Synthesis and structure of an air-stable bis(isopropylcyclopentadienyl) zirconium perfluorooctanesulfonate and its catalyzed benzylation of 1,3-dicarbonyl derivatives with alcohols

Article abstract of DOI:10.1016/j.tet.2014.12.101

An air-stable uninuclear complex of bis(isopropylcyclopentadienyl) zirconium perfluorooctane sulfonate (1a·H₂O·3THF) was successfully synthesized by the reaction of (i-PrCp)₂ZrCl₂ with C₁₇SO₃Ag. The c

Full text of DOI:10.1016/j.tet.2014.12.101

Tetrahedron xxx (2015) 1e7
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and structure of an air-stable
bis(isopropylcyclopentadienyl) zirconium perfluorooctanesulfonate
and its catalyzed benzylation of 1,3-dicarbonyl derivatives with
alcohols
,
,
b
b
a
Xiaohong Zhang a b, Renhua Qiu a , Congcong Zhou , Jingxing Yu , Ningbo Li ,
*
Shuangfeng Yin a , Xinhua Xu
,
a,
*
*
a College of Chemistry and Chemical Engineering, Hunan University, Changsha, 410082, China
b College of Chemistry and Materials Engineering, Wenzhou University, Wenzhou, 325035, China
a r t i c l e i n f o
a b s t r a c t
Article history:
An air-stable uninuclear complex of bis(isopropylcyclopentadienyl) zirconium perfluorooctane sulfonate
(1a$H2O$3THF) was successfully synthesized by the reaction of (i-PrCp)2ZrCl2 with C17SO3Ag. The
compound 1a$H2O$3THF was characterized by different techniques (such as X-ray single crystal dif-
fraction, TG-DSC, conductivity measurement and acid strength) and found to have the similar nature of
water tolerance, air-stability, thermally-stability and strong Lewis-acidity with that of our previously
reported binuclear and uninuclear zirconocenes perfluorooctanesulfonate. This novel complex was
confirmed to be an effective catalyst with good recyclability and reusability for the direct benzylation of
1,3-dicarbonyl derivatives using alcohols as alkylating agents. Various 1,3-dicarbonyl and alcohols de-
rivatives can participate in the reaction, affording the corresponding monobenzylated products in
competitive yields as compared to its counterparts, such as Cp2Zr(OSO17)2$3H2O$THF and the traditional
Lewis-acid catalysts.
Received 9 December 2014
Accepted 29 December 2014
Available online xxx
Keywords:
Bis(isopropylcyclopentadienyl) zirconium
Perfluorooctanesulfonate
Benzylation
Ó 2015 Elsevier Ltd. All rights reserved.
1. Introduction
electrophiles. The used catalysts included PMA/SiO2,5 Phospho-
tungstic acid (PWA),6 trimethylsilyl trifluoromethanesulfonate
Alkylation of 1,3-dicarbonyl derivatives is one of the most
common methods to construct CeC bonds and has received much
attention in organic synthesis.1 The alkylation was initially ac-
complished using alkyl halides, carboxylates, phosphonates or
carbonates as the alkylating agents in the presence of base, which
resulted in the production of large amounts of waste salts as by-
products2 and limited the application of this protocol. Therefore, it
is highly desirable to develop an environmental friendly and atom-
economical process to improve this transformation. Among the
numerous works devoted to this alkylation of 1,3-dicarbonyl
compounds,3 the most ideal protocol would be the use of alco-
hols as the alkylating agents,4 wherein alcohols can be obtained
more easily and H2O is the only side product (Scheme 1). Very
recently, various catalytic systems have been successfully applied
in the direct alkylation of active methylenes using alcohols as
(TMSOTf),7 Yb(OTf)3,8 B(C6F5)3,9 NPW/SiO2,10 InCl3,11 FeCl3,12
Fe(ClO4)3,13 bipyeruthenium complexes,14 TfOH-SiO2,15 NaHSO4/
17
SiO2,16 Bi(OTf)3 and so on. Compared to other known alkylation
reactions, these catalytic systems have the advantages of low
catalyst-loading as well as wide availability of the starting materials
and the generation of H2O as the only side product. However, most
of these catalysts have one or more disadvantages such as air- or
moisture-sensitive and the need of strictly anhydrous reaction
* Corresponding authors. Fax: þ86 731 88821546; e-mail addresses: renhuaqiu@
Scheme 1. A comparison between a common process and an ideal process for the
alkylation of 1,3-dicarbonyl derivatives.
hnu.edu.cn (R. Qiu), sf_yin@hnu.edu.cn (S. Yin), xhx1581@hnu.edu.cn (X. Xu).
http://dx.doi.org/10.1016/j.tet.2014.12.101
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.
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2
X. Zhang et al. / Tetrahedron xxx (2015) 1e7
conditions. Moreover, most of them can not be recycled owing to
their decomposition with the water. Therefore, it is still highly
demanded to develop some air-stable, water-tolerant, strongly
Lewis-acidic and recyclable catalysts to realize the alkylation of 1,3-
dicarbonyl derivatives with alcohols.
Recently, cationic group
4 metallocene compounds have
Scheme 2. Synthesis of 1a$H2O$3THF.
