Catalytic auto-condensation of 2,4-pentanedione promoted by Sm(III) acetylacetonate: The X-ray structure of a novel complex [Sm(CH3COO)3(H2O)2](H2 O)2

Article abstract of DOI:10.1016/S0020-1693(00)00257-7

An efficient one-pot catalytic method to obtain 4,6-dimethyl-2-hydroxyacetophenone (A) is reported, the reaction proceeds via the intermolecular auto-condensation of 2,4-pentanedione using samarium(III) acetylacetonate (Sm(AcAc)₃) as promoter. A novel complex [Sm(CH₃COO)₃(H₂O)₂](H₂ O)₂ (I) was isolated from the reaction media. The structure of I was determined by X-ray crystallography showing that the central atom is ennea-coordinated (monocapped square-antiprism geometry). This complex I also shows activity in the named autocondensation reaction.

Full text of DOI:10.1016/S0020-1693(00)00257-7

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 310 (2000) 261–264
Note
Catalytic auto-condensation of 2,4-pentanedione promoted by
Sm(III) acetylacetonate: the X-ray structure of a novel complex
[
Sm(CH COO) (H O) ](H O)
3
3
2
2
2
2
a,1
b,2
b
b
Jos e´ Luis Arias* , Armando Cabrera* , Pankaj Sharma , No e´ Rosas ,
b
b
Jos e´ Luis Garc ´ı a , S. Hernandez
a
Facultad de Estudios Superiores Cuautitl a´ n, Uni6ersidad Nacional Aut o´ noma de M e´ xico, Cuautitl a´ n Izcalli, C.P. 54700,
Estado de Mexico, Mexico
b
Instituto de Qu ´ı mica, Uni6ersidad Nacional Aut o´ noma de M e´ xico, Ciudad Uni6ersitaria, Coyoac a´ n, 04510 Mexico D.F., Mexico
Received 3 March 2000; accepted 28 July 2000
Abstract
An efficient one-pot catalytic method to obtain 4,6-dimethyl-2-hydroxyacetophenone (A) is reported, the reaction proceeds via
the intermolecular auto-condensation of 2,4-pentanedione using samarium(III) acetylacetonate (Sm(AcAc) ) as promoter. A novel
3
complex [Sm(CH COO) (H O) ](H O) (I) was isolated from the reaction media. The structure of I was determined by X-ray
3
3
2
2
2
2
crystallography showing that the central atom is ennea-coordinated (monocapped square-antiprism geometry). This complex I
also shows activity in the named autocondensation reaction. © 2000 Elsevier Science B.V. All rights reserved.
Keywords: Catalytic auto-condensation; Sm(III) acetylacetonate; Metallic acetylacetonates; Homogeneous catalysis
basic media with low yields and complicated work-up
[6].
Here we wish to report the catalytic autocondensa-
1
. Introduction
There are some reports on the use of Sm
3
+
com-
pounds as catalytic promotors with applications in
organic chemistry, e.g. condensation between 2,4-pen-
tanedione with benzaldehyde assisted by Sm , to pro-
duce a,b-unsatured carbonylic compounds [1] and the
addition of a-haloketones to carbonylic compounds [2],
the product obtained in both the cases was probably
tion of 2,4-pentanedione in the presence of Sm(AcAc)3
3
+
to give 4,6-dimethyl-2-hydroxyacetophenone (A) in one
step as the regiospecific product, we also observed the
presence of some by-products (B, C and D) (Fig. 1). In
addition, from the reaction mixture a novel complex
3
+
[Sm(CH COO) (H O) ](H O) was obtained. Some
based on the Lewis acidity of Sm
species. A similar
3 3 2 2 2 2
other metal acetylacetonates (M(AcAc) ) were also
type of product viz. 4,6-dimethyl-2-hydroxyacetophe-
none, an interesting molecule with analgesic and anti-
inflammatory properties [3], is normally produced by
phenol acylation [4] or through a Fries rearrangement
x
tested for the same reaction.
2
. Experimental
[
5] or even synthesized by autocondensation of pentane-
dione on refluxing for a long period in presence of a
2.1. Synthesis
3
+
3+
3+
2+
1
Acetylacetonates of Co , Fe , La
and Co
*
Corresponding author. Fax: +52-5-622 4515; e-mail:
were purchased from Aldrich Chemicals Company Inc.
jlartell@servidor.unam.mx
2
3+
1+
3+
*
Corresponding author.
Acetylacetonates of Mn , Ni
and Sm
were ob
0
020-1693/00/$ - see front matter © 2000 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(00)00257-7

