Sonogashira cross-coupling using carbon aerogel doped with palladium nanoparticles; a recoverable and reusable catalyst

Article abstract of DOI:10.1055/s-2007-983888

The Sonogashira cross coupling of aryl iodides with terminal alkynes has been carried out in the presence of carbon aerogels doped with metallic palladium nanoparticles. Coupling products have been isolated in excellent yields and the catalyst system can

Full text of DOI:10.1055/s-2007-983888

3
068
PAPER
Sonogashira Cross-Coupling Using Carbon Aerogel Doped with Palladium
Nanoparticles; A Recoverable and Reusable Catalyst
S
R
onogashira Cros
o
s-Coupling U
g
sing Palladi
e
um-Carbon
r
Aerogel Soler, Sandro Cacchi,* Giancarlo Fabrizi, Giovanni Forte, Laura Martín, Sandra Martínez,d
a,d
a
a
b
c,d
c
d, 1
b
c
d
d
Elies Molins, Marcial Moreno-Mañas, Francesco Petrucci, Anna Roig, Rosa M. Sebastián, Adelina Vallribera*
a
Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università degli Studi ‘La Sapienza’,
P. le A. Moro 5, 00185 Rome, Italy
Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Cerdanyola 08193, Spain
b
c
d
Department of Chemistry, Universitat Autònoma de Barcelona, Cerdanyola 08193, Spain
Fax +39(6)49912780; E-mail: sandro.cacchi@uniroma1.it
Received 31 May 2007
In this context, we decided to investigate the utilization of
carbon aerogels doped with palladium nanoparticles as
catalysts in the Sonogashira reaction (Scheme 1).
Abstract: The Sonogashira cross coupling of aryl iodides with ter-
minal alkynes has been carried out in the presence of carbon aero-
gels doped with metallic palladium nanoparticles. Coupling
products have been isolated in excellent yields and the catalyst sys-
6
Aerogels represent a new class of porous solids, obtained
tem can be easily recovered in the presence of air without any par- via sol-gel processes coupled with supercritical drying of
ticular precautions and reused several times.
wet gels, which have been shown to exhibit a great poten-
Key words: palladium, nanoparticles, Sonogashira cross coupling, tial for the preparation of heterogeneous catalysts. Herein
7
carbon aerogels, catalysis
we report the results of this study.
Pd-carbon aerogel
CuI
The palladium-catalyzed cross coupling of terminal
alkynes with aryl and vinyl halides or triflates in the pres-
ence of a copper salt as co-catalyst is one of the most pow-
Ar
R
ArI
+
R
1
2
3
erful tools for the formation of C–C bonds. This reaction, Scheme 1
2
known as the Sonogashira cross coupling, allows alkyny-
lation to be performed under milder conditions than those
Carbon aerogels doped with metallic palladium nanopar-
ticles were synthesized as described previously. Before
their utilization, the catalysts were washed with N,N-di-
methylformamide. A sample of palladium-carbon aerogel
containing 46% of palladium in 4 mL of N,N-dimethyl-
3
4
typical of Heck and Cassar protocols and it has found a
variety of applications ranging from the preparation of
fine chemicals to the synthesis of biologically active sub-
stances.
8
Since its discovery, a great deal of work has been done to formamide was heated at 120 °C for two days and then re-
modify the original protocol so as to include an even wid- covered by decantation. The procedure was repeated three
er range of reactants as well as to limit one of the major times.
drawbacks of this process in industrial applications: the
The reaction of 4-iodoacetophenone with hept-1-yne in
utilization of two metals that hinder the recovery and re-
the presence of 6 mol% of palladium-carbon aerogel, di-
utilization of the expensive palladium catalyst (its recov-
isopropylamine (1.5 equiv) in N,N-dimethylformamide at
ery would be the best way to overcome cost-related
1
00 °C was initially tested. Only traces of the cross-cou-
problems). As to the latter point, interesting results have
been achieved by enhancing the catalyst efficacy by em-
pling derivative 3a were formed after 24 hours under
these conditions. When the same reaction was carried out
in the presence of copper(I) iodide (12 mol%), 3a was iso-
lated in 90% yield after 24 hours. However, when 4-io-
doanisole, a model of electron-rich aryl iodides, was
2
d
ploying more efficient phosphines. However, these
phosphines are not readily available and some limits to
their use in large-scale applications still remain.