aroused much interest.18 For example, metallocene dichloride and
metallocene triflates ([Cp2MY2], Cp¼C5H5; M¼Zr, Ti, Hf, Y¼Cl,
CF3SO2) were successively applied in organic synthesis, such as
olefin polymerization and the CeC bond forming reactions.19
However, the weak acidity of Cp2MCl2 as well as the unstable na-
ture and facile hydrolysis of Cp2M (OTf)2 greatly limited their ap-
plication.20 Otera and co-workers found that the incorporation of
perfluoroalkyl (aryl)sulfonate moieties to organometallic (i.e., Sn,
Zr, and Ti) cations could enhance acidity and stability.21 With such
understanding, several air-stable metallocene complexes bearing
perfluorooctanesulfonate groups (Cp2M(OSO2C8F17)2, M¼Ti, Zr, Hf)
were reported successively in our group and were confirmed to
show strong Lewis acidity and high catalytic activity in the CeC and
CeO bond forming reactions.22
However, their relatively low solubility in organic solvents ow-
ing to the strong lipophobic nature of C8F17 group possibly declines
the catalytic efficiency. To overcome this shortcoming, we found
that alkyl group incorporated with Cp ring can increase the solu-
bility as well as the catalytic efficiency. For example, bis(ethylcy-
clopentadienyl) and bis(methylcyclopentadienyl) zirconium
perfluorooctanesulfonates were synthesized, respectively and were
found to have slightly higher catalytic activity than Cp2Zr(O-
SO2C8F17)2.23 Moreover, it was interesting to summarize that one of
the EtCp/MeCp ligands of bis(ethylcyclopentadienyl)/bis (methyl-
cyclopentadienyl) zirconium perfluorooctanesulfonates is removed
and replaced by OH to form the stable binuclear structures, dif-
The crystal structure of 1a$H2O$3THF together with selected
bonds and angles is shown in Fig. 1. It is clear that bis(i-PrCp) zir-
conocene is cationic. Moreover 1a$H2O$3THF has the same unin-
uclear structure with [(Cp)2Zr(H2O)3](OSO2C8F17)2,22b different
from the binuclear structure of [{EtCpZr(OH2)3}2(
[OSO2C8F17]4$4H2O$2THF and [{MeCpZr(OH2)3}2(
m
m
2-OH)2]
2_OH)2]
[OSO2C8F17]4$2H2O$1THF$2(C3H6O) even though their synthetic
procedures are identical.23 Based on the experimental process and
results, we hence deduce that the generation of the binuclear or
uninuclear structures depends on the amount of H2O from the air.
One of the Cp ligands can be easily removed and replaced by OH to
form the binuclear structures in moist air. Further studies on the
crystal structures are ongoing in our laboratory. In the crystal
structure of 1a$H2O$3THF, the zirconium atom is stabilized by
three water molecules and not by THF. The three H2O molecules
also lie on the plane that bisects the angle between the Cp ring
planes. The ZreO distances of 1a$H2O$3THF are 2.196(3), 2.241(3)
and 2.255(3) A, respectively. The C8F17SOꢁ3 ions, the dissociated H2O
ꢀ
molecules, the solvating ligand THF are packed around the complex
cation in such a way that their oxygen atoms point towards the H2O
ligands. The C8F17 chains of the anion, on the other hand, are
clustered together to produce hydrophobic domains in the crystal
structure.
ferent from the uninuclear structure of Cp2Zr(OSO2C8F17)2 even
though their synthetic procedures are identical.22a These in-
teresting findings encouraged us to expand more zirconocene
catalysts and study their structures and catalytic efficiency. Fortu-
nately, bis(isopropylcyclopentadienyl) zirconium perfluorooctane-
sulfonate (1a$H2O$3THF) was synthesized and confirmed by X-
ray analysis to be uninuclear structure. In the context, we wish to
report its synthesis, characterization and catalytic application in
the alkylation of 1,3-dicarbonyl derivatives with alcohols in detail.
2. Results and discussion
The synthesis of 1a$H2O$3THF was shown in Scheme 2. Treat-
ment of bis(isopropylcyclopentadienyl)zirconium dichloride [(i-
PrCp)2ZrCl2] (1 equiv) with silver perfluorooctanesulfonate (AgO-
SO2C8F17) (2 equiv) in dry THF afforded 1a$xH2O$yTHF (after re-
crystallization from THF). The water molecules in the complex
originated from air or the solvent, and the hydrate numbers x and
solvating ligand THF y varied according to the reaction conditions
from the results of 1H NMR spectroscopic (in dry acetone-d6) and
the X-ray analysis. The X-ray analysis showed that the freshly pre-
pared crystal sample, after recrystallization by diffusion of hexane
into saturated THF solution, contains four water and two THF mol-
ecules. Of the four water molecules, three waters attached with the
zirconium atom to stabilize the uninuclear complex. The results of
1H NMR spectroscopic showed that THF still existed in the freshly
prepared sample after vacuum treatment at room temperature for
1 h and then disappeared until the temperature was raised to 60 ꢀC
for a continual 1 h (see ESD). Similar to our previous reported
metallocene complexes, 1a$H2O$3THF remained as dry powder
after being kept in open air over a month, and exhibited no sign of
structural change by 1H NMR spectroscopy analysis (see ESD),
showing a great advantage over zirconocene bis(triflate) and the
traditional Lewis-acid catalysts from an operational point of view.
Fig.
1. Crystal
structure
of
[(i-propylCp)2Zr(OH2)3][OSO2C8F17]2$H2O$3THF
ꢀ
(1a$H2O$3THF), Hydrogen atoms are omitted for clarity. Selected bond distances (A)
and angles (ꢀ): Zr(1)eO(2), 2.196(3); Zr(1)eO(3), 2.241(3); Zr(1)eO(1), 2.255(3); Zr(1)e
C(6), 2.481(5); Zr(1)eC(5), 2.522(5); Zr(1)eC(12), 2.568(4); O(2)eZr(1)eO(3),
72.24(12); O(2)eZr(1)eO(1), 72.72(12); O(3)eZr(1)eO(1), 144.95(12); O(2)eZr(1)e
C(6), 122.24(15); O(1)eZr(1)eC(14), 75.25(14).
The compound 1a$H2O$3THF was also characterized by differ-
ent techniques (such as TG-DSC, solubility, conductivity measure-
ment and acid strength, see ESI) and found to have the nature of
good solubility in polar solvents, thermally-stability and strong
Lewis-acidity. These excellent properties urged us to evaluate its
performances as Lewis acid for the direct alkylation of 1,3-
dicarbonyl derivatives with alcohols.