2
62
J.L. Arias et al. / Inorganica Chimica Acta 310 (2000) 261–264
Table 1
tained from Strem Chemical and 2,4-pentanedione was
procured from Eastman Organic Chemical. All reac-
tives were used without further purification.
Crystal data and measurements conditions for complex
Sm(CH COO) (H O) ](H O)
[
3
3
2
2
2
2
Crystal size (mm)
Formula
Formula weight
Crystal system
Space group
0.20×0.10×0.08
C H O Sm
2.2. Procedure
6
17 10
399.55
Triclinic
P1
(
A mixture of pentanedione (116.85 mM) and
Sm(AcAc) (1.34 mM) were refluxed for 24 h. After this
Unit cell dimensions
3
period, the solution was cooled to room temperature
a (A
,
)
)
)
8.985(5)
9.365(5)
10.563
91.630(5)
113.960(5)
118.330(5)
687.4(6)
2
1.930
0.71069
4.307
293(2)
390
ꢀ–2q
2558
b (A
,
(
r.t.), affording a solid product which was identified as
c (A
,
the Sm complex (I) in 85.82% yield (m.p.\270°C). The
filtrate was analyzed on a Hewlett–Packard 5895 B,
GC–MS equipment with a 25 m×0.3 mm glass
column packed with 5% phenyl silicone in order to
characterize the other reaction products and quantified
by GC in a Hewlett–Packard 5890 analyzer with a 30
m×0.53 mm×2.65 mm glass column packed with HP-
h (°)
i (°)
k (°)
3
V (A
Z
,
)
Dcalc (g cm−3)
u (Mo Ka) (A
,
)
v (Mo Ka) (mm−1)
1
crosslinked methyl silicone. The filtrate was concen-
Temperature (K)
F(000)
Scan type
trated and then treated with ethanol–water (1:2),
affording a light-yellow crystalline compound, which
Reflections collected
Independent reflections
Absorption correction
Solution
2390 (Rint=0.0364)
semi-empirical
SIR-92
Refinement method
Goodness-of-fit
R
full-matrix least-squares
1.005
0.0365
Rw
0.0706
System used
SHELXL-97 (Sheldrick, 1997)
1
13
was characterized by H and C NMR as 4,6-dimethyl-
2
-hydroxyacetophenone (A), was isolated as the re-
giospecific product 75.65%.
A similar procedure was carried out with other metal
acetylacetonates when used as promotors.
Fig. 1. By-products of the autocondensation of 2,4-pentanedione in
the presence of Sm(AcAc)3.
2.3. X-ray structure determination
Fig. 2 shows an ORTEP drawing of Sm complex I.
X-ray crystallographic data were obtained on a Siemens
P4/PC diffractometer using Mo Ka radiation at r.t.
Crystallographic data are given in Table 1. Selected
bond distances and angles are presented in Table 2. The
structure was solved by direct methods (SIR-92) [7] and
2
refined by full-matrix least-squares on F using
SHELXTL-97 [8].
3
. Results and discussion
The main product (A) can be formed by initial
aldolic process (condensation–dehydration) followed
by intermolecular ring closure after eliminating the
second molecule of water, finally this ring is aromatized
by tautomeric equilibria.
Fig. 2. ORTEP drawing of the complex [Sm(CH COO) (H O) ](H O) .
3
3
2
2
2
2

