PMA-silica gel catalyzed propargylation of aromatic compounds with arylpropargyl alcohols under solvent-free conditions

Article abstract of DOI:10.1055/s-2008-1067083

PMA-silica gel has been utilized to catalyze efficiently the propargylation of aromatic compounds with arylpropargyl alcohols in the absence of solvent under environmentally benign conditions.

Full text of DOI:10.1055/s-2008-1067083

PAPER
1853
PMA–Silica Gel Catalyzed Propargylation of Aromatic Compounds with
Arylpropargyl Alcohols under Solvent-Free Conditions1
PMA–Silica
G
a
el
C
atalyze
b
d Propargyl
b
tion of Arom
a
a
tic Comp
r
ound aja Srihari,* Joolakanti Shyam Sunder Reddy, Satadru Sekhar Mandal, Kamani Satyanarayana,
Jhillu Singh Yadav
Organic Division-I, Indian Institute of Chemical Technology, Hyderabad 500007, India
Fax +91(40)27160512; fax +91(40)27160387; E-mail: srihari@iict.res.in
Received 27 July 2007; revised 3 March 2008
In continuation of our investigations on PMA–silica gel as
a solid reagent system, we disclose herein the propargyla-
tion of aromatic compounds with arylpropargyl alcohols 1
both in the presence and absence of solvent media
(Scheme 1).
Abstract: PMA–silica gel has been utilized to catalyze efficiently
the propargylation of aromatic compounds with arylpropargyl alco-
hols in the absence of solvent under environmentally benign condi-
tions.
Key words: propargylation, nucleophilic substitution, Nicholas
reaction, Friedel–Crafts alkylation
At the beginning of our study, phenol and PMA–silica gel
were added to 1,3-diphenylprop-2-yn-1-ol (1a),15 in ace-
tonitrile and the reaction mixture was stirred until the
starting material disappeared. The reaction mixture was
filtered and the filtrate was concentrated to provide the
crude product, which was further purified and character-
ized as the propargylated product, 4-(1,3-diphenylprop-2-
ynyl)phenol (2a).
Electrophilic attack on an aromatic carbon is a useful
method for the functionalization of aromatic compounds.
Reactions such as the Friedel–Crafts alkylation or acyla-
tion and the Baylis–Hillman reaction, which provide func-
tionalized aromatic compounds2 with special properties,
have been greatly studied as C–C bond forming reactions,
however, very little attention has been focussed on the
propargylation of aromatic compounds, which would af-
ford scaffolds that are key intermediates for the synthesis
of several natural products.3a–g Propargylation of aromatic
compounds3h,i is achieved by the Nicholas reaction using
a stoichiometric amount of octacarbonyldicobalt, and a
few reports use Brønsted acids;4 complexes involving
metals such as rhenium,5 ruthenium,6 gold,7,8 and
bismuth9 are also well precedented. Zhan et al. have re-
cently achieved propargylation of aromatic compounds
with propargyl acetates and nucleophilic substitution of
propargylic alcohols employing iron(III) chloride as a cat-
alyst.10 The high cost of the reagents, multistep reactions,
or harsh conditions limit many of these existing method-
ologies, thus an inexpensive reagent system, which could
catalyze the reaction more efficiently, is always desirable.
Encouraged by this result and to investigate further the ef-
ficiency of PMA–silica gel, phenol was propargylated
with 1,3-diphenylprop-2-yn-1-ol (1a) using different con-
centrations of PMA, and the results show that as the con-
centration of PMA–silica gel increased from 0.025 mol%
to 1 mol% the yield is enhanced and also the duration of
the reaction is decreased (Table 1). Furthermore, to check
the role of the catalyst, different acids such as 4-toluene-
sulfonic acid, phosphomolybdic acid, silica gel, silica gel
supported sodium bisulfate, and silica gel supported per-
chloric acid, heterogeneous catalysts such as Amberlyst
and Montmorillonite K-10 were also tested for propargy-
lations. It was found that PMA–silica gel and perchloric
acid were the best in terms of yields and reaction time,
while others including phosphomolybdic acid without sil-
ica gel took longer for complete conversion (Table 2).