The reaction between dibenzoylmethane and benzhydrol using
5 mol % of 1a$H2O$3THF as the catalyst was chosen to screen the
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X. Zhang et al. / Tetrahedron xxx (2015) 1e7
3
Table 1
Screening optimal conditionsa
Table 2
The direct alkylation of 1,3-dicarbonyl derivatives with benzhydrylic alcohols cata-
lyzed by complex 1a$H2O$3THFa,b
Entry
Solvent
1a$H2O$3THF (mol %)
Yield (%)b
1
2
3
4
5
6
7
8
9
DMSO
THF
5
5
5
5
5
5
5
d
70
85
65
87
CH3CN
ClCH2CH2Cl
CH2Cl2
Toluene
H2O
95 (81,c 90c, 92c, 93c)
Trace
24
0
CH2Cl2
CH2Cl2
2.5
75
a
Dibenzoylmethane (2a, 0.5 mmol), benzhydrol (2b, 0.55 mmol), catalyst
1a$H2O$3THF (39.8 mg, 5 mol %), solvent (2 mL), 4 h.
b
Isolated yields.
Using Cp2ZrCl2 (5 mol %), Cp2Zr(OSO2C8F17
) -
(5 mol %), [{EtCpZr(OH2)3}2(m2
2
c
OH)2][C7F17SO3]4$4H2O$2THF (2.5 mol %) and [{MeCpZr(OH2)3}2(
[C7F17SO3]4$2H2O$1THF$2(C3H6O) (2.5 mol %) as catalyst, respectively.
m
2-OH)2]
optimal conditions. The results are summarized in Table 1. CH2Cl2
was found to be the most effective solvent with 95% yield of desired
products at 60 ꢀC (entries 1e6). The yield was competitive to its
metal-catalyzed counterparts, such as the anhydrous FeCl3 (98%),12
Cp2ZrCl2 (81%), Cp2Zr(OSO2C8F17 2
)
(90%), [{EtCpZr(OH2)3}2(m2
-
-
OH)2] [C7F17SO3]4$4H2O$2THF (92%) and [{MeCpZr(OH2)3}2(m2
OH)2] [C7F17SO3]4$2H2O$1THF$2(C3H6O) (93%). These findings also
displayed that the alkylation reaction can proceed in water, but
giving the target product in a low yield of 24%. The low yield maybe
resulted from the poor/difficult solubility of the complex, 1,3-
dicarbonyl and alcohols in water (entry 7). Controlled experi-
ments showed that no target product was obtained in the absence
of 1a$H2O$3THF (entry 8) and obvious decrement of the yield was
observed when lowering the catalyst loading to 2.5 mol % (entry 9,
75%).
After optimizing the reaction conditions, we tested the substrate
compatibility with regard to both coupling partners (Table 2). The
reactions of dibenzoylmethane and acetylacetone with benzhy-
drylic alcohols proceeded smoothly, giving the corresponding
products in excellent yields (88e96 %) (entries 1e16). Generally, the
electron-withdrawing groups on the phenyl ring of benzhydrylic
alcohols benefited the yields slightly (entries 5e7, 13e15). Good
yields (88e95 %) were also obtained when benzoylacetone was
employed as the 1,3-dicarbonyl derivative (entries 17e24). The
unsymmetric benzhydrylic alcohols gave two inseparable di-
astereomers (entries 19e21), except the separable diastereomers of
compound 21 in the ratio of 1:1 (entry 18). To our delight, ethyl
benzoylacetate and ethyl acetoacetate were also tolerable, giving
the alkylated products in high yields (entries 25e26, yield 93e95%).
It is notable that when 1,3-cyclohexanediones and 5, 5-
dimethylcyclohexane-1,3-diones reacted with benzhydrylic alco-
hols, the desired compounds 30, 31 and 32 were also isolated in
moderate yields (entries 27e29).
To test the reusability of the catalyst and the reproducibility of
catalytic performance, 1a$H2O$3THF was subjected to recycle in
the direct alkylation of dibenzoylmethane with benzhydrol
(Table 3). The detected change in product yield was minimal in
a trial of five cycles, demonstrating that the catalyst is stable and
suitable for reuse.
To explain the reaction mechanism, (R)-1-phenylethanol was
selected to react with dibenzoylmethane, leading to the isolation of
completely racemized product, in 88% yield (Scheme 3).
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4
X. Zhang et al. / Tetrahedron xxx (2015) 1e7
Table 3
from sodium/benzophenone. Acetonitrile was distilled from CaH2.
Acetone was refluxed for 4 h and distilled with KMnO4, then dried
with K2CO3, after that, it was distilled, and kept in the dry box. NMR
spectra were recorded at 25 ꢀC on Bruker Avance 500 MHz spec-
trometer calibrated with tetramethylsilane (TMS) as an internal
reference. Conductivity was measured on REX conductivity meter
DDS-307. The crystal was mounted on a Bruker APEX area-detector
Yield of the direct alkylation of dibenzoylmethane with benzhydrol catalyzed by
recovered 1a$H2O$3THFa
Entry of cycle
1
2
3
4
5
Yield (%)b
95
80
92
79
91
80
92
78
90
78
Cat. (%)c
a
Dibenzoylmethane (2a, 0.5 mmol), benzhydrol (2b, 0.55 mmol), catalyst
1a$H2O$3THF (39.8 mg, 5 mol %), CH2Cl2 (2 mL), 4 h.
diffractometer equipped with a graphite-monochromatic MoK
a
b
Isolated yield.
Isolated yield of recovered catalyst.
ꢀ
(l¼0.71073 A) radiation. The structures were solved by direct
c
methods using the SHELXLS-97 program and refined by using the
SHELXL-97 program.
4.1.1. Synthesis of complex 1a$H2O$3THF. To a solution of (i-
PrCp)2ZrCl2 (188 mg, 0.5 mmol) in 5 mL THF was added a solution of
AgOSO2C8F17 (605 mg, 1 mmol) in 10 mL THF. After the mixture was
stirred at 25 ꢀC for 1e2 h in the absence of light, it was filtrated. The
filtrate was placed in a small jar and then put into a larger jar, which
was added dry hexane (20 mL) and then the larger jar was obdu-
rate. After keeping in the refrigerator for 24e48 h, the white crystal
was obtained (477 mg, 60%). mp 145e146 ꢀC. 1H NMR (500 MHz,
Scheme 3. Benzylation of dibenzoylmethane with (R)-1-phenylethanol.
