Microwave-assisted acetalization of
pentaerythritol catalyzed by ammonium hydrogen sulfate
Zhang Jinmei, Li Yiqun
(Department of Chemistry, Jinan University, Guangzhou 510632)
Received Jul. 14, 2003.
Abstract Efficient
conversion of carbonyl compounds, aldehyde or ketone, with pentaerythritol to the
corresponding compounds in the presence of ammonium hydrogen sulfate under microwave
irradiation without solvent is described.
Keywords diacetal of pentaerythritol, microwavae
irradiation, ammonium hydrogen sulfate.
The diacetal of pentaerythritol are a
series of useful organic compounds. They have been used as plasticizers and vulcanizer, as
active physiologically substance, and as potential protective groups in organic synthesis.
The preparation of these compounds has been well investigated. A variety of acidic
catalysts, such as hydrochloric acid, sulfuric acid, p-toluenesulfonic acid, zinc
chloride, acidic cation exchanger, Montmorillonite clay [1], expansive graphite[2]and anhydrous ferrous sulfate[3] have
been used for this purpose.
Microwave dielectric heating has recently attracted much attention and
become an important technique in organic synthesis[4]. Recently p-
toluenesulfonic acid[5] in dry media, 12-tungstophosphoric acid[6]
in acetonitrile coupled with microwave irradiation has been proven to be an efficient
method for the synthesis of diacetal of pentaerythritol. However these methods are not
entirely satisfactory, due to such drawbacks as using organic solvent, corrosive acid, or
tedious work-up, etc. Therefore, there is a need for developing an efficient and
convenient catalytic method for the reaction using inexpensive and non-polluting reagent.
Surprisingly the potentiality of ammonium hydrogen sulfate as a
catalyst has not, hitherto, been studied in the synthesis of diacetal of pentaerythritol.
We have found that this common commercial available reagent can catalyzed the reaction
under the microwave irradiation to produce the corresponding diacetates in good purity and
moderate yields. The results are summarized in the Table 1,Table 2 and Table 3.
Scheme 1
Table 1 Microwave-assisted acetalization of pentaerythritol
Entry |
Aldehydes
(1) |
Power
(W) |
Time (min) |
m.p.b
( ºC) |
Lit.m.p.
( ºC) |
Yields
(%)a |
a |
n-C3H7CHO |
750 |
1.2 |
44-45 |
43-44[7] |
63 |
b |
C6H5CHO |
750 |
1.5 |
157-158 |
159-160[6] |
72 |
c |
4-Cl-C6H5CHO |
750 |
1.5 |
197-199 |
199-200[6] |
60 |
d |
cyclohexanone |
750 |
1.2 |
114-115 |
115-116[6] |
64 |
e |
2-NO2-C6H5CHO |
750 |
2.4 |
165-167 |
163-164[5] |
56 |
f |
4-MeO-C6H5 |
750 |
1.0 |
184-185 |
180-182[3] |
43 |
g |
2-Furylaldhyde |
750 |
0.6 |
162-163 |
158-159[6] |
72 |
h |
3-NO2-C6H5CHO |
750 |
2.0 |
185-186 |
185-186[3] |
63 |
a isolated yields
brecrystallization solvent: ethanol for 3b, 3d, 3e, 3g, 3h;
Butanol for 3c, 3f; water-ethanol for 3a
Table 2 IR and NMR spectral
data
Compd. |
IR (KBr,cm-1) |
1 H-NMR (CD3COCD3, d) |
3a |
2963,2865,1464,1394,1161,1099,1029 |
0.89(6H,t),1.39(4H,m),1.51(4H,m),
3.20-3.60(6H,m),4.41(2H,d),4.47(2H,t) |
3b |
3036,2995,2919,2854,1457,1386,1078,1028 |