To study the role of the solvent, reactions were performed
with 1,3-diphenylprop-2-yn-1-ol (1a) and cresol (Table 3)
in different solvents such as nitromethane, dichloro-
methane, 1,2-dichloroethane, polyethylene glycol (PEG),
and water and also under solvent-free conditions. We ob-
served no solvent influence except that in PEG, where no
reaction was observed, and in water where only 20% con-
version was observed even after five hours at room tem-
perature. Also, we found that the reaction proceeded much
faster without the solvent (50% progress in absence of sol-
vent against 10% in presence of solvent). However, the re-
action went to completion in about the same time both in
the presence and absence of solvent (Table 3). It is note-
worthy to mention that, after completion of the reaction,
the solid catalyst could be washed with diethyl ether and
reused up to three times with small variations in yield.16
Our efforts towards green chemistry11 has led to the devel-
opment of new synthetic methodologies. One of the key
principles involved in green chemistry is to minimize sto-
ichiometric amount of reagents to catalytic amounts and
allow the process to run with high efficiency. Many het-
eropoly acids fall under this category as they exhibit high
catalytic activity and good selectivity.12 Recently, to this
end, Montmorillonite K-10 was used as a mild acid13 for
the Nicholas reaction. We have shown that phosphomo-
lybdic acid supported on silica gel (PMA–silica gel)
works as an excellent solid reagent system that catalyzes
acetal deprotection and Ferrier rearrangement reactions.14
SYNTHESIS 2008, No. 12, pp 1853–1860
x
x.
x
x
.
2
0
0
8
Advanced online publication: 16.05.2008
DOI: 10.1055/s-2008-1067083; Art ID: T11707SS
© Georg Thieme Verlag Stuttgart · New York

1854
P. Srihari et al.
PAPER
Ar
OH
PMA-SiO2 (1 mol%)
R1
R1
+
Ar-H
R2
R2
r.t., 0.5–3.5 h
90–96%
1
2
R1 = H, OMe, F
R
2 = TMS, Ph, n-pentyl
Ar-H = phenol, anisole, indole, 2-naphthol, o-cresol
Scheme 1 Propargylation of aromatic compounds
Table 1 PMA–Silica Gel Catalyzed Propargylation of Phenol with 1,3-Diphenylprop-2-yn-1-ol (1a)a
Time
Conversionb (%) to 2a with varying concentration of PMA–silica gel (mol%)
0.025 mol% 0.05 mol% 0.10 mol% 0.15 mol% 0.20 mol% 0.25 mol% 0.30 mol% 0.5 mol% 1.0 mol% 5.0 mol%
20 min
30 min
45 min
60 min
90 min
5
10
15
20
30
15
30
20
40
35
55
40
62
55
85
100
–
65
85
100
–
80
90
–
90
100
–
90
100
–
40
50
80
83
80
90
90
92
–
–
–
100
100
100
100
–
–
–
–
–
a 1,3-Diphenylprop-2-yn-1-ol (1a), PhOH, MeCN, r.t.
b Monitored and measured by TLC analysis.
Table 2 Acid-Catalyzed Propargylation of Phenol with 1-(4-Meth-
oxyphenyl)-3-(trimethylsilyl)prop-2-yn-1-ol (1b)a
Table 3 PMA–Silica Gel Catalyzed Propargylation of Cresol with
1,3-Diphenylprop-2-yn-1-ol (1a) Using Various Solvents
Acida
Conversionb (%) to 2f with varying time
Entry Solvent
Catalyst
Time
(h)
Conversionb
(%) to 2c
45 min
2 h
3–5 h
no reaction
85
1
2
3
4
5
6
7
H2O
PMA–silica gel
(1 mol%)
1.0
1.0
1.0
1.0
1.0
1.0
1.0
>20
silica gel
no reaction
no reaction
PMA
65
100
88
70
–
MeCN
CH2Cl2
DCE
PMA–silica gel
(1 mol%)
>95
PMA–silica gel
HClO4
–
PMA–silica gel
(1 mol%)
>95
>90
87
70
85
75
75
–
PTSA
80
>90
>90
>90
>90
>90
PMA–silica gel
(1 mol%)
>95
NaHSO4–silica gel
HClO4–silica gel
Amberlyst
60
MeNO2
PEG 400
no solvent
PMA–silica gel
(1 mol%)
>95
80
70
PMA–silica gel
(1 mol%)
no reaction
>95
Montmorillonite
72
a 1-(4-Methoxyphenyl)-3-(trimethylsilyl)prop-2-yn-1-ol (1b) and
PhOH were treated with 1 mol% of acid in MeCN, r.t.
b Monitored and measured by TLC analysis.
PMA–silica gel
(1 mol%)
a 1,3-Diphenylprop-2-yn-1-ol (1a) and cresol were treated with 1
mol% of PMA–silica gel at r.t.
b Monitored and measured by TLC analysis.
