Synthesis of new boron complexes: Application to transfer hydrogenation of acetophenone derivatives

Article abstract of DOI:10.1002/aoc.1779

Two new boron complexes were synthesized from N-[3-(methylmercapto)aniline] -3,5-di-tert-butylsalicylaldimine (LH) with boron reagent BPh₃ or BF₃.Et₂O. These boron complexes are stable and easily soluble in protic solvents such as ethanol (C₂H₅OH) but hardly soluble in nonprotic solvents such as chloroform (CHCl₃), dichloromethane (CH₂Cl₂) and tetrahydrofuran (THF). All new boron complexes have been fully characterized by both analytical and spectroscopic methods. The catalytic activities of complexes [LBPh₂], 2, and [LBF₂], 3, in the transfer hydrogenation of acetophenone derivatives were tested. Stable boron complexes were found to be efficient catalysts in the transfer hydrogenation of aromatic ketones in good conversions up to 99% in the presence of iso-PrOH/KOH.

Full text of DOI:10.1002/aoc.1779

Full Paper
Received: 26 November 2010
Revised: 6 January 2011
Accepted: 6 January 2011
Published online in Wiley Online Library: 4 April 2011
(wileyonlinelibrary.com) DOI 10.1002/aoc.1779
Synthesis of new boron complexes: application
to transfer hydrogenation of acetophenone
derivatives
Ahmet Kilica∗, Cezmi Kayanb, Murat Aydemirb, Feyyaz Durapb,
Mustafa Durguna, Akın Baysalb, Esref Tasc and Bahattin Gu¨mgu¨mb
Two new boron complexes were synthesized from N-[3-(methylmercapto)aniline]-3,5-di-tert-butylsalicylaldimine (LH) with
boron reagent BPh3 or BF3.Et2O. These boron complexes are stable and easily soluble in protic solvents such as ethanol
(C2H5OH) but hardly soluble in nonprotic solvents such as chloroform (CHCl3), dichloromethane (CH2Cl2) and tetrahydrofuran
(THF). All new boron complexes have been fully characterized by both analytical and spectroscopic methods. The catalytic
activities of complexes [LBPh2], 2, and [LBF2], 3, in the transfer hydrogenation of acetophenone derivatives were tested. Stable
boron complexes were found to be efficient catalysts in the transfer hydrogenation of aromatic ketones in good conversions up
c
to 99% in the presence of iso-PrOH/KOH. Copyright ꢀ 2011 John Wiley & Sons, Ltd.
Keywords: boron complexes; transfer hydrogenation; BPh3; BF3.Et2O; synthesis
Introduction
havefoundthatbothstericandelectronicfactorshaveasignificant
impact on the catalytic properties of this class of molecules.
Boron is essential for healthy plants. Its biochemical role is not
fully understood even 60 years after its recognition as an essential
element, although it is known to be involved in nucleic acid
synthesis, possibly linked to adequate provision of pyrimidine
nucleotides. Boron also plays a part in carbohydrate metabolism,
hormone action and membrane formation.[1] Its complexes
with conjugated light-emitting π-systems have recently received
considerable attention due to their potential use in organic light-
emitting devices (OLEDs)[2,3] as well as fluorescent probes for
proton or heavy metal ion detection.[4] There are three main types
of fluorine–boron complexes, classified as N,N bidentate, N,O
bidentate and O,O bidentate compounds (Scheme 1).
