Palladium chloride-cryptand-22 complex: An efficient catalyst for the copper-, phosphorus-, and solvent-free synthesis of ynones

Article abstract of DOI:10.1007/s00706-013-0996-5

The palladium chloride-cryptand-22 complex was found to be an efficient catalyst for the copper-, phosphorus-, and solvent-free coupling reaction of terminal alkynes with different acyl chlorides in the presence of triethylamine as base, at room temperatu

Full text of DOI:10.1007/s00706-013-0996-5

Monatsh Chem (2013) 144:1363–1367
DOI 10.1007/s00706-013-0996-5
ORIGINAL PAPER
Palladium chloride–cryptand-22 complex: an efficient catalyst
for the copper-, phosphorus-, and solvent-free synthesis of ynones
Mozhgan Navidi Barahman Movassagh
•
Received: 27 February 2013 / Accepted: 10 April 2013 / Published online: 14 May 2013
Ó Springer-Verlag Wien 2013
Abstract The palladium chloride–cryptand-22 complex
was found to be an efficient catalyst for the copper-,
phosphorus-, and solvent-free coupling reaction of terminal
alkynes with different acyl chlorides in the presence of
triethylamine as base, at room temperature and under aer-
obic conditions. The simple, mild, and green procedure,
short reaction times, and moderate to excellent yields make
this method well-suited for ynone synthesis.
alkynes with nitriles [10], and finally the most efficient
method to be mentioned is (e) the reaction between metal
acetylides and carboxylic acid derivatives such as acid
chlorides, acid anhydrides, esters, and acyl cyanides
[11–14]. Strong bases such as n-BuLi [15, 16] and elements
such as silver [17], zinc [18], tin [13], indium [19], gallium
[20], silicon [21], lithium [22], boron [23], palladium
[24–30], and copper [31–34] could be used in these reac-
tions. However, the above synthetic protocols suffer from
serious disadvantages such as long reaction times [34],
high temperatures [32, 33], use of air and moisture sensi-
tive catalysts such as phosphorus containing catalysts
Keywords Ynones Á Terminal alkynes Á
PdCl –C22 complex Á Acyl chlorides Á
2
Solvent-free reaction
[
24–30], use of copper catalysts which are very much prone
to form diyne side products, use of hazardous organic
solvents [35], use of toxic carbon monoxide gas [30], and
need of special instruments [29]. Taking these constraints
into account, the development of new, mild, simple, and
efficient copper- and phosphorus-free synthetic procedures
would have significant value [36–38].
Introduction
Ynones or a,b-acetylenic ketones are useful synthetic
intermediates for the preparation of many biologically
active compounds and heterocyclic derivatives [1–3].
Different methodologies for the preparation of a,b-acety-
lenic ketones have been reported which include:
As part of our studies to find robust and easily prepared
system to catalyze C–C bond forming reactions [39], we
found that a Pd(II) catalyst system based on a commer-
cially available diazacrown ether, 1,7,10,16-tetraoxa-4,13-
(
a) oxidation of propargylic alcohols [4] which are usually
obtained by nucleophilic addition of acetylides to alde-
hydes, (b) cross-coupling reaction of terminal alkynes with
organic halides in the presence of carbon monoxide gas [5,
Ò
diazacyclooctadecane (Kryptofix 22 or cryptand-22) is
very active homogeneous catalyst under aerobic condi-
tions. This catalyst was prepared in our laboratory by an
easier method than previously reported procedure [40].
The remarkable chelating effect of this N- and O-con-
taining ligand and its flexibility assists in stabilizing the
reactive palladium intermediates [41] suppresses the Pd
black formation even at high temperature under air. The IR
6
], (c) oxidation of alkynes [7–9], (d) reaction of terminal
Electronic supplementary material The online version of this
article (doi:10.1007/s00706-013-0996-5) contains supplementary
material, which is available to authorized users.
spectrum of the complex displays m
stretch at
N–H
M. Navidi Á B. Movassagh (&)
-1
,224 cm which is at a lower frequency than that of the
3
Department of Chemistry, K. N. Toosi University
of Technology, P. O. Box 16315-1618, Tehran, Iran
e-mail: bmovass1178@yahoo.com
-
1
free ligand (3,327 cm ) indicating coordination of the
cryptand nitrogens to Pd(II) ion.
123