After standardizing the conditions, the generality of the
reaction was studied further by examining the propargyla-
tion of various aromatic compounds with propargyl alco- present protocol (Table 4, entries 5, 9, 13). Even the aryl-
hols 1a–e (Table 4).17 Gratifyingly, phenols, anisole, and propargyl alcohol with a free terminal acetylene 1e gave
2-naphthol responded well to these conditions and substi- the corresponding product 2q in good yield (Table 4, en-
tution was always present at the electron-rich position of try 17), A propargylic alcohol without the aryl group 1f
the aromatic compounds (Table 4, entries 1–4, 6–8 10–12, did not react under the present conditions (Table 4, entry
14–16).18 Mechanistically,19 we believe that a carbon nu- 18). Attempts at the nucleophilic substitution reaction us-
cleophile adds on to the propargylic cation. However, no ing heteroatom-centered nucleophiles (such as O-, S-, and
attempts were made to study the exact mechanism. Simple N-centered nucleophiles) did not yield the required prod-
benzene and toluene did not give the expected products uct under the present protocol. However, this could be
whereas the heterocycle indole responded well under the achieved by heating the reaction mixture.20
Synthesis 2008, No. 12, 1853–1860 © Thieme Stuttgart · New York

PAPER
PMA–Silica Gel Catalyzed Propargylation of Aromatic Compound
1855
Table 4 PMA–Silica Gel Catalyzed Propargylation of Aromatic Compounds
Entry Propargyl alcohol
Aromatic
compound
Producta
Time
(h)
Yieldb
(%)
OH
OH
0.5
0.5
96
1
1a
1a
1a
phenol
anisole
o-cresol
2a
2b
2c
96c
Ph
Ph
Ph
Ph
Ph
Ph
OMe
OH
2
2.0
92
Ph
Ph
Ph
OH
OH
1.0
1.0
96
3
96c
Ph
Ph
Ph
OH
HO
Ph
4
1a
1a
2-naphthol
2d
2e
2.0
3.5
95
92
Ph
Ph
Ph
H
N
OH
5
1H-indole
Ph
Ph
Ph
Ph
OH
OH
6
1b
phenol
2f
0.45
96
91
SiMe3
MeO
SiMe3
MeO
OMe
OH
7
1b
1b
anisole
2g
2h
2.0
SiMe3
MeO
SiMe3
MeO
OH
2.0
2.0
94
HO
8
2-naphthol
94c
SiMe3
MeO
SiMe3
MeO
Synthesis 2008, No. 12, 1853–1860 © Thieme Stuttgart · New York

1856
P. Srihari et al.
PAPER
Table 4 PMA–Silica Gel Catalyzed Propargylation of Aromatic Compounds (continued)
Entry Propargyl alcohol
Aromatic
compound
Producta
Time
(h)
Yieldb
(%)
H
N
OH
9
1b
1c
1H-indole
2i
2j
3.5
90
SiMe3
MeO
SiMe3
MeO
OH
OH
3.0
3.0
96
10
phenol
96c
Ph
F
Ph
F
OH
Me
OH
1.5
1.5
95
11
1c
o-cresol
2k
95c
Ph
F
Ph
Ph
F
OH
HO
12
1c
1c
2-naphthol
2l
2.0
94
Ph
Ph
F
F
H
N
OH
3.5
3.5
91
13
1H-indole
2m
91c
F
Ph
F
OH
OH
0.45
0.45
95
14
1d
phenol
2n
95c
MeO
MeO
OH
OH
15
1d
1d
o-cresol
2o
2p
1.0
94
MeO
MeO
OH
2.0
2.0
93
HO
16
2-naphthol
93c
MeO
MeO
Synthesis 2008, No. 12, 1853–1860 © Thieme Stuttgart · New York

PAPER
PMA–Silica Gel Catalyzed Propargylation of Aromatic Compound
1857
Table 4 PMA–Silica Gel Catalyzed Propargylation of Aromatic Compounds (continued)
Entry Propargyl alcohol
Aromatic
compound
Producta
Time
(h)
Yieldb
(%)
OH
OH
17
1e
1f
phenol
2q
0.45
93
MeO
MeO
OH
18
phenol
no reaction
PMBO
a Products characterized by 1H NMR and 13C NMR spectroscopy and mass spectrometry.
b Isolated and optimized yields.
c Reactions were run under solvent-free conditions.
plete (TLC), the mixture was diluted with Et2O and filtered. The
combined organic filtrates were evaporated to dryness in vacuo to
yield the crude product, which was purified by column chromatog-
raphy (EtOAc–hexane). The silica gel supported PMA was separat-
ed and resubjected to this protocol with the same propargyl alcohol
for propargylation to produce the products with consistent yields.