For the former two kinds of fluorine-boron complexes, BODIPY
(boradipyrromethane)and1,3,2-dioxaborinearetheircorrespond-
ing representatives.[5] Four-coordinate organoboron compounds
have been extensively investigated in the past decade as emissive
materials for use in OLEDs, because of their high thermal and
chemical stability.[6,7] In contrast to three-coordinate boron com-
pounds,whichcanfunctionasaLewisacidoranelectron-transport
material in optoelectronic devices through the empty p orbital of
the boron center,[8] four-coordinate organoboron compounds
can also function as electron-transport materials by means of the
boron-stabilized π∗ orbital of the conjugated chelate ligands.[7,8]
It is known that boron is strongly electrophilic by virtue of its
tendency to fill the vacant orbital and complete the octet, so in
contrast to organometallic compounds, organoboron compounds
are in general more stable owing to the increased covalency of
B ← O and B ← N bonds. Thus, boron complexes may pro-
vide extra stability to counteract the instability of C N bonds in
salicylaldimines as catalyts compounds.
Experimental
All reagents and solvents were of reagent-grade quality and
obtained from commercial suppliers (Aldrich or Merck). IR spectra
were recorded on a Perkin Elmer Spectrum 100 FT-IR spectrometer
as KBr pellets. 1H (400.1 MHz) and13C NMR (100.6 MHz) spectra
were recorded on a Bruker AV 400 spectrometer, with δ referenced
to external tetramethylsilane (TMS). Elemental analysis was carried
out on a Fisons EA 1108 CHNS-O instrument. Electronic spectral
studies were conducted on a Perkin-Elmer model Lambda 25
UV–vis spectrophotometer in the wavelength range from 200 to
1100 nm. Melting points were measured in open capillary tubes
with an Electrothermal 9100 melting point apparatus and are
uncorrected.
GC Analyses
GC analyses were performed on a HP 6890N gas chromatograph
equippedwithacapillarycolumn(5%biphenyl,95%dimethylsilox-
ane; 30 m × 0.32 mm × 0.25 µm). The GC parameters for transfer
hydrogenation of ketones were as follows: initial temperature,
110 ◦C; initial time, 1 min; solvent delay, 4.48 min; temperature
∗
Correspondence to: Ahmet Kilic, Harran University, Department of Chemistry,
63190, Sanliurfa, Turkey. E-mail: kilica63@harran.edu.tr
a
b
c
Harran University, Department of Chemistry, 63190, Sanliurfa, Turkey
Dicle University, Department of Chemistry, 21280 Diyarbakır, Turkey
Siirt University, Department of Chemistry, 56100 Siirt, Turkey
In this paper, we report the synthesis, characterization and
catalytic activity in transfer hydrogenation of aromatic ketones of
the two boron complexes bearing BPh2 or BF2 and ligand (LH). We
c
Appl. Organometal. Chem. 2011, 25, 390–394
Copyright ꢀ 2011 John Wiley & Sons, Ltd.

Synthesis of new boron complexes
Scheme 1. The examples of N,N, N,O and O,O-type chelate boron complexes.
ramp 80 ◦C/min; final temperature, 200 ◦C; final time, 21.13 min;
injector port temperature, 200 ◦C; detector temperature, 200 ◦C,
injection volume, 2.0 µl.
