAuCl (0.038 mmol, 19 mg) and AgOTf
(0.076 mmol, 20 mg). The mixture was stirred at 60 °C and moni-
tored by TLC or GC–MS. After 2.0 h, the solvent was removed by
evaporation. The residue was purified by chromatography on silica
gel (230–400 mesh) eluting with n-hexane/ethyl acetate mixture
60/40 to afford the pure derivative 6b (94 mg, 63% yield).
33 mg; 21% yield; IR (neat):
m .
= 1670, 1590, 680 cmꢁ1 1H NMR
(CDCl3, 200 MHz) d = 2.35 (s, 3H), 4.01 (s, 2H), 6.18 (s, 1H), 7.25–
7.87 (m, 10H). MS (70 EV, EI, relative intensity): 276 [M+, 100],
261 (90), 233 (16).
3.10. Ph3PAuCl/AgOTf catalyzed reaction of 1-phenylprop-2-yn-1-ol 1
with 1,3-diphenyl-propane-1,3-dione (2c)
3.16. Ph3PAuCl/AgOTf catalyzed reaction of 1-phenylprop-2-yn-1-ol 1
To
a
solution of 1-phenylprop-2-yn-1-ol (1) (1.51 mmol,
with 1,3-cyclopentanedione (2f)
200 mg) in THF (2 mL) were added the 1,3-dicarbonyl compound
2c (0.76 mmol, 170 mg), Ph3PAuCl (0.038 mmol, 19 mg) and AgOTf
(0.076 mmol, 20 mg). The mixture was stirred at 60 °C and moni-
tored by TLC or GC–MS. After 3.0 h, the solvent was removed by
evaporation. The residue was purified by chromatography on silica
gel (230–400 mesh) eluting with n-hexane/ethyl acetate mixture
80/20 to afford the pure derivatives 4b (167 mg, 62% yield).
To a solution of 1-phenylprop-2-yn-1-ol 1 (0.76 mmol, 100 mg)
in anhydrous THF (2 mL) were added the 1,3-dicarbonyl compound
2f (2,27 mmol, 223 mg), Ph3PAuCl (0.038 mmol, 19 mg) and AgOTf
(0.076 mmol, 20 mg). The mixture was stirred at 60 °C and moni-
tored by TLC or GC–MS. After 2.0 h, the solvent was removed by
evaporation. The residue was purified by chromatography on silica

A. Arcadi et al. / Journal of Organometallic Chemistry 694 (2009) 576–582
581
gel (230–400 mesh) eluting with n-hexane/ethyl acetate mixture
90/10 to afford the pure derivative 7.
in the range 2.38–2.54 ppm and peak at 34.0 ppm and between
multiplet in the range 2.64–2.89 ppm and peak at 28.4 ppm allow
to assign those signals to the methylenes of the five membered
ring. The carbons connectivity, in the backbone, as been inferred
from HETCORLR experiment. The long range correlation 1H–13C be-
tween peaks at 2.18 ppm and 201.5 ppm allows assigning the lat-
ter resonance to carbonyl C-9 and the resonance at 205.3 to
carbonyl C-1. The long range correlation 1H–13C between peaks
at 2.18 ppm and 87.6 ppm allows assigning the latter resonance
to methine C-8 and the resonance at 106.8 to methine C-2, assign-
ment confirmed by long range correlation 1H–13C between peaks at
5.20 ppm and 28.4 ppm. The long range correlation 1H–13C be-
tween multiplet in the range 2.38–2.54 and peaks at 205.3 and
187.9 ppm allows assigning the resonance at 187.9 ppm to carbon
C-3 and resonance at 34.0 ppm to carbon C-4. The long range cor-
relation 1H–13C between peak at 5.45 ppm and both peaks at 132.9
and 126.8 ppm allows assigning the former resonance to carbon C-
11 and the latter to carbons C-12 and C-16 confirming as well the
assignment of resonance at 87.6 ppm to carbon C-8. MS (70 EV, EI,
relative intensity): 230 [M+, 100], 187 (23), 105 (23).
3.17. 3-(2-Oxo-1-phenylpropoxy)-cyclopent-2-en-1-one (7)
90 mg; 53% yield; IR (neat):
m .
= 1730, 1700,1590, 670 cmꢁ1 1H
NMR (CDCl3, 300.20 MHz) d = 2.18 (s, 3H, CH3), 2.38–2.54 (m, 2H,
CH2 protons 4a–b), 2.64–2.89 (m, 2H, CH2 protons 5a–b), 5.20 (s,
1H, CH proton 2a), 5.45 (s, 1H, CH proton 8a), 7.36–7.49 (m, 5H,
CH aromatic). 13C NMR (CDCl3, 75.49 MHz) d = 25.3 (CH3), 28.4
(CH2 carbon 5), 34.0 (CH2 carbon 4), 87.6 (CH carbon 8), 106.8
(CH carbon 2), 126.8 (CH carbons 12 and 16), 129.1 (CH carbons
13 and 15), 129.5 (CH carbon 14), 132.9 (C carbon 11), 187.9
(C carbon 3), 201.5 (CO carbon 9), 205.3 (CO carbon 1). The
structure was confirmed by one and two-dimensional NMR exper-
iments. Namely 1H NMR, 13C NMR, NOE Difference Spectroscopy,
DEPT (Distortionless Enhancement by Polarization Transfer), HET-
COR 2D (the two-dimensional C,H-Correlation by Polarization
Transfer) and HETCORLR 2D (the two-dimensional Long-Range
C,H-Correlation by Polarization Transfer). The HETCOR 2D
experiment yield cross-signal for all protons and 13C nuclei that
are connected by a 13C, 1H coupling over one bond. Instead
HETCORLR 2D experiment yield cross-signal for 13C, 1H coupled
over more than one bond, generally two and three. Therefore the
assignment of one member of a spin-coupled pair leads immedi-
ately to the assignment of the other. Proton and carbons are num-
bered as shown in Fig. 1 and the assignment of the peaks in the
spectra was done as follow. The peaks position and integral value
in the 1H NMR spectrum showed that, identifying the broad peak
centered at 7.42 ppm as the aromatic resonance and imposing to
that signal an integral value of five, peak at 2.18 ppm identifies
the methyl resonance, peaks at 5.20, 5.45 ppm identify the
methine resonances and multiplets in the range 2.38–2.54 and
2.64–2.89 ppm identify the methylene resonances. The peaks posi-
tion in the 13C NMR spectrum and the DEPT experiment identify
that peak at 25.3 ppm is due to a methyl carbon, peaks at 87.6,
106.8, 126.8, 129.1, 129.5 ppm are all due to methine carbons,
peaks at 28.4 and 34.0 ppm are due to methylene carbons and
peaks at 132.9, 187.9, 201.5 and 205.3 ppm are all due to quater-
nary carbons. Carbon-13 peaks at 201.5 and 205.3 ppm, for their
resonance position can be assigned to carbonyl carbons. The HET-
COR 2D experiment shows, beside the obvious correlations of the
Acknowledgement
Work supported by the University of L’Aquila (Italy).
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