In conclusion, the PMA–silica gel reagent system works
as a green catalyst for the propargylation of aromatic com-
pounds with arylpropargyl alcohols. The simple reaction
conditions involve an inexpensive catalyst and, also, the
reusability of the catalyst system makes this an useful and
attractive protocol over existing procedures. Further work
on the exploration of PMA–silica gel for substitution re-
actions with tertiary propargylic alcohols/acetates is cur-
rently underway and the results will be published in due
course.
4-(1,3-Diphenylprop-2-ynyl)phenol (2a)
Brownish yellow sticky liquid. Data are in accordance with the lit-
erature.5,9a
1H NMR (300 MHz, CDCl3): d = 4.98 (br s, 1 H, OH), 5.09 (s, 1 H),
6.71 (d, J = 8.3 Hz, 2 H), 7.15–7.32 (m, 9 H), 7.36 (d, J = 7.5 Hz, 2
H), 7.41–7.47 (m, 1 H).
Column chromatography was performed using silica gel (60–120
mesh). All solvents (MeCN, CH2Cl2, DCE, MeNO2, and PEG 400)
were of AR grade and commercially available and used without fur-
ther drying. IR spectra were recorded on a Perkin-Elmer Infrared
spectrophotometer as KBr wafers, neat, or a thin film (CHCl3). 1H
NMR and 13C NMR data were recorded on a Varian Gemini 200 or
Bruker Avance 300 instrument using TMS as an internal standard.
Mass spectra were recorded on a Micromass Quatro LC triple qua-
drupole mass spectrometer for ESI analysis. HRMS data were ob-
tained through use of ESI-QTOF high-resolution techniques on an
AB Systems QSTAR plus mass spectrometer.
1-(1,3-Diphenylprop-2-ynyl)-4-methoxybenzene (2b)
Yellow sticky liquid.
IR (KBr): 3447, 3058, 3028, 2927, 2852, 2381, 2186, 1600, 1508,
1448, 1252, 1175, 1031, 756, 695 cm–1.
1H NMR (300 MHz, CDCl3): d = 3.69 (s, 3 H), 5.04 (s, 1 H), 6.73
(d, J = 9.0 Hz, 2 H), 7.17–7.25 (m, 8 H), 7.27–7.32 (m, 2 H), 7.35–
7.41 (m, 2 H).
13C NMR (75 MHz, CDCl3): d = 43.0, 55.3, 84.9, 90.7, 114.1,
123.7, 127.6, 127.9, 128.0, 128.3, 128.7, 129.0, 131.9, 134.0, 142.2,
158.7.
Preparation of the PMA–Silica Gel Reagent
MS (ESI): m/z = 299 [M + H]+.
HRMS: m/z [M + H]+ calcd for C22H19O: 299.1436; found:
H3PMo12O40·2 H2O (1.0 g, 1 equiv by wt) was dissolved in MeOH
(5 mL) and to this was added slowly silica gel (9 g, 9 equiv by wt,
60–120 mesh). The mixture was stirred at r.t. for 30 min and then
the solvent was removed under vacuo to afford a dry yellowish
green powder that contained 10% w/w of PMA.
299.1432.
4-(1,3-Diphenylprop-2-ynyl)-2-methylphenol (2c)
Brownish yellow sticky liquid.
3,3-Diarylpropy-1-ynols 2; General Procedure Using a Solvent
To a soln of arylpropargyl alcohol 1 (1 mmol) and nucleophile (1
mmol) in MeCN (5 mL) was added PMA–silica gel (1 mol%). The
mixture was stirred at r.t. for the appropriate time. When the reac-
tion was complete (TLC), the mixture was filtered and washed with
CH2Cl2. The combined organic filtrates were evaporated to dryness
in vacuo. The crude product was purified by column chromatogra-
phy (EtOAc–hexane).
IR (KBr): 3422, 3026, 2923, 2856, 2396, 2210, 1951, 1879, 1705,
1599, 1490, 1448, 1263, 1112, 756, 694 cm–1.
1H NMR (300 MHz, CDCl3): d = 2.20 (s, 3 H), 4.53 (br s, 1 H, OH),
5.06 (s, 1 H), 6.63 (d, J = 7.5 Hz, 1 H), 7.03–7.11 (m, 2 H), 7.15–
7.30 (m, 6 H), 7.35–7.39 (m, 2 H), 7.42–7.45 (m, 2 H).