J.L. Arias et al. / Inorganica Chimica Acta 310 (2000) 261–264
263
Table 2
Selected bond lengths (A
complex [Sm(CH COO) (H O) ](H O)
2
nificant steric effect may also be involved in this unfa-
vored pathway. Fig. 4 shows the (%) conversion versus
time function. It was observed that the main product
obtained was compound A and only a small amount of
the by-products were detected in the reaction media.
When complex I was used as a promotor in the same
reaction we found an induction time in the reaction
,
) and bond and torsion angles (°) for
3
3
2
2
2
Sm(1)–O(8)
Sm(1)–O(7)
Sm(1)–O(1)c1
Sm(1)–O(4)
Sm(1)–O(5)
Sm(1)–O(2)
Sm(1)–O(6)
Sm(1)–O(3)
Sm(1)–O(1)
Sm(1)–C(3)
Sm(1)–C(5)
2.398(4)
2.417(4)
2.430(4)
2.462(4)
2.477(4)
2.495(5)
2.497(5)
2.501(5)
2.586(8)
2.864(6)
2.869(6)
Sm(1)–C(1)
O(1)–C(1)
O(1)–Sm(1)c1
O(2)–C(1)
O(3)–C(3)
O(4)–C(3)
O(5)–C(5)
O(6)–C(5)
C(1)–C(2)
C(3)–C(4)
C(5)–C(6)
2.948(6)
1.270(7)
2.443(4)
1.261(8)
1.250(8)
1.277(8)
1.275(8)
1.261(8)
1.484(9)
1.506(9)
1.501(10)
(
Fig. 4), which may be due to the decomposition of the
dimeric moiety in monomeric species containing acety-
lacetonate ligands in order to catalyse the transforma-
3
+
tion. In the absence of the Sm
species in the reaction
media, no autocondensed product was obtained, sug-
O(8)–Sm(1)–O(7)
75.17(17) O(8)–Sm(1)–O(1)c1 83.82(17)
98.75(18)
O(7)–Sm(1)–O(1)c1 77.81(15) O(8)–Sm(1)–O(4)
O(7)–Sm(1)–O(4)
O(8)–Sm(1)–O(5)
131.57(16) O(1)c1–Sm(1)–O(4) 150.34(16)
125.34(17) O(7)–Sm(1)–O(5)
144.24(15)
78.36(16)
84.12(18)
77.37(18)
74.24(17)
O(1)c1–Sm(1)–O(5) 76.26(15) O(4)–Sm(1)–O(5)
O(8)–Sm(1)–O(2) 148.42(19) O(7)–Sm(1)–O(2)
O(1)c1–Sm(1)–O(2) 115.12(14) O(4)–Sm(1)–O(2)
O(5)–Sm(1)–O(2)
O(7)–Sm(1)–O(6)
O(4)–Sm(1)–O(6)
O(2)–Sm(1)–O(6)
O(7)–Sm(1)–O(3)
O(4)–Sm(1)–O(3)
O(2)–Sm(1)–O(3)
O(8)–Sm(1)–O(1)
85.04(17) O(8)–Sm(1)–O(6)
143.08(17) O(1)c1–Sm(1)–O(6) 78.82(16)
73.59(17) O(5)–Sm(1)–O(6)
131.96(17) O(8)–Sm(1)–O(3)
52.31(15)
77.84(19)
79.98(15) O(1)c1–Sm(1)–O(3) 154.15(15)
52.21(15) O(5)–Sm(1)–O(3)
75.23(17) O(6)–Sm(1)–O(3)
139.25(15) O(7)–Sm(1)–O(1)
129.39(15)
112.82(17)
73.55(15)
121.56(16)
50.54(14)
120.83(15)
105.45(17)
26.40(17)
74.12(16)
25.82(17)
99.60(18)
O(1)c1–Sm(1)–O(1) 64.58(15) O(4)–Sm(1)–O(1)
O(5)–Sm(1)–O(1)
O(6)–Sm(1)–O(1)
O(8)–Sm(1)–C(3)
73.27(14) O(2)–Sm(1)–O(1)
120.16(15) O(3)–Sm(1)–O(1)
88.54(18) O(7)–Sm(1)–C(3)
O(1)c1–Sm(1)–C(3) 170.66(15) O(4)–Sm(1)–C(3)
O(5)–Sm(1)–C(3)
O(6)–Sm(1)–C(3)
O(1)–Sm(1)–C(3)
O(7)–Sm(1)–C(5)
O(4)–Sm(1)–C(5)
O(2)–Sm(1)–C(5)
O(3)–Sm(1)–C(5)
C(3)–Sm(1)–C(5)
O(7)–Sm(1)–C(1)
O(4)–Sm(1)–C(1)
O(2)–Sm(1)–C(1)
O(3)–Sm(1)–C(1)
C(3)–Sm(1)–C(1)
104.11(16) O(2)–Sm(1)–C(3)
93.95(18) O(3)–Sm(1)–C(3)
124.64(15) O(8)–Sm(1)–C(5)
153.30(17) O(1)c1–Sm(1)–C(5) 75.59(16)
74.85(17) O(5)–Sm(1)–C(5)
109.27(18) O(6)–Sm(1)–C(5)
125.15(16) O(1)–Sm(1)–C(5)
100.51(18) O(8)–Sm(1)–C(1)
26.30(17)
26.02(17)
96.77(16)
153.28(16)
+
Fig. 3. Sm3 assisted pathway for C C selective ring closure in
1
6
autocondensation of 2,4-pentanedione.
78.11(17) O(1)c1–Sm(1)–C(1) 90.06(14)
99.34(18) O(5)–Sm(1)–C(1)
25.07(16) O(6)–Sm(1)–C(1)
98.16(17) O(1)–Sm(1)–C(1)
99.17(17) C(5)–Sm(1)–C(1)
77.73(15)
130.03(16)
25.47(15)
104.02(17)
93.4(4)
177.3(5)
121.8(6)
60.3(3)
C(1)–O(1)–Sm(1)c1 151.2(4)
C(1)–O(1)–Sm(1)
C(4)–C(3)–Sm(1)
O(6)–C(5)–C(6)
O(6)–C(5)–Sm(1)
C(6)–C(5)–Sm(1)
O(4)–C(3)–Sm(1)
O(6)–C(5)–O(5)
O(5)–C(5)–C(6)
O(5)–C(5)–Sm(1)
59.0(3)
119.7(6)
118.6(6)
59.4(3)
177.7(5)
The ring closure may ocurr at two different positions
leading to two possible isomers, A and 2,6-dimethyl-4-
hydroxyacetophenone (A%) (Fig. 3), however, the reac-
tion is regiospecific and only gives A. The ring closure
between C –C may be favored because of the stabiliza-
1
6
3
+
tion of the Sm ion through the coordination with the
Fig. 4. Catalytic autocondensation of pentanedione by Sm(AcAc)3
(ꢀ) and complex I (ꢁ). In both (A) Main product and (B)+(C)+
(D) byproducts. Condition 2,4-pentanedione (11.85 mM), promotor
Sm(AcAc)3 (1.34 mM), complex (I) (0.67 mM).
acetylacetonate C -alkylated (in a six-membered ar-
3
rangement), which is not possible in the other case if
the ring closure occurs at C –C . Additionally, a sig-
7
2