1
364
M. Navidi, B. Movassagh
Results and Discussion
To examine the general scope of this coupling reac-
tion, a variety of terminal alkynes (aliphatic and
aromatic) with various acid chlorides (aliphatic, aro-
matic, and heteroaromatic) were used (Scheme 1;
Table 2). The reaction tolerates a wide range of func-
tional groups giving isolated purified products in high
yields. As shown in Table 2, aromatic terminal alkynes
proceeded at relatively higher rates compared with that
of the aliphatic ones. Both aryl and alkyl acid chlorides
coupled with alkynes in a solvent-free condition in air
and at ambient temperature. The reaction was almost
equally facile with both electron-donating and electron-
withdrawing substituents on the aroyl chlorides. More-
over, no significant steric effect was observed owing to
the presence of the methyl group at the ortho position of
2-methylbenzoyl chloride. Heteroaryl acid chlorides such
as 2-thiophenecarbonyl chloride and 2-furancarbonyl
chloride also reacted with terminal alkynes to give the
products in high yields.
Chen and Li [33] reported the synthesis of ynones cata-
lyzed by PdCl (PPh ) /CuI with a catalytic amount of
2
3 2
sodium lauryl sulfate as the surfactant and K CO as the
2
3
base in water. However, their methodology involved the
use of 5 mol% CuI and the reactions were carried out at
6
5 °C for 4 h. One year later, Cox et al. [26] reported the
room temperature palladium catalyzed coupling of acyl
chlorides with terminal alkynes. Their protocol also
involved the use of CuI and PdCl (PPh ) in THF. Srini-
2
3 2
vasan et al. [27] reported a copper-, ligand-, and solvent-
free synthesis of ynones by coupling of acid chlorides with
terminal alkynes catalyzed by Pd(OAc) at room temper-
2
ature, but the reactions were carried out under argon
atmosphere. Chen et al. [25] reported the synthesis of
ynones catalyzed by a nanosized MCM-41 anchored pal-
ladium bipyridyl complex; however, their procedure
involved the use of CuI and PPh and performed at 50 °C.
3
Najera et al. [35] reported a similar reaction catalyzed by
an oxime derived palladacycle under copper- and phos-
phane-free conditions at high temperature in toluene. In
their study, they also reported the coupling of acid chlo-
In summary, we have successfully demonstrated a sol-
vent-, copper-, and phosphorus-free cross-coupling
reaction of terminal alkynes with various acyl halides
catalyzed by PdCl –C22 complex. The simple, mild, and
2
rides with terminal alkynes employing Pd(OAc) as the
2
green procedure, short reaction times, and moderate to
excellent yields make this method well-suited for ynone
synthesis.
catalyst, but the yields of the products were moderate.
A comparative study of the reaction conditions and results
for the palladium catalyzed cross-coupling of benzoyl
chloride with phenyl acetylene using other methods and that
reported in this work is given in Table 1 which clearly
demonstrates the advantages of the present methodology.
We describe here a new and efficient methodology to
prepare ynones using this homogeneous thermally and air-
Experimental
Chemicals were purchased from Merck chemical company.
1
Yields refer to the isolated products. H (300 MHz) and
1
3
stable palladium chloride–cryptand-22 (PdCl –C22) com-
2
C (75 MHz) NMR spectra were recorded using a Bruker
plex. In our initial investigation, the catalytic activities of
AQS-300 Avance spectrometer. IR spectra were obtained
using an ABB FTLA 2000 instrument.
PdCl –C22 complex were studied using phenyl acetylene
2
and benzoyl chloride as substrates under various conditions
(
base, solvent, and Pd concentration). It was concluded that
Typical experimental procedure for preparation
of the catalyst
Et N as base at room temperature in the presence of
3
0
.9 mol% of the catalyst under solvent-free conditions is
the optimized condition for the coupling reaction, which
after 1 h gave the product in 95 % yield.
Palladium chloride (67 mg, 0.382 mmol), was added into a
3
solution of 100 mg cryptand-22 (0.382 mmol) in 15 cm
Table 1 Comparison of the reaction conditions and results for the palladium-catalyzed coupling of benzoyl chloride with phenyl acetylene
a
Yield /%
Entry
Catalyst
Condition
Time
Reference
1
2
3
4
5
PdCl
PdCl
2
(PPh
3
)
)
2
/CuI
/CuI
H
2
O/65 °C
4 h
98
96
93
93
70
75
95
[33]
[26]
[27]
[25]
[35]
2
(PPh
3
2
THF/r.t.
10 min
10 min
36 h
1 h
Pd(OAc)
NS-MCM-41-Pd/CuI
Pd(OAc)
Palladacycle
PdCl –C22
2
Neat/r.t./Ar
NEt
3
/50 °C/N
2
2
PhCH
3
/110 °C
/110 °C
PhCH
3
1 h
6
2
Neat/r.t.
1 h
This work
a
Isolated yields
1
23