13C NMR (75 MHz, CDCl3): d = 15.8, 42.8, 84.6, 90.6, 114.9,
123.5, 124.0, 126.3, 126.7, 127.7, 127.8, 128.1, 128.5, 130.4, 131.6,
133.8, 142.1, 152.6.
3,3-Diarylpropy-1-ynols 2; General Procedure under Solvent-
Free Conditions
To a mixture of arylpropargyl alcohol 1 (1 mmol) and nucleophile
(1 mmol) was added PMA–silica gel (1 mol%). The mixture was
stirred at r.t. for the appropriate time. When the reaction was com-
MS (ESI): m/z = 299 [M+ + H].
HRMS: m/z [M + H]+ calcd for C22H19O: 299.1436; found:
299.1435.
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1858
P. Srihari et al.
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1-(1,3-Diphenylprop-2-ynyl)naphthalen-2-ol (2d)
Brownish yellow sticky liquid. Data are in accordance with the lit-
erature.5,9a
HRMS: m/z [M – H]+ calcd for C23H23O2Si: 359.1480; found:
359.1467.
3-[1-(4-Methoxyphenyl)-3-(trimethylsilyl)prop-2-ynyl]-1H-
indole (2i)
Yellow sticky liquid.
1H NMR (300 MHz, CDCl3): d = 6.21 (s, 1 H), 6.35 (br s, 1 H, OH),
7.10 (d, J = 9.0 Hz, 1 H), 7.15–7.35 (m, 7 H), 7.38–7.51 (m, 5 H),
7.68–7.79 (m, 2 H), 7.96 (d, J = 8.3 Hz, 1 H).
IR (KBr): 3415, 3056, 2958, 2836, 2369, 2169, 1610, 1508, 1458,
1250, 1176, 1031, 844, 744 cm–1.
3-(1,3-Diphenylprop-2-ynyl)-1H-indole (2e)
Pale yellow sticky liquid.
1H NMR (300 MHz, CDCl3): d = 0.11 (s, 9 H), 3.68 (s, 3 H), 5.07
(s, 1 H), 6.71 (d, J = 8.3 Hz, 2 H), 6.90–6.94 (m, 2 H), 7.03 (t,
J = 8.3 Hz, 1 H), 7.15–7.24 (m, 3 H), 7.37 (d, J = 7.5 Hz, 1 H), 7.77
(br s, 1 H, NH).
13C NMR (75 MHz, CDCl3): d = 0.08, 35.0, 55.1, 87.0, 107.4,
111.1, 113.7, 116.6, 119.2, 119.5, 121.9, 122.4, 125.8, 128.7, 133.2,
136.6, 158.2.
IR (KBr): 3745, 3417, 3055, 2923, 2853, 2392, 2210, 1596, 1488,
1451, 1416, 1339, 1216, 1091, 1024, 749, 692 cm–1.
1H NMR (200 MHz, CDCl3): d = 5.34 (s, 1 H), 6.90–7.13 (m, 3 H),
7.10–7.26 (m, 7 H), 7.33–7.50 (m, 5 H), 7.86 (br s, 1 H, NH).
13C NMR (75 MHz, CDCl3): d = 35.5, 83.3, 90.5, 111.2, 117.0,
119.6, 122.2, 122.5, 123.7, 126.1, 126.8, 127.8, 127.9, 128.1, 128.3,
128.4, 131.7, 136.7, 141.3.
MS (ESI): m/z = 333 [M]+.
MS (ESI): m/z = 308 [M+ + H].
HRMS: m/z [M – H]+ calcd for C21H22NOSi: 332.1476; found:
332.1470.
HRMS: m/z [M + H]+ calcd for C23H18N: 308.1470; found:
308.1458.
4-[1-(4-Fluorophenyl)-3-phenylprop-2-ynyl]phenol (2j)
Yellow sticky liquid.
4-[1-(4-Methoxyphenyl)-3-(trimethylsilyl)prop-2-ynyl]phenol
(2f)
IR (KBr): 3379, 2924, 2386, 2169, 1600, 1506, 1443, 1226, 1156,
832, 757, 691 cm–1.
Pale yellow sticky liquid.
IR (neat): 3415, 2957, 2927, 2855, 2376, 2169, 1608, 1508, 1459,
1248, 1174, 1034, 842, 761, 573 cm–1.