Preparation of [LBF2] (3)
1 ml, 8 mmol BF3.OEt2 and 50 ml anhydrous benzene were added
to a 100 ml reaction flask. To this solution was added 0.72 g,
2 mmol of ligand 1 in 15 ml anhydrous benzene. After the reaction
mixture had been heated to reflux under nitrogen for 30 min, 1 ml
Et3N was added to the reaction solution, and the mixture was
heated to reflux for 12 h. A light green-yellow solid precipitated
from the solution. The solid product was collected by filtration and
purified by recrystallization and sublimation. Color, green-yellow;
m.p., 129 ◦C; yield (%), 70%; anal. calcd for [C22H28BF2NOS] (FW:
403.2 g mol−1), C, 65.51; H, 7.00; N, 3.47. Found, C, 65.48; H, 6.97; N,
3.42%. 1H-NMR (400.1 MHz, CDCl3) δ = 8.46 (s, 1H, HC N), 7.78 (d,
1H, J = 2.4 Hz, Ar-CH11), 7.51 (d, 1H, J = 2.4 Hz, Ar-CH8), 7.35 (d, 1H,
J = 2.4 Hz, Ar-CH12), 7.31 (d, 1H, J = 7.2 Hz, Ar-CH5), 7.18 (d, 1H, J =
2.0 Hz, Ar-CH10), 7.08 (s, 1H, Ar-CH3), 2.48 (s, 3H, S-CH3), 1.43 (s, 9H,
C-CH3), 1.35 (s, 9H, C-CH3); 13C NMR (100.6 MHz, CDCl3), δ = 164.3
(CH N), 158.3 (Ar-C7), 157.2 (Ar-C1), 149.3 (Ar-C4), 139.9 (Ar-C2),
139.6 (Ar-C9), 129.8 (Ar-C11), 129.7 (Ar-C3), 127.0 (Ar-C10), 126.7
(Ar-C5), 120.9 (Ar-C12), 120.0 (Ar-C6), 118.2 (Ar-C8), 35.2 and 29.5
[C(CH3)3], 31.5 and 31.2 [C(CH3)3], 15.7 (S-CH3); FT-IR [KBr pellets,
υmax (cm−1)], 3057 υ(Ar-H), 2955-2870 υ(Aliph-H), 1622 υ(C N),
1473-1439 υ(C C), 1172 υ(C–O), 1189 υ(B–O), 1045 υ(B–N), 876
υ(B–F); UV–vis [λmax (nm) (logε)] 224 (4.27), 279 (3.67), 301 (3.42),
367 (2.18) in C2H5OH and 278 (4.33), 301 (3.78), 366 (2.05) in
DMSO.
Synthesis of Ligand (LH) (1)
Ligand (LH) was synthesized according to the a previously
published method.[9] Color, yellow; m.p., 93 ◦C; yield (%), 65;
anal. calcd for [C22H29NOS] (FW: 355 g mol−1), C, 74.34; H, 8.17;
N, 3.94. Found, C, 74.40; H, 8.45; N, 3.71%. 1H-NMR (400.1 MHz,
CDCl3) δ = 13.59 (s, 1H, -OH, D-exchangeable), 8.63 (s, 1H, HC N),
7.52–6.99(m, 6H, Ar-CH), 2.53(s, 3H, S-CH3), 1.49(s, 9H, C-CH3), 1.34
(s, 9H, C-CH3); 13C NMR (100.6 MHz, CDCl3): δ = 163.3 (CH N),
158.4, 145.9, 140.5, 137.1, 134.6, 128.3, 127.1, 126.9, 125.2, 124.8,
118.4, 117.5 (Ar-CH), 35.2, 34.2 [C(CH3)3], 31.5, 29.5 [C(CH3)3],
14.8 (S-CH3); FT-IR [KBr pellets, υmax (cm−1)], 3643–3172 υ(OH),
2955–2867 υ(Aliph-H), 1615 υ(C N), 1467–1440 υ(C C), 1173
υ(C–O); UV–vis [λmax (nm) (logε)] 206 (4.07), 226 (4.04), 272 (3.96),
305 (3.72), 354 (3.65) in C2H5OH and 253 (4.20), 274 (4.40), 305
(4.21), 355 (4.14) in DMSO.
Preparation of [LBPh2] (2)
0.20 g of N-[3-(methylmercapto)aniline]-3,5-di-tert-butylsalicy-
laldimine (LH) 1 (0.56 mmol) and 25 ml anhydrous tetrahydro-
furane (THF) were added to a 50 ml reaction flask. To this solution
it was added 2.5 ml of the 0.25 M solution of BPh3 in tetrahy-
drofuran (THF) (∼0.60 mmol) and the mixture was stirred at
room temperature for 6 h. The solution was then concentrated
to dryness and the residue was subjected to vacuum subli-
mation at 110 ◦C. Light yellow solid of [LBPh2] was obtained
from recrystallization in a mixture of chloroform (CHCl3) and hex-
ane. Color, light-yellow; m.p., 223 ◦C; yield (%), 68; anal. calcd
for [C34H38BNOS] (FW, 519.6 g mol−1), C, 78.60; H, 7.37; N, 2.70.