Based on the result and according to the reported findings,7, 13
the proposed mechanism of direct alkylation of 1,3-dicarbonyl
derivatives with benzhydrylic alcohols is shown in Scheme 4. The
first step is the formation of complex A by coordination of the 1,3-
dicarbonyl compound to Lewis acidic complex of 1a$H2O$3THF.
Then alcohol (R-1-phenylethanol) is activated by the complex A to
form species B, which immediately releases the carbocation and
the intermediate C. Subsequently, the nucleophilic carbon atom of C
attacks the carbocation to form the products, as well as the by-
product H2O.
acetone-d6)
d
¼6.65e6.63 (m, 8H, Cp), 3.10e3.02 (m, 2H), 1.24 (s,
6H), 1.23 (s, 6H); 19F NMR (470 MHz, acetone-d6): ꢁ81.67 (br, 3F),
ꢁ114.70 (br, 2F), ꢁ121.00 (br, 2F), ꢁ122.13e122.45 (m, 6F), ꢁ123.26
(br, 2F), ꢁ126.75 (br, 2F). Crystallographic data for [(i-
PrCp)2Zr(H2O)3](OSO2C8F17)2$2H2O$3THF: C44H56F34O14S2Zr, white
ꢀ
prism, formula weight 1592.21, Triclinic, P-1, a¼10.5728(11) A,
3
ꢀ
ꢀ
ꢀ
b¼17.2998(18) A, c¼19.395(2) A, V¼3222.0(6) A , Z¼2,
Dcalcd¼1.641
g
cmꢁ3
,
R(int)¼0.0330, R1¼0.0810, wR2¼0.2255,
GOF¼1.031, CCDC No. 1010459.
4.1.2. Typical procedure for direct benzylation of 1,3-dicarbonyl de-
rivatives using alcohols as alkylating agents catalyzed by 1a. To
a 10 mL sealed tube was added dibenzoylmethane (112 mg,
0.5 mmol), benzhydrol (101 mg, 0.55 mmol), CH2Cl2 (2 mL) and
catalyst (39.8 mg, 5 mol %). The mixture was stirred at 60 ꢀC for 4 h.
Then the reaction mixture was evaporated in vacuum, CH2Cl2
(3ꢂ10 ml) was added to the reaction mixture and the catalyst was
filtered for the next cycle of reaction. The combined CH2Cl2 solution
was removed by evaporation in vacuum and was then subject to
silica gel column chromatograph; the product (4) was obtained:
185 mg, isolated yield 95%.
Scheme 4. Plausible mechanism of direct alkylation of 1,3-dicarbonyl derivatives with
benzhydrylic alcohols catalyzed by complex 1a$H2O$3THF.
4.2. Characterization data
(4).4e White
3. Conclusions
4.2.1. 2-Benzhydryl-1,3-diphenylpropane-1,3-dione
solid. 1H NMR (500 MHz, CD3COCD3)
8.05e8.03 (m, 4H),
d
In summary,
a novel air-stable Lewis acidic complex of
7.54e7.49 (m, 6H), 7.40e7.37 (m, 4H), 7.17e7.14 (m, 4H), 7.04e6.99
(m, 3H), 5.24 (d, J¼11.5 Hz, 1H); 13C NMR (125 MHz, CD3COCD3)
1a$H2O$3THF ([(i-PrCp)2Zr(H2O)3](OSO2C8F17)2$H2O$3THF) was
successfully synthesized and its structure was determined by X-ray.
The complex was also characterized with other techniques such as
TG-DSC analysis, conductivity measurement and acid strength (H0).
It can be used as a highly efficient catalyst for the direct alkylation
of 1,3-dicarbonyl derivatives with benzhydrylic alcohols with
good to excellent yields. The novel complex has the advantages
of water tolerance, air-stability, thermally-stability, highly catalytic
efficiency and reusability with better solubility, competitive yields
as compared to its counterparts, such as Cp2Zr(O-
SO2C8F17)2$3H2O$THF and the traditional Lewis-acid catalysts.
d
194.5, 143.5, 137.9, 134.1, 129.6, 129.4, 129.3, 129.1, 127.2, 61.2,
53.8.
4.2.2. 1,3-Diphenyl-2-(phenyl(o-tolyl)methyl)propane-1,3-dione
(5). White solid. 1H NMR (500 MHz, CD3COCD3)
d 8.05e8.02 (m,
4H), 7.81 (d, J¼8.0 Hz, 1H), 7.54e7.49 (m, 2H), 7.42e7.36 (m, 6H),
7.12e7.09 (m, 2H), 7.07e7.05 (m, 3H), 6.99e6.96 (m, 2H), 5.47 (d,
J¼11.5 Hz, 1H), 2.42 (s, 3H); 13C NMR (125 MHz, CD3COCD3)
d
195.4, 194.1, 142.2, 141.9, 137.8, 137.1, 134.2, 134.1, 131.4, 130.6,
129.9, 129.7, 129.5, 129.4, 129.3, 129.0, 127.5, 127.2, 127.1, 126.8,
61.3, 48.9, 20.2.
4. Experimental section
4.1. General
4.2.3. 1,3-Diphenyl-2-(phenyl(p-tolyl)methyl)propane-1,3-dione
(6). White solid. 1H NMR (500 MHz, CD3COCD3)
d 8.07e8.04 (m,
4H), 7.54e7.48 (m, 4H), 7.41e7.37 (m, 6H), 7.14 (t, J¼8.0 Hz, 2H),
All reactions were carried out under nitrogen atmosphere with
freshly distilled solvents unless otherwise noted. THF was distilled
7.03e6.99 (m, 2H), 6.97e6.95 (m, 2H), 5.20 (d, J¼11.5 Hz, 1H), 2.13
(s, 3H); 13C NMR (125 MHz, CD3COCD3)
d 194.6, 194.5, 143.7, 140.5,
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X. Zhang et al. / Tetrahedron xxx (2015) 1e7
5
137.94, 137.90, 136.5, 134.2, 129.8, 129.6, 129.5, 129.4, 129.3, 129.2,
129.1, 127.1, 61.2, 53.3, 20.9.