1H NMR (300 MHz, CDCl3): d = 0.12 (s, 9 H), 3.69 (s, 3 H), 4.66
(br s, 1 H, OH), 4.77 (s, 1 H), 6.62 (d, J = 8.3 Hz, 2 H), 6.71 (d,
J = 9.0 Hz, 2 H), 7.07 (d, J = 8.3 Hz, 2 H),7.12 (d, J = 8.3 Hz, 2 H).
13C NMR (75 MHz, CDCl3): d = 1.0, 42.4, 55.2, 88.6, 107.2, 113.9,
115.3, 128.7, 128.9, 134.0, 134.2, 154.3, 158.4.
1H NMR (300 MHz, CDCl3): d = 4.82 (br s, 1 H, OH), 5.08 (s, 1 H),
6.73 (d, J = 9.0 Hz, 2 H), 6.96 (t, J = 9.0 Hz, 2 H), 7.20–7.26 (m, 5
H), 7.31–7.35 (m, 2 H), 7.40–7.44 (m, 2 H).
13C NMR (75 MHz, CDCl3): d = 42.1, 84.9, 90.2, 115.2, 115.5,
123.3, 128.1, 128.3, 129.1, 129.3, 129.4, 131.6, 133.9, 137.3, 137.7,
138.1, 154.5, 163.5, 167.2.
MS (ESI): m/z = 301 [M – H]+.
MS (ESI): m/z = 311 [M+ + H].
HRMS: m/z [M – H]+ calcd for C21H14FO: 301.1032; found:
301.1028.
HRMS: m/z [M + H]+ calcd for C19H23O2Si: 311.1475; found:
311.1467.
4-[1-(4-Fluorophenyl)-3-phenylprop-2-ynyl]-2-methylphenol
(2k)
[3,3-Bis(4-methoxyphenyl)prop-1-ynyl]trimethylsilane (2g)
Light brownish yellow sticky liquid.
Pale yellow sticky liquid.
IR (KBr): 3418, 2924, 2391, 2016, 1599, 1505, 1265, 1224, 1113,
1017, 840, 756, 690 cm–1.
1H NMR (300 MHz, CDCl3): d = 2.14 (s, 3 H), 4.80 (br s, 1 H, OH),
4.97 (s, 1 H), 6.59 (d, J = 7.5 Hz, 1 H), 6.87–7.00 (m, 4 H), 7.17–
7.22 (m, 3 H), 7.25–7.30 (m, 2 H), 7.34–7.38 (m, 2 H).
13C NMR (75 MHz, CDCl3): d = 16.0, 42.4, 64.6, 85.0, 90.5, 115.2,
115.3, 115.6, 123.6, 124.2, 126.6, 128.2, 128.4, 129.4, 129.5, 130.6,
131.8, 133.9, 138.1, 153.0, 160.3, 163.5.
IR (KBr): 3444, 2959, 2382, 2171, 1614, 1511, 1460, 1249, 1173,
1030, 845, 761 cm–1.
1H NMR (300 MHz, CDCl3): d = 0.18 (s, 9 H), 3.75 (s, 6 H), 4.85
(s, 1 H), 6.77 (d, J = 8.9 Hz, 4 H), 7.19 (d, J = 7.5 Hz, 4 H).
13C NMR (75 MHz, CDCl3): d = 0.1, 37.6, 55.1, 92.42, 104.0,
113.1, 113.6, 128.8, 129.3, 131.2, 134.2, 159.1, 159.7.
MS (ESI): m/z = 325 [M+ + H].
HRMS: m/z [M + Na]+ calcd for C20H24NaO2Si: 347.1443; found:
MS (ESI): m/z = 317 [M + H]+.
HRMS: m/z [M + H]+ calcd for C22H18FO: 317.1342; found:
347.1441.
317.1338.
1-[1-(4-Methoxyphenyl)-3-(trimethylsilyl)prop-2-ynyl]naph-
thalen-2-ol (2h)
Yellow sticky liquid.
1-[1-(4-Fluorophenyl)-3-phenylprop-2-ynyl]naphthalen-2-ol
(2l)
Brownish yellow sticky liquid.
IR (neat): 3414, 2958, 2835, 2381, 2166, 1625, 1508, 1250, 1176,
1027, 843, 751 cm–1.
1H NMR (200 MHz, CDCl3): d = 0.15 (s, 9 H), 3.63 (s, 3 H), 5.79
(s, 1 H), 6.66 (d, J = 9.5 Hz, 2 H), 6.79 (s, 1 H), 7.01–7.34 (m, 5 H),
7.55–7.67 (m, 2 H), 7.75 (d, J = 8.1 Hz, 1 H).