Found, C, 78.65; H, 7.29; N, 2.73%. 1H-NMR (400.1 MHz, CDCl3)
δ = 8.67 (s, 1H, HC N), 7.58 (d, 1H, J = 2.4 Hz, Ar-CH11), 7.49
[d, 2H, J = 6.4 Hz, Ar-Ph(H)], 7.39 [d, 2H, J = 2.4 Hz, Ar-Ph(H)],
7.28 (s, 1H, Ar-CH8), 7.21 (d, 1H, J = 7.6 Hz, Ar-CH12), 7.19–7.10
[m, 6H, Ar-Ph(H)], 7.08 (d, 1H, J = 2.4 Hz, Ar-CH10), 6.86 (d, 1H,
J = 8.0 Hz, Ar-CH5), 6.79 (s, 1H, Ar-CH3), 2.55 (s, 3H, S-CH3), 1.41
(s, 9H, C-CH3), 1.36 (s, 9H, C-CH3); 13C NMR (100.6 MHz, CDCl3),
δ = 163.5 (CH N), 159.5 (Ar-C7), 158.3 (Ar-C1), 146.1 (Ar-C4), 140.6
(Ar-C2 and C9), 139.8 [Ar-Ph(C)], 139.5 (Ar-C11), 134.1 [Ar-Ph(C)],
129.6 [Ar-Ph(C)], 129.0 (Ar-C3), 126.9 (Ar-C10), 126.1 (Ar-C5), 122.0
(Ar-C12), 120.9 (Ar-C8), 119.2 (Ar-C6), 35.1 and 29.7 [C(CH3)3], 31.6
and 31.2 [C(CH3)3], 15.2 (S-CH3); FT-IR [KBr pellets, υmax (cm−1)]:
3054 υ(Ar-H), 2986–2848 υ(Aliph-H), 1608 υ(C N), 1476–1427
υ(C C), 1170 υ(C–O), 1187 υ(B–O), 1030 υ(B–N), 885 υ(B–Ph);
UV–vis [λmax (nm) (logε)] 212 (4.11), 233 (3.96), 274 (3.78), 303
(3.52), 435 (2.03) in C2H5OH and 268 (4.22), 275 (4.03), 306 (3.89),
424 (2.14) in DMSO.
General Procedure for the Transfer Hydrogenation of Ketones
In a typical procedure for the catalytic hydrogen-transfer reaction,
a solution of the boron complexes [LBPh2], 2, or [LBF2], 3
(0.005 mmol), KOH (0.025 mmol) and the corresponding ketone
(0.5 mmol) in degassed iso-PrOH (5 ml) were refluxed for 9 h. After
this time, a sample of the reaction mixture was taken off, diluted
with acetone and analyzed immediately by GC; the yields obtained
were related to the residual unreacted ketone.
Results and Discussion
Preparation and Characterization
The ligand (LH), 1, was prepared in moderate yield by refluxing the
equivalent amount of 3,5-di-tert-butyl-2-hydroxybenzaldehyde
and 3-methylmercapto aniline (one equivalent ratio) in abso-
lute methanol and three to four drops of formic acid as catalyst.
The boron complexes containing substituted phenyl or fluorine
moiety were synthesized according to slightly modified method
reported by Hou et al. and Chen et al.[10,3] The overall synthetic
scheme of the two boron complexes is shown in Scheme 2.
As expected, treatment of the ligand (LH), 1, with the boron
reagent BPh3 in THF solution at room temperature and with the
c
Appl. Organometal. Chem. 2011, 25, 390–394
Copyright ꢀ 2011 John Wiley & Sons, Ltd.
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A. Kilic et al.