J¼8.0 Hz, 2H), 7.35 (d, J¼9.0 Hz, 2H), 7.28 (d, J¼7.5 Hz, 2H), 7.17 (d,
J¼7.0 Hz, 1H), 6.85e6.84 (m, 2H), 5.13 (d, J¼12 Hz, 1H), 4.80 (d,
J¼12 Hz, 1H), 3.74 (s, 3H), 2.04 (s, 3H), 2.03 (s, 3H); 13C NMR
4.2.4. 2-((4-Methoxyphenyl) (phenyl)methyl-1,3-diphenylpropane-
(125 MHz, CD3COCD3) d 202.8, 202.7,159.4,143.7,135.1,129.8,129.5,
1,3-dione (7).1d White solid. 1H NMR (500 MHz, CDCl3)
d
7.84e7.82
128.7, 127.4, 114.9,73.6, 55.5, 51.3, 30.4.
(m, 4H), 7.48e7.45 (m, 2H), 7.35e7.31 (m, 4H), 7.24e7.23 (m, 2H),
7.17e7.13 (m, 4H), 7.08e7.03 (m, 1H), 6.68 (d, J¼8.5 Hz, 2H), 6.31 (d,
J¼11.5 Hz, 1H), 5.28 (d, J¼11.5 Hz, 1H), 3.67 (s, 3H); 13C NMR
4.2.13. 3-((4-Chlorophenyl) (phenyl)methyl)pentane-2,4-dione
(16).16 White solid. 1H NMR (500 MHz, CD3COCD3)
d 7.49e7.44
(125 MHz, CDCl3)
d
194.2, 194.1, 158.2, 142.1, 137.03, 137.00, 133.9,
(m, 4H), 7.33e7.28 (m, 4H), 7.19 (t, J¼7.5 Hz, 1H), 5.23 (d, J¼12 Hz,
133.2, 132.1, 129.2, 128.7, 128.62, 128.59, 128.53, 128.1, 127.9, 126.5,
113.9, 62.6, 55.2, 51.6.
1H), 4.85 (d, J¼12 Hz, 1H), 2.09 (s, 3H), 2.05 (s, 3H); 13C NMR
(125 MHz, CD3COCD3)
d 202.4, 202.3, 142.8, 142.4, 132.8, 130.5,
129.6, 129.5, 128.8, 127.7, 73.1, 51.2, 30.6, 30.5.
4.2.5. 2-((4-Chlorophenyl) (phenyl)methyl-1,3-diphenylpropane-1,3-
dione (8).24 White solid. 1H NMR (500 MHz, CD3COCD3)
4.2.14. 3-(Bis(4-chlorophenyl)methyl)pentane-2,4-dione
d
8.07e8.05 (m, 4H), 7.55e7.49 (m, 6H), 7.42e7.38 (m, 4H),
(17).13 White solid. 1H NMR (500 MHz, CDCl3)
d 7.23e7.21 (m, 4H),
7.20e7.14 (m, 4H), 7.05e7.03 (m, 2H), 5.23 (d, J¼11.5 Hz, 1H); 13C
7.15e7.14 (m, 4H), 4.77 (d, J¼12 Hz, 1H), 4.63 (d, J¼12 Hz, 1H), 1.99
NMR (125 MHz, CD3COCD3)
d
194.5, 194.4, 142.9, 142.6, 137.8, 134.3,
(s, 6H); 13C NMR (125 MHz, CDCl3)
74.4, 49.7, 29.6.
d 202.1, 139.3, 133.2, 129.2, 129.0,
134.2, 132.5, 131.0, 129.64, 129.62, 129.5, 129.4, 129.3, 129.2, 129.1,
128.7, 127.4, 60.9, 53.1.
4.2.15. 3-(Bis(4-fluorophenyl)methyl)pentane-2,4-dione
(18).13 White solid. 1H NMR (500 MHz, CD3COCD3)
7.48e7.45 (m,
4H), 7.05e7.02 (m, 4H), 5.18 (d, J¼12 Hz, 1H), 4.85 (d, J¼12 Hz, 1H),
2.04 (s, 6H); 13C NMR (125 MHz, CD3COCD3)
202.3, 162.4 (d,
4.2.6. 2-(Bis(4-chlorophenyl)methyl)-1,3-diphenylpropane-1,3-dione
d
(9).24 White solid. 1H NMR (500 MHz, CDCl3)
d 7.82e7.80 (m, 4H),
7.49 (t, J¼7.5 Hz, 2H), 7.34 (t, J¼8.0 Hz, 4H), 7.12e7.10 (m, 8H), 6.22
d
(d, J¼12 Hz, 1H), 5.26 (d, J¼12 Hz, 1H); 13C NMR (125 MHz, CDCl3)
J¼242.1 Hz), 139.3, 130.6 (d, J¼7.8 Hz), 116.2 (d, J¼21.3 Hz), 73.4,
d
193.6,139.8, 136.7, 133.6, 132.7, 129.5,128.8, 128.7, 128.6, 62.3, 51.1.
50.2, 30.5.
4.2.7. 2-(Bis(4-fluorophenyl)methyl)-1,3-diphenylpropane-1,3-dione
(10).24 White solid. 1H NMR (500 MHz, CD3COCD3)
8.05 (d,
4.2.16. 3-(1-Phenylethyl)pentane-2,4-dione (19).16 White solid. 1H
NMR (500 MHz, CD3COCD3) d 7.29e7.28 (m, 4H), 7.21e7.18 (m, 1H),
d
J¼7.5 Hz, 4H), 7.55e7.52 (m, 6H), 7.42e7.38 (m, 4H), 7.01 (d,
4.29 (d, J¼11.5 Hz, 1H), 3.56e3.52 (m, 1H), 2.23 (s, 3H), 1.83 (s, 3H),
J¼11.5 Hz, 1H), 6.93 (t, J¼9.0 Hz, 4H), 5.25 (d, J¼11.5 Hz, 1H); 13C
1.18e1.16 (s, s, 3H); 13C NMR (125 MHz, CD3COCD3)
d 203.4, 203.3,
NMR (125 MHz, CD3COCD3)
d
194.5, 162.3 (d, J¼241.8 Hz), 139.4,
144.8, 129.4, 128.4, 127.5, 75.9, 40.9, 30.5, 21.1.