13C NMR (75 MHz, CDCl3): d = 0.07, 33.6, 55.2, 90.8, 106.0,
114.3, 117.5, 119.4, 123.1, 123.5, 126.4, 128.3, 128.8, 129.4, 129.7,
131.1, 132.3, 152.6, 158.5.
IR (KBr): 3422, 3059, 2924, 2853, 2163, 1870, 1626, 1439, 1224,
1157, 814, 751 cm–1.
1H NMR (300 MHz, CDCl3): d = 6.18 (s, 1 H), 6.33 (br s, 1 H, OH),
6.94 (t, J = 8.6 Hz, 2 H), 7.12 (d, J = 8.8 Hz, 1 H), 7.23–7.32 (m, 4
H), 7.36–7.47 (m, 5 H), 7.70–7.78 (m, 2 H), 7.93 (d, J = 8.4 Hz, 1
H).
13C NMR (75 MHz, CDCl3): d = 33.2, 86.2, 88.5, 115.5, 115.7,
117.7, 119.2, 122.6, 123.2, 123.6, 127.0, 128.5, 128.7, 128.9, 129.0,
129.5, 129.9, 131.1, 131.9, 132.4, 135.5, 135.6, 152.3, 160.4, 163.6.
MS (ESI): m/z = 359 [M – H]+.
Synthesis 2008, No. 12, 1853–1860 © Thieme Stuttgart · New York

PAPER
PMA–Silica Gel Catalyzed Propargylation of Aromatic Compound
1859
MS (ESI): m/z = 353 [M + H]+.
H), 7.25–7.33 (m, 1 H), 7.55–7.66 (m, 2 H), 7.78 (d, J = 8.5 Hz, 1
H).
HRMS: m/z [M + H]+ calcd for C25H18OF: 353.1341; found:
353.1334.
13C NMR (75 MHz, CDCl3): d = 12.6, 17.7, 21.0, 27.3, 30.0, 31.6,
54.0, 78.3, 86.0, 108.4, 112.9, 116.8, 118.3, 122.0, 122.3, 125.3,
125.6, 126.6, 127.1, 127.6, 128.4, 131.2, 151.5, 157.3.
3-[1-(4-Fluorophenyl)-3-phenylprop-2-ynyl]-1H-indole (2m)
Pale yellow sticky liquid.
MS (ESI): m/z = 381 [M + Na]+.
IR (KBr): 3751, 3416, 3057, 2962, 2379, 2176, 1890, 1601, 1505,
1453, 1341, 1261, 1222, 1094, 1018, 801, 748, 691 cm–1.
1H NMR (200 MHz, CDCl3): d = 5.33 (s, 1 H), 6.88–7.00 (m, 2 H),
7.04–7.11 (m, 2 H), 7.17–7.26 (m, 5 H), 7.34–7.44 (m, 5 H), 7.88
(br s, 1 H, NH).
HRMS: m/z [M + Na]+ calcd for C25H26NaO2: 381.1843; found:
381.1830.
4-[1-(4-Methoxyphenyl)prop-2-ynyl]phenol (2q)
Light yellow liquid.
13C NMR (75 MHz, CDCl3): d = 34.9, 83.7, 90.4, 111.5, 115.3,
115.6, 116.8, 119.7, 119.8, 122.5, 122.8, 123.7, 126.1, 128.1, 128.4,
129.5, 129.6, 131.8, 136.9, 137.1, 137.2, 160.3, 163.5.
MS (ESI): m/z = 326 [M + H]+.
HRMS: m/z [M + H]+ calcd for C23H17FN: 326.1345; found:
1H NMR (200 MHz, CDCl3): d = 2.46 (d, J = 2.7 Hz, 1 H), 3.77 (s,
3 H), 4.77 (d, J = 2.4 Hz, 1 H), 5.41 (br s, 1 H, OH), 6.75 (d, J = 8.7
Hz, 2 H), 6.83 (d, J = 8.7 Hz, 2 H), 7.21 (d, J = 9.0 Hz, 2 H), 7.25
(d, J = 9.0 Hz, 2 H).
13C NMR (75 MHz, CDCl3): d = 41.4, 55.5, 72.7, 85.4, 114.2,
115.6, 128.9, 129.1, 133.8, 154.7, 158.7.
326.1342.
MS (ESI): m/z = 239 [M + H]+.
4-[1-(4-Methoxyphenyl)oct-2-ynyl]phenol (2n)
Brownish yellow sticky liquid.
HRMS: m/z [M + K]+ calcd for C16H14KO2: 277.0630; found:
277.0628.