Scheme 2. The structure of the proposed boron complexes.
boron reagent BF3•OEt2 in benzene solution at reflux tempera-
ture gave the complexes [LBPh2], 2, and [LBF2], 3, respectively
(Scheme 2). These two boron complexes were hardly soluble and
stable in nonprotic solvents such as chloroform, dichloromethane
and tetrahydrofuran, but easily soluble in protic solvents such as
ethanol.
The 1H NMR spectra of the ligand (LH), 1 with two boron
complexes and the chemical shifts of the different types of protons
are listed in the Experimental section. In the 1H-NMR spectrum
of [LBPh2], 2, and [LBF2], 3, the resonance for the azomethine
CH proton is a singlet at 8.67 ppm for [LBPh2], 2, and 8.46 ppm
for [LBF2], 3, while the resonance (δ = 163.5 for [LBPh2], 2 and
δ = 164.3 for [LBF2], 3) for the imino C-atom in the 13C-NMR
spectra shifts to lower field in comparison with the corresponding
signals of free ligand.[11] It can be stated that the position of the
azomethine proton is affected by the nature of the BPh2 and BF2
groups. Also, the protons of the tert-butyl groups of ligand exhibit
singlet resonances at δ = 1.41 and 1.36 ppm for LBPh2, 2 and
δ = 1.43 and 1.35 ppm for [LBF2], 3 indicating that the tert-butyl
protons of these compounds are magnetically nonequivalent
(Scheme 2).[12]
The IR spectra of the two boron complexes were compared with
that of the free ligand in order to determine the coordination sites
that may be involved in chelation. The low- or high-frequency
shift of the C N stretchings (between 1608 and 1622 cm−1),
in comparison with the free ligand, was consistent with N-
coordination of boron atoms to the azomethine ligand.[13] The
IR spectrum of the ligand was characterized by the appearance
of a band at range 3643–3172 cm−1, due to the υ(O–H) groups.
In the IR spectra of the boron complexes this band disappeared,
as expected. This is because the O–H band of ligand disappeared
upon formation of boron complexes, namely BPh2 or BF2. The
existence of υ(B–O) and υ(B ← N) at 1187 and 1030 cm−1 for
[LBPh2], 2, and at 1189 and 1045 cm−1 for [LBF2], 3, respectively,
provides evidence for the formation of the foregoing boron
complexes.
Figure 1. The UV–vis spectra of [LBPh2] 2 (a) and [LBF2] 3 (b) dissolved in
C2H5OH at room temperature.
bands at range 212–435 nm in C2H5OH solution. This may have
beencausedbythedisparatespecialstructuresofthesetwoboron
complexes. Moreover, the absorption bands for these complexes
had a large molar extinction coefficient, which was insensitive
to solvent polarity. Thus, the characteristic absorption bands can
reasonably be assigned to ligand-centered π → π∗ and n → π∗
of the C N chromophore. The absorption bands below 279 nm in
two polar solvents (C2H5OH and DMSO) were practically identical
and can be attributed to π → π∗ transitions in the benzene ring or
Electronic spectra of boron complexes were recorded in the
200–1100 nm range in C2H5OH or DMSO solution and their
corresponding data are given in the Experimental section and
Fig. 1. As shown in Fig. 1, the UV–vis absorption spectra of two
boroncomplexesexhibiteddifferentspectralfeatureswithintense
c
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Appl. Organometal. Chem. 2011, 25, 390–394

Synthesis of new boron complexes
Scheme 3. Hydrogen transfer from iso-PrOH to acetophenone.
As shown in Table 1, increasing the substrate-to-catalyst ratio
does not lower the conversions of the product in most cases.
In addition, we have expanded the substrate-to-catalyst ratio to
observe the effect on the catalytic efficiency. As shown in Table 1,
increasing the substrate-to-catalyst ratio does not damage the
conversions of the product in most cases except time of the
reaction lengthened. Remarkably, the transfer hydrogenation of
acetophenone could be achieved to 99% yield even when the
substrate-to-catalyst ratio reached 500 : 1.