A subject that has attracted the attention of several re- subjected to the same conditions, it produced only trace
search groups is the utilization of solid-supported palladi- amounts of the desired cross-coupling derivative 3b after
2
d,f
um catalysts.
Indeed, in addition to facilitating the 48 hours. After some experimentation, we found that the
recovery and reutilization of palladium, the use of solid- alkynylation of 4-iodoanisole proceeded smoothly upon
supported palladium catalysts could also reduce the palla- addition of 12 mol% of triphenylphosphine and 3b was
dium contamination of the isolated product, a significant isolated in 87% yield after 23 hours.
problem for the pharmaceutical industry.5
The remarkable effect of the added phosphine ligand
might be accounted for by assuming that a higher amount
of palladium might be dissolved by coordination. Howev-
er, sector field inductively coupled plasma mass spec-
trometry (SF-ICP-MS) analysis indicated the level of
SYNTHESIS 2007, No. 19, pp 3068–3072
x
x.
x
x
.
2
0
0
7
Advanced online publication: 11.09.2007
DOI: 10.1055/s-2007-983888; Art ID: Z13807SS
Georg Thieme Verlag Stuttgart · New York
©

PAPER
Sonogashira Cross-Coupling Using Palladium–Carbon Aerogel
3069
palladium in N,N-dimethylformamide, after decanting, to bon aerogel used in the coupling reactions to the same
be essentially the same with and without triphenylphos- washing procedure utilized at the beginning of the recy-
phine (6–9 ppm). This behavior has not been investigated cling process (DMF, 120 °C, 2 d) regenerated its activity.
and will not be commented upon further.
The same treatment was repeated after runs 6 and 12.
Copper(I) iodide and triphenylphosphine were then used Furthermore, no appreciable leaching of palladium was
as the reaction was extended to other aryl iodides and ter- observed. Indeed, after fifteen cycles only a slight varia-
minal alkynes. Several examples of palladium-carbon tion in the total amount of palladium was observed (within
aerogel-catalyzed Sonogashira cross-coupling reactions experimental error; 35.3% in the initial sample and 32.1%
are listed in Table 1. A variety of electron-rich and elec- in the sample recovered after 15 cycles) and still in the
tron-poor aryl iodides 1 and terminal alkynes 2 reacted form of a palladium(0) species, as shown by an X-ray dif-
smoothly under these conditions to give the correspond- fraction (XRD) analysis (Figure 2). A decrease of the sur-
ing cross-coupling derivatives in excellent yields.
face area was observed by comparison between the BET
parameters of the fresh aerogel and the used one, after fif-
We also investigated the recyclability of the palladium
catalyst. The results of this study, performed with 3-io-
doanisole and hept-1-yne using a sample containing
2
–1
teen cycles (from 422 to 265 m ·g ). This is related to the
collapse of the smallest pores (mostly micropores) due to
the air manipulation (also supported by the increase of the
average pore size). However, no decrease in its catalytic
activity was observed.
3
5.6% of palladium, are summarized in Figure 1.
The upper limit of utilization of the palladium-carbon
aerogel catalyst was not determined. It was recovered
(
simply decanting the solution and mechanically separat-
ing the palladium-carbon aerogel from the salts in the
presence of air and without any particular precaution) and
reused several times. A loss of activity was observed after
the second run. Run 3 gave the coupling product in 63%
yield. However, subjecting the sample of palladium-car-
Table 1 The Sonogashira Cross Coupling of Aryl Iodides 1 and
a
Alk-1-ynes 2 Catalyzed by Palladium-Carbon Aerogel
Entry Ar
R
Time Product Yieldb
(
h)
(%)
97c
87
96
98
99c
99
92
97
99
95
96
94
98
97
92
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
4-AcC H4
(CH ) Me
8
3a
3b
3c
3d
3e
3f
6
2 4
4-MeOC H4
(CH ) Me
23
16
14
16
6
Figure 1 Recycling studies for the Sonogashira cross coupling of 3-
iodoanisole and hept-1-yne in the presence of palladium-carbon aero-
gel as catalyst. Reactions were carried out under standard conditions;
yields are given for isolated products.