137.7, 134.3, 131.1 (d, J¼8 Hz), 129.6, 129.5, 115.8 (d, J¼21.25 Hz),
61.2, 52.1.
4.2.17. 2-Benzhydryl-1-phenylbutane-1,3-dione (20).16 White solid.
1H NMR (500 MHz, CDCl3)
d
7.95 (d, J¼7.0 Hz, 2H), 7.54 (t,
4.2.8. 1,3-Diphenyl-2-(1-phenylethyl)propane-1,3-dione
J¼7.0 Hz, 1H), 7.42 (t, J¼8.0 Hz, 2H), 7.37 (t, J¼7.0 Hz, 2H), 7.31 (t,
J¼8.0 Hz, 2H), 7.24e7.20 (m, 3H), 7.14 (t, J¼8.0 Hz, 2H), 7.04 (t,
J¼8.0 Hz, 1H), 5.61 (d, J¼12 Hz, 1H), 5.10 (d, J¼12 Hz, 1H), 2.04 (s,
(11).14 White solid. 1H NMR (500 MHz, CD3COCD3)
d 8.19e8.17 (m,
2H), 7.90e7.88 (m, 2H), 7.65e7.61 (m, 1H), 7.53e7.47 (m, 3H),
7.42e7.40 (m, 2H), 7.36e7.33 (m, 2H), 7.18e7.14 (m, 2H), 7.06e7.03
(m, 1H), 6.08 (d, J¼10 Hz, 1H), 3.98e3.94 (m, 1H), 1.33 (d, J¼7.0 Hz,
3H); 13C NMR (125 MHz, CDCl3)
d 202.9, 194.3, 141.7, 141.2, 136.9,
133.6, 128.9, 128.7(overlap), 128.6, 128.1, 127.7, 127.1, 126.7, 68.9,
51.5, 27.8.
3H); 13C NMR (125 MHz, CD3COCD3)
d 195.7, 195.0, 145.2, 138.3,
137.8, 134.4, 134.0, 129.8, 129.6, 129.4, 129.0, 128.9, 127.2, 63.3, 42.2,
20.8.
4.2.18. 1-Phenyl-2-(phenyl(o-tolyl)methyl)butane-1,3-dione (21-1,
21-2). Mixture of two diastereoisomers, ca. 1:1. combined yield
4.2.9. 3-Benzhydrylpentane-2,4-dione (12).16 White solid. 1H NMR
90%. 21-1 White solid. 1H NMR (500 MHz, CDCl3)
d 7.87 (d,
(500 MHz, CD3COCD3)
d
7.44e7.42 (m, 4H), 7.28 (t, J¼8.0 Hz, 4H),
J¼7.5 Hz, 2H), 7.51e7.47 (m, 2H), 7.37 (t, J¼7.5 Hz, 2H), 7.23e7.21
(m, 3H), 7.17e7.09 (m, 4H), 7.01 (t, J¼7.5 Hz, 1H), 5.58
(d, J¼12 Hz, 1H), 5.30 (d, J¼12 Hz, 1H), 2.40 (s, 3H), 2.02 (s, 3H);
7.17 (t, J¼8.0 Hz, 2H), 5.21 (d, J¼12 Hz, 1H), 4.80 (d, J¼12 Hz, 1H),
2.04 (s, 6H); 13C NMR (125 MHz, CD3COCD3)
133.1, 131.8, 77.5, 56.3, 34.8.
d 207.2, 147.5, 133.8,
13C NMR (125 MHz, CDCl3)
d 202.9, 194.9, 140.4, 139.2, 137.1,
136.4, 133.5, 131.2, 128.7, 128.6, 128.5, 128.4, 127.0126.7, 126.6,
4.2.10. 3-(Phenyl) (o-tolyl)methyl)pentane-2,4-dione (13). White
solid. 1H NMR (500 MHz, CD3COCD3)
126.4, 69.4, 47.1, 27.4, 19.9. 21e2 White solid. 1H NMR (500 MHz,
d
7.56 (t, J¼7.5 Hz, 1H),
CDCl3)
d
7.94e7.92 (m, 2H), 7.54 (t, J¼7.5 Hz, 1H), 7.42 (t,
7.40e7.39 (m, 2H), 7.28 (t, J¼7.5 Hz, 2H), 7.20e7.09 (m, 4H), 5.22 (d,
J¼12 Hz, 1H), 5.03 (d, J¼12 Hz, 1H), 2.43 (s, 3H), 2.04 (s, 3H), 1.99 (s,
J¼7.5 Hz, 2H), 7.32e7.30 (m, 2H), 7.27e7.25 (m, 2H), 7.20e7.15
(m, 2H), 7.03e7.02 (m, 1H), 6.97e6.95 (m, 2H), 5.64 (d, J¼12 Hz,
1H), 5.26 (d, J¼12 Hz, 1H), 2.44 (s, 3H), 2.00 (s, 3H); 13C NMR
3H); 13C NMR (125 MHz, CD3COCD3)
d 203.0, 202.3, 142.1, 141.3,
136.9, 131.7, 129.44, 129.40, 127.5, 127.4, 127.2, 127.1, 73.6, 47.2, 31.2,
30.3, 20.2.
(125 MHz, CDCl3) d 203.1, 193.9, 140.6, 139.9, 136.9, 136.5, 133.6,
131.0, 128.8, 128.7, 128.5, 126.9, 126.5, 126.4, 126.1, 125.4, 68.9,
46.9, 28.9, 20.1.