Palladium chloride–cryptand-22 complex
1365
Scheme 1
CH CN while stirring. The mixture was refluxed until the
3
complete dissolution of the palladium salt. Then, the sol-
vent was evaporated to obtain a yellow precipitate which
was recrystallized from dichloromethane-diethyl ether and
O
O
Et N, neat, r.t.
R2
3
+
H
R2
R1
PdCl2-C22 cat.
Cl
R1
H
finally dried in air to give the complex PdCl –C22 in
2
N
O
O
O
quantitative yield. M.p.: 199–200 °C (Ref. [40]
196–198 °C).
Cl Pd Cl
O
N
H
General procedure for ynone synthesis
PdCl -C22 Cat.
2
A mixture of acid chloride (1.0 mmol), terminal alkyne
(
1.0 mmol), Et N (1.2 mmol), and 4 mg PdCl –C22
3
2
Table 2 C–C Coupling reaction of acyl chlorides and terminal alkynes
1
2
a
Yield /%
Entry
1
R
R
Product 3
Time/h
1
Reference
[35]
Ph
Ph
Ph
Ph
95
93
90
O
3
a
2
2-Me–C
H
6 4
0.5
[27]
O
CH3
3b
3
2-Thienyl
1
[27]
O
O
S
3c
4
2-Furanyl
Ph
1
93
[27]
O
3d
5
6
4-Cl–C H
4
Ph
1
80
[27]
O
Cl
3e
6
4-MeO–C
6
H
4
Ph
0.75
83
[23]
O
MeO
3f
123

1
366
M. Navidi, B. Movassagh
Table 2 continued
1
2
a
Yield /%
Entry
7
R
R
Product 3
Time/h
1
Reference
[27]
4-NO
2
–C
6
H
4
Ph
Ph
Ph
85
85
89
O
O N
2
3
g
8
Cyclohexyl
0.66
[29]
O
3
h
9
4-CN–C
6
H
4
0.17
[29]
O
NC
3i
1
1
0
1
4-MeO–C
6
H
4
n-C
4
H
9
1
1
52
45
[24]
[18]
O
MeO
3j
2-Me–C
6
H
4
n-C
4
H
9
O
CH3
O
3
k
1
2
2-Thienyl
4-MeO–C
n-C
4
H
9
2
30
[18]
S
3
l
1
1
a
3
4
6
H
4
n-C
6
H
13
1.5
2.5
54
30
[42]
[25]
O
MeO
3
m
Cyclohexyl
n-C
6
H
13
O
3
n
Isolated yields
3
layer was washed with water (2 9 5 cm ), dried over
(
0.9 mol%) was stirred at room temperature (25 °C) under
aerial and solvent-free conditions. The progress of the
anhydrous MgSO , filtered, and concentrated in vacuo. The
4
3
reaction was monitored by TLC. After completion, 10 cm
crude product was further purified by preparative TLC
chloroform was added to the reaction mixture. The organic
(silica gel) using n-hexane/EtOAc (9:1) to afford the
1
23