6
2 4
3-MeOC H4
(CH ) Me
2 4
6
4-EtO CC H
(CH ) Me
2
6
4
2 4
3-O N-4-MeC H
(CH ) Me
2
6
3
3
3
2 4
In conclusion, we have shown that carbon aerogels doped
with metallic palladium nanoparticles represent an effi-
cient and ready-to-use catalyst for the Sonogashira cross-
coupling reaction. The catalyst can be easily recovered in
the presence of air, without any particular precautions and
reused several times.
4-AcC H4
Ph
Ph
Ph
Ph
Ph
6
6
3-MeOC H4
7
3g
3h
3i
4-MeOC H4
20
6
6
4-EtO CC H
4
2
6
1
1
1
1
1
3-O N-4-MeC H
6
3j
2
6
4-AcC H4
CH OH
16
18
28
16
16
3k
3l
6
2
3-MeOC H4
CH OH
6
2
4-MeOC H4
CH OH
3m
3n
3o
6
2
4-EtO CC H
CH OH
2
6
4
2
1
3-O N-4-MeC H
CH OH
2
6
2
a
Reactions were carried out under argon on a 0.79 mmol scale at 100
C using: ArI (1 equiv), alk-1-yne (1.5 equiv), 46% Pd-C aerogel
0.06 equiv), CuI (0.12 equiv), Ph P (0.12 equiv), i-Pr NH (1.5
°
(
3
2
equiv), deoxygenated DMF (0.5 mL).
Figure 2 XRD patterns of: (a) original palladium-carbon aerogel
and (b) recovered palladium-carbon aerogel after 15 cycles.
b
Yields are given for isolated products.
c
Same results were obtained using 0.03 equiv of 46% Pd-C aerogel.
Synthesis 2007, No. 19, 3068–3072 © Thieme Stuttgart · New York

3
070
R. Soler et al.
PAPER
Melting points were determined with a Büchi B-545 apparatus and
are uncorrected. All reagents and solvents are commercially avail-
able and were used as purchased, without further purification. Re-
action products were purified on axially compressed columns,
packed with 25–40 mm silica gel (Macherey Nagel), connected to a
Gilson solvent delivery system and to a Gilson refractive index de-
1-(4-Methoxyphenyl)hept-1-yne (3b)
Oil.
IR (neat): 2926, 2200, 1603, 1510, 1245, 834 cm–1.
1
H NMR (CDCl ): d = 7.84 (d, J = 8.4 Hz, 2 H), 7.37 (d, J = 2.4 Hz,
3
2
H), 3.81 (s, 3 H), 2.42 (t, J = 7.2 Hz, 2 H), 1.62 (p, J = 7.2 Hz, 2
1
H), 1.41–1.29 (m, 4 H), 0.97 (t, J = 7.2 Hz, 3 H).
tector, and eluted with n-hexane–EtOAc mixtures. H NMR spectra
(
400 MHz) and 13C NMR spectra (100.6 MHz) were recorded with
13
C NMR (CDCl ): d = 159.0, 132.9, 116.3, 113.8, 88.8, 80.2, 55.2,
3
a Bruker Avance 400 spectrometer. IR spectra were recorded with
a Jasco FT/IR-430 spectrophotometer. Mass spectra were recorded
with a Shimadzu GC-MS QP-2010S spectrometer.
3
1.2, 28.6, 22.3, 19.4, 14.0.
+
MS (EI, 70 eV): m/z (%) = 45 (100), 147 (55), 41 (50), 202 (M , 47).
Anal. Calcd for C H O: C, 83.12; H, 8.97. Found C, 83.20; H,
1
4
18
1
-(3-Methoxyphenyl)hept-1-yne (3c); Typical Procedure
In a 10-mL closed-cap flask containing 46% Pd-C aerogel (11 mg,
.047 mmol) were placed CuI (19 mg, 0.1 mmol), Ph P (25 mg, 0.1
8.99.
0
Ethyl 4-(Hept-1-ynyl)benzoate (3d)
Oil.