4.2.11. 3-(Phenyl (p-tolyl)methyl)pentane-2,4-dione (14). White
solid. 1H NMR (500 MHz, CD3COCD3)
d
7.27e7.26 (m, 2H), 7.16e7.10
4.2.19. 1-Phenyl-2-(phenyl(p-tolyl)methyl)butane-1,3-dione
(m, 4H), 7.02e7.01 (m, 1H), 6.94 (d, J¼7.5 Hz, 2H), 4.98 (d, J¼12 Hz,
(22).6 Mixture of two diastereoisomers, ca. 1.8:1. White solid. 1H
1H), 4.63 (d, J¼12 Hz, 1H), 2.09 (s, 3H), 1.88, 1.87 (s, s, 6H); 13C NMR
NMR (500 MHz, CDCl3)
d 7.98e7.94 (m, 2H), 7.55e7.52 (m, 1H),
(125 MHz, CD3COCD3)
d
202.63, 202.59, 143.5, 140.3, 136.9, 130.1,
7.44e7.40 (m, 2H), 7.37e7.28 (m, 2H), 7.25e7.18 (m, 3H),
7.14e7.10 (m, 3H), 7.04e6.93 (m, 1H), 5.62e5.58 (dd, J1,J2¼12 Hz,
1H), 5.08e5.05 (dd, J1,J2¼12 Hz, 1H), 2.29, 2.17 (s, s, 3H), 2.05,
129.5, 128.7, 128.6, 127.4, 73.5, 51.7, 30.32, 30.31, 20.9.
4.2.12. 3-((4-Methoxyphenyl) (phenyl)methyl)pentane-2,4-dione
2.03 (s, s, 3H); 13C NMR (125 MHz, CDCl3)
d 203.1, 203.0, 194.4,
(15).16 White solid. 1H NMR (500 MHz, CD3COCD3)
d
7.42 (d,
194.2, 141.9, 141.5, 138.7, 138.2, 137.0, 136.9, 136.7, 136.2, 133.6,
Please cite this article in press as: Zhang, X.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2014.12.101

6
X. Zhang et al. / Tetrahedron xxx (2015) 1e7
132.3, 129.6, 129.3, 128.9, 128.8, 128.7, 128.7, 128.6, 128.1, 128.0,
127.6, 127.5, 127.0, 126.6, 69.1, 69.0, 51.1, 51.0, 27.8, 27.7, 21.0,
20.9.
(125 MHz, CD3COCD3) d 201.5, 168.3,143.4,143.1,129.5,129.3,129.0,
127.5, 127.4, 64.9, 61.7, 51.6, 30.1, 14.1.
4.2.27. 2-(Bis(4-chlorophenyl)methyl)cyclohexane-1,3-dione
4.2.20. 2-((4-Methoxyphenyl) (phenyl)methyl-1-phenylbutane-1,3-
(30). White solid. 1H NMR (500 MHz, CDCl3)
d 7.34e7.31 (m, 4H),
dione (23). Mixture of two diastereoisomers, ca. 1:1. White solid.
7.23e7.22 (m, 4H), 6.05 (s, 1H), 5.31 (s, 1H), 2.54 (t, J¼6.5 Hz, 2H),
1H NMR (500 MHz, CDCl3)
d 7.96e7.94 (m, 4H), 7.55e7.52 (m, 2H),
2.32 (t, J¼6.0 Hz, 2H), 2.02e1.97 (m, 2H); 13C NMR (125 MHz, CDCl3)
7.44e7.40 (m, 4H), 7.36e7.35 (m, 2H), 7.31e7.28 (m, 4H), 7.22e7.19
(m, 3H), 7.16e7.12 (m, 4H), 7.05e7.02 (m, 1H), 6.85e6.82 (m, 2H),
6.68e6.65 (m, 2H), 5.56 (dd, J¼12 Hz, 2H), 5.06 (d, J¼12 Hz, 2H),
3.76 (s, 3H), 3.65 (s, 3H), 2.05 (s, 3H), 2.03 (s, 3H); 13C NMR
d 199.4, 175.8, 137.7, 134.4, 129.1, 127.9, 105.5, 80.4, 36.6, 29.2, 21.1.
4.2.28. 2-Benzhydryl-5,5-dimethylcyclohexane-1,3-dione
(31). White solid. 1H NMR (500 MHz, CDCl3)
7.36e7.26 (m, 10H),
6.12 (s, 1H), 5.35 (s, 1H), 2.43 (s, 2H), 2.17 (s, 2H), 1.07 (s, 6H); 13C
NMR (125 MHz, CDCl3) 199.5, 147.6, 139.6, 128.8, 128.2, 126.5,
d
(125 MHz, CDCl3)
d 203.1, 203.0, 194.4, 194.3, 158.6, 158.2, 142.1,
141.6, 137.0, 133.9, 133.6, 133.3, 129.2, 128.9, 128.7, 128.6, 128.0,
127.6, 127.0, 126.9, 126.6, 114.4, 114.0, 69.2, 69.1, 55.2, 55.1, 50.73,
50.72, 27.7.
d
104.3, 81.9, 50.7, 43.2, 32.6, 28.3.
4.2.29. 2-(Bis(4-chlorophenyl)methyl)-5,5-dimethylcyclohexane-1,3-
4.2.21. 2-((4-Chlorophenyl) (phenyl)methyl-1-phenylbutane-1,3-
dione (32). White solid. 1H NMR (500 MHz, CD3COCD3)
d
7.41e7.38
(m, 4H), 7.31e7.28 (m, 4H), 6.35 (s, 1H), 5.14 (s, 1H), 2.36 (s, 2H), 1.96
(s, 2H), 0.91 (s, 6H); 13C NMR (125 MHz, CD3COCD3)
198.0, 174.2,
dione (24).6 Mixture of two diastereoisomers, ca. 1:1. White solid.
1H NMR (500 MHz, CDCl3)
d
7.97e7.93 (m, 4H), 7.58e7.53 (m, 2H),
d
7.46e7.41 (m, 4H), 7.35e7.20 (m, 8H), 7.14e7.10 (m, 9H), 7.07e7.06
(m, 1H), 5.56 (d, J¼12 Hz, 1H), 5.08 (d, J¼12 Hz, 1H), 2.05e2.03 (s, s
140.1, 134.3, 129.7, 129.1, 104.9, 80.3, 51.2, 43.3, 33.1, 28.3.