Palladium chloride–cryptand-22 complex
1367
desired product. All compounds were characterized by IR,
1
20. Han Y, Fang L, Tao WT, Huang YZ (1995) Tetrahedron Lett
36:1287
13
H, and C NMR spectroscopy.
2
2
1. Gallagher WP, Maleczka RE (2003) J Org Chem 68:6775
2. Stefani HA, Cella R, Doerr FA, De Pereira CMP, Gomes FP, Zeni
G (2005) Tetrahedron Lett 46:2001
Acknowledgments The authors gratefully acknowledge the K.
N. Toosi University of Technology Research Council and Iranian
National Science Foundation (INSF, Grant No. 90006262) for
financial support.
2
2
2
2
2
2
2
3
3. Nishihara Y, Saito D, Inoue E, Okada Y, Miyazaki M, Inoue Y,
Takagi K (2010) Tetrahedron Lett 51:306
4. Bakherad M, Amin AH, Keivanloo A, Bahramian B, Raessi M
(
2010) Chin Chem Lett 21:656
5. Chen JY, Lin TC, Chen SC, Chen AJ, Mou CY, Tsai FY (2009)
Tetrahedron 65:10134
6. Cox RJ, Ritson DJ, Dane TA, Berge J, Charmant JPH, Kantacha
A (2005) Chem Commun 1037
7. Palimkar SS, Kumar PH, Jogdand NR, Daniel T, Lahoti RJ,
Srinivasan KV (2006) Tetrahedron Lett 47:5527
8. Wang JX, Wei B, Huang D, Hu Y, Bai L (2001) Synth Commun
References
1
. Adlington RM, Baldwin JE, Pritchard GJ, Spencer KC (2000)
Tetrahedron Lett 41:575
2
3
. Bagley MC, Hughes DD, Taylor PH (2003) Synlett 259
. Zhou J, Zhang GL, Zou JP, Zhang W (2011) Eur J Org Chem
3
1:3337
3
. Normant JF (1972) Synthesis 63
. Jianming L, Xingao P, Wei S, Yongwei Z, Chungu X (2008) Org
Lett 10:3933
412
9. Baxendale IR, Schou SC, Sedelmeier J, Ley SV (2010) Chem Eur
J 16:89
0. Fusano A, Fukuyama T, Nishitani S, Inouye T, Ryu I (2010) Org
Lett 12:2410
4
5
6
7
8
9
. Perrone S, Bona F, Troisi L (2011) Tetrahedron 67:73864
. McLaughlin EC, Doyle MP (2008) J Org Chem 73:4317
. Ajjou AN, Ferguson G (2006) Tetrahedron Lett 47:3719
. Ryu JY, Heo S, Park P, Nam W, Kim J (2004) Inorg Chem
Commun 7:534
3
3
3
3
3
3
1. Davies KA, Abel RC, Wulff JE (2009) J Org Chem 74:3997
2. Oh CH, Reddy VR (2004) Tetrahedron Lett 45:8545
3. Chen L, Li CJ (2004) Org Lett 6:3151
4. Chowdhury C, Kundu NG (1996) Tetrahedron Lett 37:7323
5. Alonso DA, Najera C, Pacheco MC (2004) J Org Chem 69:1615
6. Santra S, Dhara K, Ranjan P, Bera P, Dash J, Mandal SK (2011)
Green Chem 13:3238
1
1
1
0. Shen Q, Huang W, Wang J, Zhou X (2008) Organometallics
7:301
1. Brown HC, Racherla US, Singh SM (1984) Tetrahedron Lett
5:2411
2. Yamaguchi M, Shibato K, Fujiwara S, Hirao I (1986) Synthesis
21
2
3
3
3
4
4
4
7. Santra S, Ranjan P, Bera P, Ghosh P, Mandal SK (2012) RSC
Adv 2:7523
8. Likhar PR, Subhas MS, Roy M, Roy S, Kantam ML (2008) Helv
Chim Acta 91:259
9. Navidi M, Movassagh B, Rayati S (2013) Appli Catal A Gen
2
4
1
1
1
1
1
1
3. Himbert G (1979) Angew Chem Int Ed 18:405
4. Woltermann CJ, Shechter H (2005) Helv Chim Acta 88:354
5. Yim SJ, Kim MH, An DK (2010) Bull Korean Chem Soc 3:286
6. Humptman H, Mader M (1978) Synthesis 307
7. Davis RB, Scheiber DH (1956) J Am Chem Soc 78:1675
8. Keivanloo A, Bakherad M, Bahramian B, Rahmani M, Taheri
SAN (2011) Synthesis 325
4
52:24
0. Hsu MH, Hsu CM, Wang JC, Sun CH (2008) Tetrahedron
4:4268
6
1. Streieter ER, Blakmond DG, Buchwald SL (2003) J Am Chem
Soc 125:13978
2. Liang B, Huang M, You Z, Xiong Z, Lu K, Fathi R, Chen J, Yang
Z (2005) J Org Chem 70:6097
1
9. Perez I, Sestelo JP, Sarandeses LA (2001) J Am Chem Soc
1
23:4155
123