3
mmol), 3-iodoanisole (189 mg, 0.79 mmol), i-Pr NH (0.17 mL, 1.2
2
mmol), hept-1-yne (0.16 mL, 1.2 mmol), and previously degassed
DMF (0.5 mL) under argon. To avoid the fragmentation of the cat-
alyst, the reactor was orbitally stirred at 600 rpm using a Synthesis
IR (neat): 2930, 1710, 2225, 1250, 830 cm–1.
1
H NMR (CDCl ): d = 7.95 (d, J = 8.4 Hz, 2 H), 7.43 (d, J = 8.4 Hz,
3
2
H), 4.35 (q, J = 7.2 Hz, 2 H), 2.41 (t, J = 7.2 Hz, 2 H), 1.61 (p,
1
Heidolph apparatus at 100 °C for 16 h. After cooling, the soln was
J = 7.2 Hz, 2 H), 1.43–1.36 (m, 4 H), 1.37 (t, J = 6.8 Hz, 3 H), 0.92
removed by means of a Pasteur pipet and the catalyst was washed
(
t, J = 7.2 Hz, 3 H).
with DMF (3 × 0.3 mL). The combined organic extracts were dilut-
1
3
ed in Et O (100 mL), washed with brine (3 × 30 mL), dried
C NMR (CDCl ): d = 166.0, 131.3, 129.3, 129.1, 128.8, 93.8,
2
3
(
Na SO ), and evaporated at reduced pressure. The residue (a yel-
80.1, 60.9, 31.1, 28.3, 22.2, 19.4, 14.2, 13.9,
2
4
low oil) was purified by high pressure column chromatography (sil-
ica gel, n-hexane–EtOAc, 99.5:0.5) to give 3c as a yellow oil; yield:
MS (EI, 70 eV): m/z (%) = 129 (100), 117 (65), 41 (62), 143 (50),
+
1
15 (47), 128 (46), 244 (M , 36).
1
53 mg (96%).
Anal. Calcd for C H O : C, 78.65; H, 8.25. Found C, 78.57; H,
1
6
20
2
IR (neat): 2927, 2228, 1598, 1575, 1486, 1463, 1287, 1045, 780,
8
.27.
–
1
6
80 cm .
1
H NMR (400.13 MHz, CDCl ): d = 7.22 (t, J = 7.8 Hz, 1 H), 7.04
1-(4-Methyl-3-nitrophenyl)hept-1-yne (3e)
Oil.
3
(
d, J = 7.6 Hz, 1 H), 6.98 (br s, 1 H), 6.86 (dd, J = 8.4 Hz, J = 2.4
1
2
Hz, 1 H), 3.82 (s, 3 H), 2.44 (d, J = 7.2 Hz, 2 H), 1.64 (m, 2 H), 1.48
(
–
1
IR (neat): 2930, 2230, 1530, 1346, 895, 826 cm .
m, 2 H), 1.41 (m, 2 H), 0.99 (t, J = 7.2 Hz, 3 H).
1
H NMR (CDCl ): d = 7.97 (s, 1 H), 7.49 (d, J = 7.8 Hz, 1 H), 7.24
1
3
3
C NMR (100.3 MHz, CDCl ): d = 159.3, 129.2, 125.1, 124.1,
3
(
d, J = 7.8 Hz, 1 H), 2.57 (s, 3 H), 2.40 (t, J = 7.2 Hz, 2 H), 1.61 (p,
1
16.4, 114.0, 90.4, 80.5, 51.2, 31.2, 28.5, 22.3, 19.4, 14.0.
J = 7.2 Hz, 2 H), 1.45–1.31 (m, 4 H), 0.93 (t, J = 7.2 Hz, 3 H).
+
MS: m/z (%) = 202 (100, M ), 145 (81), 115 (73), 147 (69).
1
3
C NMR (CDCl ): d = 149.0, 135.6, 132.6, 132.5, 127.4, 123.4,
3
Anal. Calcd for C H O: C, 83.12; H, 8.97. Found C, 83.03; H,
8
92.7, 78.3, 31.1, 28.2, 20.20, 22.2, 19.3, 13.9.
14
18
.95.
MS (EI, 70 eV): m/z (%) = 43 (100), 129 (17), 199 (16), 214 (14),
+
2
31 (M , 3).