6H). 13C NMR (125 MHz, CDCl3)
d 202.6, 202.5, 194.0, 193.9, 141.2,
Acknowledgements
140.7, 140.3, 139.8, 136.8, 136.7, 133.9, 133.8, 133.0, 132.5, 129.5,
129.1, 129.1, 128.9, 128.8, 128.7, 128.7, 128.7, 128.1, 127.7, 127.3, 126.9,
68.8, 68.7, 50.8, 50.7, 27.9, 27.8.
The authors thank the National Natural Science Foundation of
China (21273068, 21373003 and 21302144), the NSF of Hunan
Province (14JJ7027), and the Fundamental Research Funds for the
Central Universities, Hunan university, for financial support.
4.2.22. 2-(Bis(4-chlorophenyl)methyl-1-phenylbutane-1,3-dione
(25).4a White solid. 1H NMR (500 MHz, CDCl3)
d
7.92 (d, J¼8.0 Hz,
2H), 7.55 (t, J¼7.5 Hz, 1H), 7.42 (t, J¼7.5 Hz, 2H), 7.28e7.27 (m, 4H),
Supplementary data
7.12e7.09 (m, 4H), 5.49 (d, J¼12 Hz, 1H), 5.05 (d, J¼12 Hz, 1H), 2.02
(s, 3H); 13C NMR (125 MHz, CDCl3)
d 202.1, 193.6, 139.7, 139.3, 136.6,
The crystal data of complex 1a$H2O$3THF, copies of the 1H NMR
and 13C NMR of all the products; additional information as needed
can be seen in the Supplementary data. Supplementary data related
to this article can be found at http://dx.doi.org/10.1016/
j.tet.2014.12.101.
CCDC 1010459 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
the cambridge Crystallographic Data Centre via www.ccdc.cam.a-
c.uk/ata_request/cif.
134.0, 133.2, 132.8, 129.4, 129.3, 129.0, 128.9, 128.8, 128.7, 68.7, 50.0,
27.9.
4.2.23. 2-(Bis(4-fluorophenyl)methyl-1-phenylbutane-1,3-dione
(26).7 White solid. 1H NMR (500 MHz, CDCl3)
d
7.94 (d, J¼8.0 Hz,
2H), 7.56 (t, J¼7.5 Hz, 1H), 7.44 (t, J¼7.5 Hz, 2H), 7.33e7.30 (m,
2H), 7.18e7.15 (m, 2H), 7.01 (t, J¼8.0 Hz, 2H), 7.18e7.15 (t,
J¼8.0 Hz, 2H), 5.51 (d, J¼12 Hz, 1H), 5.09 (d, J¼12 Hz, 1H), 2.04 (s,
3H); 13C NMR (125 MHz, CDCl3)
d 202.4, 193.9, 161.8 (d,
J¼245 Hz), 161.5 (d, J¼244.5 Hz), 137.3 (d, J¼3.3 Hz), 136.8 (d,
J¼3.1 Hz), 136.7, 133.9, 129.6 (d, J¼8.0 Hz), 129.1 (d, J¼8.0 Hz),
128.8, 128.7, 116.0 (d, J¼21.3 Hz), 115.6 (d, J¼21.3 Hz), 69.1, 49.9,
27.8.
References and notes
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C. A.; Li, C.-J. Tetrahedron Lett. 2010, 51, 1172.
4.2.24. 1-Phenyl-2-(1-phenylethyl)butane-1,3-dione (27).4a White
2. (a) Arcadi, A.; Cerichelli, G.; Chiarini, M.; Giuseppe, S. D.; Marinelli, F. Tetrahe-
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solid. 1H NMR (500 MHz, CDCl3)
d 7.78e7.76 (m, 2H), 7.47
(t, J¼7.0 Hz, 1H), 7.34 (t, J¼8.0 Hz, 2H), 7.18e7.13 (m, 4H),
7.07e7.04 (m, 1H), 4.80 (d, J¼11.0 Hz, 1H), 3.85e3.81 (m, 1H), 2.22
(s, 3H), 1.28 (d, J¼7.0 Hz, 3H); 13C NMR (125 MHz, CDCl3)
d 203.7,
195.3, 143.5, 137.0, 133.4, 128.6, 128.5, 127.4, 126.6, 71.5, 40.4, 27.5,
20.3.
4.2.25. Ethyl 2-benzhydryl-3-oxo-3-phenylpropanoate (28).16 White
solid. 1H NMR (500 MHz, CD3COCD3)
d
8.12 (d, J¼7.5 Hz, 2H), 7.63 (t,
J¼7.5 Hz, 1H), 7.54e7.50 (m, 4H), 7.42 (d, J¼7.5 Hz, 2H), 7.29 (t,
J¼7.5 Hz, 2H), 7.18e7.14 (m, 3H), 7.04 (t, J¼7.5 Hz, 1H), 5.82 (d,
J¼12 Hz, 1H), 5.01 (d, J¼12 Hz, 1H), 3.86 (q, J¼6.0 Hz, 2H), 0.87 (t,
J¼7.0 Hz, 3H); 13C NMR (125 MHz, CD3COCD3)
d 193.5, 168.4, 143.5,
143.3, 137.5, 134.5, 130.4, 129.62, 129.60, 129.2, 128.8, 128.7, 127.4,
127.2, 61.8, 59.3, 52.1, 14.0.
4.2.26. Ethyl 2-benzhydryl-3-oxobutanoate (29).16 White solid. 1H
NMR (500 MHz, CD3COCD3) d 7.44e7.40 (m, 4H), 7.28e7.24 (m, 4H),
7.17e7.13 (m, 2H), 4.83 (d, J¼12.5 Hz, 1H), 4.75 (d, J¼12.5 Hz, 1H),
3.98e3.92 (m, 2H), 2.11 (s, 3H), 0.98 (t, J¼7.0 Hz, 3H); 13C NMR
13. Thirupathi, P.; Kim, S. S. Tetrahedron 2010, 66, 2995.
Please cite this article in press as: Zhang, X.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2014.12.101

X. Zhang et al. / Tetrahedron xxx (2015) 1e7
7
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Please cite this article in press as: Zhang, X.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2014.12.101