Table 1. Transfer hydrogenation of acetophenone with iso-PrOH
catalyzed by [LBPh2], 2, and [LBF2], 3
Conversion
(%)e
TON
(h−1 f
Entry Catalyst S–catalyst–KOH Time
)
1
2
3
4
5
6
7
8
2a
3a
2b
3b
2c
3c
2d
3d
100 : 1 : 5
100 : 1 : 5
100 : 1
24 h
24 h
12 h
12 h
24 h
24 h
9 h
<1
<1
<5
<5
98
–
–
–
100 : 1
–
In Table 1, entries 7 and 8, when the reaction temperature
was increased to 82 ◦C smooth reduction of acetophenone into
1-phenylethanol occurred, with conversion ranging from 98 to
97% after 9 h for [LBPh2], (2) and for [LBF2], 3 of reaction. Results
obtained from optimization studies indicate clearly that both
complexes are active and efficient catalysts leading to nearly
quantitative conversions, with no significant difference between
the catalytic activities. The catalytic reduction of acetophenone
derivatives was all tested with the conditions optimized for
acetophenone and the results are summarized in Table 2. The
fourth column in Table 2 illustrates conversions of the reduction
performed in 0.1 M iso-PrOH solution containing [LBPh2], 2, or
[LBF2], 3, and KOH (ketone–catalyst–KOH = 100 : 1 : 5).
500 : 1 : 5
500 : 1 : 5
100 : 1 : 5
100 : 1 : 5
20
20
98
97
99
98
9 h
97
Reaction conditions: a at room temperature, acetophe-
none–catalyst–KOH, 100 : 1 : 5; b refluxing in iso-PrOH, acetophe-
none–catalyst, 100 : 1, in the absence of base; c refluxing in iso-
PrOH, acetophenone–catalyst–KOH, 500 : 1 : 5; d refluxing in iso-PrOH,
acetophenone–catalyst–KOH, 100 : 1 : 5. e Determined by GC (three
independent catalytic experiments). f Referred to the reaction time
indicated in column 4. TON (mol product mol−1 catalyst).
Asalreadystated, electronicproperties(thenatureandposition)
of the substituents on the phenyl ring of the ketone caused the
changes in the reduction rate. An ortho- or para- substituted
acetophenone with an electron-donor substituent, i.e. 2-methoxy
or 4-methoxy is reduced more slowly than acetophenone (Table 2,
entries 4, 5, 9 and 10).[19] In addition, the introduction of electron-
withdrawing substituents, such as F, Cl and Br, to the para-position
of the aryl ring of the ketone decreased the electron density of the
azomethine (-C N) group for boron complexes. The absorption
bands observed within the range of 301–367 nm in two polar
solvents (C2H5OH and DMSO) were most probably due to the
transition of n → π∗ of the imine group corresponding to the
boron complexes. Also, the absorption bands observed at 424 and
435 nm in two polar solvent for [LBPh2], 2, were most probably
due to the charge transfer.
C
O bond so that the activity was improved, giving rise to easier
hydrogenation.[20,21]
Catalytic Transfer Hydrogenation of Acetophenone
Derivatives
iso-PrOH is the conventional hydrogen source having favorable
properties; it is stable, easy to handle (b.p. 82 ◦C), non-toxic,
environmentally friendly, inexpensive and the acetone product
is readily removable.[14] In this context, complexes 2 and 3 were
selected as catalysts, iso-PrOH/KOH as the reducing system and
acetophenone as a model substrate (Scheme 3); the results are
listed in Table 1.
Atroomtemperaturenoappreciableformationof1-phenylethanol
was observed (Table 1, entries 1 and 2). As can be inferred from the
Table 1 (entries 3 and 4), the catalysts as well as the presence of
KOH are necessary to observe appreciable conversions. The base
facilitates the formation of alkoxide by abstracting proton of the
alcohol and subsequently alkoxide undergoes β-elimination to
give ruthenium hydride, which is an active species in this reaction.