Recycling Procedure
After each run, the Pd-C aerogel was recovered by decanting the
soln and separating the catalyst system mechanically from the salts
in the presence of air, without any particular precaution. It was sim-
ply picked up with a spatula, washed with DMF (3 × 0.3 mL),
MeCN (5 × 1 mL), MeOH (5 × 1 mL), and DMF (0.3 mL), and im-
mersed in DMF to keep it wet until subsequent utilization. In case
of loss of activity, the Pd-C aerogel can be reactivated by heating it
in DMF at 120 °C for 2 d.
Anal. Calcd for C14
H17NO : C, 72.70; H, 7.41; N, 6.06. Found: C,
2
72.78; H, 7.40; N, 6.04.
4-(Phenylethynyl)acetophenone (3f)
Mp 96–7 °C.
IR (KBr): 2992, 2217, 1677, 1262, 830, 750, 690 cm–1.
1
H NMR (CDCl ): d = 7.95 (d, J = 8.4 Hz, 2 H), 7.62 (d, J = 8.4 Hz,
3
2
H), 7.57 (m, 2 H), 7.39 (m, 3 H), 2.62 (s, 3 H).
1
3
4
Oil.
-(Hept-1-ynyl)acetophenone (3a)
C NMR (CDCl ): d = 196.8, 135.7, 131.3, 131.2, 128.3, 127.98,
3
127.8, 127.7, 122.2, 92.3, 88.2, 26.1.
–
1
+
IR (neat): 2926, 2230, 1684, 1260, 825 cm .
MS (EI, 70 eV): m/z (%) = 205 (100), 220 (M , 76), 176 (50), 43
1
(46).
H NMR (CDCl ): d = 7.82 (d, J = 8.2 Hz, 2 H), 7.43 (d, J = 8.2 Hz,
3
2
H), 2.59 (s, 3 H), 2.42 (t, J = 7.2 Hz, 2 H), 1.60 (p, J = 7.2 Hz, 2
Anal. Calcd for C H O: C, 87.25; H, 5.49. Found C, 87.14; H,
1
6
12
H), 1.40–1.30 (m, 4 H), 0.90 (t, J = 7.1 Hz, 3 H).
5.51.
1
3
C NMR (CDCl ): d = 197.4, 135.7, 131.7, 129.2, 128.2, 94.5,
3
1
-(3-Methoxyphenyl)-2-phenylacetylene (3g)
8
0.1, 31.1, 28.3, 26.6, 22.3, 19.5, 14.0.
Mp 74–75 °C.
MS (EI, 70 eV): m/z (%) = 43 (100), 129 (17), 199 (16), 41 (15), 114
–
1
+
IR (KBr): 2930, 2250, 1595, 1229, 865, 762, 684 cm .
(
10), 214 (M , 9).
1
H NMR (CDCl ): d = 7.59 (m, 2 H), 7.39 (m, 3 H), 7.31 (d, J = 8.0
Anal. Calcd for C H O: C, 84.07; H, 8.47. Found C, 84.13; H,
3
15
18
Hz, 1 H), 7.19 (d, J = 7.6 Hz, 1 H), 7.12 (m, 1 H), 6.94 (dd, J = 8.0
8
.46.
1
Hz, J = 2.4 Hz, 1 H), 3.86 (s, 3 H).
2
Synthesis 2007, No. 19, 3068–3072 © Thieme Stuttgart · New York

PAPER
Sonogashira Cross-Coupling Using Palladium–Carbon Aerogel
3071
1
3
IR (neat): 3370, 2936, 2227, 1600, 1050, 850 cm–1.
1
C NMR (CDCl ): d = 158.9, 131.2, 128.9, 127.9, 127.8, 123.8,
3
1
23.7, 122.7, 115.9, 114.5, 88.9, 88.7, 54.8.
H NMR (CDCl ): d = 7.21 (dd, J = 8.4 Hz, J = 7.6 Hz, 1 H). 7.04
3
1
2
+
MS (EI, 70 eV): m/z (%) = 208 (M , 100), 178 (23), 165 (22), 139
(d, J = 7.6 Hz, 1 H), 6.99 (s, 1 H), 6.88 (dd, J = 8.4 Hz, J = 2.0 Hz,
1
2
(
9).