3.50-3.95(6H,m), 4.80(2H,d), 5.42(2H,s),
7.20-7.58(10H,m) |
3c |
748,702,2921,2861,1383,1077,1025,814 |
3.20-3.60(6H,m),4.31(2H,s),4.55(2H,d),
7.00-7.58(8H,m), |
3d |
2936,2859,1445,1370,1251,1160,1087,1043,917 |
1.20-2.0(20H,m), 3.20-3.60(6H,m),
4.50(2H,d), |
3e |
2969,2917,2858,1526,1356,1070,737 |
3.21-3.60(6H,m),4.32(2H,s),4.56(2H,d),
6.76-7.98(8H,m), |
3f |
3010,2965,2851,1614,1517,1456,1388,
1250,1161,1067,1032,829 |
3.20-3.60(6H,m)3.92(6H,s),4.30(2H,s),
4.58(2H,d),6.80-7.78(8H,m) |
3g |
3126,2979,2921,2864,1504,1460,
1414,1364,1160,1084,1029,952,748 |
3.50-3.95(6H,m), 4.80(2H,d), 5.55(2H,s)
6.30-6.53(4H,m),7.40(2H,s) |
3h |
3082,2978,2857,1620,1526,1347,1080,732,682 |
3.21-3.62(6H,m),4.32(2H,s),4.56(2H,d),6.80-7.90 (6H,m) |
Table 3 The effect
of power and time of irradiation to the yield
of 3b
Power (W) |
Time (min) |
Yields (%)a |
750 |
1 |
60 |
750 |
1.5 |
72 |
750 |
2 |
62 |
637 |
2 |
68 |
495 |
2 |
52 |
The
acetalization of both aldehydes and ketone have been investigated, in many cases, our
experiment gave shorter reaction time and moderate yield. Ketone show lower reactivity
than aldehydes for this reaction, aromatic aldehydes with strong electron-donor groups
show less reactivity and give lower yields.
In conclusion, we provide an alternative protocol for the
preparation of diacetals from aldehydes, because of its simplicity in operation, moderate
yields, short reaction time and minimal environment impact.
EXPERIMENTAL SECTION
Melting point are uncorrected and determined on WRS-1 digital melting point apparatus
in open capillary. IR spectra were recorded using KBr pellet on Bruke Equinox 55
sectrometer. 1H NMR spectra were recorded in acetone on Unity Inova 500 (500
MHz) with TMS as an internal standard. Benzaldehyde and Furyl aldehyde was purified by
distillation. All other chemicals used were of commercial grade without further
purification.
Typical procedure: A mixture of carbonyl compound (10 mmol),
pentaerythritol (5 mmol) and sulfamic acid (2 mmol) was introduced into a Galanz WP 750A
domestic microwave oven in an open 25ml vessel. Microwave irradiation was carried out for
0.6-2.4 minutes at 495-750W power, followed by adding a lot of cool water and shaking the
vessel rigorously to precipitate the solid. The solid materials was filtered off and
treated with saturated sodium hydrogen sulfate solution, and then washed with water for
several times until the filtrate became neutral. The crude products were purified by
recrystallization to give the title compound.
REFERENCES
[1] Zhang Z H, Li T S, Jin T S et al. J. Chem.Res.(S), 1998, 640-641.
[2] Jin T S, Li T S, Zhang Z H. Synth.Commun.1999, 29: 1601-1606.
[3] Jin T S, Ma Y R,Li T S et al. J. Chem. Res.(S), 1999, 268-269.
[4] Varma, R. S.Solvent-free organic syntheses. Green Chem., 1999, 1: 43-55.
[5] Wang C D, Shi X Z, Xie R J. Synth. Commun., 1997, 27: 2517-2520.
[6] Peng Y Q, Song G H, Qian X H. Synth.Commun., 2001, 31: 3735-3738.
[7] Chen X£¬Xu Y T£¬Jin C X. Synth. Chem. (Hecheng Huaxue), 1997, 5 (2): 212-214.
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