IR (KBr): 3750, 3447, 2928, 2857, 2382, 2192, 1612, 1510, 1252,
1028, 761 cm–1.
1H NMR (300 MHz, CDCl3): d = 0.85 (t, J = 6.8 Hz, 3 H), 1.25–
1.35 (m, 4 H), 1.44–1.51 (m, 2 H), 2.19 (t, J = 6.8 Hz, 2 H), 3.73 (s,
3 H), 5.27 (s, 1 H), 6.73–6.80 (m, 4 H), 7.13–7.19 (m, 2 H), 7.35 (d,
J = 8.3 Hz, 2 H).
Acknowledgment
Two of us (J.S.S.R.) and (S.S.M.) thank CSIR, New Delhi for finan-
cial assistance.
13C NMR (75 MHz, CDCl3): d = 14.0, 18.8, 22.6, 28.7, 31.1, 41.6,
55.3, 81.2, 84.8, 113.8, 115.3, 128.7, 128.9, 134.8, 135.2, 154.4,
158.1.
References
(1) IICT Communication No. 061220
MS (ESI): m/z = 307 [M – H]+.
HRMS: m/z [M – H]+ calcd for C21H23O2: 307.1699; found:
(2) (a) Basavaiah, D.; Jaganmohan Rao, A.; Satyanarayana, T.
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4-[1-(4-Methoxyphenyl)oct-2-ynyl]-2-methylphenol (2o)
Yellow sticky liquid.
IR (KBr): 3422, 2957, 2929, 2859, 2393, 2056, 1882, 1607, 1507,
1460, 1252, 1176, 1110, 1033, 811, 610 cm–1.
1H NMR (200 MHz, CDCl3): d = 0.84 (t, J = 6.2 Hz, 3 H), 1.18–
1.52 (m, 6 H), 2.09–2.22 (m, 5 H), 3.69 (s, 3 H), 4.50 (br s, 1 H,
OH), 4.69 (s, 1 H), 6.53 (d, J = 7.8 Hz, 1 H), 6.69 (d, J = 8.6 Hz, 2
H), 6.91 (d, J = 11.7 Hz, 2 H), 7.12 (d, J = 8.6 Hz, 2 H).
13C NMR (75 MHz, CDCl3): d = 14.2, 16.0, 19.1, 22.4, 28.9, 31.3,
41.8, 55.4, 81.4, 84.9, 114.0, 115.0, 123.9, 126.4, 128.8, 130.5,
135.2, 135.3, 152.7, 158.4.
MS (ESI): m/z = 323 [M + H]+.
HRMS: m/z [M + Na]+ calcd for C22H26NaO2: 345.1824; found:
345.1830.
1–[1-(4-Methoxyphenyl)oct-2-ynyl]naphthalen-2-ol (2p)
Brownish yellow sticky liquid.
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1248, 1214, 1174, 1031, 961, 810, 748 cm–1.
1H NMR (300 MHz, CDCl3): d = 0.81 (t, J = 6.9 Hz, 3 H), 1.17–
1.45 (m, 4 H), 1.44–1.58 (m, 2 H), 2.21 (t, J = 7.2 Hz, 2 H), 3.62 (s,
3 H), 5.77 (s, 1 H), 6.66 (d, J = 8.3 Hz, 2 H), 6.81 (br s, 1 H, OH),
6.93 (d, J = 7.0 Hz, 1 H), 7.04 (d, J = 8.7 Hz, 1 H), 7.12–7.21 (m, 2
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1860
P. Srihari et al.
PAPER
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(15) Propargyl alcohols were prepared according to the earlier
known procedures from monosubstituted acetylenes and
corresponding aldehydes using EtMgBr.
(16) The compound 1a (Table 4, entry 1) was studied for three
runs (90%, 88%, and 85% yields respectively).
(17) All the reactions were run with 1 mol% PMA–silica gel at r.t.
in MeCN unless specified.
(18) Substitution was present at the para position (least hindered
site with high electron density) and was confirmed by 1H
NMR spectroscopy. No other products were formed in this
reaction.
(19) For the mechanism of transition-metal-stabilized propargyl
cations, see: Müller, J. J. T. Eur. J. Org. Chem. 2001, 2021.
(20) For more details see: Srihari, P.; Reddy, J. S. S.; Bhunia, D.
C.; Mandal, S. S.; Yadav, J. S. Synth. Commun. 2008, 38,
1448.
Synthesis 2008, No. 12, 1853–1860 © Thieme Stuttgart · New York