1 H), 4.51 (s, 2 H), 3.82 (s, 3 H), 2.96 (s, 1 H).
1
3
Anal. Calcd for C H O: C, 86.51; H, 5.81. Found C, 86.59; H,
C NMR (CDCl ): d = 158.7, 128.9, 123.8, 123.1, 116.1, 114.5,
15
12
3
5
.80.
86.8, 84.9, 54.8, 50.9.
+
MS (EI, 70 eV): m/z (%) = 162 (M , 100), 91(64), 63 (32), 104 (31),
8 (30), 145 (13).
1
-(4-Methoxyphenyl)-2-phenylacetylene (3h)
7
Mp 57–59 °C.
Anal. Calcd for C H O : C, 74.06; H, 6.21. Found C, 74.13; H,
–
1
10 10
2
IR (KBr): 2930, 2211, 1510, 1244, 833, 750, 690 cm .
6
.22.
1
H NMR (CDCl ): d = 7.58 (m, 2 H), 7.53 (d, J = 8.8 Hz, 2 H), 7.37
m, 3 H), 6.92 (d, J = 8.8 Hz, 2 H), 3.86 (s, 3 H).
3
(
3-(4-Methoxyphenyl)prop-2-ynol (3m)
1
3
Oil.
C NMR (CDCl ): d = 159.2, 132.6, 131.0, 127.9, 127.5, 123.2,
3
–
1
1
14.9, 113.6, 89.0, 87.6, 54.8.
IR (neat): 3334, 2926, 2235, 1600, 1247, 826 cm .
+
1
MS (EI, 70 eV): m/z (%) = 208 (M , 100), 193 (44), 165 (37), 139
12).
H NMR (CDCl ): d = 7.37 (d, J = 8.8 Hz, 2 H), 6.82 (d, J = 8.8 Hz,
3
(
2 H), 4.49 (s, 2 H), 3.78 (s, 3 H), 2.92 (s, 1 H).
1
3
Anal. Calcd for C H O: C, 86.51; H, 5.81. Found C, 86.44; H,
C NMR (CDCl ): d = 159.2, 132.7, 114.2, 113.5, 85.6, 85.0, 54.8,
1
5
12
3
5
.79.
50.9.
MS (EI, 70 eV): m/z (%) = 162 (M , 100), 91 (50), 131 (39), 145
38).
Anal. Calcd for C H O : C, 74.06; H, 6.21. Found C, 73.97; H,
+
Ethyl 4-(Phenylethynyl)benzoate (3i)
Mp 72–73 °C.
(
–
1
10 10
2
IR (KBr): 2984, 2214, 1710, 1262, 850, 750, 688 cm .
6
.23.
1
H NMR (CDCl ): d = 7.58 (m, 2 H), 8.05 (d, J = 8.4 Hz, 2 H), 7.61
3
(
(
1
d, J = 8.4 Hz, 2 H), 7.38 (m, 3 H), 4.41 (q, J = 7.2 Hz, 2 H), 1.43
Ethyl 4-(3-Hydroxyprop-1-ynyl)benzoate (3n)
Mp 63–64 °C.
IR (KBr): 3462, 2992, 2150, 1699, 1288, 1015, 855, 778 cm–1.
t, J = 7.2 Hz, 3 H).
3
C NMR (CDCl ): d = 166.1, 131.3, 131.0, 129.3, 129.0, 128.3,
3
1
28.0, 127.4, 122.2, 91.8, 88.2, 60.7, 13.8.
1
H NMR (CDCl ): d = 7.93 (d, J = 8.0 Hz, 2 H), 7.42 (d, J = 8.0 Hz,
3
+
MS (EI, 70 eV): m/z (%) = 250 (M , 100), 205 (88), 176 (47), 222
2 H), 4.51 (s, 2 H), 4.35 (q, J = 7.2 Hz, 2 H), 3.17 (s, 1 H), 1.36 (t,
J = 7.2 Hz, 3 H).
(
33).
1
3
Anal. Calcd for C H O : C, 81.58; H, 5.64. Found C, 81.64; H,
C NMR (CDCl ): d = 165.7, 131.0, 129.4, 128.9, 126.80, 90.0,
1
7
14
2
3
5
.62.
84.1, 60.8, 50.8, 13.1.
