1
08
Y. Masuyama et al. / Applied Catalysis A: General 387 (2010) 107–112
onate (2) in water via the formation of a -allylpalladium complex
prepared from allyl methyl carbonate (1) [1–5]; and (3) the demon-
stration of the reusability of the PdHAP for the allylic alkylation in
water.
under air in a shaking water bath (AS ONE Co., SWB-17, stroke:
30 mm, speed: 130 rpm), the solution was separated from PdHAP-B
by centrifugation followed by decantation. The separated PdHAP-B
was washed with methanol (3 mL × 2) and ether (3 mL × 5) suc-
cessively by the same operations. Over 97% of the PdHAP-B was
recovered on the average and could be reused. The residue after
removal of the methanol was combined with more ether (200 mL).
The mixed ethereal solution was washed with water (30 mL) and
2
. Experimental
2.1. General methods
brine (30 mL), and then was dried over anhydrous MgSO . After
4
Hydroxyapatite [Ca10(PO ) (OH) ] (HAP) was purchased from
evaporation of ether, purification by column chromatography (sil-
ica gel, hexane/EtOAc = 25:1) and HPLC (Japan Analytical Industry
Co. Ltd., LC-908, JAIGEL-2H; CHCl3) afforded 0.16 g (84%) of ethyl
2-ethoxycarbonyl-4-pentenoate (3) as a colorless oil.
4
6
2
Taihei Chemical Industrial Co. Ltd. and was used as received or after
◦
calcining with a heating rate of 10 C/min from room temperature
◦
◦
to 800 C and then at 800 C for 3 h. Palladium nitrate was pur-
chased from Furuya Metal Co. Ltd. and was used as received. Allyl
methyl carbonate and allyl acetate were purchased from Tokyo
Chemical Industry Co. Ltd. Ethyl cyanoacetate and malononitrile
were purchased from Kanto Chemical Co. Inc. Diethyl malonate, 2-
ethoxycarbonylcyclopentanone, 2-ethoxycarbonylcyclohexanone
and 2,2-dimethyl-1,3-dioxane-4,6-dione were purchased from
Sigma–Aldrich, Inc. The commercial compounds were purified by
distillation or by column chromatography. Inductively coupled
plasma (ICP) analysis was carried out on a Seiko Instruments
Inc. SPS7700. The textural properties of fresh PdHAP-B and used
PdHAP-B were determined by nitrogen adsorption at 77 K (BEL
JAPAN, BELSORP-mini). XRD measurements were performed on a
RIGAKU Electronic RINT 2100/PC X-ray diffraction spectrometer
equipped with a carbon monochromator and Cu K˛ (40 kV, 40 mA)
Ethyl 2-ethoxycarbonyl-4-pentenoate (3): colorless oil; Rf = 0.53
(hexane:ethyl acetate = 3:1); 1H NMR (CDCl3) ı 1.28 (t, J = 7.0, 6H),
2.62–2.66 (m, 2H), 3.42 (t, J = 7.5, 1H), 4.15–4.24 (m, 4H), 5.06 (d,
J = 10.5, 1H), 5.12 (d, J = 17.0, 1H), 5.78 (dd, J = 17.0, 10.5, 1H); IR
(neat) 3086, 3017, 2986, 2939, 1736, 1643, 1605, 1466, 1443, 1373,
1335, 1273, 1219, 1188, 1157, 1119, 1057, 1034, 926, 856, 810,
−
1
702 cm
.
Ethyl 2-(2-propenyl)-2-ethoxycarbonyl-4-pentenoate (4): col-
orless oil; Rf = 0.63 (hexane:ethyl acetate = 3:1); 1H NMR (CDCl3) ı
1.25 (t, J = 7.0, 6H), 2.64 (d, J = 7.0, 4H), 4.18–4.22 (m, 4H), 5.09–5.14
(m, 4H), 5.62–5.70 (m, 2H); IR (neat) 3040, 3017, 2932, 2862, 1720,
1651, 1605, 1512, 1458, 1373, 1258, 1234, 1218, 1096, 1018, 903,
−
1
864, 818 cm
.
The structures of all products were confirmed by the compari-
son of spectroscopic values (IR and NMR) with those of authentic
samples in the literature; ethyl 2-ethoxycarbonyl-4-pentenoate
(3) [5,23], ethyl 2-(2-propenyl)-2-ethoxycarbonyl-4-pentenoate
◦
◦
irradiation, covering 2ꢀ values between 20 and 55 . Samples were
run as fine powders mounted on glass slides. XPS measurements
were performedonaULVAC-Phi ESCA 5800ci usingmonochromatic
Al K˛ (14 kV, 25 mA) irradiation. Samples were mounted on the
spectrometer probe using a piece of double-sided adhesive tape.