This is the mechanism proposed by several workers on the studies
of ruthenium-catalyzed transfer hydrogenation reaction by metal
hydride intermediates.[15,16] Similarly this may the mechanism
proposed for the boron catalyzed transfer hydrogenation reaction
by boron hydride intermediates.[17,18]
Conclusion
In this study, two new boron complexes containing substituted
phenyl or fluorine moiety were synthesized. These boron
complexes have been characterized and their spectroscopic
properties were investigated. The results are agreed with the
proposed structure. We found that these complexes are efficient
homogeneous catalytic systems that can be readily implemented
and lead to secondary alcohols from good to excellent yields.
Furthermore, the influence of phenyl and fluorine groups in
the catalytic transfer hydrogenation of aromatic ketones was
investigated and their catalytic activities were very similar. The
procedure is simple and efficient towards various aryl ketones.
Acknowledgment
Partial support of this work by Harran University and Dicle Univer-
sity (project number DUAPK 05-FF-27) is gratefully acknowledged.
¨
c
Appl. Organometal. Chem. 2011, 25, 390–394
Copyright ꢀ 2011 John Wiley & Sons, Ltd.
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A. Kilic et al.
•
a
Table 2. Transfer hydrogenation results for substituted acetophenones with the catalyst systems prepared from LH and BPh3 and BF3 OEt2
Catalyst
Entry
R
Time
Conversion (%)b
TON (h−1 c
)
[LBPh2], 2
1
2
3
4
5
4-F
4-Cl
9 h
9 h
9 h
9 h
9 h
99
98
95
90
83
99
98
95
90
83
4-Br
2-MeO
4-MeO
[LBF2], 3
6
7
4-F
4-Cl
9 h
9 h
9 h
9 h
9 h
99
97
94
91
80
99
97
94
91
80
8
4-Br
9
2-MeO
4-MeO
10
a Catalyst (0.005 mmol), substrate (0.5 mmol), iso-PrOH (5 ml), KOH (0.025 mmol%), 82 ◦C, 9 h for 2 and 3, respectively; the concentration of
acetophenone derivatives is 0.1 M.
b Purity of compounds is checked by NMR and GC (three independent catalytic experiments); yields are based on methyl aryl ketone.
c TON (mol product mol−1 catalyst).
References
[9] E. Tas, A. Kilic, N. Konak and I. Yilmaz, Polyhedron 2008, 27(3), 1024.
[10] Q. Hou, L. Zhao, H. Zhang, Y. Wang, S. Jiang, J. Luminescence 2007,
126, 447.
[11] X. Liu, H. Xia, X. Fan, Q. Su, W. Gao, Y. Mu, J. Phys. Chem. Solids 2009,
70, 92.
[1] a) A. G. Massey, Main Group Chemistry, 1st edn, Ellis Horwood:
Chichester, 1990, p. 487; b) S. Yadav, M. Swami, and R. V. Singh,
Phosphorus, Sulfur, and Silicon 2010, 185, 394.
[2] a) S. Wang, Coord. Chem. Rev. 2001, 215, 79; b) S. Anderson,
M. S. Weaver, A. J. Hudson, Synth. Met. 2000, 111–112, 459.
[3] H. Y. Chen, Y. Chi, C. S. Liu, J. K. Yu, Y. M. Cheng. K. S. Chen,
P. T. Chou, S. M. Peng, G. H. Lee, A. J. Carty, S.J. Yeh C. T. Chen, Adv.
Funct. Mater. 2005, 15(4), 567.
[4] a) G. Beer, J. Daub, K. Rurack, Chem. Commun. 2001, 1138; b)
K. Rurack, M. Kollmannsberger, J. Daub Angew, Chem. Int. Ed. 2001,
40, 385.
[12] A. Kilic, E. Tas, B. Deveci I. Yilmaz, Polyhedron 2007, 26, 4009.