2
64
J.L. Arias et al. / Inorganica Chimica Acta 310 (2000) 261–264
Table 3
,6-Dimethyl-2-hydroxyacetophenone formation by catalytic auto-
condensation of 2,4-pentanedione mediated by M(AcAc)x
presence of acetate anion in the molecule, which was
4
produced by the retrocondensation of pentanedione
a
3+
promoted by Sm according to the following reaction:
Sm3+
Run Catalyst
Total conversion
Main product (%) (A)
CH COCH COCH +H O X CH COCH
3
2
3
2
3
3
(
%)
+
CH COOH
(1)
3
1
2
3
4
5
6
7
8
Co(AcAc)2
Ni(AcAc)2
0.73
1.96
1.39
2.37
8.78
52.76
58.50
91.22
0.39
1.96
1.39
2.06
8.19
48.52
53.81
75.65
The average M–O bond length around the Sm atom
Co(AcAc)3
,
,
is 2.473(4) A (2.398–2.586 A). The bond length Sm(1)–
O(1), 2.586(8) A, is longer than Sm(1)–O(2), 2.495(5)
, or Sm(1)–O(1)a, 2.430(4) A
C(1)–O(2)–Sm(1), 98.0(3)°,
Fe(AcAc)3
,
Mn(AcAc)3
La(AcAc)3
Sm(AcAc)3
Sm(AcAc)3
A
,
,
, and the bond angles
C(1)–O(1)–Sm(1),
b
93.4(4)°, C(1)–O(1)–Sm(1)a, 151.2(4)°, are in the re-
spective standard ranges of the Z,E-type acetate ligand.
In crystal packing we observe the presence of inter-
molecular hydrogen bonds between the two dimeric
units.
a
1
16.85 mmol of 2,4-pentanedione and 1.34 mmol of catalyst, 24 h.
t=40 h.
b
gesting that the substrate needs the presence of a Lewis
acid to promote the reaction. Some other metal acety-
lacetonates were also tested in the process without
exhibiting activity (Table 3), only samarium and lan-
tane acetylacetonates gave good results.
Acknowledgements
We thank DGAPA-UNAM (IN216197) and CONA-
CYT 27492E for financial support and L. Velasco for
mass-spectra measurements.
3
+
The structure of the aquo carboxylate Sm complex
obtained from pentanedione and Sm(AcAc) was deter-
3
mined by single-crystal data and revealed the follow
composition, [Sm(CH COO) (H O) ](H O) . The new
3
3
2
2
2
2
References
complex formed in neutral conditions and appears as a
dimer showing an Z,E-conformation with each Sm
atom coordinated to three acetate ligand, two of these
acetate anions act as bidentate ligand forming a four-
membered chelate ring and the third acetate anion acts
as a tridentate ligand forming a bridge with a second
Sm atom. In addition to each samarium atom there are
two water molecules. The dimeric complex has crystal-
lographic inversion symmetry. Both the Sm atoms are
coordinated to nine oxygen atoms having monocapped
square antiprism geometry with a oxygen atom of a
bidentate acetate ligand at the cap position as shown in
Fig. 2. The crystal structure of this complex shows the
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