The binding energies of XPS spectra of Ca(2p) and Pd(3d) were cal-
ibrated by the observed binding energy of C(1s). Allylic alkylations
were carried out on an AS ONE Co. shaking water bath SWB-17
(4)
(5) [25], 2-ethoxycarbonyl-2-(2-propenyl)cyclohexanone (6)
[23], 2,2-dimethyl-5,5-(di-2-propenyl)-1,3-dioxane-4,6-dione
(7) [26], ethyl 2-cyano-4-pentenoate (8) [24], and ethyl
2-(2-propenyl)-2-cyano-4-pentenoate (9) [24]. Electronic
[5,24],
2-ethoxycarbonyl-2-(2-propenyl)cyclopentanone
(
7
stroke: 30 mm, speed: 130 rpm) or on a NISSIN block shaker NX-
0B (stroke: 1.5 mm). TLC analyses were carried out with silica gel
supplementary information is available: IR and NMR spectra of
products.
plates (Merck Art.5735), and column chromatography was carried
out with silica gel (Kanto Chemical Co. Inc. Cat. No. 37564). HPLC
purification was carried out on a Japan Analysis Industry Co. Ltd.
3. Results and discussion
LC-908 (JAIGEL-2H; CHCl ). NMR spectra were recorded on a JEOL
3
JMS-LA500 spectrometer. IR spectra were recorded on a Shimadzu
FTIR-8300 spectrometer.
3.1. Palladium(II)-exchanged hydroxyapatite (PdHAP)
Palladium ion-exchange to HAP was carried out with Pd(NO )
3
2
◦
at 70 C in water to prepare three kinds of palladium-exchanged
2.2. Preparation of palladium(II)-exchanged hydroxyapatite
−
1
(
PdHAP)
hydroxyapatites: namely, PdHAP-A (Pd content: 0.02 mmol g ),
−
1
PdHAP-B (Pd content: 0.05 mmol g ) and PdHAP-C (Pd content:
0.1 mmol g 1). ICP analysis revealed that almost no Pd2+ was
−
A calcium hydroxyapatite (2.0 mmol) sample of Ca/P = 1.67
−
4
[
Ca10(PO ) (OH) ] (HAP) was stirred with 150 mL of a 6.3 × 10
M
present in any filtrate that included over 1.6 equimolar amounts
4
6
2
−2
◦
2+
2+
aqueous Pd(NO ) (9.5 × 10 mmol) solution at 70 C for 24 h. The
of Ca relative to the amount of Pd consumed, in contrast to
the preparation of PdHAP in organic solvents [12,14]. The pow-
der X-ray diffraction (XRD) peaks for every PdHAP were the same
as those of commercial HAP or calcined HAP. The XRD spectra of
PdHAP-Bs together with those of HAPs are shown in Fig. 1. There-
fore, all prepared PdHAPs and used PdHAP-Bs were found to retain
the structural properties of the HAP surfaces. The specific surface
3
2
obtained slurry was filtered, washed with deionized water, and
◦
dried overnight at 110 C to afford a Pd(II)-exchanged hydroxya-
−1
patite (PdHAP-B, Pd content: 0.05 mmol g ) as a brown powder.
Since no Pd(II) was detected in the filtrate or in the washing water
by ICP analysis, the Pd content was estimated to be the same molar
amount as that of the Pd(NO ) used. The specific surface of PdHAP-
B area calculated according to the B.E.T. model was 18.7 m g , and
the pore volume of PdHAP-B calculated according to the Dollimore
and Heal model was 0.0462 cm g
.3. Typical procedure for PdHAP-catalyzed allylic alkylation
To a suspension of PdHAP-B (0.2 g, 1 mol% Pd) and triph-
3
2
2
−1
2
−1 −1
3
(20.3 m g ) and the pore volume (0.0501 cm g ) of used PdHAP-
2
−1
,
B were almost the same as those of fresh PdHAP-B (18.7 m g
3
−1
3
−1
.
0.0462 cm g ). We investigated the variation of binding energy
and intensity of Pd 3d5/2 peaks between fresh PdHAP-B and repet-
itively used PdHAP-B by X-ray photoelectron spectroscopy (XPS)
2
(Fig. 2) [27–31]. A small peak was obtained in the Pd 3d5/2 region for
each repetitively used PdHAP-B. Since the peaks for used PdHAP-Bs
seem to exhibit almost the same binding energies as the peak for
fresh PdHAP-B, the oxidation state of palladium nuclear in PdHAP-B
can be kept as divalent between before being used for the reaction
enylphosphine (3 mg, 0.01 mmol) in water (1 mL) were added
diethyl malonate (2, 0.32 g, 2 mmol) and allyl methyl carbonate (1,
◦
0
.12 g, 1 mmol). After the suspension was shaken at 50 C for 24 h