[13] O.N. Kadkin, J. An, H. Han, Y.G. Galyametdinov, Eur. J. Inorg. Chem.
2008, 10, 1682.
[14] G. Zassinovich, G. Mestroni, S. Gladiali, Chem. Rev. 1992, 92, 1051.
[15] H. Doucet, T. Ohkuma, K. Murata, T. Yokozawa, M. Kozawa,
E. Katayama, F. A. England, T. Ikariya, R. Noyori, Angew. Chem. Int.
Ed. 1998, 37, 1703.
[16] H. Zhang, B. C. Yang, Y. Y. Li, Z. R. Donga, J. X. Gao, H. Nakamura,
K. Murata, T. Ikariya, J. Chem. Com., Chem. Commun. 2003, 142.
[17] a) M. M. Midland, S. Zderic, J. Am. Chem. Soc. 1982, 104, 525;
b) J. Chandrasekharan, P. V. Ramanchadran, H.C. Brown, J. Org.
Chem. 1985, 50, 5446; c) J. S. Cha, E. J. Kim, O. O. Kwon, S. Y. Kwon,
W. W. Seo, S. W. Chang, Org. Prep. Proceed. Int. 1995, 27, 541.
[18] a) J. S. Cha, E. J. Kim, O. O. Kwon, J. M. Kim, Bull. Korean Chem. Soc.
1995, 16, 691; b) E. J. Corey, R. K. Bakshi, S. Shibata, J. Am. Chem. Soc.
1987, 109, 5551.
[5] a)
V. Christou,
S. E. Watkins,
R. McCann,
C. Redshaw,
M. R. J. Elsegood, Inorg. Chem. Acta 2010, 363, 1173; b) P. Oleynik,
Y. Ishihara, G. Cosa, J. Am. Chem. Soc. 2007, 129, 1842; c) D. Rohde,
C. J. Yan, L. J. Wan, Langmuir 2006, 22, 4750; d) C. Risko, E. Zojer,
P. Brocorens, S.R. Marder, J.L. Bredas, Chem. Phys. 2005, 313, 151.
[6] a) A. Wakamiya, T. Taniguchi, S. Yamaguchi, Angew. Chem. 2006,
118, 3242; Angew. Chem. Int. Ed. 2006, 45, 3170; b) A. Fukazawa,
H. Yamada, S. Yamaguchi, Angew. Chem. 2008, 120, 5664; Angew.
Chem.Int.Ed. 2008, 47, 5582;c) Q. D. Liu, M. S. Mudadu, R. Thummel,
Y. Tao, S. Wang, Adv. Funct. Mater. 2005, 15, 143.
[19] R. Guo, X. Chen. C. Elphelt, D. Song, R. H. Morris, Organic Letters
2005, 7, 9.
[7] a) Y. Qin, I. Kiburu, S. Shah, F. Ja¨ckle, Macromolecules 2006, 39,
9041; b) Y. Qin, I. Kiburu, S. Shah, F. Ja¨ckle, Org. Lett. 2006, 8, 5227;
c) H. Amarne, C. Baik, S. K. Murphy S. Wang, Chem. Eur. J. 2010, 16,
4750.
[20] P. Pelagatti, M. Carcelli, F. Calbiani, C. Cassi, L. Elviri, C. Pelizzi,
U. Rizzotti, D. Rogolino, Organometallics 2005, 24, 5836.
[21] J. W. Faller, A. R. Lavoie, Organometallics 2001, 20, 5245.
[8] a)M. Elbing,G. C. Bazan,Angew.Chem.2008,120,846;Angew.Chem.
Int. Ed. 2008, 47, 834; b) T. W. Hudnall, C. W. Chiu, F. P. Gabbai, Acc.
Chem. Res. 2009, 42, 388; c) Z. M. Hudson, S. Wang, Acc. Chem. Res.
2009, 42, 1584.
c
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