MS (EI, 70 eV): m/z (%) = 131 (100), 77 (58), 103 (48), 159 (44),
1
-(4-Methyl-3-nitrophenyl)-2-phenylacetylene (3j)
+
2
04 (M , 30).
Mp 106–107 °C.
Anal. Calcd for C H O : C, 70.57; H, 5.92. Found C, 70.46; H,
–
1
12 12
3
IR (KBr): 2995, 2214, 1525, 1350, 826, 761, 690 cm .
5
.94.
1
H NMR (CDCl ): d = 8.14 (s, 1 H), 7.64 (dd, J = 7.6 Hz, J = 1.2
3
1
2
Hz, 1 H), 7.56 (m, 2 H), 7.40 (m, J = 3.2 Hz, 3 H), 7.34 (d, J = 8 Hz,
3-(4-Methyl-3-nitrophenyl)prop-2-ynol (3o)
1
H), 2.64 (s, 3 H).
Oil.
1
3
IR (neat): 3363, 2928, 2237, 1526, 1350, 1033, 882, 834, 800 cm–1.
C NMR (CDCl ): d = 148.6, 135.0, 133.0, 132.4, 131.2, 128.4,
3
1
28.0, 127.0, 122.1, 121.9, 90.8, 86.4, 19.9.
1
H NMR (CDCl ): d = 7.95 (d, J = 1.2 Hz, 1 H), 7.49 (dd, J = 7.6
3
1
+
MS (EI, 70 eV): m/z (%) = 237 (M , 100), 189 (66), 220 (52), 165
Hz, J = 1.2 Hz, 1 H), 7.24 (d, J = 7.6 Hz, 1 H), 4.50 (s, 2 H), 2.94
2
(
50).
(s, 1 H), 2.55 (s, 3 H).
1
3
Anal. Calcd for C H NO : C, 75.94; H, 4.67; N, 5.90. Found C,
C NMR (CDCl ): d = 148.4, 135.2, 133.3, 132.3, 127.0, 121.3,
15
11
2
3
7
5.86; H, 4.68; N, 5.92.
88.8, 82.5, 50.7, 19.8.
MS (EI, 70 eV): m/z (%) = 115 (100), 91 (87), 174 (70), 191 (M+,
4
-(3-Hydroxyprop-1-ynyl)acetophenone (3k)
5
3).
Mp 81–82 °C.
Anal. Calcd for C H NO : C, 62.82; H, 4.74; N, 7.33. Found C,
–
1
10
9
3
IR (KBr): 3350, 2900, 2250, 1662, 1270, 820 cm .
6
2.76; H, 4.72; N, 7.30.
1
H NMR (CDCl ): d = 7.82 (d, J = 7.2 Hz, 2 H), 7.43 (d, J = 7.2 Hz,
3
2
H), 4.51 (s, 2 H), 3.40 (s, 1 H), 2.55 (s, 3 H).
Acknowledgment
1
3
C NMR (CDCl ): d = 197.6, 135.7, 131.2, 127.7, 127.2, 90.6,
3
8
4.0, 50.8, 26.1.
Work carried out in the framework of the National Project ‘Stereo-
selezione in Sintesi Organica. Metodologie ed Applicazioni’ and
FIRB 2003 supported by the Ministero dell’Università e della
Ricerca Scientifica e Tecnologica and by the University ‘La Sapi-
enza’. Financial support from ‘Ministerio de Educación y Ciencia’
+
MS (EI, 70 eV): m/z (%) = 43 (100), 159 (88), 77 (71), 174 (M , 50),
1
31 (50).
Anal. Calcd for C H O : C, 75.84; H, 5.79. Found C, 75.90; H,
5
1
1
10
2
.80.
(
Projects CTQ2005-04968-C02-01 and MAT2006-13572-C02-01
and grants of L.M, S.M and R.S.) and ‘DURSI-Generalitat de Cata-
lunya’ (Projects SGR 2005-00452 and SGR 2005-00305) are grate-
fully acknowledged.
3
Oil.
-(3-Methoxyphenyl)prop-2-ynol (3l)
Synthesis 2007, No. 19, 3068–3072 © Thieme Stuttgart · New York

3
072
R. Soler et al.
PAPER
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Synthesis 2007, No. 19, 3068–3072 © Thieme Stuttgart · New York